header advert
Orthopaedic Proceedings Logo

Receive monthly Table of Contents alerts from Orthopaedic Proceedings

Comprehensive article alerts can be set up and managed through your account settings

View my account settings

Visit Orthopaedic Proceedings at:



Volume 87-B, Issue SUPP_III September 2005

P.A. Rust G.W. Blunn S.R. Cannon T.W. Briggs

Introduction: The treatment of bone defects that occurs following fractures, the excision of bone tumours and at revision arthroplasty surgery, often involves the use of either autologous or allogenous bone grafts. However, both grafts have limitations. The aim of tissue engineering is to produce cells within an extracellular matrix that resembles tissue, which can be implanted into a patient to heal a tissue defect. The potential to engineer bone tissue grafts from patients’ autologous cells would improve the treatment of bone defects.

Bone marrow contains cells, known as mesenchymal stem cells (MSCs), which have the ability to differentiate into osteoblasts. To create a 3-dimensional structure necessary for the reconstruction of tissue, cells need to be grown on a scaffold, for which hydroxyapatite (HA) was used, as it is osteoconductive. In living bone, increased extravascular perfusion increases new bone formation. Thus, these physiological conditions were reproduced in our novel bioreactor by perfusing MSCs seeded on porous HA scaffolds at a rate of 6ml/hr. Hypotheses: 1. Culture in this bioreactor improves cell penetration through a HA scaffold. 2. MSCs cultured on HA in this bioreactor differentiated into osteoblasts.

Method: MSCs were isolated from 8 bone marrow aspirates, which were taken from patients during orthopaedic procedures following informed consent. For each experiment, MSCs from each patient were seeded onto 2 x 1cm3 scaffolds. To test cell penetration, the HA scaffolds were cultured for 7 days, then sectioned longitudinally and the number of cells were counted at increasing depths. Observations of MSCs on HA were compared under scanning (SEM) and transmission (TEM) electron microscopy. The HA scaffolds were cultured with MSCs in the bioreactor for 5, 10 & 15 days, after which time alkaline phosphatase (ALP) and type I pro-collagen protein levels were measured.

Results: Penetration of cells through the porous HA scaffold was significantly greater when the cells had been cultured in the bioreactor (P< 0.05). Observing MSCs after 7 days in bioreactor culture under SEM, adherent fibroblastic cells formed a network over the HA. However, by 14 days the HA was covered with cuboidal cells, consistent with osteoblasts. TEM results showed that MSCs cultured on HA in the bioreactor produced organised collagen matrix after 28 days. Osteoblastic protein levels were significantly greater at each time point when MSCs were cultured in bioreactor conditions: ALP (P< 0.005) and type I pro-collagen (P< 0.05).

Discussion and Conclusions: These results show that when cultured in our novel bioreactor, MSCs penetrated uniformly through the porous HA scaffold, whereas few cells penetrated in static culture conditions. Thus, our bio-reactor significantly improves the 3-dimensional growth of cells, resembling tissue. Moreover, in this study MSCs grown on HA in the bioreactor produced significantly larger amounts of ALP and type I pro-collagen, indicating that the MSCs differentiated into osteoblasts. Observations under TEM showed extracellular collagen matrix production which, when mineralized, produces bone.

Therefore, this culture method could potentially be used to convert MSCs, isolated from patients’ bone marrow, into tissue-engineered bone.

B.J.C. Freeman R.M. Walters R.J. Moore R.D. Fraser

Objective: To investigate the effects of intra-discal electro-thermal therapy (IDET) on an experimentally induced posterolateral annular inter vertebral disclesion in sheep.

Summary of Background Data: IDET is being used increasingly as a minimally-invasive treatment for chronic discogenic low back pain, with success reported in up to 70% of cases. The mechanism of action however is poorly understood. Proposed mechanisms include the contraction of collagen and the coagulation of annular nociceptors. An ovine model was used to assess the innervation of peripheral posterolateral annular lesions and the potential for IDET to denervate this region.

Methods: Posterolateral annular incisions were made in 36 lumbar discs of 18 sheep. After twelve weeks the sheep underwent IDET at one level and a sham treatment at the other level. IDET was performed using a modified intradiscal catheter (SpineCATH™, Oratec Interventions Inc., Menlo Park, CA). Temperatures were recorded in the nucleus (TN) and the posterior annulus (TPa). The spines were harvested at intervals up to eighteen months. Histological sections of the discs were stained with haematoxylin and eosin and an antibody to the general neuronal marker PGP 9.5.

Results: The target temperature of 90°C at the catheter was tip was reached in all cases. The mean maximum TPa was 63.6°C and the mean maximum TN 67.8°C. Vascular granulation tissue consistent with a healing response was observed in the region of the posterior annulus tear of all incised discs from 12 weeks. PGP 9.5 positive nerve fibres were clearly identified in the adjacent periannular tissue, but were scarce within the outer few lamellae of the annulus. There were no fewer nerve fibres identified in those specimens that had undergone IDET. From six weeks after IDET there was evidence of thermal necrosis in the inner annulus, sparing the periphery of the disc.

Conclusions: IDET delivered at 90°C in the sheep consistently heats the posterior annulus and the nucleus to a temperature range associated with coagulation of nociceptors and collagen contraction. Thermal necrosis was observed within the inner annulus from six weeks after IDET. In this model IDET did not produce denervation of the experimentally induced posterior annular lesion.

C.J. Pendegrass M.J. Oddy S.R. Cannon A.E. Goodship G.W. Blunn

Introduction: Functional outcome following proximal tibial replacement can be impaired by extensor mechanism inefficiency. Current methods used to re-attach the patellar tendon result in varied levels of extensor function. Successful attachment of the patellar tendon requires initial mechanical stability and long-term biological fixation. We have employed a prosthesis, to model patellar tendon re-attachment, to test the hypothesis that biological augmentation of an implant which can provide sufficient mechanical integrity will allow a tendon-implant interface to develop that is similar in function and morphology to a normal tendon-bone interface.

Methods: The right patellar tendon in 24 Skeletally mature Friesland ewes was transfixed between the interlocking spikes of a hydroxyapatite-coated, customized tendon clamp to simulate patellar tendon re-attachment to a proximal tibial replacement. In 12 animals (Autograft group) the clamp attachment was augmented with autologous cancellous bone and marrow graft harvested from the ipsilateral iliac crest at the time of surgery, whilst the remaining animals (HA group) served as un-supplemented controls. Functional outcome was assessed using force plate measurements and two-dimensional optical kinematic gait analysis. Animals were euthanised at 6 and 12 weeks. The specimens were harvested, processed for histology and examined using light microscopy.

Results: The clamp device provided sufficient mechanical fixation of the patellar tendon to allow immediate weight bearing. Gait analysis showed that the range of movement of the stifle (knee) joint was not compromised by the surgical intervention at 6 or 12 weeks post-operation. An extensor lag observed at 6 weeks in both the Autograft and HA group was seen to fully recover by 12 weeks post-operation. There was a significant increase in functional weight bearing through the operated limb of the Autograft group animals between 6 and 12 weeks, which was not observed in the HA group. The tendon-implant interface in the HA group animals showed a fibrous tissue encapsulation of the HA coated surface, with collagen fibrils running parallel to the implant surface. In the Autograft group at 6 weeks post-operation a soft tissue – bone – HA interface had developed, similar in morphology to that of an indirect-type enthesis. Perpendicular orientated Sharpey’s-like fibres were observed spanning the region between the tendon and the HA coated implant and the bone graft material was seen to be undergoing active remodelling. By 12 weeks post-operation the interface was layered with regions of fibrocartilage clearly visible, more closely resembling the morphology of a direct-type enthesis.

Discussion: The clamp device provided sufficient mechanical fixation of the patellar tendon to allow immediate use the operated limb. The incorporation of a bio-active implant coating and biological augmentation encouraged a neo-enthesis to develop with near normal functional properties, and morphology similar to that of a normal patellar tendon-bone direct-type enthesis.

S.C. Fang M.J. Coathup G.W. Blunn A.E. Goodship

Introduction: The aim of this study is to develop a novel approach to tissue engineering in vivo, in which the adaptive response of skeletal tissues to the imposed mechanical environment will be utilised to induce a cartilaginous resurfacing of the acetabular articulation in a hemi-arthroplasty model of hip replacement. Our hypothesis was that a cartilaginous resurfacing of subchondral bone can be induced by applying stresses of 0 to 3 MPa to the articular surface of the acetabulum. We used an ovine hemiarthroplasty model where the stresses on the acetabulum were engineered by using different femoral head sizes.

Methods: Three groups of six sheep received unilateral hip hemi-arthroplasties and were sacrificed 24 weeks post-operatively to harvest the acetabula. At operation, acetabular cartilage was removed completely and the subchondral bone was reamed down and left bleeding. Three femoral head sizes, 25, 28, and 32-mm, were used to induce different contact stress levels. Vertical ground reaction force (GRF) data were measured and normalised by body weight for both limbs pre-operatively and every 4 weeks post-operatively. Five specimens from each group and eight unoperated controls were processed and stained with Safranin O and Sirius Red. Cartilage proteoglycans in the regenerated tissues from four specimens in the 25-mm group were detected by immunoblotting using specific monoclonal antibodies.

Results: The operated limbs were subjected to an average of 80 to 90% pre-operative GRF after the eighth post-operative week and maintained till the end of the study. No significant difference was noted during the period between the three groups. A layer of regenerated tissue was noted on all specimens processed and was Sirius positive. Four operated specimens processed in the 25-mm group and three in the 28-mm group were Safranin O positive. The presence of cartilage aggrecan, cartilage link proteins, biglycan, and decorin was confirmed by immunoblotting.

Discussion and Conclusion: We conclude that a cartilaginous resurfacing of acetabulum can be induced in vivo under the mechanical environment imposed by our hemi-arthroplasty model. This approach may be advantageous in clinical practice as a regenerated acetabular cartilaginous surface would avoid the problems associated with wear of the plastic acetabular cup and replacement of the acetabulum.

P.A. Rust P. Kalsi G.W. Blunn S.R. Cannon T.W. Briggs

Introduction: Bone grafts are frequently used in orthopaedic operations to augment bone healing. Autologous bone graft is the gold standard for osteogenesis, but the amount available from the patient’s iliac crest is often insufficient to fill the defect and donor site morbidity is a significant complication. Alternatively, allograft can be implanted into patients, however, processing is necessary to reduce the immunicity of the graft and the risk of transmission of infection, but this destroys osteoprogenitor cells and hence reduces the osteogenic properties of the graft. Mesenchymal stem cells (MSCs) are present in bone marrow and have the ability to differentiate into osteoblasts. Therefore our study examined the use of MCSs, from bone marrow, to enhance the osteogenic properties of allograft.

Hypothesis: MSCs cultured on freeze-dried ethylene oxide treated bone allograft differentiate into osteoblasts, thereby increasing the osteogenic nature of the graft material.

Method: After informed consent, bone marrow aspirates were taken from 10 patients during elective orthopaedic operations. MSCs were characterized using Stro-1 antibody and grown on freeze-dried ethylene oxide treated bone allograft in vitro.

The hypothesis was tested on three groups of graft, with eight samples in each group. Firstly, freeze-dried ethylene oxide treated bone graft was tested (group 2). For a negative control, allograft was heated to 70°C to denature the osteogenic proteins (group 1). The final group tested the effect of additional osteogenic supplements (100nM dexamethasone, 0.05mM ascorbic acid and 10mM (-glycerol phosphate) on MSCs on allograft (group 3).

Osteoblastic differentiation of MSCs was observed under scanning (SEM) and transmission (TEM) electron microscopy, and by measuring protein levels: alkaline phosphatase (ALP), osteopontin and type I pro-collagen over 14 days.

Results: SEM confirmed that MSCs could be successfully cultured on bone allograft. Cells grown in groups 2 and 3 were characteristic of metabolically active osteoblasts and collagen extracellular matrix was observed under TEM. The amount of ALP protein produced by MSCs cultured in groups 2 and 3 increased significantly over 14 days (P< 0.05), but there was no increase in group 1. ALP, osteopontin and type I pro-collagen production was significantly greater for group 2 than for group 1 and for group 3 than for group 2 (P< 0.05).

Discussion and Conclusions: ALP, type I pro-collagen and osteopontin proteins are known to be produced by osteoblasts during increasing cell maturation and the levels of each of these proteins increased significantly when MSCs were cultured on allograft for 14 days compared with the negative control. The addition of osteogenic supplements significantly increased production of these proteins. Furthermore, MSCs cultured in groups 2 and 3 produced extracellular collagen matrix. These results are consistent with allograft causing MSCs to differentiate into osteoblasts and that this differentiation increases with additional osteogenic supplements.

This study confirms that MSCs, derived from autologous bone marrow, could be used to increase the osteogenic potential of allograft, thereby increasing bony healing in patients.

P.T.H. Lee M.T. Clarke S.A. Clarke N. Rushton

Introduction: In the 1970’s, ‘viscosupplementation’ with hyaluronan was proposed as a potential treatment for OA with the idea that it would improve joint lubrication. However, despite studies showing its ability to reduce pain, the fact that the resident time within a joint (48 hours) is much less than its clinical effect (several months) along with pharmacological effects on chondroctyes and synoviocytes has confirmed that injected hyaluronan acts as a pharmaceutical rather than as a lubricant as originally thought. In this regard, the effects of inert synthetic lubricants on arthritic joints have not previously been adequately investigated.

This study examines the effect of injecting an inert synthetic lubricant, perfluoroalkylether (PFAE16350), as a mechanical joint lubricant to prevent the development of osteoarthritis in a surgically induced model of osteoarthritis in the adult guinea pig.

Materials & Methods: Osteoarthritic changes were initiated in the hind knee joint of 12 adult male Dunkin-Hartley guinea-pigs by excision of the medial meniscus and anterior cruciate ligament.

After wound closure, the animals were randomly assigned to 1 of 2 groups: (1) Single intra-articular injection of 1ml synthetic, sterile lubricant (PFAE16350) or (2) Control group with single intra-articular injection of 1ml 0.9% sterile saline.

At 9 weeks after surgery, after sacrifice, knee arthrotomy was performed, the presence of synthetic lubricant noted and the articular cartilages examined for macroscopic evidence of osteoarthritis. These cartilages were then fixed, embedded, sectioned, stained and graded histologically for osteoarthritis according to a modified Mankin scoring system.

Immunohistochemical studies were performed to assess for any inflammatory or cytotoxic effect by the lubricant.

Results: All guinea-pigs remained healthy and mobile throughout the study.

Subjective macroscopic assessment of the medial tibial plateau osteophyte was noted to be larger and the articular surface more roughened in the control cases compared to the lubricated cases. Synthetic lubricant was noted at arthrotomy in all cases where it was injected.

Guinea-pig joints treated with the synthetic lubricant showed a mean modified Mankin score of 3.0 points compared with the guinea-pig joints treated with saline where the median modified Mankin score was 8.5 points (p< 0.001). There was no evidence of an inflammatory or cytotoxic response by immunohistochemical studies.

Discussion: This study has confirmed that inert synthetic perfluoroalkylether lubricants can remain in the articular space for prolonged periods and inhibit the development of osteoarthritis without initiating an inflammatory response. Synthetic lubricants such as PFAE16350 warrant further investigation for potential use in osteoarthritis.

P.V. Fearon T. Lind A.W. McCaskie M.A. Birch

Background: The next generation of biomaterial surfaces for use in orthopaedic surgery will be functionalised to promote osteogenesis. This will be achieved in part by the stable addition of functional bioactive molecules onto the biomaterial surface. Heparan sulphate is a complex glycosaminoglycan (GAG) that displays cell and tissue specific differences in size and levels of sulphation. It is this heterogeneity that underlies the numerous biological roles of heparan sulphate, including binding of growth factors and proteases. Findings by others have shown that the addition of heparan sulphate proteoglycans stimulate osteoblast differentiation in vitro.

Aims: To characterise heparan sulphate structures that support and enhance osteogenesis and have the potential for tissue engineering.

Experiment 1. In order to further investigate the role of heparan-sulphate proteoglycans (HSPGs) in osteogenesis we supplemented cultures of differentiating rat osteo-blasts with sodium chlorate (an inhibitor of the enzyme that sulphates GAG chains) or 4-methylumbelliferyl-b-D-xyloside, BDX (an artificial acceptor of GAG chain synthesis). Interestingly the addition of chlorate to our culture system significantly stimulated alkaline phosphatase levels and increased the area of Von Kossa stained bone-like nodules. Whereas, when BDX was added to differentiating rat osteoblasts there was no increase in alkaline phosphatase activity or nodule area.

Experiment 2. Further characterisation of the HSPGs in chlorate treated osteoblasts showed that whilst they were less sulphated than untreated cells (as shown by low salt elution from an anion exchange chromatography column) they were much more abundant. These observations led us to hypothesise that less sulphated forms of heparan sulphate may well stimulate osteo-blast differentiation.

Experiment 3. To test this hypothesis we took the fully sulphated form of heparan sulphate, heparin and selectively desulphated it using DMSO/methanol (9:1) at 97°C and specifically N-resulphated or N-acetylated. These partially desulphated heparins were then added to osteoblasts cultured under osteogenic conditions. Quantification of bone nodule formation showed that specifically desulphated heparin significantly increased mineralised areas compared to controls whilst the addition of heparin inhibited osteogenesis. How these modified heparan sulphates exert their effect on bone cells is unknown, but a well characterised role of heparan sulphate is the support of FGF signalling. In preliminary studies we have shown through the activation of p42/44 MAPK and proliferation assays that the modified heparan sulphates are able to support FGF signalling in bone cells.

Experiment 4. Currently were are attaching our desulphated heparin to biomaterial scaffolds and examining osteoblast attachment and migration/ingrowth in cell culture.

Conclusion: We have isolated heparan sulphate chains that demonstrate osteogenic properties and have the potential for enhancing biological interactions of orthopaedic implant materials.

D.S.L. Shirley G. Li G.R. Jordan D.R. Marsh

Introduction: Osteoblasts precursors reside in the marrow and small numbers circulate in the blood. Our previous work demonstrated an increase in circulating cells following fracture in humans. Skeletal injury is recognised to stimulate a distant osteogenic response.

We hypothesised that in response to fracture, some integral osteoblasts are recruited via the circulation from remote bone marrow sites.

Method: We established a fracture union model in 3-month-old, male, New Zealand White rabbits and reimplanted labelled autologous osteoblast precursors. At date of submission we have 20 rabbits allocated into 4 groups. Three groups had labelled cells re-implanted, whilst the fourth control group did not receive cells. In groups I, II and III the cells were re-implanted into the fracture gap, into the circulation and into a remote bone marrow cavity respectively. There were six animals in groups I and IV, and four in both II and III.

All animals had bone marrow harvested from their right tibia by saline flush. The mononuclear cells were isolated and culture-expanded in osteogenic medium for 3 weeks. Fluorescent reporter molecules were incorporated into the cell membranes, 24 hours prior to re-implantation of the cells into the fracture model. A 3 mm ulnar defect was preformed in all the animals. In groups I–III this was established 48 hours prior to cell re-implantation.

The animals were sacrificed at least 3 weeks after fracture surgery. Representative samples of the fracture callous, lung, liver, spleen and kidney were harvested from all animals and cryo-sectioned. Using confocal microscopy, the labelled cells were expressed as the average in 5 high power fields for each solid tissue. In addition, cyto-spins were made from blood and marrow and the cell number expressed as a percentage of the total cells.

Results: In group I, labelled cells were identified in the fracture callous, establishing their viability in vivo. Following intravenous re-implantation a smaller number of labelled cells were identified in the callous. When the cells were re-implanted into a remote marrow site, the number of cells in the callous was greater than after venous reimplantation, but less numerous than those in group I.

In all sections, these labelled cells appeared on trabecular surfaces in an osteoblastic fashion, but occasionally they were surrounded by osteoid, corresponding to osteocytes.

A small number of labelled cells were found in the blood, bone marrow, lung, liver and spleen of all animals in groups I–III. No labelled cells were identified in the kidney tissue.

Discussion and Conclusions: We have demonstrated that cells from remote sites are integral in fracture healing. Their presence in callous following venous administration supports recruitment via the circulation. This preliminary data is a proof of concept. This is an exciting new phenomenon, which could provide alternatives for harvesting skeletal progenitor cells and for their delivery in the treatment of bony pathology.

G. Li L. McILmurray J.T. Ryaby D. H. Carney H. Wang

The thrombin-related peptide, TP508, is a synthetic 23 amino acid peptide, which represents the receptor binding domain of thrombin. TP508 mimics thrombin by interacting with receptors on cells involved in tissue repair. TP508 has been shown to enhance revascularization of injured tissue, and promote soft tissue wound healing, cartilage repair, and fracture repair. The aim of this study is to (1) test the effect of TP508 on bone regeneration during distraction osteogenesis; (2) study the chemotactic effect of TP508 on human osteoblasts.

Unilateral tibial osteoectomies were performed and stabilized with MX100 Orthofix lengthener in 5 male adult NZW rabbits. After 7 days, distraction was initiated at rates of 1.4 mm / day for 6 days. TP508 (100 μg/ml, n=2; 10 μg/ml, n=1) or saline (300 μl, n=2) was injected into the osteotomy / lengthening gap at days 1, 7 and 14 post surgery. Animals were sacrificed at 2 weeks after leg lengthening. Bone formation in the regenerate was assessed by radiography, quantitative computed tomography (pQCT) and histology. For chemotaxis studies, MG63 cells were cultured on glass cover slips for three days, and then inverted onto a Dunn chamber slide and sealed with dental wax. Gradients of TP508 (1, 10, 100 μg/ml) were added to the outer well and plain medium to the inner well. A sequence of images of the cells between the wells was taken via a CCD camera for 9 hours at interval of 10 minutes. Movements of individual cells were tracked and statistically analysed by a specially written Macro program. The Rayleigh test for unimodal clustering was used to determine the directional chemotactic movements.

The radiographic evaluation indicated a significant increase in new bone in the distraction regenerate in the TP508 treated groups at 1 and 2 weeks. pQCT images at 2 weeks demonstrated more advanced bone formation in the TP508 treated animals compared to the control. The mean total bone mineral density (BMD) of the regenerate, obtained from 3 slices was significantly greater (p = 0.019, t-test) in the TP508 treated group (BMD = 479.20 +/− 35.57 mg/ccm) than that in the saline control group (BMD = 355 +/− 2.83 mg/ccm). The histological evaluation supported the radiographic and the pQCT results. For chemotaxis study, no directional movements of the cells were found in the controls, whereas the MG63 cells were strongly chemotactic to TP508 at 1, 10 and 100 μg/ml concentrations.

This preliminary study shows that administration of TP508 enhances bone formation during distraction osteogenesis in the rabbit. The findings also show that TP508 has a chemotactic effect on osteoblasts, consistent with the effect of TP508 on fracture repair. A large animal study is in the process to confirm these findings and explore the underlying mechanisms.

M.L. Costa L. Shepstone S.T. Donell T.L. Thomas

Acute Achilles tendon pain is a common clinical entity, particularly in sportsmen and women. Fortunately, the majority of such pain is self limiting. However, there are a significant number of people for whom the pain becomes chronic and debilitating. A recent Cochrane review found that there was no randomised controlled evidence of an effective treatment for chronic Achilles pain. The aim of this study was to test the efficacy of shockwave therapy in a double-blind randomised controlled trial. The study has the approval of Local Research Ethics Committees.

Forty nine patients with Achilles tendon pain for a minimum of 4 months were included in the study. Patients were randomised to either shockwave therapy (n=27) or sham dose control therapy (n=22). Ultrasound was used to focus the shocks onto the affected area of tendon. The treatment group were given 2000 shocks at upto 1500mJ per shock, titrated to the patients pain tolerance. The control (sham) treatment was applied using the same parametres but with bubble-wrap interposition between the shockwave generator and the Achilles, to disperse the shockwaves. Each patient was treated once a month over 3 months. Primary outcome measure was pain on walking indicated on a 100mm visual analogue score (VAS) at 3 months. Secondary outcome measures included clinical and patient centred questionnaire scores. . An intention-to-treat approach was used for the analysis. Where patients had missing pain scores at 3 month follow-up, the last available pain score was carried forward.

The walking pain scores were very similar at baseline between the two groups. In the treatment group the mean (standard deviation) was 55.5mm (30.6) and in the control group 55.6mm (26.5). By 3 months, the pain scores had reduced in both groups to a mean (standard deviation) of 34.5 mm (34.2) and 50.3 mm (36.3). Although lower in the treatment group this difference was not statistically significant at the 5% level (t-test, p = 0.127, 95% C.I. : −4.7 to 36.2). No statistically significant differences were found with respect to any of the other clinical variables.

Two elderly patients in the treatment group sustained spontaneous rupture of the tendon after falls, during the course of the trial.

The results of this trial provided no evidence for the use of shockwave therapy in the treatment of patients with chronic Achilles tendinopathy. However, a treatment effect cannot be ruled out since the 95% confidence interval was wide and included a potential clinically relevant difference. The 2 cases of rupture suggest extreme caution in treating the elderly.

S.M. Ong G.J.S. Taylor

Introduction: Activated matrix metalloproteinases (MMPs) are responsible for the osteolytic process in aseptic loosening. Fluvastatin has been shown in previous studies to inhibit MMPs. The purpose of this study was to investigate the potential pharmacological effect of fluvastatin on aseptic loosening.

Materials and methods: A radiolabelled mouse calvaria and human interface membrane cells culture system was used to study the effect of fluvastatin on bone resorption induced by interface membrane cells. The experimental conditions were: 1) test culture consisted of culturing a dead radiolabelled bone disc with cells from human interface membrane in culture medium containing fluvastatin for 14 days 2) control culture consisted of similar culture system without fluvastatin and 3) baseline control culture consisted of bone disc only. The bone discs from each test and control groups comparison were from the same parietal bone to ensure equal amount of radioactive calcium in the bone discs at the start of the experiment. Supernatant were sampled on day 7, 10 & 14 for scintillation counting. The total Ca45 remained in the bone discs at the completion of the culture were measured by scintillation counting. Eight sets of experiments were performed in this study. The results were expressed as the ratio of Ca45 in the fluvastatin exposed culture over culture containing bone disc only. In the control, the results were expressed as ratio of bone disc exposed to cells over culture containing bone disc only.

Results: In the supernatant Ca45, both the fluvastatin and control ratios increased with time confirming bone resorption in both culture. The fluvastatin culture consistently showed a lower ratio compared with control indicating an inhibitory effect. In the fluvastatin culture the mean ratios on day 7, 10 & 14 were 0.79, 1.53 and 2.55. The mean ratios in the control culture were 1.03, 1.81 and 3.20 (n = 8, p = 0.0001 ANOVA, General Linear Model). The mean ratio of total Ca45 remaining in the bone disc in the fluvastatin culture was 0.87 and the control was 0.70 (p = 0.01, t test). This implies 55% less bone resorption in the presence of fluvastatin.

Conclusions: In this in vitro study we found fluvastatin has the ability to inhibit osteolysis by cells from interface membrane of aseptically loosened hips. We believe fluvastatin inhibit bone resorption by MMPs inhibition. This may have therapeutic implication in the treatment of patients with aseptic loosening of total joint replacements.

S. Glyn-Jones H.S. Gill P. McLardy-Smith D.W. Murray

Introduction: The Birmingham Hip Resurfacing (BHR) is a metal on metal prosthesis with no published independent clinical studies. It is increasingly used as an alternative to stemmed prostheses in younger patients.

This study presents the 2 year migration results of the BHR femoral component using Roentgen Stereophoto-grammteric Analysis (RSA).

Methods: 26 hips in 24 subjects underwent a BHR, through the postero-lateral approach using CMW3G cement. RSA marker balls were placed in the cortical bone of the femur intra-operatively. The femoral component migration was measured at intervals of 3, 6, 12 and 24 months postoperatively using the Oxford RSA system. The implants were un-modified, geometric algorithms were used to identify the femoral component.

Results: The BHR femoral component showed no significant displacement from its immediate post-operative position. All components of migration showed no significant displacement in any direction, at 1 or 2 years.

Conclusion: The BHR femoral component does not migrate significantly within the first two post-operative years. Its’ migration compares favourably to other designs of femoral component. The BHR is therefore likely to remain stable in the future, as the majority of implant migration occurs within the first two years.

A.P. Davies P.A. Campbell C.P. Case I.D. Learmonth

Metal-on-metal joint replacements have been reintroduced despite some concerns regarding the potential risks posed by soluble metallic by-products. We have investigated whether there are metal selective differences between the levels of genetic damage caused to a human cell line when cultured with synovial fluids retrieved from orthopaedic joint replacement prostheses at the time of revision arthroplasty.

Methods: Synovial fluids were retrieved from revision hip and knee arthroplasty patients with bearings made from Cobalt chrome-on-Cobalt chrome, Cobalt chrome-on-polyethylene and Stainless Steel-on-polyethylene. Control synovial fluids were retrieved from primary arthroplasty cases with osteoarthritis and no implant in situ. Synovial fluid was cultured with human primary fibroblasts for 48 hours in a cell culture system under standardised conditions. The ‘Comet’ assay was used with an image analysis system to measure levels of DNA damage caused by the various synovial fluid samples. Metal levels were measured in the synovial fluid samples using atomic absorption spectroscopy.

Results: Synovial fluids from Cobalt Chrome-on-Cobalt Chrome and Cobalt Chrome-on-polyethylene joint replacements both caused substantial levels of genetic damage as detected by the Comet assay. Synovial fluids retrieved from Stainless Steel-on-polyethylene joints caused low levels of damage. The difference between these groups was highly statistically significant (p< 0.001). Control synovial fluids from osteoarthritic joints caused minimal changes. Atomic absorption spectroscopy demonstrated that the metal-on-metal synovial fluids contained substantially more cobalt and chromium than the fluids retrieved from cobalt chrome-on-polyethylene joints. Stainless steel-on-polyethylene synovial fluids contained the least metal.

Conclusions: Different alloys used in Orthopaedic implants are associated with different levels of DNA damage to cultured human cells in vitro. We are able to demonstrate that this damage is attributable at least in part to the metal content of the synovial fluid samples. We have no evidence for any long-term health risk to patients with such implants. Further research is needed in this field.

A.M. Ali L. Yang M. Saleh R. Eastell

Background: The stability of fracture fixation is influenced by the type of fixation, densitometric and geometric structure of the bone. DXA measures the integral mass of trabecular and cortical bone mineral but cannot discriminate between the structurally and mechanically separate constitutes. Distribution and organisation of bone mass (the geometric structure) has the final determination of the mechanical properties of bone. Pq CT scan is able to measure densitometric and geometric parameters of bone structure. However, there are no reports in the literature on the relationship between these measurements and the strength of fracture fixation. Our aim is to study the correlation between geometric and densitometric measurements of Pq CT scan, with the strength of fixation of bicondylar tibial plateau fractures and to assess the role of both trabecular and cancellous bone in that strength.

Method: Eight Fresh frozen human cadaveric tibias were collected from subjects without a medical history of skeletal pathology. The proximal 10% of the tibia was scanned in a peripheral quantitative computer tomography scanner 1mm thick transverse slides, the cancellous and cortical bone mineral density of the proximal tibia were measured. The geometrical parameters: cortical area, trabecular area, bone strength index (BSI) and the Stress strain index (SSI) as non invasive indicators of the mechanical strength of the bone, were also calculated. A bicondylar tibial plateau fracture was simulated, stabilised, and then tested. All tibias were fixed with Dual buttress plating using a standard AO technique. Cyclic axial compression tests were performed. Inter-fragmentary shear displacements were measured using four extensometers. Failure was defined as over 3mm displacement.

Results: Except for the cortical density, there was a strong correlation between failure load and geometric and densitometric parameters. The trabecular density was the best predictor of fixation strength of tibial plateau fracture.

Discussion: Trabecular density is a more reliable parameter to measure than the cortical density. Therefore, the fixation strength of tibial plateau fracture is dominantly influenced by the mechanical properties of cancelous bone. Cortical bone has a secondary role.

These results highlight the importance of fixation techniques that rely on cancellous bone anchoring such as tensioned fine wire fixation in tibial plateau fractures.

D.F.M. Lawrie M.R. Downing G.P. Ashcroft P.H. Gibson

The use of roentgen stereophotogrammetric analysis (RSA) in the assessment of total hip arthroplasty is well recognised as an accurate technique in the measurement of small movements of implants. The technique requires the insertion of tantalum beads into a stable location in the bone at the time of surgery. Failure of bead insertion leads to unstable extra-osseous beads that require to be excluded from the analysis. Previous studies have reported an incidence of extra-osseous beads in the proximal femur of between 2% and 13%. In order to further improve the accuracy of the RSA technique, we have developed a test criterion for exclusion of unstable osseous beads in RSA of total joint replacements.

Using specifically developed software each bead’s movement was determined relative to the rest of the beads in the bone segment. The bead movement was determined for radiologically identified extra-osseous beads, which were assumed loose, and for the remaining intra-osseous beads which were suitable for analysis. Analyses with a condition number greater than 100 were rejected. The rate of motion was calculated from consecutive examinations. Unstable beads were identified as those having a median rate greater than a given threshold. The sensitivity and specificity for detecting extra-osseous beads was calculated for different thresholds of median bead motion.

In 149 RSA hip study patients, 43 extra-osseous beads that could be analysed were identified and a group of 36 osseous beads were selected as a control group. This resulted in an optimum threshold of 0.36mm that gave a sensitivity of 89% and a specificity of 86% for detecting unstable (extra-osseous) beads. The remaining 1428 beads, which were assumed to be osseous, were then tested with this threshold, which gave a sensitivity of 84% and a specificity of 79%.

The median extra-osseous bead rate of movement at 6, 12, 18 and 24 months were 2.24, 0.78, 1.03 and 1.31mm respectively and for osseous beads were 0.27, 0.19, 0.18 and 0.19mm. As both groups of beads appear to show a “bedding in” period, with a higher median bead movement in the first 6 months, the test was repeated with the first 6 month period excluded from the criteria. An optimal threshold of 0.37mm was found to have a sensitivity of 73% and a specificity of 87% for identifying an extra-osseous bead.

While most radiographically classified osseous beads identified as unstable may be false-positives, it is probable that some are extra-osseous but not visibly so on radiographs. The specificity of this technique is likely to be further improved with the increased precision from digital scanning techniques. Tantalum beads in general appear to be relatively unstable in the first 6 months, consistent with the expected osteo-intergration of the bead. This new criterion for bead instability allows automatic exclusion of unstable beads increasing the reliability of the RSA technique both in future studies and retrospectively to existing data.

D.W. Green I. Leveque D. Walsh K. Partridge D. Howard S. Mann R.O.C. Oreffo

Introduction: The clinical need for a biodegradable material with broad application is evidenced by the fact that tissue loss as a result of injury or disease provides reduced quality of life for many at significant socio-economic cost. The development of simple biodegradable materials, with broad applicability and tissue/ cell specificity has to date proved elusive. Natural biopolymers such as alginate and chitosan are structural biomaterials of increasing significance to tissue repair and regeneration due to their potential for fabrication, design and efficient, environmentally benign synthesis. We describe the development of innovative microcapsule scaffolds based on chitosan and alginate that can be tailored to a range of cell types for a variety of tissues.

Methods: Semi-permeable polysaccharide microcapsules were produced by a one-step method, in which the deposition of a semi-permeable alginate/chitosan membrane around droplets of sodium alginate was coupled with in-situ precipitation of amorphous calcium phosphate as described by Leveque et al (2002)*. A variety of human cell types including mesenchymal stem cells, osteoprogenitors selected using the STRO-1 antibody by magnetically activated cell separation (MACS), osteoprogenitors transfected with adenovirus expressing Green Fluorescent Protein (GFP) and chondrocytes were mixed with sodium alginate and encapsulated within alginate/chitosan and calcium phosphate.

Results: Hybrid spheres (750–10,000um) were generated encapsulating primary human osteoprogenitor cells, STRO-1 selected osteoprogenitors and AdGFP transfected osteoprogenitors. Encapsulated cells remain viable inside the polysaccharide microcapsules for 2 weeks as shown by positive alkaline phosphatase staining of encapsulated cells. Cells expressing GFP were observed within microspheres indicating the e ability to deliver cells/factors as well as the potential for gene therapy. Encapsulation and delivery of active BMP-2 was confirmed using the promyoblast cell line C2C12 known to be exquisitely sensitive to BMP-2. Nucleation of calcium phosphate occurred within the polysaccharide membrane and could be controlled by the phosphate concentration in the alginate droplets to produce hybrid microcapsules with enhanced mechanical strength. Thin walled capsules were shown to split and degrade in culture within 2–4 days releasing viable osteoprogenitor cells indicating the ability to manipulate the mechanical integrity and to programme degradation of the microspheres. Finally we have shown that aggregation of the microspheres into extended frameworks can be achieved using a designed droplet/vapour aerosol system resulting in foams of aggregated beads.

Discussion and Conclusion: A variety of human skeletal cells have been encapsulated within polysaccharide/ calcium phosphate microspheres and extended frameworks with specifiable dimensions. These composite scaffolds offer stable mechanical and chemical biomimetic environments conducive to normal cell function. Natural polysaccharides are also highly amenable to complexation with a range of bioactive molecules and consequently offer tremendous potential in tissue engineering and regeneration of hard and soft tissues.

S. Sun H. Xu L. Danks A. Sabokbar

Purpose: Osteolysis associated with periprosthetic loosening is generally associated with the presence of wear particle-associated macrophages which (i) release inflammatory cytokines (e.g. TNFα and IL-1α) and (ii) are capable of osteoclast differentiation and bone resorption. The recently identified molecule, RANKL (expressed on osteoblastic cells) has been shown to play a central role in the macrophage-osteoclast differentiation observed in aseptic loosening. However, as TNFα and IL-1α are abundant in periprosthetic tissues and have been shown to mediate wear particle (bone cement)-associated osteolysis in animal models, and as we have recently shown that TNFa can induce osteoclastogenesis in a manner independent of RANKL mechanism, the aim of the present study was to determine whether wear particles, in particular bone cement particles, can affect RANKL- and TNFα-induced osteoclast formation and bone resorption in vitro.

Methods: Murine monocytes were cultured on glass coverslips and dentine slices with or without PMMA particles in presence of:- (i) macrophage colony stimulating factor (M-CSF) alone, (ii) M-CSF + soluble RANKL (iii) M-CSF + TNFα or (iv) M-CSF + TNFα + IL-1a. All cultures were maintained for 7–10 days after which the extent of osteoclast differentiation was determined by the expression of specific osteoclast markers including tartrate-resistant acid phosphatase (TRAP) on coverslips and evidence of lacunar resorption on dentine slices.

Results: Extensive osteoclast formation and lacunar resorption was evident in monocyte cultures in the presence of soluble RANKL and M-CSF. Addition of PMMA in these cultures increased the extent of RANKL-induced lacunar resorption by about 2 fold. In the absence of soluble RANKL, but in the presence of TNFα (± IL-1α), murine monocytes were also capable of differentiating into active bone resorbing osteoclasts. Addition of PMMA particles to these cultures resulted in a marked increase in the TNFα-induced osteoclas-togenesis. It is worth noting that monocyte cultures containing M-CSF and PMMA particles only did not differentiate into bone resorbing osteoclasts.

Conclusion: These results indicate that PMMA particles can activate both RANKL- and cytokine-induced osteoclast formation and osteolysis. Although, we had previously shown the existence of these two distinct cellular mechanisms in periprosthetic loosening, this is the first report in which wear particles have directly been shown to stimulate these cellular mechanisms independently. Our findings could provide possible therapeutic approaches to control the wear particle-associated early failure of joint replacements.

X.B. Yang N.M.P. Clarke W. Sebald S.M. Howdle K.M. Shakesheff R.O.C. Oreffo

The use of designer scaffolds to deliver biologically active osteogenic growth factors such as recombinant human bone morphogenetic protein-2 (rhBMP-2) to the sites of tissue regeneration in for example orthopaedics, has tremendous therapeutic implications. The aims of this study were to generate biomimetic biodegradable porous osteogenic scaffolds using a supercritical fluid process to encapsulate rhBMP-2, and to examine the ability of the scaffolds to promote human osteoprogenitor differentiation and bone formation in vitro and in vivo.

The rhBMP-2 encapsulated in Poly(-lactic acid) (PLA) scaffolds (100ng/mg PLA) were generated using an innovative supercritical fluid mixing method. The bioactivity of rhBMP-2 encapsulated PLA scaffolds were confirmed by induction of the C2C12 promyoblast cell line into the osteogenic lineage as detected by alkaline phosphatase expression. No induction of alkaline phosphatase-positive cells was observed using blank scaffolds. BMP-2 released from encapsulated constructs promoted adhesion, migration, expansion and differentiation of human osteoprogenitor cells on 3-D scaffolds. Enhanced matrix synthesis and cell differentiation on growth factor encapsulated scaffolds was observed following culture of human osteoprogenitors on explants of chick femoral bone wedge defects in an ex vivo model of bone formation developed using the chick chorioallantoic membrane model. In vivo studies using diffusion chamber implantation and subcutaneous implantation of human osteoprogenitors on rhBMP-2 encapsulated scaffolds showed morphologic evidence of new bone matrix and cartilage formation in athymic mice as assessed by x-ray analysis, immunocytochemistry and birefringence. These studies provide evidence of controlled release of BMP-2 from biodegradable polymer scaffolds initiating new bone formation in vivo.

The generation of 3-D biomimetic structures incorporating osteoinductive factors such as BMP-2 indicates their potential for de novo bone formation that exploits cell-matrix interactions and, significantly, realistic delivery protocols for growth factors in musculo-skeletal tissue engineering.

R. Hopcroft D. Hynd C. Willis P. Manning A. Roberts R. Lowne W.A. Wallace

Introduction: Legislation driven & technology aided reductions in mortality have been documented over the past 10 years for road traffic accidents (RTAs). However many authors have noted an increasing morbidity as a result of serious lower limb injuries. In collaboration with the Transport Research Laboratory (TRL) a 2 stage research programme has been carried out on fresh frozen PHMS lower limbs. This programme, has culminated in a specific series of PMHS tests to reproduce the most disabling lower limb injuries seen in real world accident data. The authors aimed to establish force thresholds for failure (fracture) of the calcaneus, talus and tibial plafond in frontal and frontal offset RTAs. This data is considered essential to support new pan-European legislation for better lower limb protection structures in new motor vehicles which is currently under discussion.

Methods: A 5m bungee driven sled test facility capable of creating a validated and repeatable dynamic crash pulse was used to subject 15 PMHS lower limb specimens to, axial impact loading. The pulse was modelled on the accelerometer toe-pan recordings from a full-scale automotive crash test in frontal impact. To represent brake pedal intrusion at an impact velocity of up to 14ms−1, a staggered double impact, delaying application of axial loading was used. Impact loading was achieved via a modelled brake pedal to the mid-foot. All specimens were preloaded through the Achilles tendon and by knee extension to simulate the plantar flexing response seen in the foot & ankle in driving simulator studies. Delaying the application of axial loading after the initial impact and sled deceleration effectively imparts momentum into the specimen, further preloading the foot and ankle and thus increasing pre-impact bracing. Transducer data were recorded using high frequency (20 & 100 KHz) capture systems (K-Trader and Prosig). High-speed cinematography enabled additional kinematic analysis. Each specimen was tested once only. Specimens were selected at random for five impact severity groups. All specimens underwent pre impact BMD evaluation using protocols previously designed for this type of work. Post impact analysis included X-rays and necropsy.

Results: The specimens used varied in BMD and age similar to specimens used in other centres for similar testing. In the 15 final test specimens 8 calcaneal fractures were generated, one with an additional talar neck fracture. Seven specimens did not sustain injury. Measured BMD did not appear to be a useful predictor of load to failure. Peak axial forces ranged from 5KN up to 14kN. Toe pan and foot accelerations up to 200g were generated.

Discussion: This test method appears to predispose the calcaneus to injury. It failed to create either a Pilon fracture or an isolated talus fracture. Previous research investigating axial impact loading have applied a direct impact with varing levels of pre-load. They resulted in a range of injuries and suggested pre-loading reduced injury thresholds for talar and tibial injuries. This has not been our experience.

Conclusions: This data is invaluable, enabling thresholds for legislative car crash testing to be authoritatively stated and incorporated into national and international standards.

D.W. Green D. Walsh K. Partridge S. Mann R.O.C. Oreffo

Introduction: The ability to generate bone for skeletal repair, replacement or restoration is a major clinical need. Indeed the paucity of techniques in reconstructive surgery and trauma emphasise the need for alternative bone formation strategies. Natural biological ceramic structures possess arrangements of structural elements that govern and optimise tissue function, nutrition and organisation. The aim of this study was to fabricate biomineral microporous shells with highly complex forms and to examine their ability to interact with human osteoprogenitor cells as cell and growth factor delivery vehicles.

Methods: Microporous vaterite shells were generated using a synthetic in-solution mineralisation technique in which mineral is spontaneously deposited around vesicular templates (Walsh and Mann 1999)* Porous and textured self-organising hollow microspheres (5–20 _m) were generated expressing controlled and uniform shapes. These micropores puncture the surface at high densities and are interconnected throughout the sphere. Primary human bone marrow cells labelled with Cell Tracker Green and ethidium homodimer-1 fluorescent labels and osteoprogenitors transfected with an adenoviral vector expressing Green Fluorescent Protein (AdGFP) were cultured with vaterite shells over three weeks.

Results: Cell biocompatibility of these biomimetic spheres was confirmed by confocal fluorescence and light microscopy in primary human bone marrow cultures labelled with CTG and bone marrow cultures transfected with AdGFP. At three weeks microspheres were encapsulated and integrated with osteoprogenitor cells. Histological analysis confirmed expression of alkaline phosphatase, extracellular matrix synthesis and the capacity for extensive mineralisation. Examination by SEM, fluorescent and light microscopy showed that the growth of osteoprogenitors transfected with AdGFP and microspheres in pellet culture showed vaterite spheres were encapsulated and integrated within the osteoprogenitor cell matrix indicating the potential of growth factor delivery. To determine the potential of the spheres to encapsulate selected proteins, microporous spheres were incubated with bovine haemoglobin. FITC microscopic evidence showed haemoglobin could be entrapped inside the spheres and between the biomineral crystal plates during self-assembly.

Discussion and Conclusion: These studies demonstrate the development of facile techniques for the generation of porous microsphere sponges that are biocompatible, possess the ability to aid mineralisation and for the delivery of cell and growth factors. These calcium carbonate structures provide a material with widespread application in a range of tissue engineering applications including skeletal tissue regeneration.

J. Ingram E. Ingham J.L. Tipper J. Fisher

Ultra high molecular weight polyethylene (UHMWPE) wear debris induced osteolysis is a major cause of long term failure of total hip replacements. Particles in the 0.1–1.0_m size range are believed to have greater osteolytic potential than larger wear debris. Crosslinked polyethylenes have been shown to have improved wear resistance compared to non-crosslinked materials on smooth counterfaces, however wear debris from cross-linked UHMWPE has been shown to be smaller than that produced from non-crosslinked materials. The aim of this study was to compare the wear, wear debris and biological activity of non-crosslinked and crosslinked polyethylenes when worn against smooth and scratched counterfaces.

Materials and Methods: Test pins were machined from non-crosslinked GUR1050 and GUR1050 crosslinked with either 5 or 10Mrad of gamma irradiation. Sterile endotoxin free clinically relevant wear debris was generated using a bi-directional pin-on-plate test rig. Tests were performed on scratched (Rp=1.0mm) or smooth (Ra=0.02mm) counterfaces. Particles were cultured with murine macrophages at particle volume (mm3): cell number ratios of 50:1,10:1,1:1 and 0.1:1. The levels of TNF-a produced were determined by ELISA following 0,2,4,6,8,24 and 48 hours of culture.

Results: On both smooth and scratched counterfaces crosslinked polyethylene had lower wear than non-crosslinked polyethylene. Determination of the volume distribution of the wear debris demonstrated a greater percentage of wear debris in the submicrometre size range from crosslinked material when worn on scratched counterfaces. Analysis of the debris when worn on smooth counterfaces showed a further reduction in size of debris with particles observed below 100nm in size which reduced the percentage of debris in the sub-micrometre size range for both materials. Crosslinked material worn against scratched counterfaces generated wear debris that was able to stimulate macrophages to produce significant levels of TNF-a after just six hours of co-culture at the highest volumetric concentration and after 24 hours at lower volumetric concentrations. The non-crosslinked material was able to stimulate macrophages only after 24 hours at the highest volumetric concentration. There were no differences between the biological activity of the particles from the 3 materials articulating on the smooth counterfaces they were only able to stimulate significant TNF-a release following 24 hour with the highest volumetric concentration.

Discussion: Although wear resistance is increased by cross-linking on both smooth and scratched counterfaces, when worn against a scratched counterface crosslinked polyethylene generated a greater percentage of debris in the 0.1–1.0mm size range than non-crosslinked polyethylene and this led to an increase in biological activity. However when worn against smooth counterfaces the production of nanometre size wear particles by both materials reduced the volume of debris in the 0.1–1.0mm size range which in turn lead to a lower biological activity.

H. Pandit D. Hollinghurst T. Ward H.S. Gill D. Beard D. Murray N.P. Thomas

Introduction: Total knee replacement (TKR) is a common treatment for end stage osteoarthritis of knee. The best knee replacement is one in which the kinematics of the normal knee are reproduced. Amongst several factors affecting kinematics, variation in surface geometry and the retention/ sacrifice of the PCL are considered especially important. It is not known which of these two factors is most influential for establishing optimum joint kinematics after TKR.

Method: Four groups of patients who had undergone TKR at least one year previously were recruited. Two groups of patients had undergone replacement with a single axis design (Scorpio, Stryker Howmedica) in both PCL retaining (Scorpio CR, n=15) and PCL sacrificing (Scorpio CS, n=15) variants. The other two groups had undergone replacement with the traditional polyradial design prosthesis (Sigma, Depuy, Johnson & Johnson), again with both PCL retaining (Sigma CR, n=14) and PCL sacrificing (Sigma CS, n=13) variants. An in-vivo fluoroscopic analysis was carried out on all patients. Patients were asked to perform closed chain step up and open chain extension and flexion against gravity. The kinematic profile of each knee was obtained by measuring patella tendon angle (PTA) at specific angles of knee flexion (KFA) using an established fluoroscopic method. The data was also compared with the kinematic profile of normal knees. American Knee Society, Oxford and Patella Scores were recorded for all patients.

Results: All groups were comparable in terms of age and gender. In addition, no significant difference was found between groups in clinical outcome. PTA results for a step-up exercise are shown in the figure. A one way ANOVA between groups revealed that knee kinematics after total knee replacement is different to that for normal knees. No differences were found between groups when the data was analysed using CR/CS as the independent variable. The only differences between groups were found when surface geometry was used as the independent variable. It was shown that the kinematic profile of the single axis Scorpio design (in both CR & CS ) was closer to normal, especially near extension, than the traditional polyradial design (Sigma CR & CS).

Conclusions: Kinematics after a total knee replacement differ from that for a normal knee. Differences in surface design between knee replacements appear to have greater influence on kinematics than the presence or absence of the PCL.

H.M.J. McEwen A. Kamali R. Farrar M.H. Stone J. Fisher

Introduction: Reduction of ultra high molecular weight polyethylene (UHMWPE) surface wear in total knee replacement (TKR) bearings may delay the onset of osteolysis and subsequent loosening of components. The aim of this study was to compare the effect of bearing material on UHMWPE wear using a physiological knee simulator.

Methods: LCS Rotating Platform (RP) mobile bearing TKRs (DePuy) were investigated with standard and custom insert materials (Table 1). Testing was completed on a six-station force/displacement controlled knee simulator (frequency 1 Hz). Kinematic inputs consisted of 0 – 58° extension-flexion [1], maximum 2600 N axial force [1], -262 to 110 N anterior-posterior force [1] and ± 5° internal-external rotation [2]. The test lubricant was 25% (v/v) bovine serum with 0.1% (m/v) sodium azide solution in sterile water. Six components of each material were tested for up to five million cycles. The mean wear rates of the inserts were determined gravimetrically after every million cycles.

Results and Discussion: The higher molecular weight 1050 GP exhibited a higher wear rate than 1020 NI but the difference was not statistically significant (p > 0.05) (Fig. 1). The medium level of crosslinking in the Marathon GP inserts significantly reduced wear in comparison to the uncrosslinked 1050 GP material (p < 0.05) and moderate crosslinking in the 1020 GVF also decreased wear compared with the 1020 NI base material although this was not statistically significant. However, these differences would not be considered to be clinically significant. In addition, further work should be completed to assess the biological activity of the crosslinked materials as increased biological response may negate the benefit of decreased volumetric wear. All RP materials exhibited significantly reduced wear rates (p < 0.05) in comparison to fixed bearing TKR tested under equivalent high kinematic conditions [3]. The RP translates complex motions into more unidirectional motions, benefiting from reduced wear due to decreased cross-shear on the UHMWPE compared with more multidirectional fixed bearing TKR. Therefore, TKR design is an important factor for reduction of UHMWPE wear.

M.H.A. Malik F. Jury E. Zeggini F. Salway H Platt A. Bayat W.E.R. Ollier P.R. Kay

Aims: Tumour necrosis factor-alpha is a proinflammatory cytokine that has been implicated in the inflammatory response to bacterial infection and wear debris particles around loosened total hip replacements (THR). Individual TNF responses to such stimuli may be dictated by genetic variation and we have studied the effect of single nucleotide polymorphisms (SNPs) within the TNF gene.

Methods: We performed a case control study of 9 SNPs (−1031, −863, −857, −376, −308, −238, +489, +851 and +1304) for possible association with deep sepsis or aseptic loosening. All patients included in the study were Caucasian and had had a cemented Charnley THR. Cases consisted of 44 patients with early aseptic loosening and 30 patients with microbiological evidence at surgery of deep infection. Controls consisted of 85 THRs that were clinically asymptomatic for over 10 years and demonstrated no radiographic features of aseptic loosening. DNA was extracted from venous blood and genotyped by Snapshot assay.

Results: Genotype and allele frequencies for all SNPs were in Hardy-Weinberg equilibrium between THR controls and a random sample of UK Caucasians. A significant association was found for the -863 SNP and aseptic loosening (p< 0.05; OR=2.36; 95% CI: 0.976 – 5.71). A trend towards association was found between the -863A SNP and deep infection (p=0.80; OR=2.42; CI: 0.800 – 7.34).

Conclusions: Genetic polymorphism of TNF-alpha may play a significant role in THR aseptic loosening and possibly in deep infection. SNP markers may serve as predictors of implant survival and response to therapy such as anti-TNF treatment.

I-H. Jeon N. Rosenberg I.J. Mersich L. Neumann W.A. Wallace

Introduction: This study investigates the survival (and radiological loosening) rates of prostheses following uncemented Total Shoulder Arthroplasties (TSAs) focusing on the glenoid baseplate fixation.

Methods: ALL uncemented TSAs inserted in one shoulder unit from 1989 to 2001 were entered onto a database prospectively and the patients monitored to death or failure of the implant, resulting in revision surgery. Over 80% of the surviving implants were monitored on sequential radiographs and the radiological loosening rate was observed. 273 TSAs have been monitored – 193 with a porous coated glenoid baseplate and 80 with a hydroxyapatite coating on top of the porous coating.

Results: The Survival rates (%) of the non-HA coated baseplates at 1 to 12 years using the Life Table Method were:− 97, 93, 89, 83, 83, 81, 79, 79, 77, 75, 75 & 75% respectively. The Survival rates for the HA coated glenoid base-plates at 1 to 4 years were 100, 97, 93, & 93% respectively. Failures were predominantly due to mechanical loosening and glenoid disassembly with only 3 cases of infection documented. Thus by 4 years there was a statistically significant improvement in survival of the glenoids. Survival rates were further reduced when radiological loosening was taken into account. The earlier series was analysed to assess the survival of prostheses inserted for RA and OA. The survival rates at 5 and 10 years were 78% & 70% for OA and 96% and 88% for RA.

Discussion & Conclusions: This Life Table analysis confirms the early benefit from the use of hydroxy-apatite coating of the glenoid implant of a TSA. Further improvements, particularly in relation to reducing further the small risk of disassembly are underway.

M.T. Clarke P.T.H. Lee C.P. Roberts J. Gray G.S. Keene N. Rushton

Introduction: Although there is evidence that laminar flow operating theatres (LFOTs) can reduce the incidence of wound infection over standard operating theatres (STOTs) when no routine peri-operative antibiotics were used, the evidence for the use with concurrent parenteral antibiotics is less compelling. A number of prior studies have compared the bacterial load observed in LFOTs and STOTs by wound culture and air sampling during surgery. However many organisms responsible for low grade infection after THR are not readily identified on routine culture and may be detectable only by more sensitive techniques such as the polymerase chain reaction (PCR), a molecular biology test for the presence of bacterial DNA. The purpose of this study was to compare the wound contamination rate during THRs performed in STOT with that in LFOTs using PCR.

Method: Patients undergoing primary THR for osteoarthritis without a history of joint infection were recruited for the study. Surgery was performed in either STOTs or LFOTs, using identical skin preparation solutions, surgical drapes and operating attire. Specimens of the deep tissue, taken at the beginning and end of surgery, were each immediately separated into two sterile containers, one sent for culture (aerobic, anaerobic and enriched meat broth) and the other frozen at minus 80 degrees Celsius for PCR at a later date.

Results: In each theatre type, 40 specimens from 20 THRs were analysed by both PCR and culture (80 specimens and 40 THRs in total).

Using PCR, bacterial DNA was identified on 12 of 40 specimens (30%) from STOTs. Of these 12, three were taken at the start of surgery and nine at the end of the surgery, equivalent to a 45% wound contamination rate (9 of 20). Only two specimens (5%), both taken at the end of surgery, were positive on enriched culture.

In LFOTs, bacterial DNA was identified by PCR on eight of 40 specimens (20%). Of these eight, two were taken at the start of surgery and six at the end of surgery, equivalent to a 30% wound contamination rate (6 of 20). None of the specimens were positive on enriched culture.

Discussions: We concluded that wound contamination of primary THR occurs frequently in both STOTs and LFOTs. Although STOTs showed evidence of more frequent wound contamination than LFOTs, with the numbers available, no significant difference was detected. These data are important in that they confirm that continued vigilance to technique continue to be important as significant wound contamination can occur despite the use of ultra clean air operating theatres.

A.M. Hill I.T. Jones A. Suri J. Moss A.L. Wallace

Aims: Surgical joint stabilisation can be achieved by capsular plication or thermal shrinkage. We hypothesised that there was no difference in mechanical and morphological properties after reduction of laxity in ligaments treated by either technique.

Methods: 30 skeletally mature female rabbits underwent either ‘thermal’ treatment, or ‘plication’ of their left medial collateral ligament (MCL). After 12 weeks convalescence, MCL complexes were procured from left and contralateral knees to undergo viscoelastic (creep) testing, quantitative transmission electron microscopy (TEM) and immunohistochemistry.

Results: Mean creep strain in both thermal (1.85 +/− 0.32%) and plicated ligaments (1.92 +/− 0.36%) was almost twice that of the control group (1.04 +/− 0.15%), although there was no difference between treatment modalities. However, collagen morphological parameters of all three groups were significantly different (p< 0.001). The thermal ligaments demonstrated predominantly small fibrils, whilst the plicated group displayed an intermediate distribution of heterogeneous fibrils (Fig. I). Immunohistochemistry followed by TEM revealed a random distribution of alpha-smooth muscle actin staining fibroblasts in both thermal and plicated groups.

Conclusion: Susceptibility to creep, and residual deformation after recovery, is similar after thermal shrinkage or plication, although inferior to intact ligaments. However, a different pattern of remodelling was revealed in the treatment groups. The plicated results suggest remodelling on a pre-existing fibrillar scaffold, yet the thermal group demonstrated histomorphometry similar to scar tissue, suggesting de novo synthesis. The absence of contractile myofibroblasts suggests that these cells may play an insignificant role in regulation of matrix tension during healing.

S.G. Rees C.L. Curtis C.M. Dent J.L. Harwood B. Caterson

Introduction: Previous studies have demonstrated that exposure of normal bovine and human osteoarthritic cartilage to n-3 polyunsaturated fatty acids (PUFAs) such as those present in fish oils can modulate the expression and activity of the degradative and inflammatory factors that are responsible for cartilage destruction [1,2]. In these studies, supplementation of cartilage explant cultures with n-3 PUFAs resulted in an abrogation of aggrecanase activity as well as mRNA expression of mediators of inflammation. To date, few studies have examined the effect of PUFAs on the metabolism of other tissues within the musculoskeletal system, therefore the present work examines the effect of n-3 PUFA supplementation on tendon metabolism.

Methods: Bovine deep digital flexor tendon explants were obtained from the compressed region of young metacarpophalangeal joints (2-week-old) and supplemented with eicosapentaenoic acid (EPA), as previously described [2]. Release of proteoglycan metabolites was analysed using Western blotting whilst RT-PCR analysis was used to examine the mRNA expression patterns of matrix proteases and inflammatory agents.

Results: Exposure to the n-3 fatty acid, EPA, markedly changed the overall lipid composition profile of the tendon with major changes occurring in the supplemented fatty acid (i.e., EPA), with a concomitant percentage reduction in other polyunsaturated fatty acids. Aggrecanase activity was present in the media from control cultures, as expected [3]. However, supplementation with EPA had no effect on this activity, in contrast to articular cartilage where aggrecanase catabolites were absent from the conditioned media following treatment with n-3 PUFAs [1,2]. mRNA expression for the inflammatory mediators (COX-2, IL-1β, TNF), ADAMTS-5, MMPs and TIMPs was also unchanged following supplementation with EPA, again contrasting with articular cartilage where mRNA expression was abolished.

Discussion: This study demonstrates that exposure of bovine tendon explant cultures to an n-3 PUFA, EPA, had no effect on the mRNA expression or activity of aggrecanases; similarly, expression of the inflammatory mediators was also unaffected. Importantly, within this musculoskeletal tissue, aggrecanases are constitutively active and appear to be involved in normal, everyday turnover of aggrecan, in contrast to non-pathological articular cartilage where aggrecanase-generated metabolites are only detected following treatment with catabolic agents. Similarly, COX-2 mRNA expression is present constitutively within tendons whereas in cartilage it is absent under basal (unstimulated) conditions. These data demonstrate that the incorporation of n-3 PUFAs have a differential effect on the regulatory mechanisms which control gene expression within articular cartilage versus tendon.

P. Durani I-H. Jeon T.A. McCulloch A. McLeod W.A. Wallace

Introduction: The Nottingham Hood is a polyester soft tissue reinforcement device for the treatment of weakened or torn rotator cuff tendons (RCTs). The device was introduced in 1987 and has undergone a number of modifications from a close weave polyester modified aortic vascular graft (Mark 1) to an embroidered trefoil shape (Mark 4 – Pearsall’s Ltd) which has now been available since 2000. While this device has been under development it has been used on a named patient basis for 10 years on humanitarian grounds as an alternative treatment option for patients with massive RCTs. Approximately 30 Nottingham Hoods have been inserted over the past 10 years. This study investigates the histological changes and ingrowth associated with this device.

Methods: Four patients who have had the Nottingham Hood inserted for massive RCTs have had re-operations for various reasons on five occasions. Excised material from the rotator cuff has been subjected to histological investigation. Excised biopsy material has been obtained 6 weeks, 6, 9 & 12 months and 14 years following implantation.

Transmitted and polarised light microscopy has been used in all cases.

Results: At 6 weeks birefringent clear material similar to suture material was identified, invested by fibrin and occasional red cells i.e. old thrombus. The fibrin was partly calcified and insinuated between bundles of the meshwork material. No true ingrowth of material was seen at this stage. At 6 months the material was seen macroscopically to be covered with collagenous material, rather like fascia which interdigitated closely with the embedded polyester material. At 14 years the mesh appeared to be invested, sandwich-like into a collagenous fascia-like structure with dense hyaline bands of collagen. Some fibrin was also present between the fibrils and a low grade foreign body giant cell response with light chronic inflammation. The local synovium showed detritic synovitis.

Discussion: The histological features show that there is an early organisational response to the insertion of the new tissue, which is then accompanied by long-term incorporation into host tissues by fibrosis and scarring. A small fibrin and foreign body response lingers on.

Conclusion: This long-term follow-up assessment provides evidence that long-term implantation of polyester as reinforcement for the rotator cuff tendons is not associated with serious biological problems. However the problem of stretching of the repaired rotator cuff muscles does occur and needs to be considered in more depth.

S. Williams T.D. Stewart E. Ingham M.H. Stone J. Fisher

Introduction: Following hip replacement surgery the tension of the soft tissues and the laxity of the joint may vary. Variations in surgical approach, technique and fixation method may influence the effective joint laxity and the level of force applied across the prostheses during the swing phase of gait. The aim of this study was to investigate the effect of different swing phase load conditions on the wear metal-on-metal hip prostheses using a hip simulator.

Methods: Cobalt chrome metal-on-metal bearings, 28mm in diameter were tested for five million cycles in a Prosim hip simulator with flexion-extension and internal-external rotation kinematic inputs. A Paul-type twin peak loading curve was applied, which was modified to provide three different swing phase load conditions;

Low positive swing phase load (< 100N)

Positive swing phase load (300N, as per standard ISO 14242–1)

Negative swing phase load, leading to microseparation and joint laxity.

All tests were carried out in 25% (v/v) new-born bovine serum, with gravimetric wear measurements completed every million cycles.

Results: The wear rates for the different swing phase conditions are shown in Figure I. Elevating the swing phase load from 100N to 300N (ISO load) increased the overall wear rate by 10-fold. Introducing microseparation into the gait cycle increased wear by a further 3-fold. These results indicate the sensitivity of metal-on-metal bearing wear to swing phase load conditions and joint laxity.

Discussion: Little attention to date has been paid to the importance of joint laxity and swing phase load on the wear rate of hip replacements. Elevation of wear rates with increased swing phase load was probably due to the depletion of fluid film lubrication. This was consistent with the findings under stop-start motion [Medley et al., 2002] and demonstrates the dependency of metal-on-metal hip replacements on fluid film lubrication conditions. Testing with a negative swing phase load elevated wear due to microseparation of the components, the head contacted the insert rim at heel strike which caused a stress concentration and damage to the insert rim. The results demonstrate that the wear performance of metal-on-metal hip replacements is highly dependent on swing phase load conditions. It is postulated that the fixation method and surgical technique can effect the swing phase load; over tensioning of the soft tissue may increase the swing phase load, whereas joint laxity will cause a negative swing phase load and possibly microseparation.

J.L. Ford B.E. Scammell

Introduction: Our previous work has shown that angiogenesis occurs within the cartilaginous callus during long bone fracture healing1. Our aim in this study was to investigate the mechanisms involved in endochondral ossification within callus tissue during the secondary stages of fracture healing.

Methods: In this study, immunohistochemical techniques were used to localise the following proteins within the fracture callus at different times following injury. The angiogenic factors vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) were localised; bFGF is also involved in matrix remodelling and cell proliferation. In addition, urokinase plasminogen activator and its receptor (uPA and uPAr respectively), a proteolytic enzyme involved in matrix remodelling, was immunolocalised. The model used for the study was a standardised midtibial osteotomy performed on New Zealand white rabbits.

Results: Results showed that from early time points, VEGF and bFGF were detected in pericellular locations around the chondrocytes. However, VEGF was only detected around the chondrocytes in close proximity to infiltrating vessels whereas homogenous localisation of bFGF was seen throughout the cartilage. Urokinase was localised throughout the cartilage callus as well as within vascular cavities and its receptor was detected on the chondrocyte cell surface from early time points.

Discussion: The immunolocalisation of VEGF around large hypertrophic chondrocytes in close proximity to infiltrating vessels suggests that this growth factor plays a role in chondrocyte hypertrophy and death, similar to its role in the growth plate. In contrast, bFGF was strongly detected throughout cartilage from early time points, suggesting that it may also be involved with cartilage proliferation during callus formation and subsequent matrix remodelling. The localisation of urokinase around chondrocytes and within vascular cavities suggests that this enzyme plays an important role in matrix remodelling and the vascularisation of the cartilage. In conclusion, our work suggests that the following sequence of events takes place within the cartilaginous callus. Firstly, bFGF is involved in the rapid proliferation of chondrocytes in the early stages of cartilage formation following fracture. Chondrocytes then express high levels of urokinase and its receptor which is actively involved in the degradation of cartilage matrix and formation of vascular spaces which leads to angiogenesis, VEGF expression, chondrocyte hypertrophy and eventual death.

V. Prasad E. Mughal T. Worthington D.J. Dunlop R.B.C. Treacy P.A. Lambert

Introduction: We have investigated the accuracy of a serological marker to distinguish between septic and aseptic loosening of Total Hip Replacements (THR). We present the preliminary results of our on-going prospective study.

Methods: After obtaining Ethical Committee approval, 46 patients were collected in 3 groups; “control” primary THR, revision THR for aseptic loosening, and revision THR for infection. Serum IgG responses to an exocellular bacterial antigen (Lipid S) were determined by enzyme-linked immunosorbent assay (ELISA).

Results: Our results show that the test can accurately differentiate between the patients with infected joint replacements and the control group. The test, to date, has a specificity of 93% and a sensitivity of 100%.

Discussion and Conclusion: This simple and cheap test can reliably assist in the accurate evaluation of a painful hip arthroplasty, and planning for revision surgery. It will also be useful in the management of patients in whom the microbiology results are either negative or based on a single isolate of an organism, which may be either a contaminant or a possible pathogen. This, in turn, would have implications on financial costs and the optimum use of available resources.

D.J. Cloke J.R. Williams

Aims: The use of the Oxford Shoulder Score (OSS) and the Shoulder Pain and Disability Index (SPADI), both patient-administered functional scoring systems, have been validated in groups of patients presenting with a variety of shoulder conditions. The aim of the present study is to determine the test-retest reliability for these scoring systems in patients with a clinical diagnosis of subacromial impingement.

Methods: All patients attending a specialist shoulder clinic with a likely diagnosis of subacromial impingement over a ten-week period were sent the OSS and SPADI questionaires in the week prior to their appointment. Those who, after history and physical examination, had a confirmed diagnosis of impingement were asked to complete the scores again prior to treatment. The pre-attendance and attendance scores were then analysed by the Kappa statistic and correlation coefficent for individual items, and by reliability coefficient for the total score.

Results: Thirty-eight patients completed the scoring questionnaires pre-attendance and in the clinic. For the OSS, the Kappa statistic gave poor agreement (0.127) for one question about pain, but moderate to good for the remainder (0.440 to 0.794). Similarly, the correlation coefficient for individual items on the SPADI scale showed one functional item with a result of 0.584, but the other twelve items ranging from 0.668 to 0.947. Taken as scores out of 100, the mean difference in total OSS was 0 (95% CI −2.3 to +2.3), with a coefficient of repeatability of 14.7. The mean difference in SPADI was 1.0 (95% CI −2.23 to + 4.23), the coefficient of repeatability being 20.69.

Conclusions: The OSS and SPADI show good test-retest reliability for individual question items and as overall scores in patients with subacromial impingement.

H. M. J. McEwen L. A. Knight R. Farrar M. H. Stone M. Taylor J. Fisher

Introduction: Reduction of ultra high molecular weight polyethylene (UHMWPE) wear in total knee replacement (TKR) bearings may delay the onset of osteolysis and subsequent loosening of components. This study used finite element (FE) modelling and in vitro simulator testing to investigate the effect of wear path geometry on UHMWPE surface wear.

Methods: The wear of PFC Sigma fixed bearing TKRs (DePuy) was investigated using a six-station force/ displacement controlled knee simulator (frequency 1 Hz) using previously developed methods [1]. High, intermediate and low kinematic inputs were simulated for up to five million cycles (Table 1) with identical flexion-extension and axial loading for all components. This kinematic data was also applied to a FE model of the PFC Sigma TKR and run using PAM-CRASH-SAFE software. The anterior-posterior (AP), medial-lateral (ML) and inferior-superior data were recorded and the resulting wear paths generated by selecting nodes from the contacting surface of the polyethylene relative to the femoral.

Results and Discussion: The mean wear rates with 95% confidence limits on the simulator when subjected to high, intermediate and low kinematics were 22.75 ± 5.95, 9.85 ± 3.7 and 5.2 ± 3.77 mm3 per million cycles, respectively. All FE models exhibited looped wear paths. An example wear path for the first 60% of the gait cycle for a lateral node is displayed in Figure I. The high kinematics model generated the greatest ML displacement and similar AP displacement to the intermediate kinematics model. The low kinematics model showed least ML and AP displacements. The AP displacements for medial wear paths differed little when subjected to the different kinematics. A looped wear path on the surface of UHMWPE results in greater cross shear transverse to the principal direction of motion, which is parallel to AP displacement in TKR and is the axis along which strain hardening occurs. This study revealed that increased AP displacement and tibial rotation kinematics generate more looped wear paths, increase ML and AP displacements on the surface of fixed bearing TKR and result in greater cross shear which ultimately increases UHMWPE surface wear.

A.M. Cutler S. Whitten C. Wigderowitz

Introduction: Osteoporosis is diagnosed by measurement of bone mineral density (BMD), with techniques that include single and dual energy x-ray absorptiometry (SXA, DXA) and quantitative computed tomography (QCT), which have relatively high cost and limited availability. Radiographic absorptiometry (RA), the corresponding technique based on plain radiographs, has not been favoured clinically because it required complex devices to calibrate and difficult techniques to measure the optic densitometry of films. In this paper a newly developed computerised radiographic technique is described that gives results in actual BMD units and includes a correction for soft-tissues. The technique has been developed in conjunction with a new solid phantom to facilitate the use in fracture clinics, without the need for further patient exposure. It also has the advantage of measuring the ultradistal radius, a clinically useful cancellous rich site. The design of the phantom and initial calibration testing are described.

M& M: The new phantom is constructed from a solid water equivalent material, removing the need for a soft-tissue equalising water bath. The necessary hydroxyapatite (HA) calibration wedge is built into the phantom to give results in actual BMD units. A high-density grid has been used to minimise the effects of scatter caused by soft tissues. The phantom was initially calibrated by comparing its results with those obtained from specially manufactured hydroxyapatite disks. The European Forearm Phantom (EFP) was used in studies of further calibration and testing of anatomical specimens, obtained with permission from the department of Anatomy at the University of St. Andrews.

Results: The test comparing the BMD determined by the new phantom to the known density of specially manufactured HA discs yielded a very high correlation (R> 0.999) with an error < 2%. Further studies with the EFP as a reference standard confirmed a very high correlation (R> 0.999) with an error of < 5%.

Finally a study was performed on 25 cadaver forearms that were available for imaging using DXA and the modified RA technique. BMD results showed good correlation (R=0.93, P< 0.001) with an error of less than 10%. The error is partly explained because during this part of the study a high-resolution anti-scatter grid was unavailable and a standard grid had to be used. Also some cadavers had previous fractures and dissection marks. Without these problems, it is expected that the error percentage would be significantly reduced.

Discussion: The phantom is light, small and the patient can comfortably fit even if the limb is fractured. The results compare favourably with published data for existing techniques that also used the EFP as a reference standard. The described technique carries the promise of a simple, inexpensive system, which yields superior results and can be used seamlessly in a fracture clinic. A pilot clinical study is being planned, comparing the results of the modified RA technique with peripheral DXA. This system can be quickly made available at minimum cost utilizing existing equipment. All the other advantages of computerised x-rays including more precise measurements of deformity and central analysis from a distance for isolated practices apply.

P.T.H. Lee M.T. Clarke A. Arora R.N. Villar

Introduction: Metal-on-metal (MOM) bearings after total hip arthroplasty are known to elevate the serum concentrations of metal ions, raising concerns about the long term effects. One potential modifier of ion release is the bearing diameter used. Resurfacing MOM bearings have a large surface area available for corrosion compared to the typical bearing size of 28 mm in total hip replacement (THR) but may benefit from improved lubrication and reduced production of corrodible wear debris. The net effect of these two variables on metal ion release is unknown. In this study, we compared the level of ion release in patients after large bearing MOM hip resurfacing arthroplasty with patient after small bearing MOM THR.

Methods: We measured the serum cobalt and chromium levels from 22 patients with large bearing diameter MOM hip resurfacing arthroplasty (Cormet 2000 and Birmingham Hip Resurfacing) and compared them to the serum cobalt and chromium levels of 22 patients with small bearing diameter (28 mm) MOM THR (Ultima). Patients were prospectively matched for activity level, body mass and date after surgery at blood sampling. All were at least 6 months after surgery.

Results: We found the median cobalt and chromium levels after hip resurfacing arthroplasty to be 7.6 times normal (median 38 nmol/L, range 14 to 144 nmol/L) and 10.5 times normal (median 53 nmol/L, range 25 to 165 nmol/L) respectively. This is compared to 4.4 times normal (median 22 nmol/L, range 15 to 87 nmol/L) for cobalt and 3.8 times normal (median 19 nmol/L, range 2 to 58 nmol/L) for chromium after 28 mm MOM THR (p=0.0021 and p< 0.0001).

Discussion: We concluded that large diameter MOM bearings result in greater release of cobalt and chromium ions than do small diameter MOM bearings. This may be of relevance when the potential side-effects of long-term exposure to elevated these metal ions is considered. It is not known to what extent this difference is due to corrosion of the component surfaces or of the wear particles produced.

E. Tucker R. Bayston B.E. Scammell

Objective: To determine whether Propionibacterium acnes is able to adhere to implant materials, and to develop biofilms.

Background: Most orthopaedic implant infections are caused by staphylococci, which express adhesins and can adhere to biomaterials and to plasma glycoprotein conditioning films. They then produce exopolymers and develop biofioms. P acnes, being anaerobic, is often missed as a cause of implant infection and might be more common than is realised, yet little is known about its virulence factors (ability to adhere to biomaterials or conditioning film and biofilm development).

Materials & Methods: Surgical steel or silicone coupons, with and without plasma conditioning film, were exposed to three clinical isolates of P acnes and examined by cultural methods and chemiluminescence for adherence. In further experiments, the coupons were incubated anaerobically with the P acnes strains for several days. They were then rinsed, fixed and processed for scanning electron microscopy (SEM). In a third set of experiments, coupons were again incubated anaerobically with P acnes and examined by laser confocal microscopy (LCM) for biofilm development.

Results: All three isolates of P acnes were able to adhere to the biomaterials, to a degree similar to that of a clinical isolate of Staphylococcus aureus, though not as strongly as Staphylococcus epidermidis. Unlike with the staphylococci, the presence of a conditioning film did not make a significant difference. SEM and LCM revealed biofilm development morphologically similar to that seen with S epidermidis. Exopolymer production was also demonstrated.

Conclusions: P acnes is able to adhere to biomaterials but not so avidly as S epidermidis. The adherence is not enhanced by plasma conditioning film. However, once adhered, P acnes is capable of developing a biofilm morphologically indistinguishable from that of S epidermidis. This probably explains the role of P acnes in implant infection, and the therapeutic difficulty it often poses.

F. Adie R. Bayston B.E. Scammell

Objective: To compare the in-vitro antimicrobial action of surgical irrigation fluids: 0.9% saline, 2g/L cephradine, 80mg/L gentamicin, 10% povidone-iodine (PVP-I) and 40ppm aqueous iodine (laq) for activity against Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli in the presence of blood, plasma and saline.

Materials and Methods: 5mL of antimicrobial agent was added to 5ml of blood, plasma or saline containing 105–106 CFU/mL of the test bacterium. At 15 seconds, 1 minute, 5 minutes, 1 hour and 2 hours, a 1mL sample was inactivated in 9mL of 0.5% sodium thiosulphate. The bacterial numbers were determined using a biochemical assay (Chemiluminescence) with a calibration curve and by spread plate counts. The data were transformed by a logarithmic function and analysed by linear regression to give 95% confidence intervals for their gradient of change over 2 hours. Significant differences were defined at the 5% level.

Results: In saline. All bacteria were killed within 15 seconds with PVP-I and Iaq, but showed no significant reduction with saline, cephradine or gentamicin. In plasma. E. coli was killed within 15 seconds with all irrigation fluids. S. aureus and S. epidermidis showed no significant reduction with saline, Iaq or cephradine, but did show a significant reduction in the presence of gentamicin. With PVP-I, all S. epidermidis were killed within 15 seconds and all S. aureus within 5 minutes. In blood. E.coli with PVP-I, Iaq and cephradine showed no significant reduction. E. coli with gentamicin did show a significant reduction. Both staphylococci showed a significant reduction over 2 hours with PVP-I and gentamicin, but no significant reduction with saline, cephradine and Iaq.

Conclusions: As blood has a strong chemical inactivating effect on iodine – based formulations, Iaq and PVP-I cannot be recommended for surgical irrigation. Gentamicin should be used in preference to cephradine in surgical irrigation fluids if an antimicrobial agent is required. The residual immunological components (particularly complement) in blood and plasma may enhance the susceptibility of bacteria to antimicrobial agents.

P. Mayhew N. Loveridge J. Power H.P.J. Kroger M. Parker J. Reeve

Areal BMD (aBMD) is relatively poor at discriminating those patients at risk of hip fracture. This study tested the hypothesis that a measure of bending resistance, cross section moment of inertia (CSMI) and section modulus, derived from 3D peripheral quantitative computed tomography (pQCT) images made ex-vivo, would discriminate cases of hip fracture from controls better than areal bone mineral density.

The biopsies were from (n = 20, F) subjects that had suffered an intracapsular hip fracture. The control material (n = 23, F) was from post-mortem subjects. Serial pQCT 1mm thick cross-sectional images using the Densiscan 1000 pQCT clinical forearm densitometer were obtained, and matched for location along the neck. The image voxels were converted to units of bone mass, which were then used to derive the mass weighted CSMI (MWCSMI), section modulus and areal bone mineral density, (see Table).

The aBMD results showed that the difference between the means of the fracture cases compared to the controls was 9.9% (−0.061g/cm2; +0.0055g/cm2, −0.127g/cm2; 95% confidence interval). However, the MWCSMI was 29.5% (−5966mm4; −8868mm4,−3066mm4; 95% confidence interval) lower in the fracture cases compared to the controls, while section modulus was 32.5% (−242mm3; −133mm3, −352mm3 95% confidence interval) lower. When presented as Z scores the fracture cases had considerably lower section modulus Z scores (mean −1.27 SD, p=0.0001) than aBMD – Z scores (mean −0.5 SD, p=0.07). To simulate the forces experienced during a sideways fall, the model’s neutral axis was rotated by 210°. The results were similar for section modulus to those at 0°.

This study suggests that biomechanical analysis of the distribution of bone within the femoral neck may offer a marked improvement in the ability to discriminate patients with an increased risk of intracapsular fracture. Progress towards implementing this form of analysis in clinical densitometry should improve its diagnostic value.

R.J. Pacheco L. Yang M. Saleh

Aims: To identify the distraction forces and contact pressures of the ankle joint at two different joint positions during articulated ankle distraction.

Material and Methods: Four amputated lower limbs were collected from patients undergoing amputation for vascular disease and frozen at -70° C. The ankle joint of the specimens were normal. Before use the limbs were thawed at room temperature for 24 hours. The skin and subcutaneous tissues were removed. A Sheffield ring fixator consisting of a proximal tibial ring and a foot plate connected through three threaded bars and hinges aligned with ankle axis was mounted on the limb. Force transducers were placed in the threaded bars between the tibial ring and the foot plate on the lateral, medial and posterior aspect of the ankle joint to measure the ankle distraction forces. Once the ankle distraction forces have been measured an anterior ankle arthrotomy was performed to permit the insertion of Fuji pressure sensitive film within the ankle joint. The limb-fixator construct was mounted in a loading machine and axially loaded on the tibia. The ankle joint was distracted at 2 mm intervals to a maximum of 20 mm. Pressure sensitive film was introduced in the ankle joint at each distraction interval and the tibia was axially loaded at 350, 700, 1050 and 1400N (half to two times body weight).

Results: The forces necessary to distract the ankle joint are almost double in the medial side than the lateral side. With 10° of plantarflexion the forces necessary to distract the lateral side increase by about 10%.

We found the center of pressure of the ankle joint to be situated in the antero-medial quadrant, close to the center of the ankle joint. Distraction of the ankle joint by 5 mm eliminated any contact pressures at the ankle joint when the tibia was loaded up to 700N (one time body weight). When the joint was distracted by 10 mm no contact pressures were found in the ankle when loaded up to 1400N (two times body weight)

Conclusions: With the ankle in the plantigrade position the forces necessary to distract the ankle joint are double in the medial side when compared to the lateral side. Plantarflexion increases the forces necessary to distract the lateral aspect of the ankle. This finding may have clinical implications when distracting ankle joints with equinus deformities as this can increase the risk of damaging the lateral ankle ligaments leading to ankle instability. In our opinion equinus deformities should be corrected before the start of ankle joint distraction.

The center of pressure of the ankle joint is situated in the antero-medial quadrant. Distraction of 5 mm will eliminate ankle contact pressure up to one times body weight whereas distraction of 10 mm will eliminate contact pressures up to two times body weight.

C.L. Curtis S.M. Eisenstein S. Roberts B. Caterson

Introduction: Proteoglycans are found both in the annulus fibrosus and nucleus pulposus of the intervertebral disc and contribute to the hydration of the tissue (aggrecan) and the regulation of matrix assembly (small proteoglycans) [1]. Whilst loss of proteoglycan is the main chemical change in disc degeneration seen in back pain patients, little is known of the events leading to and controlling this loss. In this study the metabolism of the most common proteoglycan, aggrecan, and others including decorin, biglycan, lumican, fibromodulin and versican, together with collagen types I and II were studied in diseased and normal discs.

Methods: Ten discs from patients aged 11–57 years (mean:39±15) with scoliosis (n=1), spondylolisthesis (n=1) and low back pain (n=8), were graded for macroscopic degeneration (Grades 1–4). Three ‘normal’ cadaveric discs from 3 individuals aged 25–27 years (mean 26±1) were also investigated. Disc was either snap-frozen (for RNA isolation) or the proteoglycans extracted with 4M GuHCl. Total RNA was isolated and RT-PCR performed using various oligonucleotide primers. GuHCl-extracted proteoglycan fragments were analysed using Western blotting with a number of antibodies to aggrecan metabolites, collagen metabolites and small leucine-rich proteoglycans.

Results: Intervertebral discs contain a very heterogenous population of proteoglycans demonstrating extensive enzymic degradation, particularly with increasing age and macroscopic degeneration such as is seen in back pain patients. Younger, less degenerate discs contained more biglycan than the older, more degenerate discs. However, the mRNA gene expression analyses demonstrated little cellular activity and potential synthetic response, there was very little expression of particularly in comparison to osteoarthritic cartilage cells which show considerable synthetic capability for all the major matrix components.

Discussion: Our analyses indicate that several biochemical, catabolic and biosynthetic changes occur in disc matrix molecules which are likely to contribute to loss of disc function with ageing and degeneration. The loss of biosynthetic capability of cells is very important in considering the potential of newer therapeutic modalities such as cellular repair and genetic engineering for the treatment of degenerative disc disease.

D. Yin L. Yang M. Saleh

Objectives: To develop a non-invasive method to assess the wire tension quantitatively which can be used in clinic.

Background: Fine-wire external fixators are widely used in the fixation of fractures and limb reconstruction. A requirement of stable fixation is that the wires maintain their tension. Recent lab tests have shown that substantial reduction in wire tension occurred during the simulated operative procedures. Clinical experience also indicated that wire site discomfort might be related to loss in wire tension. It would be very helpful if the wire tension could be assessed quantitatively by a non-invasive method.

Methods: An apparatus based on a LVDT (Linear Variable Differential Transformer) was developed to apply a constant transverse force to a wire and measure its deflection with respect to another parallel wire. An unstable oblique fracture was created in a Sawbones tibia and stabilized by a Sheffield Ring Fixator. The deflection of the testing wire was measured in four tests: (1) Two parallel wires fixation, tensioned reference wire, variable clamp to bone distance; (2) Two parallel wires fixation, loose reference wire, 80mm clamp-bone distance. (3) Two groups of parallel wires fixation with 70° crossing angle, tensioned reference wire, 80mm clamp-bone distance; (4) Two groups of parallel wires fixation with 70° crossing angle, tensioned reference wire, 80mm clamp-bone distance, osteotomy site fixed with a lag screw to simulate a stable fracture or a healing fracture. Fracture stiffness in the above conditions was derived from previous work. Stepwise multiple variable regression analyses were performed to determine the relationship between wire deflection and wire tension, clamp-bone distance, number of wires, reference wire tension, and fracture stiffness.

Results: The reference wire tension and fracture stiffness was excluded from the regression equation, indicating that they did not affect the wire deflection. The regression equation containing only the testing wire tension had an adjusted R-square value of 0.521, while the equation containing the testing wire tension and clamp-bone distance had the R-square values of 0.854. The addition of the number of wires to the regression equation resulted in a slight increase of the R-square value (0.862).

Conclusion: The wire deflection and the clamp-bone distance are the two most important factors that affect wire deflection. The measurement of wire deflection has the potential to predict wire tension and the effect of clamp-bone distance must be considered. Further work is required to refine the apparatus for clinical use.

M. Ganapathi S.L. Evans P. Roberts

Introduction: Surface replacement of the hip has been proposed as an alternative to total hip replacement, particularly in young active patients. The suggested benefits include preservation of bone stock for future revision surgery and avoidance of proximal femoral stress protection, which can cause bone resorption. However, following femoral head resurfacing, femoral neck fracture can occur.

The aim of this study was to compare the strain pattern in intact and resurfaced femurs using validated third generation composite femurs and rosette strain gauges.

Methods: Rosette strain gauges were applied to an intact and a resurfaced third generation composite femur at three sites; narrowest part of the lateral surface of the neck, narrowest part of the medial surface of the neck and medial surface at the level of lesser trochanter. The femurs were loaded with axial loads of 600N, 800N and 1000N sequentially. The tests were repeated thrice for each femur. Maximum and minimum principal strains were calculated.

Further tests were carried out in which an abductor load was included in the model. Testing was done at 600N and repeated thrice for each femur. The principal strains were calculated and compared with the the principal strains without the abductor load.

Results: The maximum principal strains in the resurfaced femur were approximately 50% higher in the lateral surface of the neck and about 30% higher in the lesser trochanteric region when loaded without including an abductor force. Inclusion of the abductor force decreased the strain particularly at the lateral surface of the neck by approximately 45% in the intact femur and approximately 25% in the implanted femur. Even with the inclusion of the abductor load the strain in the resurfaced femur remained more than 50% higher at the lateral surface of the neck and 20% higher in the lesser trochanteric region.

Conclusion: Our study suggests that proximal femoral stress protection will not occur following surface replacement of the hip. The increased strain at the lateral surface of the neck could result in fracture, particularly if there is notching of the neck or if abductor function has been compromised, which can happen particularly with the direct lateral approach.

D.S. McNally M. Clemence C.M. Naish

Introduction: Whilst conventional Magnetic Resonance Imaging (MRI) is universally used as the method of choice for examining the boundaries of the intervertebral disc clinically it gives little information about the internal structure of the disc. This is largely due to the fact that the normal resolution of such devices (typically 1mm in plane and 3mm out of plane) is just too large to resolve structures and pathologies of interest.

Aim: This work aims to describe the appearance of normal and pathological discs when imaged using a high resolution system. It then tests the hypothesis that a degeneration grading scale based upon such observations corresponds well with the graded appearance of the sectioned disc.

Method: 13 lumbar discs from 7 non-chondrodystrophoid dogs (age 2–10 yr, mean 5.7 yr) were employed in this study. They were imaged using a small bore 0.5T research imaging system using a T2* weighted pulse sequence (TR=500ms, TE=17ms), a 60mm field of view, 1 mm slice thickness, in plane resolution was 230 μm. A grading scale based on the standard visual scale was developed for grading these images.

Results: The outer and middle annulus had a strongly banded appearance with adjacent lamellae having high and low intensities (in spite of there similar chemical composition). The inner annulus (and frequently all the posterior annulus) had a uniform high intensity appearance as did the nucleus. Frequently, there has a well defined dark boundary between the annulus and nucleus. Increasing degeneration lead to disorder of the annulus structure and non-uniformity in the nucleus. Statistical comparison of the visual and MRI grading scales were extremely good (α=0.90–0.95) except for the posterior annulus (α=0.26).

Conclusion: Many features of the MRI appearance of discs at high resolution, such as the banded structure of the annulus, were not expected and must be due to some subtle physical processes. Care must therefore be taken with the interpretation of such images, in particular to assessment of hydration. Grading of high resolution images corresponded well to the ‘gold standard’ of visual appearance on sectioning. However, this scale is totally different to that used to grade discs using conventional clinical MRI.

Full Access
A.M. Hill A.M.J. Bull M. Urwin P. Aichroth

The motion of the shoulder complex, the scapulo-humero-thoracic rhythm, is an equilibrium between transmission of loads and positioning of the upper limb. This rhythm, which can be described by 12 spatial variables, is either responsible for, or affected by the genesis of shoulder pathology and trauma. Thus, imaging the articulations of the shoulder through a global range of motion is essential in aiding diagnosis, management decisions and interpreting operative outcome. As such, the objective of this study was to dynamically image the scapulo-humero-thoracic rhythm.

The subjects were seated between the toroid of the scanner and maximally slewn table on a customised tripod which both protects the target rings and provides a degree of comfort. Each subject was asked to carryout 4 movements; adduction to abduction in the scapular plane, internal rotation to external rotation at 0° and 90° abduction and flexion to extension. Each movement was carried out over a period of 5 seconds, enabling the acquisition of 20 volumes per movement.

Electron Beam Computed Tomography (EBCT) enables the scanning of a number of contiguous slices, each taking 50 msec. Previously this has facilitated real-time imaging and rendering of both cardiopulmonary function and colonography. A GE Imatron EBCT C300 scanner was used with a multislice sequence imaging protocol to collect 8 transaxial slices per volume by sweeping an x-ray beam sequentially over 4 tungsten target rings and recording x-ray intensity via two fixed detector rings after the reflected beam passes through the body.

Each slice was post-processed by semi-automatic segmention using Amira software, and reconstructed to produce three-dimensional volumes of the humerus, scapula, clavicle and selected ribs. Anatomical landmarks were then identified and the normal rhythm of the shoulder was described.

In conclusion, EBCT provides a quick and efficient method for direct realtime dynamic imaging of the shoulder girdle under normal conditions, the first time this has been achieved to the best of our knowledge. Not only do these reconstructions provide further input matter for preexisting and future computational shoulder models, but estabilishes an initial baseline for further clinical experience. As such, we hypothesise the ability of this modalitiy to image pathological and traumatic disruption to shoulder rhythm. The potential clinical application of this tool would include imaging of traumatic instability and impingement, facilitated by some minor ergonomic alterations to the apparatus.

D.P.S. Baghla J.C. Angel M. Siddique A. McPherson P. Johal W. Gedroyc G. Blunn

Background: Interventional MRI provides a novel non-invasive method of in-vivo weight-bearing analysis of the subtalar joint. Preceding in-vivo experimentation with stereophotogammetry of volunteers embedded with tantalum beads has produced valuable data on relative talo-calcaneal motion (Lundberg et al. 1989). However the independent motion of each bone remains unanswered.

Materials and Methods: Six healthy males (mean 28.8 years), with no previous foot pathology, underwent static right foot weight bearing MRI imaging at 0°, 15° inversion, and 15° eversion. Using identifiable radiological markers the absolute and relative rotational and translational motion of the talus and calcaneum were analysed.

Results and Discussion: Inversion: The calcaneum externally rotates, plantar-flexes and angulates into varus. The talus shows greater plantar-flexion with similar varus angulation, with variable axial rotation. Relative talo-calcaneal motion thus involves, 6° relative talar internal rotation, 3.2° flexion and no motion in the frontal plane. Concurrently the talus moves laterally on the calcaneum, by 6.5mm, with variable translations in other planes. This results in posterior facet gapping and riding up of the talus at its posterolateral prominence. Eversion: The calcaneum plantar-flexes, undergoes valgus angulation, and shows variable rotation in the axial plane. The talus plantar-flexes less, externally rotates, and shifts into varus. Relative motion in the axial plane reverses rotations seen during inversion (2.5° talar external rotation). The 8° of relative valgus talo-calcaneal angulation is achieved consistently through considerable varus angulation of the talus, in a direction opposite to the input motion. This phenomenon has not been previously reported. From coronal MRI data, comparative talo-calcaneal motion in inversion is prevented by high bony congruity, whereas during eversion, the taut posterior tibio-talar ligament prevents talar valgus angulation.

Conclusion: We have demonstrated that Interventional MRI scanning is a valuable tool to analysing the weight bearing motion of the talo-calcaneal joint, whilst approaching the diagnostic accuracy of stereophoto-gammetry. We have also demonstrated consistent unexpected talar motion in the frontal plane. Talo-calcaneal motion is highly complex involving simultaneous rotation and translation, and hence calculations of instantaneous axes of rotation cannot effectively describe talo-calcaneal motion. We would suggest that relating individual and relative motion of the talus / calcaneum better describes subtalar kinematics.

V.F. Harding L.A.M. Honorez I-H. Jeon K.J. Fairbairn K. Lateif J.L. Ford W.A. Wallace

Introduction: The Constant Score Functional Assessment (CS) is now the standard method of assessing shoulder disability in Europe. Previous studies have indicated that the CS values associated with a full-thickness rotator cuff tear (RCT) are lower than for normal shoulders. This study was designed to investigate which parameters of the CS were most influenced by the presence of a RCT. As ultrasonograpy has now been shown to have a high accuracy for diagnosing full-thickness RCTs it was used to establish the diagnosis.

Methods: 28 patients attending the Shoulder Clinic were invited to take part in this study for which Local Ethics Committee approval had been obtained. The majority of patients had a painful shoulder on at least one side. All patients had a CS carried out with the “Strength” measurement made in 3 ways – 1) maximum force using a fixed spring balance – FSB(max); 2) maximum force using a commercial myometer – M(max); 3) mean force from 2 to 4 seconds using a commcercial Myometer – M(mean). The CS was measured with no knowledge of the patient’s history or diagnosis and blinded to the state of the rotator cuff. The patients were then assessed using ultrasonograpy of the shoulder (Diasus with an 8–16MHz head) to establish the presence of a full-thickness RCT.

Results: The CS Values for the left and right shoulders have been analysed separately.

The results have also been analysed for each part of the Constant Score – Pain, Activities of Daily Living, Range of Movement and Strength and these will be presented.

Discussion: It was anticipated that subjects with a RCT would be found to be weaker and have a reduced CS in an affected shoulder. This was found to be the case for the left shoulder but not for the right. The reasons for this will be discussed. The abnormally low CS for the normal right shoulders (Group 1) will also be explored.

Conclusion: The CS may be a valuable method of identifying those patients with a RCT. This study indicates that a more careful evaluation of “Strength” measurements still needs to be undertaken.

A M. Ali L. Yang M. Saleh

Objective: To compare the mechanical stability of fixation of bicondylar tibial plateau fractures using available internal and external fixation techniques.

Method: A bicondylar tibial plateau fracture was simulated on a uniform synthetic bone and tested with loading to failure. Following power calculations, seven tibias were used for each fixation method; five types of fixation were tested: 1) Dual plating. 2) Ring Fixator with inter-fragmentary screws. 3) Hybrid fixator (Ring-Bar) with interfragmentary screws. 4) Lateral plate and medial monolateral external fixator. 5) Lateral plate and medial interfragmentary screws. The specimens were tested in compression to failure. The vertical subsidence in either medial or lateral plateau was measured using an electrical transducer.

Results: In all cases the mode of failure was consistent with collapse occurring in the medial plateau. There was no significant difference in the ultimate strength between dual plating and the ring fixator [4218N, 4184N respectively; P=0.28, t test]. Failure was seen at lower loads with the other fixation systems (Table).

Conclusion: The Ring Fixator and dual plating demonstrated a greater strength and the most stable fixation, choice may depend on tissue viability and surgeon preference. Furthermore mobilisation of the patient may be undertaken earlier with more confidence using these two methods rather than less stable techniques.

J. Love L. Yang M. Saleh

Introduction: Distraction osteogenesis has been used as a method of generating new bone in limb lengthening and deformity realignment; and is achieved in our unit though the use of the Sheffield Ring Fixator. The development of soft tissue tension creates an entirely different mechanical environment, and can often result in severe complications during treatment. Fixators must therefore be able to resist these forces. Furthermore, biomechanical modelling is very different from fracture and bone gap simulation.

The model developed in this study intended to look at linear distraction, i.e. lengthening.

Aims: To create a mechanical model that simulates the soft tissue effects during lengthening with an external fixator

To obtain a synthetic material with similar passive tensile properties to that measured in lengthened soft tissue

To measure the effect of tensioned synthetic soft tissue on osteotomy motion and multi-planar stiffness during cyclic loading.

Materials and Methods: A standard two 150mm ring frame was mounted on an acrylic rod, with a centrally placed osteotomy gap of 75mm. One ring was fixed with wires and the other with screws. An inter-fragmentary motion device was attached across the osteotomy, to measure axial, angular and shear deformation with both axial and off-axis loading.

Soft tissue tension was simulated with the use of neoprene rubber sheeting, attached to the nylon rod by Jubilee clips, with a gap anteriorly or medially. Extensive tensile testing was performed to determine the visco-elastic behaviour of the rubber, which showed it to be consistent and reliable. Tension of a similar magnitude to lengthened muscle (35–125N) was achieved, and could be accurately predicted for certain distraction lengths.

The stiffness of the frame was calculated from osteotomy motion with various distraction lengths both with the rubber attached and without.

Results: Tension in the soft tissues summates with the force applied in loading, with the effect of increasing the axial stiffness of the fixator by up to 70N, with a directly proportional relationship. It also acts as a restraint for shear and angulatory motion. In anterior and lateral loading positions however, the angulation stiffness remains low; this is thought to be due to the unequal distribution of soft tissues around the bony column, as seen in vivo. The stiffness of the frame is lowered by increasing the distance between rings; this effect can be counteracted by soft tissue tension in axial stiffness, but less so for angular and shear.

Conclusions: We conclude that osteotomy stability is dependent on soft tissue tension, and the magnitude of tension greatly alters the stiffness characteristics of the external fixator. This study highlights the important role of soft tissue tension in biomechanical modelling and clinical limb lengthening, and has exciting ramifications for future orthopaedic models.

I. Ahmed L. Cochrane C.A. Wigderowitz

Introduction: Substantial evidence is now available that complex multi-variate models such as Artificial Neural Networks and Finite Element Analysis can predict bone strength better than DXA. In order to build such models effectively, it is essential to determine which basic individual parameters will be used. The current study attempts to improve a number of existing parameters that reflect bone structure, originating from spectral analysis of cancellous bone in radiographic images, to assess whether their correlation with mechanical strength of bone can be improved.

M& M: Sixty standard AP x-rays of cadaveric human radii, for which mechanical data was available, have been examined. The bones had been mechanically tested to destruction and the details of the test have been published previously. The x-rays were digitized at 160 mm/ pixel, using a dedicated scanner. ROI of 64x64 pixels corresponding to 1x1 cm in the original x-rays were used for the analysis. Low pass and High pass filters were moved stepwise to determine the most effective bandwidth for the identification and measurements of the magnitude peaks in the fast Fourier transform (FFT).

Results: The spectral trabecular index had a correlation with load at fracture (LF) of −0.002 and with the work at fracture (WF) of −0.07. The filtered parameter, termed spectral index of bone structure (SIBS), increased these correlations to 0.41 and 0.46 respectively. The Longitudinal trabecular index had a correlation of 0.09 with LF and 0.04 with WF. The corresponding filtered parameter, termed longitudinal trabecular index of bone structure (LIBS), increased these correlation coefficients to 0.39 with LF and 0.41 with WF. Finally the Transverse trabecular index had a correlation of −0.19 with LF and −0.04 with WF. The Transverse index of bone structure (TIBS) altered the correlations to 0.17 with LF and 0.36 with WF. For this sample size, the 5% significance threshold for correlations is 0.25 and for the 1% level is 0.325.

Discussion: This refinement of the individual spectral parameters is an essential step towards the improvement of multivariate models, leading to a potentially improved assessment of fracture risk. The general assessment of trabeculae and particularly the longitudinal ones was substantially improved by the new method of measurement. These parameters can now be incorporated into more complex models that take into account other characteristics such as age of the patients, cortical thickness and size of the bones and which are knowingly related to bone fragility.

P.T.H. Lee M.T. Clarke A. Arora R.N. Villar

Aims: Elevated serum cobalt and chromium ion levels associated with carcinogenesis and chromosomal damage in animals has raised concerns that metal-on-metal (MOM) total hip replacement (THR) in humans may produce the same effects over time. Considering that the risks may be related to the level of these ions in the body, this study compared the serum cobalt and chromium ion levels in patients with unilateral versus bilateral 28 mm diameter MOM THR.

Methods: All patients having THR at our institution were prospectively registered on a computerised database. From our database, we identified 108 patients with Ultima (Johnson and Johnson, Leeds) MOM THR with 28 mm bearing made of cobalt-chromium alloy. After patient review in clinic and before blood results were known, patient matching was performed by date after surgery at blood sampling, activity level and body mass. Using these stringent criteria, 11 unilateral THR could be adequately matched with 11 bilateral THR. Blood serum was taken with full anti-contamination protocols and serum analysed via inductively coupled plasma mass spectrometry.

Statistical analysis used the Mann-Whitney U test.

Results: The serum cobalt ion level after unilateral MOM THR was 4.4 times normal (median 22 nmol/L, range 15 to 37 nmol/L) compared to 8.4 times normal (median 42 nmol/L, range 19 to 221 nmol/L) for bilateral MOM THR (p=0.001). The serum chromium ion level after unilateral MOM THR was 3.8 times normal (median 19 nmol/L, range 2 to 35 nmol/L) compared to 10.4 times normal (median 52 nmol/L, range 19 to 287 nmol/L) for bilateral MOM THR (p=0.04).

Conclusions: This study has shown that the serum cobalt and chromium ion levels in patients with bilateral MOM THR are significantly higher than those in patients with unilateral MOM THR. With levels of up to 50 times the upper limit of normal, this finding may be of relevance for the potential development of long-term side effects.

L.A.M. Honorez V.F. Harding I-H. Jeon J.L. Ford W.A. Wallace

Introduction: The Constant Score Functional Assessment (CS) is now the standard method of assessing shoulder disability in Europe. It has been observed that the CS values decrease with age and attempts have been made in Canada (Constant, 1986), Germany (Tempelhof, 1999), Switzerland (Gerber, 1992) and US (Romeo, 2002) to produce national norms against which the subject’s Constant Score might be compared. Unfortunately the methods used for measuring the “Strength” category of the CS have varied and thus the results are not uniformly comparable. This study has used three methods of evaluating “Strength” for the CS in a randomised group of subjects aged over 50 in order to establish the UK norms.

Methods: 200 patients stratified for age over 50 were invited to take part in this study for which Local Ethics Committee approval had been obtained. Of these 200, 46 patients (21 males) attended and all attenders had a CS carried out with the “Strength” measurement made in 3 ways – 1) maximum force using a fixed spring balance – FSB(max); 2) maximum force using a commercial myometer – M(max); 3) mean force from 2 to 4 seconds using a commercial Myometer – M(mean). The CS values have been plotted for age and sex.

Results: The results for the 25 females and 21 males using M(mean) are shown below. The middle line represents the linear regression with the 95% Confidence Intervals above and below.

Discussion: The results confirm that there is a deterioration in the CS with age in both men and women. The outliers in three of the four graphs will be discussed and the analysis represented after removal of outliers for which there is a justification for exclusion. The differences between the left and right shoulders will be discussed.

Significant differences were identified between the 3 methods of “Strength” measurement, highlighing the need for a uniform method of carrying out the CS.

Conclusion: The UK pattern of deteriorating CS with age mirrors that seen in other countries but the values are different. These differences are significant and make it necessary to reconsider the use of the corrected CS. It is probably wiser to use the uncorrected CS but refer to normal values as a guide for the expected CS at different ages.

A. Jones A. Clarke B.J.C. Freeman K. Lam M.P. Grevitt

Study Design. A reliability study of the Modic classification.

Objective. To determine the reliability and reproducibility of the Modic classification for lumbar vertebral marrow changes.

Summary of Background data. In 1988, Modic with colleagues described two degenerative stages of vertebral marrow and endplate morphology. These were Type I (inflammatory phase) and Type II (fatty phase). Later in 1988, he added a third variety; Type III where there was marked sclerosis adjacent to the endplates. No formal reliability or reproducibility studies had been performed on the Modic classification.

Methods. This study involved five independent observers of differing spinal experience using the Modic classification to grade fifty sagittal T1 and T2 weighted MRI scans. The observers repeated the assessment at three weeks. Intra- and inter-observer reliabilities were assessed using kappa statistics.

Results. There were 7 type I, 40 type II, 1 type III and 2 normal levels. The individual intra-observer agreement was substantial or excellent with kappa values ranging from 0.71 to 1.00. The overall inter-observer agreement was excellent with a kappa value of 0.85. There was complete agreement in 78% of the levels, a difference of one type in 14% and a difference of two or more in 8% of levels. The level of experience of the observer did not correlate with a better score.

Conclusions. We have shown that the Modic classification is both reliable and reproducible. It is simple and easy to apply for observers of varying clinical experience. We therefore recommend its use in clinical research and practice.

R. Mayahi A. Khot D.J. Sharp J. Powell

Study Design: A retrospective study of the clinical outcome of patients with lumbar discogenic pain with Modic changes on MRI prior to intradiscal steroid injection.

Objectives: To determine whether the clinical outcome of patients with discogenic back pain who underwent intradiscal steroid injection could be predicted from MRI Modic changes.

Methods: The pre-operative scans were studied by two senior spinal surgeons. The lumbar vertebral end-plate changes were then classified according to the method described by Modic. The intra- and inter-observer ratings were satisfactory.

Subjects: 40 patients with discogenic back pain were recruited in this study. The mean age was 43.6 years (23 to 72 years). The male to female ratio was 1 to 1.

Outcome Measures: The clinical outcomes at six months post-intradiscal steroid injection were correlated with the Modic changes. The clinical outcomes were assessed using visual analogue scores for back pain as well as Oswestry disability index (ODI). At least a 2-point improvement in visual analogue score and a 20-point improvement in ODI were required to indicate significant symptomatic relief.

Results: We found that in those patients without Modic changes there was improvement of the low back pain in 9% (1/11). In those with Modic I changes there were significant relief in 64% (9/14), moderate relief in 29% (4/14) and no relief in 7% (1/14). In those with Modic II changes there were significant relief in 27% (4/15), moderate relief in 27% (4/15) and no relief in 47% (7/15). There were no cases with Modic III changes.

Conclusions: Previous studies on intradiscal steroid injections have shown variable results. Two prospective double-blind clinical trials, using intradiscal steroids, identified no significant benefit or improvement in the clinical outcome. Our results however suggest that patients with Modic I changes on MRI are most likely to benefit from intradiscal steroid injection in the short term.

M.J. Hutton J. Bayer M. Sawant D.J. Sharp

Study Design: Retrospective review of 55 subjects who for various clinical indications had sequential MRI scans

Summary of Background data: Changes in the vertebral end plate are frequently associated with degenerative disc disease. These are called Modic changes. The changes were first classified into two types. Type I changes include decreased signal intensity on T1-weighted and increased signal intensity on T2-weighted images. In type II, signal intensity is increased in both T1- and T2-weighted sequences. Type I changes are assumed to be a result of fibrovascular replacement of subchondral bone and type II changes are the manifestation of fatty replacement of subchondral bone and are considered to be chronic. These changes can be separated only on magnetic resonance imaging (MRI). If bone sclerosis is extensive, signal intensities are decreased in both T1- and T2- weighted images, and this change in the end plate is called type III change. It is again assumed that these endplate changes represent a process that is progressive (Type I converts to Type II converts to Type III). To our knowledge there is little evidence to support such assumptions.

Objective: To investigate the hypothesis that Modic changes are a progressive degenerative process.

Subjects: The average time interval between MRI scans was two years. No subjects had had surgical intervention. The lumbar vertebral endplates were classified using the Modic system and the results compiled to provide further data on the natural history of these endplate changes.

Results: Of the endplates that had Modic type I changes on the first MRI scan, 6% had reverted to a normal MRI endplate appearance on subsequent scan. Of those with Modic type II appearance 18% were normal or type I on subsequent scan.

Conclusions: This data would not support the hypothesis that Modic changes observed on MRI are a progressive degenerative process.

A. Clarke K.S. Lam B.J.C. Freeman

Study Design: Prospective cohort study

Summary of Background data: A definite link between Modic end plate changes and discogenic low back pain has yet to be established. However, current prospective data indicates that Modic changes strongly correlate with the pain provocation of lumbar discography and improved clinical outcome following instrumented posterolateral fusion. Consequently, there is recent heightened awareness using this radiological entity in the selection of patients for interbody fusion or total disc replacement.

Objective: To prospectively evaluate whether Modic changes can predict improved clinical outcome following antero-posterior lumbar interbody fusion using femoral ring allograft.

Methods: A cohort of chronic low back pain patients were investigated with MRI and lumbar discography. Twenty-six patients with disco-graphically-proven concordant pain reproduction were prospectively entered into the study. Clinical results were collected using the Oswestry Disability Index (ODI), Visual Analogue Scale (VAS) and Short Form 36 Health Questionnaire (SF-36) at the pre-operative and two-year follow up. The minimal clinically important difference (MCID) was taken as 10 points for ODI, 2 points for VPAS, and 7 points for the physical function and bodily pain subset of the SF-36 questionnaire.

Results: MRI scans evaluated for the level fused revealed 13 patients with no end-plate changes (Type 0), whilst 2 patients had Modic Type I and 11 had Modic Type II changes. MCID in ODI were achieved in Type 0, Type 1 and Type 2, but improvement in VAS only was achieved in the Type 0 and Type 1. For SF-36, the MCID of 7 points was reached in most domains for all types of Modic change. There was no statistical difference in clinical outcome between those patients with Modic Type 0 and those with Modic type I or II.

Conclusion: This prospective study shows that Modic changes do not predict improved clinical outcome following antero-posterior interbody fusion using the femoral ring allograft.

A Golash K. Embleton A Jackson

Study Design: Non-randomised case controlled study.

Objectives: To study the relationship of CSF flow abnormality and severity of cervical spondylotic myelopathy.

Subjects: 45 consecutive patients undergoing MRI examination of the cervical spine. CSF flow measurement in the cervical spinal canal were done with phase contrast MRI in 3 subject groups consisting of 7 patients with clinical myelopathy, 8 patients with subjective myelopathy and 30 control subjects with no myelopathy. Modified JOAS scores and clinical examination findings were used to assess the severity of myelopathy. All subjects were imaged on 1.5 T Philips Magnetic Resonance scanner. A retrospective gated, phase contrast sequence was used to measure flow velocity for 15 time points in the cardiac cycle. Measurements were taken at the level of C2, above and below the levels of spinal stenosis.

Outcome Measures: Mean and Peak CSF flow velocity and caudal CSF flow was recorded at all the three levels. Differences in means were tested with one way ANOVA.

Results: Inter-group comparison showed both mean and peak CSF flow to be significantly lower in the clinical myelopathy group at above and below the stenosis but there was no difference at the level of C2. Patients with subjective myelopathy had lower range of mean and peak flow compared to the control group, but this was only significant for mean flow above the block (p< 0.05). There was significant difference between the caudal CSF flow per cardiac cycle between the groups at all the 3 levels.

Conclusions: The results suggest that a disturbance of pulsatile CSF flow in the cervical canal has high correlation with clinical myelopathy. Further study in a larger patient group would be needed to see the effect in a subjective myelopathy group.

D. Noyes M. Shaw N. Birch

Study Design: Prospective randomised controlled trial.

Objective: To determine whether topical application of autologous growth factors (AGF) and thrombin as a spray to large spinal wounds can reduce blood loss after lumbar spinal fusion.

Subjects: Seventy patients undergoing single or multi-level lumbar spinal fusion were randomised to receive a spray of AGF and thrombin to the raw surfaces of the wound as a haemostat or to receive no spray, immediately prior to wound closure.

Outcome Measures: Intra-operative swab and suction blood loss and post-operative loss into suction drains.

Results: The median intra-operative blood loss in the two groups was similar (665 ml in the AGF/Thrombin spray group and 500 ml in the non-spray group), but the post-operative loss in the AGF/Thrombin spray group was 34% less than in the controls when expressed as the ratio of intra- to post-operative blood loss (median postoperative loss in AGF / Thrombin spray group 315 ml; median loss in the non-spray group 360 ml). There was an even greater difference (44%) when intra-operative blood loss was more than 500ml (median loss in AGF/Thrombin spray group 340 ml; median loss in the non-spray group 520 ml).

Conclusions: AGF/Thrombin spray applied to lumbar spine wounds reduces blood loss generally, but more particularly when the intra-operative loss has been considerable. This effect is probably due to local replacement of haemostatic agents when these have been systemically depleted by the surgical procedure. This study provides evidence to support the use of AGF/Thrombin spray as an effective haemostatic agent in major spinal surgery.

C.E.W. Aylott K.J. McKinlay B.J.C. Freeman J. Shepperd D.S. McNally

Study Design: Cadaveric study on the effects of Dynesys.

Summary of Background Data: Dynesys is a novel form of soft stabilization that utilises pedicle screws and modular spacers mounted on a stabilising cord to control movement of the instrumented segment in all planes. In this way it provides a biomechanical alternative with greater physiological function than spinal fusion and may prevent the penalties of “overworking” adjacent levels.

Objective: The biomechanical response of both the instrumented and adjacent intervertebral discs (IVD) is investigated under compressive loading in flexion and extension. The effects of varying spacer heights on intradiscal pressure distribution are also reported.

Methods: Twelve L3-5 cadaveric lumbar segments were compressed to 1 kN in 6° flexion, neutral and 4° extension. The stress distribution in the mid-sagittal and posterolateral diameters of both the bridged and adjacent discs was measured by withdrawing a miniature pressure transducer across the IVD. Dynesys was applied across a single level and +2mm, neutral and −2mm spacer configurations tested in each position of loading. Over 2500 stress profiles were collected and the data obtained from measurements with and without application of Dynesys was analysed.

Results: In the absence of instrumentation stress peaks in the anterior annulus increased with a greater degree of specimen flexion. In 0° to 6° flexion, Dynesys eliminated the anterior stress peaks observed in the instrumented disc in 80% of specimens tested. In the +2mm to −2mm spacer range tested, posterior stress peaks were generally seen to increase with decreasing spacer height. Little effect is seen with the application of Dynesys to a non-degenerate disc. Preliminary analysis of the data suggests that stress distribution through the adjacent disc appears largely unchanged with instrumentation of the inferior segment.

Conclusions: Dynesys has the potential to relieve peak stresses in the anterior annulus seen particularly in positions of flexion. Spacer size influences the generation of peak stresses seen within the posterior annulus. Initial observations indicate that the IVD of the adjacent motion segment is not biomechanically prejudiced following the application of Dynesys.

G.W. Omlor H. Lorenz C. Carstens M.W. Kroeber T. Guehring

Study Design: Experimental in vivo study on New Zealand White Rabbits.

Summary of Background Data: We have developed an in-vivo rabbit model of lumbar disc degeneration. This model provides a defined loading of one single disc. However, the molecular mechanism that leads to mechanically-induced disc degeneration remains unclear.

Objective: To investigate the process of mechanically induced disc degeneration in New Zealand White Rabbits with respect to remodeling on the gene and the level of protein expression.

Subjects: Seven animals were treated with an external compression-device applying 200N on segment L3/4. Eight animals underwent sham surgery.

Outcome Measures: After 28 days discs were harvested and cut into two pieces in a sagittal plain. One piece was used for protein analysis utilizing immunohistochemical protocols for collagen I, II and aggrecan. The other half of the disc was used for quantitative real-time RT-PCR to determine gene expression of selected matrix genes.

Results: In the compression group matrix genes were upregulated: collagen I (6.46x; p=0,018), collagen II (2.14x), biglycan (2.97x; p=0,049), decorin (4.64x; p=0,043), aggrecan (1.2x), osteonectin (2.03x), fibronectin (3.48x), fibromodulin (2.6x; p=0,037). The MMP-13 gene could only be detected in compressed discs. Gene transcripts of the metalloproteinase-inhibitor TIMP-1 were 4.5 times upregulated (p=0,007). Immunohistochemical analysis revealed a decrease of aggrecan and collagen I.

Conclusions: In our animal model mechanical loading caused degradation of the matrix proteins collagen I and aggrecan. Metalloproteinases like MMP-13 trigger this degenerative process. The elevated expression of matrix genes and TIMP-1 transcripts may characterize a mechanism of compensation.

J. Libera V. Moos H. J. Meisel W. Hutton O. Josimovic-Alasevic

Study Design: Experimental study in dogs:

Objective: To assess the efficiency of disc chondrocyte transplantation in a canine model.

Summary of Background Data: Conventional clinical treatments of intervertebral disc herniation and degeneration are focused on excision of damaged tissue, stabilization, and spinal fusion. The development and refinement of cell-based therapeutics for tissue regeneration and repair have spawned a multitude of applications including autologous disc chondrocyte transplantation. For clinical application the efficiency of disc chondrocyte transplantation was assessed using a pre-clinical canine model to show the technical feasibility and biological relevance for disc repair and retardation of disc degeneration. This report examined the protein expression of transplanted disc chondrocytes and their role in the clinically observed disc repair following autologous disc chondrocyte transplantation.

Methods: The nucleus and inner annulus were sampled from four skeletally-mature dogs by micro-discectomy. Disc chondrocytes were isolated and propagated under GMP validated conditions including completely autologous serum conditions. Two months later, the cultured cells were transplanted through the contralateral side of experimental discs after testing complete healing of the annulus by measuring intradiscal pressure stability. After seven months the animals were humanely killed. One half of the vertically halved lumbar spines were embedded in paraffin and sections were analysed histologically and immunohistochemically.

Results: Histological examinations revealed large clusters of cells within the nucleus area of the treated discs. Cells within these cell clones were found to be viable and surrounded by de novo synthesized matrix as evidenced by a distinct histological staining and immunohistochemical expression pattern. A disc-specific expression of collagen type I and II and hyaline-specific proteoglycans was observed indicating the regenerative and reconstructive capacity of the transplanted disc chondrocytes.

Conclusions: These results indicate the contribution of transplanted disc chondrocytes to the observed clinical success of this cell-based therapy.

T. Guehring G.W. Omlor H. Lorenz C. Carstens M.W. Kroeber

Study Design: Experimental in vivo study on New Zealand white rabbits.

Summary of Background Data: Bone Morphogenetic Protein 2 (BMP-2) is of increasing orthopaedic interest due to its osteo-inductive potency. Currently it is used in human and animal studies for posterolateral spinal fusions. However, little data is available concerning the pathophysiologic role of BMP-2 in normal and degenerated discs.

Methods: A recently established animal model was used to create mechanically induced disc degeneration of one single segment. In 6 animals, an external disc compression device was attached for 28 days. For comparison 8 animals underwent a sham operation.

Outcome Measures: The discs were analysed by a) immunohistology to determine protein content of BMP-2 and b) real time RT-PCR to quantify RNA content of BMP-2.

Results: Sham controls showed a homogeneous distribution of BMP-2 throughout the annulus fibrosus and cluster-like accumulation within the nucleus pulposus. Mechanically degenerated discs determined a reduction of positive cells with areas lacking BMP-2. Real time RT-PCR results demonstrated a statistically significant (7.92 times) upregulation of BMP-2 as compared with shams (p=0.033).

Conclusions: Mechanically induced disc degeneration is associated with a loss of BMP-2 protein. Disc cells respond with a stimulation of BMP-2 gene expression. This data confirms the role of BMP-2 in the pathophysiology of disc remodeling. It remains unclear if this mechanism of BMP-2 stimulation contributes to the disc reorganization alone or if it may also play a role in osteo-inductive processes like osteophyte formation or endplate sclerosis.

H.K Wong M.M. Moe R Vaithinathan

Study Design: Prospective cohort study

Objective: To determine the rate of curve progression and factors related to curve progression in untreated adolescent idiopathic scoliosis in a prospective cohort study within a national school screening program.

Methods: Over 140,000 school children are screened annually in Singapore for common health conditions, including scoliosis. In 1996–97, a randomized sample in four age groups consisting of 72,699 children was enrolled in a scoliosis prevalence study, 263 were found to have spinal curvatures of 10 degrees or more. After exclusions, 250 children were followed up over a five year period up to 2001–02. Basic demographic data, age at menarche or break of voice, scoliometer reading, curve type, Cobb angle, curve rotation, and Risser grade were recorded. Curve progression was correlated to individual factors such as age, sex, puberty, curve type and magnitude as well as combinations of factors.

Results: Overall, 28% of the 250 curves progressed. Age at diagnosis, sex, pre-menarche status, and curve magnitude were statistically correlated to curve progression. Taking curve magnitude and age together, 53% of 11–12 year-olds with curves 20 degrees or more progressed compared to 10% of 13–14 year-olds with curves less than 20 degrees. 56% of children with curves 20 degrees or more and Risser grades 0–2 progressed, compared to 17% with curves less than 20 degrees and Risser grades 3–5. Combining curve magnitude, age, sex, and puberty together, a pre-pubertal female under 13 years old with a curve of 25 degrees or more has a 70% chance of curve progression. In comparison, a post-pubertal female older than 13 years of age and a curve of less than 25 degrees has only a 10% chance of progression. Curve progression in adolescent idiopathic scoliosis has been reported to vary from 5.2% to 56%, with the lower rates being found in school screening studies. Nachemson et al (1982) reported that 10–12 year old girls with untreated scoliosis of 20–29 degrees had a 60% risk of curve progression. Lonstein and Carlson (1984) reported progression in 23.2% of untreated children and that curve magnitude, skeletal immaturity, and curve pattern were associated with progression.

Conclusions: Our findings are similar, with pre-pubertal females under the age of 13 years old and with large curves at diagnosis having the greatest risk of progression.

A. Walsh R. W. Watson P Moroney D. McCormack M Fitzpatrick

Study Design: The effects of heat on porcine intertvertebral disc were studied experimentally.

Objective: To assess the effects of in-vitro heating of porcine nucleus pulposus on expression of inducible heat shock protein 70 and subsequent modification of biochemical responses to an inflammatory insult in the heated intervertebral disc tissue.

Subjects: Lumbar spines were harvested from six pigs. The nucleus pulposus was dissected from each intervertebral disc, divided into control (37°C) and heat shocked (42°C) groups then cultured in medium for one hour. All samples were then cultured at 37 C for a further two hours. After three hours tissue and supernatant were harvested from one third of the samples and the expression of inducible heat shock protein 70 (HSP70) was quantified via Western immunoblotting and enzyme linked immuno-sorbent assay (ELISA). The remaining samples were cultured either in normal medium or altered (pro-inflammatory) medium containing 5ug/ml bacterial lipopolysaccharide (LPS). At 24 hours the supernatant from these samples was analysed for both interleukin-8 (IL-8) and prostaglandin E2 (PGE2) secretion using ELISA.

Outcome Measures: Western immunoblotting and enzyme linked immuno-sorbent assay (ELISA) for heat shock protein 70. ELISA for interleukin-8 (IL-8) and prostaglandin E2 (PGE2).

Results: HSP70 expression was significantly increased in the heat shocked specimens. IL-8 and PGE2 secretion were significantly increased in nucleus pulposus exposed to LPS at both temperatures. The concentrations of IL-8 and PGE2 secreted in the heat shocked samples were significantly less than controls, particularly after exposure to LPS (p< 0.05, paired students t test).

Conclusions: In vitro heating of porcine nucleus pulposus causes overexpression of HSP70. This heat shock effect can alter aspects of the biochemical response of the intervertebral disc tissue to an inflammatory insult. Intradiscal electrothermal therapy (IDET) may, in theory, reduce discogenic pain at temperatures as low as 42°C by generating similar heat-induced changes in the nuclear biochemistry of degenerate intervertebral discs.

A. Ranganathan S. Rajasekaran J Naresh Babu A Prasad Shetty

Study Design: An in-vivo serial magnetic resonance imaging study of diffusion characteristics in human lumbar discs over 24 hours in healthy volunteers and patients with low back pain. Objective: Nutrition to the disc is solely by diffusion but no firm data is available on diffusion pattern in humans. This study reports diffusion patterns in a human population studied and documents the 24-hour diffusion pattern.

Methods: T1-weighted images were obtained pre and post-contrast with Gadodiamide-0.3mmol/kg at 5, 10 minutes, 2, 4, 6, 12 and 24hours. Diffusion was calculated by measuring signal intensity values in seven regions of interest (anterior and posterior annulus, anterior, posterior, peripheral (PNP) and central (CNP) parts of nucleus pulposus (NP). Enhancement percentage (EP), Peak enhancement percentage (PEP) and time to achieve PEP (Tmax) were calculated.

Subjects: Of the 215 discs in 43 persons (10 volunteers and 33 patients) 96 discs were normal and considered for study.

Results: Diffusion occurred mainly from the endplate (rather than annulus). The mean EP of PNP and CNP at 5 minutes was 6.7, 3.9; 10minutes was 7.5, 4.0; 2 hours was 36.6, 17.9; 4hrs was 42.8, 29.8; 6hrs was 51.7, 40.5; 12hrs was 35.9, 27.8 and 24 hours was 33.3, 27.9. Though PEP was achieved at 6 hours in NP, the CNP lagged behind throughout. Univariate ANOVA showed that there was significant difference (p< 0.0001) in PEP of NP between the age groups of less than ten (72.4) and higher (37.9). The mean PEP at the NP of lower two discs (26.8) was less compared to upper two discs 41.0(p=0.059). Stepwise linear regression analysis showed that diffusion to the CNP was significantly influenced by age (R2 =0.324), followed by level of disc (R2=0.5).

Conclusion: This is the first study to document the normal 24-hour diffusion pattern across lumbar discs. The data can form the basis for comparison of diffusion changes in degeneration, Modic’s endplate changes and smoking.

P. Dolan R. Taylor J. Porteous

Study design: To investigate the effects of muscle atrophy on back muscle fatigue:

Objective: To assess fibre type atrophy in patients undergoing surgery for pro-lapsed lumbar intervertebral disc, and to determine its effect upon EMG measures of fatigue.

Methods: Intra-operative biopsies were obtained from the erector spinae muscles of patients undergoing microdiscectomy. Mean fibre area of type I and II fibres were determined after myosin ATPase staining. Prior to surgery, EMG activity of the erector spinae muscles was recorded bilaterally at T10 and L3 whilst subjects performed the Biering-Sorensen fatigue test. Power spectral analysis indicated the initial median frequency and its rate of decline (median frequency gradient) at each recording site. Fibre type area was compared with the median frequency measures.

Subjects: 34 subjects (20 male) with intervertebral disc prolapse.

Results: Mean fibre area of type I and II fibres was 5890 ± 1947μm2 and 3461 ± 1946μm2 in men, and 5144 ± 1692μm2 and 1945 ± 1039μm2 in women, indicating marked type II fibre atrophy. Type II MFA was positively correlated with initial median frequency at L3 on the operated side (R=0.445) and negatively correlated with the maximum median frequency gradient of the four recording sites (R= −0.430).

Conclusion: Type II fibre atrophy influences EMG measures of fatigue. The decrease in initial median frequency with type II fibre atrophy probably reflects a reduced conduction velocity in these small fibres. The less negative median frequency gradient with decreased type II fibre size indicates a lower rate of fatigue which may be explained by an increased contribution to force generation from type I fibres which occupy a greater proportion of the muscle.

A. Anand M. Akmal M. Wiseman A. Goodship

Study Design: Experimental study to assess tissue engineered solutions to disc degeneration.

Objectives: To investigate the use of a novel biodegradable hydrogel which is capable of minimally invasive introduction into an intervertebral disc (IVD) and support of cultured nucleus pulposus (NP) cells for the purpose of developing a tissue-engineered solution to retard progression of IVD degeneration. There were 3 objectives: (1) To introduce a slowly polymerising alginate hydrogel into the NP cavity of a bovine vertebral disc model. (2) To demonstrate the viability and metabolic activity of cultured NP cells in the hydrogel in vitro. (3) To determine the effect of Synvisc (hylan G-F 20) on NP cell proliferation and extracellular matrix (ECM) production.

Summary of Background Data: The cause of intervertebral disc degeneration (IVDD) is multifactorial. One proposed mechanism is that IVDD originates in the NP and progresses radially to the annulus fibrosis (AF). There is a growing interest in tissue-engineered solutions where a biological repair is induced. By preventing the abnormality at the NP it may be possible to halt progression of IVDD. Injection of NP cells into an early degenerative IVD, where the AF is still intact, may retard the degenerative process.

Subjects/Methods: CaSO4 and CaCO3 alginates were injected into the NP cavity of a bovine tail. After 90 minutes the tail was dissected to reveal the gel. NP cells released from pooled bovine NP tissue were dispersed into the CaSO4 and CaCO3 alginate gels (10x106 cells.mL−1) with and without Synvisc and cultured for 21 days.

Results: Injectable alginate suspensions formed solid viscoelastic gels, filling the exact shape of the NP cavity. NP DNA and ECM synthesis was significantly greater in the CaCO3 alginate gel than in the CaSO4 alginate gel (p< 0.05). Synvisc significantly increased sulphated GAG (p< 0.01) and collagen (p< 0.05) production. These effects were supported histologically and immunohistologically where cells in the CaCO3 and Synvisc gels stained more intensely for proteoglycan and collagen type II.

Conclusions: Both CaCO3 alginate gel and CaSO4 alginate gel are injectable and are capable of sustaining NP cells in-vitro. Cells remain viable, maintain their phenotype, proliferate and produce ECM during the culture period. The CaCO3 alginate gel provides a three-dimensional matrix more favourable to NP cellular activity than the CaSO4 alginate gel. Synvisc behaves as a chondro-stimulant significantly enhancing NP cell metabolic activity.

V. Spiteri F.Z. Maempel M. Spiteri N. Calleja

Study Design: Retrospective cohort study.

Objectives: The aim of the study was to determine the incidence, sex distribution, age at diagnosis and any relationship this may have to handedness in 10–16 year olds with idiopathic scoliosis.

Design: A total of 611 patients with scoliosis were reviewed.

Subjects: 344 patients were diagnosed as having idiopathic idiopathic scoliosis. Those between the ages of 10–16, with a Bunnell angle greater than 5 degrees were included in the study.

Outcome Measures: Incidence in females was 0.69 % and 0.15 % in males. The female:male ratio was 5:1.

Results: Age at diagnosis was earlier in females, and typically occurred eighteen months following menarche. The incidence of left-handedness in 10–16 year olds in the general population was found to be 10%. This was the same in the scoliotic group.

Conclusions: The data showed that there was no significant relationship between handedness and the typical idiopathic pattern. However, there was a significant relationship between left handed individuals and the atypical curves (p= 0.0003, CI 1.56–6.63)

B.J.C. Freeman K.B. Mukerjee A. Clarke J.K. Webb

Study Design: Retrospective chart review.

Objective: To assess the clinical and radiological outcome of surgery for both dystrophic and non-dystrophic curves resulting from neurofibromatosis Type I.:

Subjects: 10 patients (7 females, 3 males) underwent surgical correction for neurofibromatous kypho-scoliosis between 1997–2003. The mean age at surgery was 16 years (range 8–37 years). Average follow-up 20 months (range 9 months – 4.5 years). Seven patients had MRI proven dystrophic curves (group I). These underwent 2–3 level apical vertebrectomy, followed by 2–3 weeks in Halo traction, followed by instrumented posterior spinal fusion and anterior rib strut grafting. Three patients had non-dystrophic curves (group II). Two underwent posterior instrumented fusion and one (aged 8 years) underwent convex epiphyseodesis with posterior Luque trolley.

Outcome Measures: Cobb angle, thoracic kyphosis, lumbar lordosis, global apical vertebral translation (AVT), regional AVT, coronal and sagittal balance, complications and Modified SRS Outcomes Instrument completed at final follow.

Results: For the dystrophic curves the Cobb angle improved from a mean of 81.5 degrees (mean bending film to 76 degrees) to 26.6 degrees post-operatively (68% correction) and 35.8 degrees at final follow-up (56% correction) and the global AVT improved from 61.5 mm to 29 mm at final follow-up. The average score for the modified SRS outcome instrument was 91.6 (Good). For the non-dystrophic curves the Cobb angle improved from a mean of 57.5 degrees (mean bending film to 47 degrees) to 23.5 degrees post-operatively ( 60% correction) and 24.6 degrees at final follow-up (57% correction) and the global AVT improved from 56.8 mm to 27.8 mm at final follow-up. The average score for the modified SRS outcome instrument was 98.5 (Good). All complications occurred in the dystrophic group including superficial infection in 2, dural leaks in 3, temporary brachial plexus injury in 1, worsening of lower limb neurological deficit in 1 and one death (upper GI haemorrhage). There was no failure of metalwork or evidence of pseudarthrosis identified. Seven of eight patients stated that they would have the surgery done again.

Conclusions: Non-dystrophic curves maybe treated by posterior fusion alone achieving 60% Cobb correction and 55% AVT correction. Close observation should be maintained for the appearance of dystrophic features and deterioration of correction. Dystrophic curves should be treated early and aggressively by two/three stage apical vertebrectomy, grafting and posterior spinal fusion. In this series 68% coronal Cobb and 63% AVT correction was achieved post-operatively. Complications can be expected with scoliosis associated with more than 50 degrees of kyphosis.

D.P. Tokala K.B. Mukerjee M.P. Grevitt B.J.C. Freeman J.K. Webb

Study Design: Retrospective chart review.

Summary of Background Data: Spinal osteotomy in ankylosing spondylitis is performed to restore forward gaze and sagittal balance. Closing wedge lumbar osteotomy and polysegmental thoracic osteotomy in the same patient has not been reported.

Objective: To study the factors affecting correction of sagittal balance.

Subjects: 27 patients (23 male, 4 female) operated between 1989–2002: average age 46 years: minimum follow-up: 18 months. 19 patients had lumbar osteotomy alone, 6 had both lumbar and thoracic osteotomies and 2 had thoracic osteotomy alone. Three groups were identified: A) patients with decreased lumbar-lordosis and normal thoracic-kyphosis B) Normal / increased lumbar-lordosis and increased thoracic-kyphosis C) Decreased lumbar-lordosis and increased thoracic-kyphosis.

Results: Preoperatively, mean sagittal balance was +103 mm, thoracic-kyphosis 61 degrees, and lumbar-lordosis 25 degrees. Three months postoperatively, sagittal balance was +36 mm, thoracic-kyphosis 55 degrees, and lumbar-lordosis 49 degrees. At final follow-up sagittal balance was +44 mm, thoracic-kyphosis 57 degrees and lumbar-lordosis 46 degrees. In patients who had thoracic osteotomies, thoracic-kyphosis of 78 degrees was corrected to 48 degrees. There were no spinal cord injuries or permanent nerve root palsies. Six patients had deterioration of sagittal balance (SB) (> 45 mm), 5 of them required cervical osteotomy. There was significant association between post-operative thoracic-kyphosis of > 60 degrees and SB deterioration (p-value < .001, sensitivity 100%, specificity 75%). Statistically there was no significant association between SB deterioration and post-operative sagittal balance, lumbar-lordosis, osteotomy-angle and extent of fixation.

Conclusions: Correction of thoracic-kyphosis affected final sagittal balance significantly. Consideration should be given to the simultaneous performance of lumbar osteotomy and polysegmental thoracic osteotomies in selected patients to obtain greater correction and restoration of near normal sagittal balance.

D.P. Tokala K. S. Lam B.J.C. Freeman J.K. Webb

Study Design: Retrospective case series.

Objective: To evaluate the clinical outcome, radiographic results and complications associated with single rod anterior instrumentation in neuromuscular thoracolumbar scoliosis.

Methods: Retrospective study with mean follow up of 35 months.

Subjects: Nine patients (6F, 3M), mean age 15 years, were operated on between 1994–2000. This heterogeneous patient group consisted of five cases of spinal dysraphism, one prune belly syndrome, one arthrogryposis, one myotonic dystrophy and one congenital myopathic dystrophy (muscle-eye-brain-syndrome). All patients were ambulatory and had minimal pelvic obliquity (< 15degrees).

Outcome measures: Pre-operative, post-operative and final follow-up measurements of Cobb angles, apical vertebral translation (AVT), thoracic kyphosis, lumbar lordosis, sagittal and coronal balance were recorded along with operative complications, pseudarthrosis, metalwork failure and loss of correction.

Results: There was one rod breakage and one case of proximal thoracic curve progression requiring supplementary posterior surgery. For the remaining 7 patients, the average corrections for Cobb angle was 62% (52 to 20 degrees), AVT was 53% (5.7 to 2.7cms), and both thoracic kyphosis and lumbar lordosis remained unchanged. No pseudarthrosis, vascular or neurological complications were encountered. Subjectively results were excellent in six and good in one.

Conclusions: Selective anterior instrumentation for neuromuscular scoliosis using a single rod resulted in acceptable clinical and radiographic outcomes in this highly selected series. Advantages include preservation of distal lumbar motion segments whilst maintaining sagittal and coronal alignment. We believe that this method of scoliosis correction has a definite yet select role in patients who are ambulatory, have minimal pelvic obliquity (< 15degrees), non-progressive pathology and near normal mental function.

D.P. Tokala K.S. Lam B.J.C. Freeman J.K. Webb

Study Design: Retrospective study.

Objective: To describe a modified cervico-thoracic extension osteotomy and evaluate clinical & radiographic outcomes.

Subjects: 10 patients with fixed cervico-thoracic kyphosis, average age 56 years, minimum 12 months follow-up. Three patients had psoriatic spondyloarthropathy, Three patients had previous lumbar osteotomies.

Technique: General anaesthesia and SSEP spinal cord monitoring was used. Complete laminectomy of C7, hemilaminectomy of C6 and T1, plus pedicle subtraction osteotomy and decancellisation of C7 was performed. Upon completion of the osteotomy, controlled halo manipulation allowed closure of the osteotomy: the pivot point being the anterior longitudinal ligament. Segmental fixation with lateral mass and pedicle screws plus bone graft was then added. All patients were immobilised for three months in halo-jacket.

Results: Restoration of normal forward gaze was achieved in all patients. Mean preoperative kyphosis of 17 degrees was corrected to lordosis of 36 degrees (mean total correction 53 degrees). No spinal cord injuries or permanent nerve root palsies occurred. Three patients had mild sensory radiculopathies lasting a few weeks. No loss of correction, no pseudarthrosis, one patient had 50% anterior subluxation that later united. Two deep infections were successfully treated with wound washout and antibiotics.

Conclusions: Cervico-thoracic osteotomy in ankylosing spondylitis continues to be challenging and hazardous. C7 decancellisation and extension osteotomy supplemented with segmental internal fixation provides immediate spinal stability, reduces sagittal spinal translation and associated high risk of neurological injury, whilst maintaining correction until bony union.

K. El-Abed S. Ali S. Dixon M. J. Hutchinson I.W. Nelson

Study Design: Prospective Cohort Study.

Summary of Background Data: It has previously been suggested that fulcrum bending radiographs (Cheung et al Luk 1997) and traction radiography under anaesthetic (Davis et al 2003) predict the flexibility and correction obtained following surgery better than conventional supine bending radiographs.

Objective: To compare fulcrum bending radiographs and traction radiographs for the prediction of surgical correction of idiopathic scoliosis.

Subjects: The study was based on 16 patients with a diagnosis of idiopathic scoliosis who underwent corrective surgery.

Outcome measures: The Cobb angle of the major curve was compared on the standing AP and fulcrum bending radiograph taken in the pre-op assessment clinic, the traction film undertaken under anaesthetic immediately prior to surgery and the first post operative standing radiograph taken. The post operative correction of the major curve was analysed using regression techniques and adjusted for the base line curve angle of the major curve.

Results: The results were presented as an estimate of the parameter coefficient in the model associated with 95% confidence intervals. The median pre-operative Cobb angle of the major curve was 69 degrees, on the fulcrum bending film was 47 degrees, on the traction film was 30 degrees, and on the first post operative film was 30 degrees. There was no evidence to suggest that the fulcrum Cobb had an effect on the post operative correction of the major curve. There was however evidence to suggest that the traction Cobb angle had an effect on the post operative correction of the major curve (parameter estimate 0.87) 95% CI (0.174, 1.399), T value = 2.83, P = 0.016.

Conclusion: Traction radiographs under anaesthetic better predict the surgical correction obtained in adolescent idiopathic scoliosis compared to fulcrum bending radiographs. These two techniques have not been directly compared before.

H.K. Wong H.T. Hee Z.R. Yu D.H.C. Wong

Study Design: Compartative cohort study.

Objective: To compare the safety and efficacy of conventional posterior instrumented fusion versus thoracoscopic instrumented fusion for the surgical treatment of King Type III adolescent idiopathic scoliosis.

Methods: The results of 34 consecutive patients with King type 3 scoliosis treated with one of the above techniques were analyzed independantly. Twenty-two patients underwent posterior spinal fusion (PSF) and instrumentation (Moss-Miami). Twelve patients had thoracoscopic fusion (TF) and instrumentation (Eclipse).

Results: Baseline demographics (age at menarche and surgery, pre-operative Cobb angles in coronal and sagittal planes), estimated blood loss at surgery and duration of parenteral analgesia did not differ between the two groups. PSF patients had significantly higher transfusion requirements (p=0.032). Operative time (p = 0.0001), ICU stay (p = 0.005), and hospital stay (p = 0.037) were longer in TF cases. There were no complications in PSF patients. Complications in TF patients included lobar collapse (1 patient) and scapula winging (1 patient). Improvement in scoliosis among PSF patients averaged 75% (1 week), 70% (6 months), and 65% (1 year). In TF patients, mean improvement in scoliosis was 66% (1 week), 62% (6 months), and 62% (1 year). The differences between the two groups in terms of scoliosis improvement were not significant. Curves with apex at T8 or higher had better correction of scoliosis (p = 0.05). The sagittal alignment (thoracic kyphosis and lumbar lordosis) after surgery was similar between the two groups at 1 week, 6 months, and 1 year post-operatively.

Conclusion: The efficacy of thoracoscopic anterior fusion and instrumentation is similar to standard posterior instrumented fusion. The advantages of the thoracoscopic technique are the avoidance of a long posterior midline scar, and lower transfusion requirement. A longer operative time, ICU and hospital stay was attributed to the steep learning curve of this endoscopic technique.

Full Access
R.S. Bhangoo S. Sgouros

Study Design: Prospective cohort study.

Objective: To study the relationship between scoliosis and Chiari I malformation, with reference to the possible role of cranio-vertebral decompression in preventing the need for scoliosis correction.

Methods: Prospective data collection on all Chiari I patients referred to a single paediatric neurosurgeon with an interest in Chiari malformation.

Subjects: From a total of 35 patients with symptomatic Chiari I who underwent primary cranio-vertebral decompression, 13 had clinically detected scoliosis. Of these 13, 10 (7 males) had no other structural spine abnormality, which could influence the natural history of scoliosis and were included in this study. Mean age at diagnosis was 11.5 years (range 8.8– 15.9 years).

Results: Of the 10 patients, 8 had left-sided curves and two had right sided curves. Six patients did not require corrective scoliosis surgery following cranio-vertebral decompression. The mean Cobb angle for those not requiring scoliosis correction was 29 degrees compared to 76 degrees for those requiring correction (p=0.001, one way ANOVA). The mean age of patients requiring corrective surgery was 12.75 years versus 10.33 years for those not requiring correction (p=0.084, one way ANOVA). These findings were confirmed by multivariate analysis, which also confirmed that symptom duration, syrinx length and site were not significant in predicting the need for corrective surgery following cranio-vertebral decompression.

Conclusion: Cranio-vertebral decompression for Chiari I may prevent the need for corrective scoliosis surgery when performed before the age of ten and below a Cobb angle of 30 degrees.

I. Harding D Carrizo S Charossky D Chopin

Study Design: Retrospective chart review.

Objective: To assess the pulmonary function and rib deformity of patients following Schollner and modified Schollner costoplasty. Little is described in the literature concerning the long term effects of costoplasty.

Methods: Retrospective analysis of patients undergoing costoplasty at our institution with a minimum of three year and a maximum of 22 years follow-up.

Subjects: 23 (20 female) patients with a primary diagnosis of late-onset idiopathic scoliosis with a rib hump deformity underwent costoplasty at age 25 (16–36). 10 had surgery on the convexity alone and 13 had additional ‘concave surgery’ (6 of these had silastic implants). 3 patients had simultaneous correction of spinal deformity and costoplasty. The remainder underwent delayed procedures (0.6–19 years) following the index operation. Harrington instrumentation was used in all patients for primary curve correction.

Outcome measures: Forced Vital Capacity (FVC) – including % normal expected for age and rib hump (clinically and from radiographs) were measured pre and post-operatively at each attendance to assess the outcome of the procedure.

Results: The mean follow up was 10.7 years (3–22). Average reduction in rib hump was 33 mm at 6 months and 25 mm at the latest follow-up. There was no significant difference in the pre-operative and long-term FVC (p=0.4, paired t-test), although 6 months post-operatively there was a significant reduction in FVC (p=0.03, paired t-test). Subgroup analysis (convex only, convex/concave without silastic implant, convex/concave with silastic implant) revealed a similar pattern for rib hump correction and maintenance of FVC in all 3 groups at latest follow-up. However for patients undergoing convex surgery alone, the difference between FVC at 6 months and at latest follow-up was significant (p=0.01, paired t-test).

Conclusions: Rib hump correction and lung function (even accounting for age) are preserved in the long term following costoplasty. This study does not show any benefit of additional surgery on the concavity of the curve in reducing the rib hump on the convexity or on the FVC.

I. Gill M.J. Gibson

Study Design: A prospective observational study of 12 Adolescent Idiopathic Scoliosis patients undergoing corrective surgery.

Objective: To assess the recovery of respiratory function (specifically diaphragmatic function) after thoracotomy or thoraco-abdominal surgery for Adolescent Idiopathic Scoliosis (AIS) using spirometry and Sniff Nasal Inspiratory Pressure (SNIP).

Summary of Background Data: SNIP is one of the best measures of global inspiratory muscle strength and specifically of diaphragmatic muscle strength. FVC and FEV1 are a better measure of restrictive and obstructive lung function than muscle strength. To the best of our knowledge no study has specifically looked at the recovery of diaphragmatic function following scoliosis surgery.

Subjects: 6 patients (2M, 4F) with thoracic scoliosis underwent a thoracotomy followed by a second stage posterior instrumentation 5–7 days later. The other 6 patients (1M, 5F) with thoraco-lumbar curves had a single stage correction and instrumentation using thoraco-abdominal approach. All patients were operated by the same surgeon.

Outcome Measures: All patients underwent conventional lung function tests (spirometry) and SNIPs during their pre-operative assessment. Spirometry and SNIPs were repeated postoperatively before discharge, at 6 weeks, 3 months and 6 months follow up. The values were compared between the thoracic and thoraco-abdominal groups.

Results: Overall mean preoperative SNIP was 56.75 cm H2O and overall FVC was 2.79L. The mean SNIP in the thoracotomy group was 57.8 and 55.67 in the thoraco-abdominal group. The mean FVC in the thoracotomy group was 2.9 and in thoraco-abdominal group was 2.66. The difference between the 2 groups was not statistically significant. SNIP values returned to normal within 3 months in the thoraco-abdominal as well as in the thoracotomy groups. The FVC returned to within 95% of pre-operative values in 6 months in the two groups.

Conclusion: This study shows that SNIP return to pre-operative values within 3 months of scoliosis surgery after both thoracotomy and thoraco-abdominal approaches. The thoraco-abdominal approach appears not to have a more detrimental effect on global inspiratory muscle function and diaphragmatic function when compared to thoracotomy.

E.R.S. Ross K.J. Daly H. Norris C.N. McCollum

Study Design: Case report of four consecutive case reports of revision surgery for anterior dislocation of the Acroflex disc (DePuy Acromed, MA, USA) all of whom required vascular surgery are described.

Objective: To describe vascular complications of explanting an artificial inter-vertebral disc replacement following spontaneous anterior displacement.

Subjects: Four consecutive patients required explantation of the Acroflex disc. Two patients were male and two female with median age 44 years (range 33–51). All patients gave informed consent to enter a clinical trial, which had ethical approval.

Outcome measures: Symptom relief, vascular injury and deep vein thrombosis.

Results: All patients gained good symptomatic relief following disc replacement. Four patients suffered anterior displacement of the disc with a deterioration in symptoms during the 1st year. Three suffered vascular damage to the iliac vessels. In two cases division and re-anastomosis of the iliac vein was required to allow disc removal. Ilio-femoral deep vein thrombosis occurred pre-operatively in one patient and post-operatively in a second, no deaths occurred.

Conclusions: Anterior intervertebral disc displacement is associated with vascular injury. Preventing anterior disc displacement must form an essential part of disc design with (i) rapid fixation to bone and (ii) a failsafe design to prevent local damage in case of failure. In the case of displacement, disc removal should be planned and performed with a vascular surgeon.

G. Heilpern G. Marsh A. Knibb

Study Design: Prospective randomized double blind trial.

Objective: To assess the effectiveness of intrathecal fentanyl in the relief of post operative pain in patients undergoing lumbar decompression or fusion.

Summary of Background Data: Morphine has been shown to be effective intrathecally in spinal surgery but there is an increased incidence of respiratory complications. Fentanyl has not been formally evaluated in this setting.

Methods: All patients received our standard analgesic regime with PCA via a syringe driver. They were also randomised to receive either 15 micrograms of fentanyl intrathecally, or nothing. The fentanyl was administered by the operating surgeon under direct vision one or two levels above the site of operation at the end of the procedure.

Subjects: 30 patients undergoing lumbar spinal surgery were prospectively recruited.

Outcome measures: VAS pain scores were taken at 2, 4, 24 and 48 hours post operatively. Time to first bolus delivery of morphine from the PCA was also recorded as was the total dose of morphine required.

Results: The patients randomized to receive fentanyl showed a significant increase in the time to first bolus delivery of morphine as well as a 40% reduction in the total morphine dose delivered. There was also a decrease in their mean VAS scores. There was no increased incidence of side effects in the group receiving fentanyl. No patients suffered respiratory compromise requiring treatment and only two patients required HDU observation overnight. The remainder of the cohort left recovery after 2 hours to be nursed on an open ward.

Conclusion: Intrathecal fentanyl is effective at reducing morphine use via a PCA and mean pain VAS scores after lumbar spinal surgery. We would support its use over intrathecal morphine because of the reduced incidence of respiratory complications and the ability to nurse patients on the open ward.

D. Wardlaw S. Choudhary T. Muthukumar S. Gibson

Study Design: A prospective randomised controlled trial with blind radiological assessment.

Objective: To assess the radiological outcome of instrumented posterolateral lumbar fusion in a prospective randomised study comparing the use of allograft (fresh frozen human femoral head) to autologous bone (from the posterior iliac crest) using a validated method.

Methods: Sixty-nine patients having instrumented postero-lateral fusion using the Steffee plate were randomised to one of two groups, to receive either allograft bone or autologous bone. The same surgeon using the same surgical technique performed or supervised all cases. The radiological results of the two groups were assessed as well as the quality of fusion.

Outcome measures: The radiographs were assessed for fusion or non-fusion by three independent observers using the same criteria, and a second time by one of the observers. The Kappa scores for the inter-observer and intra-observer agreement were calculated. Some of these patients had fusion status verified by the gold standard of surgical exploration and the sensitivity and specificity calculated. The clinical outcome is the subject of a different paper.

Results: Both the inter-observer and intra-observer kappa scores (k) were 100%. The sensitivity of the method was 87.9% and the specificity was 100%. Thirty-seven patients received allograft and 32 patients received autograft. There was no significant difference in the fusion rate, or the quality and quantity of the graft between the groups.

Conclusions: There is no difference in the fusion rates comparing the use of autograft and allograft for postero-lateral instrumented lumbar fusion.

I. Gill M. Eagle J. Mehta M.J. Gibson K. Bushby R. Bullock

Study Design: A prospective observational study of scoliosis patients who were on non-invasive night ventilation for respiratory failure.

Objective: To report the results of spinal deformity correction in a group of patients with progressive scoliosis and rare forms of muscular dystrophy/myopathy with respiratory failure who were on nocturnal ventilatory support at the time of surgery.

Subjects: 9 patients (6 males, 3 females) with scoliosis and respiratory failure. The mean age at surgery was 12.4years (range 8–16yrs). There were 4 patients with multicore myopathy, 2 with merocin negative congenital muscular dystrophy, 1 with Ullrichs muscular dystrophy, 1 patient with congenital AcylCOA dehyrogenase deficiency and 1 with congenital scoliosis and dextrocardia. All the patients had overnight pulse oximetry, which showed episodes of desaturation at night. This was reversed with the onset of nocturnal ventilation. All the patients underwent posterior fusion performed by the same surgeon. Mean follow-up was 40 months (range 10 to 75)

Outcome Measures: Lung function, Cobb angle, Length of ICU stay, complications

Results: Mean vital capacity at time of surgery was 20% (range 13–28%). All patients recovered well following surgery with no cardiac or pulmonary complications. The mean stay in the ICU was 2.7 days (range 2–5). The mean hospital stay was 14.2 days (range 10–21). The mean preoperative Cobb angle was 70.2 degrees (range 55–85). The average change in the Cobb angle post-operatively was 32 degrees (range 16–65 degrees). The mean vital capacity of patients at latest follow up was 18% (range 10–32%). There was no loss of correction at latest follow-up. None of these patients lost their ambulatory capacity following surgery.

Conclusion: This is the first study reporting results of deformity correction in patients on ventilatory support. Spinal deformity correction in patients on non-invasive nocturnal ventilation presented no increased risk of complications.

DP Tokala KB Mukerjee MP Grevitt

Study design: Retrospective study.

Objectives: To determine whether apical vertebrectomy for correction of severe spinal deformity in patients with cerebral palsy or mental retardation significantly improves curve correction and to study complications of such a procedure.

Summary of Background data: Although a combined anterior-posterior procedure for correction of severe deformity in cerebral palsy patients is well established, apical vertebrectomy to improve correction has not been described.

Subjects: 5 patients (2M, 3F) operated on between 2000–2003 (anterior apical vertebrectomy followed by posterior instrumented fusion), mean age 14 years, average follow-up 1.5 years. All had group II (Lonstein & Akbarnia) rigid (mean 96degrees bending to 83degrees) thoracolumbar/lumbar curves with marked pelvic obliquity.

Results: Preoperative mean Cobb angle of 96 degrees corrected to 36 degrees, (63% correction, and 57% correction over and above the bending Cobb angle), 42 degrees at final follow-up. Mean apical vertebral translation (AVT) correction was 57 % (86mm to 37mm) and regional AVT correction 53%. Pelvic tilt correction was 72% (29degrees to 9degrees). Thoracic kyphosis remained unchanged but lumbar lordosis of 4.2 degrees (range−66 to +68) was corrected to 63 degrees. Mean blood loss was 1100mls (range 300–3000) for anterior surgery and 3400mls for posterior surgery. Operative time was 3 hours for anterior surgery. There were no intra-operative or post-operative complications (infection, pseudarthrosis, metalwork failure). Subjective outcome was excellent in all patients.

Conclusion: In patients with rigid, rotated curves with wide apical translation, apical vertebrectomy and posterior instrumented fusion can achieve significant correction of Cobb angle over and above the bending cobb angle and also the AVT and pelvic tilt leading to high parent / caregiver satisfaction and improvement in functional status of the patient.

Y. Barzilay J.C. Le Huec G.R. Reddy T. Friesem

Study Design: Prospective Cohort study.

Objective: To prospectively evaluate the Maverick Lumbar Disc Prosthesis (Medtronic, USA) at one year follow-up.

Methods: Prospective analysis of the Maverick Lumbar Disc Prosthesis implanted in the first 30 consecutive patients for the treatment of single-level degenerative disc disease of the lumbar spine resistant to conservative treatment for more than one year.

Subjects: Sixteen females and 14 males with an average age of 44 years and minimum follow-up of 1 year. The prosthesis was implanted at L4-L5 in 18 patients and at L5-S1 in 12.

Outcome Measures: Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS) preoperatively and at routine scheduled follow-ups. Radiographic analysis included sagittal balance parameters on standing full length lateral radiographs of the spine and range of motion on flexion/extension dynamic radiographs.

Results: Clinical success (ODI improvement > 15), was 82% and 86%, at 6 months and one year follow-up respectively. The VAS showed an improvement in back pain from 7.1 (+/− 2) pre-operatively to 3.0 (+/− 1.8) post-operatively. At one year there were no device related complications. The measured range of motion in flexion-extension ranged from 3 to 12 degrees (mean range of motion, 6 +/− 4 degrees). There was no significant change in sacral tilt, pelvic tilt, or overall lordosis after disc replacement. In one case the ureter was injured during the approach.

Conclusions: The results of total disc arthroplasty presented here compare favourably with results reported in the literature following ALIF. It appears that the disc prosthesis has enough freedom of motion to allow the patient to maintain normal sagittal and spino-pelvic balance with radiographic evidence of normal range of motion. These early favourable clinical results and the influence on adjacent motion segments can be assessed only after long term follow-up.

I. Harding E. Davies E. Buchanan J. Fairbank

Study Design: Prospective cohort study

Objective: To assess the ‘red flag’ symptom of night pain as an indicator for serious disease in patients attending a back pain triage clinic (BPTC).

Summary of Background Data: Although common in patients with known serious pathology, the prevalence of night pain in this population is not known.

Methods: 482 consecutive patients attending BPTC were assessed (including history of frequency and duration of night pain). Clinical examination was performed and demographic data obtained. MRI was performed if indicated according to local guidelines.

Outcome measures: Oswestry (ODI), Visual Analogue Scales (for pain, distress and coping) and Hospital Anxiety Depression (HAD) patient based outcome scores were obtained. Serious pathology was defined as infection or tumour as per AHCPR Guidelines (1994) which state that these symptoms are associated with severe night time pain.

Results: 213 patients had night pain with 90 having pain every night. No serious pathology was identified. Patients with night pain had 4.95 hours continuous sleep (2–7) and were woken 2.5 times/night (0–6). Patients with pain every night exhibited higher ODI and HAD scores than those that did not.

Conclusions: Although it is a significant and disruptive symptom for patients, these results challenge the sensitivity of the presence of night pain per se as a useful diagnostic indicator for serious spinal pathology in a back pain triage clinic.

C. Armitstead A. Khot D. Sharp J. Powell

Study Design: A retrospective cross sectional cohort study of degeneration of the lumbar spine, using pre- and post-discography MRI scans of 28 patients, as compared to two consecutive MRI scans of an age and sex matched control group of 32 patients.

Objective: To determine whether injection of steroid into a lumbar intervertebral disc causes degeneration, as assessed by magnetic resonance imaging (MRI).

Methods: Twenty-eight patients with chronic discogenic low back pain were selected. Each had been investigated with an MRI, discography (with intradiscal injection of methylprednisolone), and a post-discography MRI scan. A randomly selected control group of thirty-two age and sex matched patients, having been examined on two occasions with MRI, was established. Two interpreters blinded to the patient groups assessed the degree of lumbar disc degeneration on the MRI scans on two separate occasions, using the Pfirrmann grading system.

Results: Kappa values proved interpretation consistency as compared with the published Pfirrmann paper. Variables of age and sex in the two groups showed no true variation in whether the discs improved, stayed the same or degenerated. The difference in the proportions for those with and without the injection gave a test statistic of 11.92 (p-value=0.002), indicating a discrepancy in the degeneration between those discs with and without an injection.

Conclusion: Previous studies on intradiscal steroid injections have shown variable results. Animal studies have shown that steroid administered intradiscally causes degeneration and primary calcification in discs. Two prospective double blind clinical trials using intradiscal steroids identified no significant benefit or improvement in the clinical outcome. This study indicates that intradiscal steroid injections cause MRI visible disc degeneration. In association with the results of the clinical trials, this study questions the indications for the use of intradiscal steroids in the management of discogenic low back pain.

P. Saxena D.S. O’Donoghue R. Pillay J. Walls

Study Design: Prospective case series of patients with tumour involvement of the spinal column consecutively admitted to a spinal unit for consideration of surgical treatment.

Objectives: To assess the impact of surgery on the quality of the life of patients suffering from metastatic or primary tumours of spine. Pre-operative assessment included the SF-36 and Oswestry Disability Index (ODI). Other scores (eg Tokuhashi) were prospectively calculated but were not used to determine suitability for surgery.

Subjects: A total of 38 patients were assessed. Of these 25 were considered suitable for surgery. Of these 25 patients, 3 died within 3 months and one had incomplete follow-up. The remaining 21 patients underwent further assessment at 3 and 6 months. A total of 8 patients are now dead in this group. Of 13 non-operated patients, one was unable to do an initial self-assessment. Of the other 12 patients, 4 were dead before second assessment. The remaining 8 patients provided us with another self-assessment. A total of 5 patients are now dead in this group.

Outcome measures: The SF-36 and ODI were repeated at 3 and 6 months. Those patients who were not considered suitable for surgery were also reassessed at 3 and 6 months, although the groups were not strictly comparable.

Results: At the time of presentation, most of the patients were severely or completely disabled. As expected, their Physical and Mental Health Component Scores of SF-36 were lower than reference values for patients with chronic ill health. The mean Bodily Pain scores were 12.84 in the operated group and 31.19 in the group managed conservatively. The initial ODI were 57 in the operated group and 59 in the conservative group. Of 25 patients who underwent surgery, 15 had posterior stabilisation and 7 had anterior reconstruction. 1 patient had a combined approach. 1 patient was stabilized with a halo vest and another had his procedures abandoned. Pre-operative and postoperative scores were compared using a paired two tail students t test. Mean Oswestry scores showed significant improvement at the 3rd month (from 57 to 48, p=0.02) and this was maintained at the 6th month. Among the various components of the SF-36 score, the most significant improvement was seen in Bodily Pain (from 12.8 to 46.8, p=0.00006). This was also maintained at 6 months. The mean Mental component scores improved significantly at the 3rd month (from 39.5 to 48, p=0.0009) and remained improved at the 6th month (44). In the non-operated group, the situation deteriorated in all respects. Mean Bodily pain scores (from 31.16 to 14.63, p=0.001), Physical component scores (from 28.48 to 19.72, p= 0.007) & Mental component scores (from 46.41 to 38.83, p= 0.05) were all significantly worse than at the initial assessment. The mean Oswestry disability score, also showed increasing disability (from 57 to 73.5) but did not reach statistical significance (p=0.16).

Conclusions: Surgery in these patients leads to a less painful and less disabled life. The quality of life improved in terms of mental health and physical health.

D. Noyes G. Walker N. Birch

Study Design: Prospective observational study.

Objective: To establish the sensitivity, specificity and cost-effectiveness of motor evoked potential (MEP) monitoring of lower lumbar nerve roots during instrumented spinal fusion.

Subjects: 161 patients undergoing elective lumbar spinal fusion monitored with the Neurosign 800 machine.

Outcome Measures: MEP evidence of pedicle breaches and nerve root over-distraction. Symptoms and signs of new neurological deficits postoperatively. EMG confirmation of neurological deficits in symptomatic post-operative patients.

Results: True positive results consisted of pedicle breaches detected in 15 patients (9.3%). Nerve root irritation on distraction was found in 9 patients (5.6%). These results allowed modification of the surgical technique to prevent subsequent neural injury. True negative results on active pedicle probing occurred in 134 patients (83.2%) and in 146 patients (90.7%) on passive monitoring. False positive results were detected in 7 patients (4.3%). Four patients had electrical connection problems and in three patients pedicle probing was positive but direct screw testing was negative. True negative results consisted of a failure of monitoring to detect clinically significant neurological events in five patients (3.1%). In four the symptoms and signs were transient, resolving within six weeks of surgery. In one, revision decompression of the L5 nerve roots was required.

Conclusions: MEP monitoring in our hands has a specificity of 95.4% and a sensitivity of 75%. The cost per case is around £75.

M.F. Grainger A. J. Stirling D.S. Marks A. Jackowski J.B. Spillsbury

Study Design: A retrospective review of case notes and histology reports.

Summary of Background Data: Up to 8% of cancer patients develop second malignancies. The vertebral column is frequently involved in metastatic disease and may represent the first manifestation of malignancy in up to 40% of patients. The rate of vertebral metastasis from a second tumour in patients with a known primary is not well known.

Objective: We sought to identify the incidence of a second primary in patients referred to our unit with spinal malignancy and a previously diagnosed primary tumour.

Subjects: 222 patients underwent definitive surgery for spinal metastatic disease of whom 135 had a prior history of malignancy.

Outcome measures: Histological tissue of origin of spinal metastasis in light of previous known malignancy.

Results: In 16 patients (11.9%) the vertebral histology differed from the initial primary. The period between first and second malignancies varied widely (19 months – 22 years). Thirteen patients (9.6%) had identifiable tissue origins for the metastasis that was not in keeping with the previous malignancy. Three further patients showed sufficient histological and imunohistochemical differences such that a further tumour of unknown origin and not de-differentiation of the previous tumour was suspected. Three previously unrecognised tumours were diagnosed on biopsy and eight on tissue obtained at definitive surgery.

Conclusion: The incidence of second primaries, in particular myeloma, presenting with vertebral metastases is significant and should always be borne in mind when assessing patients and planning treatment. Biopsy should be performed when possible. Comparison needs to be made between the histological features of the previous primary and metastasis.

Full Access
M.D. Jenkinson C. Simpson R.S. Nicholas G.F.G. Findlay T.J.D. Pigott

Study Design: Retrospective case review.

Objective: To assess factors influencing functional outcome, recurrence and survival following surgery for intradural spinal tumours

Subjects: Between January 1994 and December 2001, 115 patients had surgery for intradural spinal tumours: 76 extramedullary (48 male, mean age 54 years): 39 intramedullary (22 male, mean age 44 years).

Outcome measures and analysis: Functional outcome: Frankel scale. Recurrence: new symptoms with tumour growth. Death: post-operative or disease progression. Univariate and multivariate analysis was performed to identify features predicting post-operative functionally useful Frankel scale (4–5), recurrence and survival.

Results: 64 extramedullary tumours were excised, 12 debulked. 21 intramedullary tumours were excised, 13 debulked, 5 biopsied. Commonest tumours: meningioma, schwannoma, ependymoma, astrocytoma. 14 intramedullary tumours received radiotherapy. Mean follow-up was 45 months (range 4–117 months). There were 12 recurrent tumours. There were 8 deaths (2 post-operative, 6 disease-progression). 23% had complications (CSF leak, meningitis, wound infection/dehiscence). Functionally 96% of extramedullary tumours were unchanged/improved, 82% of intramedullary tumours were unchanged/improved. Multivariate analysis demonstrated that recurrence (Odds Ratio 28.2; 95% Confidence Interval 2.3–342.4) was the only significant factor influencing survival for intramedullary tumours. No factors investigated predicted functional outcome or recurrence in intramedullary tumours. No factors predicted any outcome in extramedullary tumours.

Conclusions: Our results were comparable to other studies. The two cases of MRSA meningitis (one death, one paralysis) reflect the growing problem of MRSA in neurosurgical units. Recurrence predicted poor survival in intramedullary tumours.

I. Collins W. Burgoyne G. Chami C. Pasapula J. Wilson-Macdonald A. Berendt J. Fairbank G. Bowden

Study Design: A six-year retrospective analysis of all instrumented spinal fusions performed in the Nuffield Orthopaedic Centre and the John Radcliffe Hospital.

Objective: To assess the incidence of infection following instrumented spinal fusion, the nature of the infecting organisms and their subsequent management.

Subjects: All patients who had undergone removal of spinal metalwork were analysed for evidence of infection. The indications for removal of metalwork included proven deep infection, refractory postoperative pain or planned removal after thoraco-lumbar fracture.

Outcome Measures: Successful treatment of infection was documented when the patient was asymptomatic and inflammatory markers remained within normal limits following cessation of antibiotic therapy. Failure was documented when the patient had recurrent sepsis, refractory pain following removal of metalwork or died.

Results: 80 spinal infections following instrumented fusions were found between 1997 and 2003. 34 of the infecting organisms were propionibacteria, 19 were coagulase negative staphylococcus, 10 were staphylococcus aureus, 8 were methicillin resistant staphylococcus aureus, 3 were coliforms, 2 were proteus, 2 were diphtheroids, 1 was alpha haemolytic streptococcus and 1 was anaerobic streptococcus. 29 of these infections were polymicrobial. Of 55 patients who had metalwork removed secondary to pain, 20 patients had proven infection postoperatively (36.3%). Preoperative inflammatory markers failed to accurately predict the presence of infection for trauma patients. Our management of infection is removal of metalwork with six intraoperative samples sent for culture and histology specimens, followed by administration of at least six weeks of intravenous or oral antibiotic, depending on the organism and its antibiotic sensitivity. Prolonged treatment is used where inflammatory markers remain raised.

Conclusions: Infection of spinal implants presents different management problems to those which follow infected total joint replacement. The lack of specific clinical, laboratory and radiological findings in patients who are subsequently diagnosed as having infections associated with spinal instrumentation presents a challenging clinical problem. We found the most predictive sign of infection following instrumented fusion of scoliotic spines was postoperative pain. CRP and ESR were unreliable as predictors of infection.

E.F. Shenouda E. Al-Delami T.J. Germon

Study Design: Retrospective outcome measurement study.

Objective: To study the functional outcome of surgery for patients presenting with severe extradural spinal cord compression.

Subjects: All patients who: 1) were surgically treated for spinal cord compression between January 2001 and December 2003, 2) presented with Frankel grade A, B or C, 3) had extradural spinal cord compression secondary to tumour or infection, and 4) were operated on by a single surgeon.

Outcome: Pre- and post-operative functional assessment was made by medical staff, a physiotherapist or both, using the Frankel grading. Frankel grade at 3 months was taken as the end point, unless death had occurred before this time, in which case the best postoperative Frankel’s grade was used.

Results: The records of 41 patients with spinal extradural tumour or infection were reviewed. Fourteen patients had Frankel grade A, B, or C. Four were female and 10 male. The median age of the group was 63.5 (range 36 to 73 years). Two had infection and 12 had tumour. The surgical objective was to decompress the neural elements and to restore and maintain the alignment of the vertebral column. One patient had multiple laminotomies alone. Ten had posterior decompression and fusion. Three had anterior and posterior decompression and fusion. Twelve immobile patients became mobile (Frankel grade D and E) and two remained unchanged. Complications were; two superficial wound infection treated with antibiotics, one deep-seated infection requiring open drainage and one extradural haematoma requiring evacuation.

Conclusions: Appropriate spinal cord decompression and reconstruction of the spinal column has a very good chance of restoring spinal cord function despite the severity of the presenting neurological deficit.

A.T. Helm P.J. Sell K.S. Lam

Study Design: A retrospective case note review.

Objective: To report on the accuracy of the Harlow-Wood bone biopsy trephine used via a percutaneous approach to obtain tissue from vertebral lesions.

Methods: 82 patients undergoing this procedure in either the University Hospital Nottingham or Leicester Royal Infirmary between 1995 and 2003 were included in the study. Data was collected regarding the provisional diagnosis, MRI diagnosis and final diagnosis based on micro-biological and histological reports.

Outcome Measures: Microbiological and histological reports were reviewed to determine the pathological nature of each biopsy. If the biopsy returned a positive diagnosis, or if the biopsy confirmed normal vertebral microbiology and histology in a patient who was subsequently disease-free, then the biopsy was deemed to have provided a diagnosis.

Results: The technique provided a diagnosis in 88% of cases, with a sensitivity of 87% and specificity of 100%. Where the provisional diagnosis was of a neoplastic lesion (n = 48), the diagnosis rate was 88%. Where the provisional diagnosis was of an infective lesion (n = 26), the diagnosis rate was 89%. Where the provisional diagnosis was uncertain (n = 8), the diagnosis rate was 88%.

Conclusions: Percutaneous biopsy of vertebral lesions using the Harlow-Wood bone trephine under fluoroscopic guidance can be performed safely and efficaciously. The high accuracy and sensitivity of this closed percutaneous technique, particularly in infective lesions, allows a timely diagnosis and subsequent early commencement of appropriate treatment.

A. Amin J Bernard F Gow N Davies S Tucker

Study Design: A retrospective case-note study.

Objective: To evaluate causes of delayed admission for patients with spinal injuries.

Subjects: 432 patients admitted between March 1998 and March 2003.

Outcome Measures: Patients were analysed with respect to Injury Severity Score (ISS); date of injury, referral and admission independently and length of hospitalisation. The delays between injury and referral (> 3 days) and between referral and admission (> 7days) were correlated to the length of hospitalisation.

Results: There were 322 males (average age, 38.6 years) and 110 females (average age, 41.8 years), with 108 complete injuries, 115 incomplete and 209 intact. The average time between injury and referral was 5.5 days (range 0–94), and between referral and admission was 10.7 days (range 0–130). 161 patients (37%) experienced a delay between injury and referral, of whom 59 (37%) were subsequently also delayed to admission. The principal reason for delay was the treatment of concurrent injuries. Even patients with complete injuries (15/43) experienced delayed referral. 112 patients (26%) experienced a delay between referral and admission. Principal reasons included the provision of beds and stabilisation of concurrent injuries. We found the delay between referral and admission (p< 0.001), the ISS (p< 0.001) and increasing neurological severity of injury (p< 0.001) to be highly significant factors predisposing to longer hospitalisation.

Conclusions: Delayed admission for patients with spinal injuries is common. Provision of beds being the most common preventable reason for delay following referral. Early liason with a designated spinal injuries unit, especially for patients with cord injury remains vitally important.

K.S. Lam R.W. Kerslake J.K. Webb

Study Design: Retrospective review.

Objective: A prospective study to evaluate for the presence of occult spinal injuries using MRI following aircraft ejection.

Summary of Background Data: The use of an ejection seat in order to escape from a stricken aircraft is associated with the exposure of significant forces. These vertical accelerative forces on the body are in the order of 15 – 25G with rates of onset of up to 250G per second. Therefore, it is common to see vertical compression fractures, mainly in the thoraco-lumbar region. Although most vertebral fractures are evident on plain radiographs, other subtle spinal injuries elsewhere may not be immediately apparent.

Methods: Between 1996 and 2003, 22 ejectees from 18 aircrafts, mean age 32 years (range 24 to 48), were admitted to a regional spinal unit for comprehensive evaluation of their injuries that included whole spine radiographs and Magnetic Resonance Imaging (T1, T2 weighted and STIR sagittal sequences). All ejections occurred within the ejection envelope and were flying below 2000 ft (mean 460 feet) and below 500 knots airspeed (mean 275 knots).

Results: All 5 ejectees (23%) with vertebral compression fractures (one at T6 and 4 in thoraco-lumbar region) had pain and tenderness in the appropriate area of the spine that was evidently detected on plain radiographs. 3 of these patients with a thoraco-lumbar fracture (AO A3.3) had more than 50% canal compromise and more than 30 degrees angular kyphosis underwent surgery. Neurological compromise consisting of acute cauda equine syndrome occurred in one patient with a L2 AO A3.3 fracture. More importantly 10 ejectees (45%) had MRI evidence totalling 21 occult thoracic and lumbar vertebral fractures. 4 ejectees had a single occult fracture, 4 had double, 1 had 3 and 1 had 6 occult fractures.

Conclusion: This study confirms the high incidence of occult vertebral injuries following vertical acceleration insult to the spine consequent to emergency aircraft ejection. Once life-saving priority measures have taken place, MRI of the entire spine remains mandatory as part the comprehensive evaluation of the patient. Early use of MRI scanning in the management will significantly increase an ejectee’s safe return to flying duties.

R.V. Kalyan A. Hamilton P. Nolan E. Cooke N. Eames M. Crone D. Marsh

Study Design: Prospective observational study.

Objectives: To score the severity of injury to (a) vertebrae and (b) intervertebral discs following thoraco-lumbar fracture, and compare the two in their ability to predict clinical outcome at 1–2 years.

Methods: 44 patients with fractures between T11 and L5 without neurological deficit were treated conservatively. All had plain X-rays and MRI scans immediately and at one year post-injury. Bony injury severity was scored on a seven-point ordinal scale based on a) comminution, b) apposition and c) kyphosis. Disc injury severity was scored on a six-point ordinal scale based on a) change in signal, b) change in height, c) indentation /herniation. Outcome was assessed at one to two years from injury (av. 18.1 + 5.6 months) Non-parametric correlation coefficients were calculated between injury severity variables and outcome variables.

Outcome measures: Modified Oswestry disability questionnaires, SF-36 questionnaires (physical and mental component summary scores – PCS and MCS), verbal and numeric rating scale of ability to perform pre-morbid activities/work. Detailed analysis of a.) pain (intensity, duration, character, distribution, etc.), b.) early morning stiffness (severity, frequency, and duration).

Results: According to the AO classification, 25% of the fractures were A1 (wedge), 9% were A2 (split), 45% were A3 (burst) and 20% were B1 (flexion-distraction with posterior ligament injury). Disc injuries scored as: grade 3 (mild) in 14%, grade 4 in 36%, grade 5 in 36% and grade 6 (very severe) in 14%. The spearman correlation coefficients between injury severity and outcome were consistently higher with disc injury severity than bony. For the Oswestry disability score the correlation coefficients for disc and bone injury severity respectively were 0.50 (p< .0001) and 0.40 (p< .05), for SF36-PCS: 0.43 (p< .005) and 0.32 (p< .05), for SF36-MCS: 0.43 (p< .005) and 0.06 (NS), for return to pre-morbid activities and work: 0.32 (p< .05) and 0.25 (p< .5), for pain intensity by numeric rating scale: 0.69 (p< .0001) and 0.41 (p< .01), and for pain intensity by verbal rating scale: 0.65 (p< .0001) and 0.28 (p< 0.1).

Conclusion: In all clinical outcomes assessed, there was consistently better prediction by measures of injury severity to the disc than the bone. This study offers possible explanation for previously low or conflicting evidence of correlation between clinical outcome and bony injury in thoraco-lumbar spine fractures uncomplicated by neurological injury. It implies that in selected patients with severe disc injury, treatment focused on eliminating the effects of the disc injury may result in better clinical outcome.

J R Crawford R J K Khan GW Varley

Study Design: A prospective randomised controlled trial.

Objective: The early management of acute soft tissue injuries of the neck remains controversial. The aim of this study was to compare an early mobilisation regime versus with treatment with a soft collar for recovery of function and activity levels after soft tissue injuries of the neck.

Subjects: Over a one year period, 108 patients presenting with a soft tissue neck injury were enrolled in a prospective trial. Each patient was randomised to either early mobilisation using an exercise regime (55 patients) or 3 weeks treatment in a soft collar followed by the same exercise regime (53 patients). Patients were followed up at 3, 12 and 52 week intervals from injury.

Outcome Measures: Visual Analogue Scores for pain, range of neck movements, activities of daily living and time taken to return to work.

Results: No differences were found between the two groups for pain, range of neck movements or for activities of daily living at any of the follow up intervals. The collar treatment group took significantly longer to return to work after injury (21 days) compared to the early mobilisation group (9 days), p< 0.05.

Conclusions: Treatment in a soft collar had no clinical benefit compared to early mobilisation in terms of recovery of function, pain or range of neck movements, but was associated with an increased time to return to work.

P Lakshmanan A Jones J Mehta S Ahuja P R Davies J Howes

Study Design: Retrospective Series.

Objectives: To analyse loss of correction of the anterior wedge angle and the components responsible for the recurrence of kyphosis after surgical stabilisation of dorsolumbar fractures, and to assess the return of functional capacity in these patients.

Materials and Methods: Between January 1998 and March 2003, 34 patients had posterior stabilisation performed with the Universal Spine System (Synthes) for dorsolumbar fracture at a single level with no neurological deficit. There were 26 AO Type A fractures, 5 Type B fractures, and 3 Type C fractures. Serial standing lateral radiographs were taken from the immediate postoperative period to the most recent follow-up. The anterior wedge angle, the heights of the discs above and below the fractured vertebra, and the heights of the vertebral bodies above, at, and below the fractured level were measured. The height at each level was measured in three segments (anterior, middle and posterior). The values were normalised to avoid discrepancies while comparing radiographs. The difference in the height of each segment measured between the immediate postoperative period and the most recent follow-up were computed. Short Form 36 (SF-36) was used to assess the functional outcome in each.

Results: The mean follow-up period was 23.6 months (9 to 48 months). The mean anterior wedge angle was 10.1 ± 7.2 degrees in the immediate postoperative period and 17.1 ± 10.9 degrees at latest follow-up (p< 0.001). The mean loss of correction was 7.0 ± 8.5 degrees (−11 to 24) and this showed a linear relationship to the preoperative anterior wedge angle. Furthermore there was a linear increase in the loss of correction of the angle as the follow-up period increased. The correlation between the corresponding difference in the height of each segment and the degree of loss of correction of the anterior wedge angle showed significant correlation to the decrease in the anterior segment height at the fractured vertebral body level (Pearson’s coefficient r=0.53 significant at 0.01 level, p=0.001). The mean physical function score from SF-36 was 56.3 and the mean bodily pain score was 49.7. There was no relationship to the angle of kyphosis at follow-up to the physical function score (r=0.12, p=0.50) and the bodily pain score (r=0.14, p=0.44).

Conclusions: There is a progressive loss of correction (increasing kyphosis) after posterior stabilisation with instrumentation that roughly approximates the initial decrease in anterior height of the fractured vertebral body. The degree of loss of correction does not depend on the type of fracture. The loss of correction is related to the preoperative angle of kyphosis.

H. Zaki T. Pigott G. Findlay

Study Design: Retrospective case review

Summary of Background Data: The Chiari malformation is a condition characterised by herniation of the posterior fossa contents below the level of the foramen magnum.

Objectives: To present the long term outcome and complication rate following hindbrain decompression for this condition.

Methods: We retrospectively analysed the results of patients who underwent hind brain decompression between 1994 and 2003. There were 70 cases with a mean age of 32 years. Follow up was carried out with clinical examination and repeat MRI scans. The mean follow up was 4.7 years. Thirty-six patients had associated syringomyelia. Patients underwent hind brain decompression through a small posterior fossa craniectomy, opening of the foramen magnum with or without removal of arch of C1.

Results: One patient died and one had a stroke which resolved except for mild facial weakness. Long term follow up revealed that 50% of the patients were asymptomatic following surgery and another 26% had marked improvement in their symptoms. One patient deteriorated post-operatively and the remainder (23%) had unchanged condition. Of the patients presenting with scoliosis 67% had no further progression in their curve.

Conclusion: This is the largest series presented from a single centre with pre- and postoperative MRI fol1ow up. Our results compare favourably with previously published literature.

N. Farooq C.E.J. Docker N. Rukin M.F. Brown E.B. Ahmed V. Jasani

Study Design: An analysis of patients admitted with cervical trauma, comparing: those managed with rigid collars until definitive management; rigid collar usage overnight; and no rigid collar usage from outset.

Objectives: To determine the safety of omitting a rigid collar following cervical trauma, whilst awaiting definitive management.

Summary of Background Data: The use of a rigid collar can result in pain, occipital sores, as well as raised intracranial pressure in head injured patients.

Subjects: Fifty one patients with proven cervical fractures were analysed. Three groups of patients were identified with respect to their initial management after admission to the ward until definitive management: 1) Hard collar, sandbags and bed rest 2) Hard collar in situ overnight and then sandbags and bed rest. 3) Sandbags and bed rest. All patients had full spinal care and precautions, with rigid collars used for any transfers. The spectrum of injury severity was similar throughout all 3 groups.

Outcome measures: Loss of alignment, neurological compromise and complications related to the rigid collar.

Results: There was no loss of reduction or progression of neurological deficit in any group. There were compliance issues in the rigid collar group. Two patients developed occipital skin problems following rigid collar use. All groups proceeded to definitive management successfully.

Conclusion: No significant adverse events were noted in any group. Management without a rigid collar depends on good nursing care. It is more comfortable for the patient and avoids the potential problems encountered with rigid collar use. In compliant patients not requiring immediate definitive management the omission of the rigid collar did not result in loss of reduction or neurological compromise. We feel such collars should be for transport and extrication only.

S Fafaxal P Sell

Study design: Prospective longitudinal cohort study with two-year follow up.

Objective: To define the standard outcome measures that describe a patient’s subjective outcome following elective spinal surgery. What constitutes a clinically important change in outcome is not well understood and few studies have addressed this issue.

Subjects: 193 patients undergoing elective spinal surgery (110 discectomy, 72 spinal decompressions and 11 other procedures) Average age 48 years.

Outcome measures: Oswestry disability index (ODI), Low back outcome score (LBO), Visual analogue score (VAS) and patient subjective assessment of outcome as Excellent, Good, Fair and Poor.

Results: There were 100 Excellent results, ODI 54 pre and 19 post. 62 Good results ODI 53 pre and 29 post. The 18 Fair results started with an ODI of 63 and improved to 51. The 13 Poor results started with an ODI of 66 and ended with 61. Similar changes occurred in VAS and Low back outcome score. An excellent outcome for discetomy, ODI reducing from 57 to 13 was different to an excellent outcome for a decompression, where the ODI changed from 54 to 26.

Conclusion: Generic spinal outcome scores are the current measurement tool of clinical change. Clinically significant change as perceived by the patient may be different for different conditions. Only a Poor outcome was associated with an ODI change of less than 10 points.

S. Morris W. Dar I. Kelly

Study Design: Prospective Cohort Study.

Objective: To describe the natural history of a cohort of patients with osteoporotic vertebral fractures treated conservatively with bedrest and a Taylor brace.

Summary of Background Data: Interest is growing in minimally invasive techniques to treat vertebral fractures in the elderly population. Amongst the benefits mooted are relief of pain and prevention of deformity. However limited background data is available concerning the long-term outcome of such patients treated conservatively.

Patients and Methods: All patients admitted to our institution over a five-year period following a vertebral fracture were identified (n=223) Of these, 61 were suitable for inclusion in the study. Following departmental approval all patients were contacted by phone and invited to participate in the study. Patients were examined in the clinic, plain radiographs were performed and the Oswestry pain score, a visual analogue pain score (VAS), and SF-36 questionnaire were completed. Patients over 65 years, involved in minor trauma without neurological deficit were included. Patients over 65 years who were involved in major trauma or non-Irish residents were excluded from the study.

Results: Mean patient age at the time of injury was 72.1 years. Mean duration of follow up was 8.2 years with a minimum follow up of 5 years. Seven patients were lost to follow up. Of the remaining fifty-four patients, five had died since their admission. According to family members none had any pain or neurological symptoms related to their spinal injuries. Forty patients attended the clinic for review while nine completed telephone questionnaires. Two patients had a clinically evident kyphosis. The mean range of anterior flexion was 78.9° ± 15°. The mean VAS pain score was 2.2 ± 2.0. No significant correlation existed between the magnitude of the initial vertebral collapse and the Oswestry or SF-36 scores. Physical Function and Bodily Pain subsets of SF-36 were no different to an age matched Irish population. No significant further vertebral collapse was noted on radiographic follow up. A small cohort of patients did develop chronic back pain. These patients’ outcome could not be predicted on the basis of initial radiographs.

Conclusion: This study supports conservative management: most patients recovered normal function and suffered little long-term pain. It was not possible to predict which patients would develop chronic back pain on the basis of initial radiographs. This calls into question the indications for undertaking vertebroplasty or kyphoplasty in the treatment of such patients.

T Pincus S Vogel A de C de Williams A Field

Study Design: To design and test a new questionnaire to assess depression and other mood states.

Summary of Background Data: Measurement of depression and of other mood states in pain patients has been criticised in recent years on the grounds that most questionnaires were not developed in pain populations and suffer from criterion contamination by somatic items. In addition, there is no accepted measurement for positive emotions which are more than the absence of depression.

Objective: To develop a reliable and brief tool to assess mood in pain patients.

Method: Non-somatic items concerning depression, anxiety and positive outlook were extracted using exploratory factor analysis from commonly used instruments (Beck Depression Inventory and Hospital Anxiety and Depression Scale) completed by over 900 chronic pain patients. Confirmatory factor analysis was used to test the internal structure of the final item set. Items were then reworded and presented as a new questionnaire (the Depression, Anxiety and Positive Outlook Scale: DAPOS) to two new samples: patients attending pain management and patients attending osteopathy. The new questionnaire was compared with several well-known questionnaires (SF-36, BDI, PCS). The structure was calibrated and tested using confirmatory factor analysis on both samples. Finally, a sub-set of patients carried out a sorting task to test for face validity.

Results and conclusion: The DAPOS performed well, indicating that it is a reliable measure of the three mood states with good initial evidence of validity in these samples.

J. Webber A. Khot D. Sharp J. Powell

Study Design: Prospective cohort study.

Objectives: To evaluate outcomes for back pain following primary single level spinal decompression for nerve root pain.

Subjects: All patients were managed in a single spinal unit with two spinal surgeons following the same management protocol. Any patient undergoing spinal fusion was excluded. Over a five-year period there were 217 patients, with a mean age of 39 years (15 to 78 years). The male to female ratio was 1:1. All had specific single level nerve root pain and definite nerve root compromise confirmed on MRI.

Outcome Measures: All patients were assessed preoperatively and followed at 3, 6, 12 and 24 months using a standard back pain questionnaire including visual analogue scores for leg and back pain, a pain diagram, Oswestry disability index (ODI), Zung depression index and somatisation scores.

Results: We report a statistically significant improvement in back pain post-operatively with 68.6% of patients improving their score (p < 0.001 sign test) with 19.5% reporting complete relief. This improvement was sustained over the follow-up period. Post-operative improvements in back pain correlated well with post surgical reduction in leg pain score, and ODI. Patients with increased back pain scores (> 5) at presentation, were more likely to report an improvement. In this group 80.5% reported a significant reduction in their back pain following surgery. No correlation could be identified between back pain scores and somatisation and Zung depression indices, age, gender or employment status.

Conclusions: These results are contrary to other reported series and suggest the prognosis for back pain following primary single level spinal decompression may be better than anticipated.

J. Andrews A. Jones S. Ahuja J. Howes P. R. Davies

Study Design: Retrospective review.

Objectives: Rugby union has recently become a highly-paid professional sport. Players requiring anterior cervical discectomy wish to know the effect this will have on their career. To answer this question, the result of the above procedure in professional rugby players was studied.

Methods: A retrospective notes review and telephone interview were conducted on 19 professional rugby players who had a cervical discectomy between 1998 and 2003. Pre and post operative symptoms and numbers returning to rugby after surgery were assessed.

Results: Neck pain was eradicated in eight (42%) of the players, nine (47%) achieved partial relief and two were not helped. Brachalgia was eradicated in fifteen (79%) individuals, improved in two (10.5%) and two (10.5%) had no relief. Fourteen (74%) returned to rugby union, the majority at six months post operatively (range – five to 17 months). Thirteen (68.5%) returned to their pre-operative level of rugby; one dropped to a lesser division and five have never played rugby again (three due to physical inability, one due to club reluctance to insure and one because of a separate injury). Two of the players that returned to rugby have subsequently retired because of neck symptoms. They played three and two years post-operatively at first-class level.

Conclusion: Return to rugby union after anterior cervical discectomy is both likely and safe and therefore need not be a career ending procedure.

J. Fairbank H. Frost J.Wilson MacDonald L. Yu O. Rivero-Arias H. Campbell A. Gray

Study Design: Prospective randomized study.

Objectives: To compare the strategy of spinal fusion with that of rehabilitation for patients with chronic low back pain.

Methods: A multicentre trial of 349 candidates for spinal fusion (where both patient and surgeon were uncertain of the outcome) were randomised to either an operation that the surgeon considered was most appropriate for that patient or to an intensive rehabilitation programme. Rehabilitation was based on a 3 week (15 day) model of exercise therapy, spine stabilisation techniques and education using cognitive behavioural principles. Follow-up was at least 2 years from randomisation. The trial was 90% powered to show a 4 point difference between groups at α= 0.05. A full economic analysis is available.

Outcomes Measures: Oswestry Disability Index (ODI); the Shuttle Walking Test (SWT); SF-36 and EuroQol EQ-5D.

Results: 176 patients were randomized to surgery and 173 to rehabilitation. Demographic features including sex, age, diagnosis (spondylolisthesis, post-laminectomy syndrome, others) duration of back pain, smoking history, litigation, employment status, planned numbers of fused levels and baseline ODI were similar for both groups.

Results: For the surgery group the mean ODI improved from 46.6 (SD 14.5) to 34.9 (SD 21) at two years. For the rehabilitation group mean ODI improved from 44.8 (SD 14.8) to 36.2 (SD 20.6) at two years. For the surgery group the mean SWT improved from 254 (SD 209) to 350 (SD 244.8) at two years. For the rehabilitation group mean SWT improved from 247 (SD 185) to 310 (SD 203) at two years. For the surgery group the mean SF-36 Physical component score improved from 22.2 (SD 18) to 43.6 (SD 32.1) at two years. For the rehabilitation group the mean SF-36 Physical component score improved from 24.0 (SD 20.6) to 40.5 (SD 31.1) at two years.

Conclusions: This is a comparison of treatment strategies: There was no clinical or statistical difference in outcome between the strategy of spinal fusion and that of rehabilitation. Patients randomised to surgery (spinal stabilisation) and patients randomised to rehabilitation have indicated a treatment effect, but this may be due to natural history. The surgery results parallel those reported in other trials. At two years the treatment costs of the surgery arm were approximately twice those of the rehabilitation arm. The costs of rehabilitation depend on how many patients opt for surgery (22% in this trial). “Failed” non-operative treatment is commonly listed as an indication for surgery. “Failed” non-operative treatment should include intensive rehabilitation appropriately supported by the treating surgeon.

P Sell

Study design: Prospective longitudinal cohort study with three month and one year follow up.

Objective: To determine what factors influence standard spine and urinary outcome measures at 3 months in cauda equine syndrome with particular attention being given to timing of onset of symptoms and timing of surgery.

Subjects: There were 31 cases submitted from the membership of BASS who underwent urgent surgery for cauda equina syndrome. Three month follow up was achieved in 25 (80%).

Outcome measures: Oswestry disability index (ODI), Visual analogue score for leg pain, Visual analogue score for back pain and incontinence questionnaire using a short form MRC outcome tool.

Results: The average age was 43 years. Ten patients had surgery within 48 hours of onset of symptoms, the remainder had more than 48 hours to surgery. Most patients received prompt attention after reaching secondary care with only four waiting more than 24 hours for surgery after scanning. There was no difference in ODI. VAS leg and back were better in the less than 48 hours group. Urinary symptoms and satisfaction did not appear to be influenced by surgery within 48 hours.

Conclusion: The duration of symptoms prior to surgery does not appear to influence the short-term outcome as measured by the Oswestry Disability Index and specific questions related to satisfaction with urinary outcome measures.

C.I. Adams B.J.C. Freeman A. J. Clark S. Pickering

Study Design: A consecutive retrospective cohort including all patients treated by a single consultant spinal surgeon (BJCF) with targeted foraminal epidural steroid injection (FESI) for radicular pain.

Objective: To assess the efficacy of targeted foraminal epidural steroid injection (FESI) for radicular pain in preventing surgical intervention.

Summary of Background Data: 90% of sciatica resolves within 90 days. Beyond this period, decompresssive surgery for pain relief maybe considered. Open surgery however carries attendant risk including nerve root injury, dural laceration, cauda equina syndrome, deep infection, recurrent disc prolapse, epidural fibrosis and post-discectomy lumbar instability. Peri-radicular infiltration of local anaesthetic and steroid has been shown to reduce pain, at least in the short term. We were interested in whether FESI could obviate the need for surgery in refractory cases of nerve root pain.

Methods: 83 consecutive patients (45 female, 38 male) with a mean age of 51 years (range 24 to 87) presenting between November 2000 and February 2003 with radicular pain were treated with targeted FESI. 55 patients had a principal diagnosis of disc prolapse, 20 had lateral canal stenosis and 8 had degenerative spondylolisthesis. Fourteen had previous surgery and 38 had previous caudal or lumbar epidural injections.

Outcome Measures: Pain was assessed using the Visual Analogue Score and disability by the Oswestry Disability Index. The product-limit method of Kaplan Meier was used to assess the time to further procedure or the date of last review.

Results: 21 of 83 patients (25.3%) underwent an open procedure (discectomy/decompression) within the designated time period (median 20 months). Median time to open procedure was 6.5 months (mean 8.2 months). Repeat FESI was required in 16 patients (19.2%). The remaining 46 (55.4%) patients avoided any further procedure at a median of 20 months (range 13 to 36). No complications resulted from these procedures.

Conclusions: Targeted foraminal epidural steroid injection can resolve radicular pain caused by varying pathologies. Surgical procedures (decompression/discectomy) can be avoided in 74.7% of cases up to a median of 20 months thereby avoiding unnecessary surgical risk.

G.L. Cribb D.C. Jaffray

Study Design: Review of patients with massive disc prolapse, with a minimum of 50% canal occlusion, treated non-operatively.

Objectives: To demonstrate the behaviour of massive disc prolapse treated non-operatively.

Subjects: Patients with massive disc prolapse whose symptoms had started to resolve or who had refused surgery.

Outcome Measures: Spontaneous reduction of disc herniation on MRI scans.

Results: There were 10 patients who have had massive lumbar disc prolapse treated non-operatively. All had MRI scans which showed a lumbar disc prolapse occluding greater than 50% of the canal diameter on the axial cuts. The average occlusion of the canal was 62%. Repeat MRI scans showed reduction of the disc prolapse in all cases, with an average of 83% (range 68–100) reduction in the canal occlusion. The scans were performed between 6 and 68 months apart. 9/10 patients had resolution of leg pain. One patient had persistent leg pain despite complete resolution of the disc prolapse. He went on to have an exploration of the right S1 nerve root. No disc prolapse was identified and the S1 root was free and healthy. This however resolved the majority of his leg pain.

Conclusion: We have demonstrated that the natural history, in these cases of massive prolapse was to resolve both clinically and radiologically in the majority of cases.

S. Aspinall S. Mohammed J Burke P.L. Sanderson

Study Design: A prospective evaluation of 40 consecutive patients with sciatica who had ‘Normal’ MRI scans, were further investigated with Nerve Root Injections (NRI), and subsequent surgery in those who had relief of symptoms.

Objectives: To evaluate the diagnostic value of NRI’s in the presence of normal MRI scans and to assess the aetiology of the sciatica.

Summary of Background Data: Since the advent of MRI scans the use of NRI’s has been in decline as a diagnostic tool. There has been no study in their usefulness when the MRI has been reported as showing no evidence of nerve root compression, and furthermore what the surgical findings were in the patients who went on to exploration.

Methods: 40 Patients with sciatica, of minimal duration of one year, in whom the MRI scan had been reported as showing no evidence of nerve root compression by an independent observer, had diagnostic NRI’s performed. Those patients that had reproduction of and subsequent temporary relief of their sciatica had surgery.

Outcome Measures: Walking distance, Analgesic Requirements, Sleep disturbance and VAS.

Results: Of the 40 patients, 25 had no benefit, 4 patients had permanent relief and 11 had temporary relief. These 11 patients underwent surgery. All patients undergoing surgery were L5 nerve root explorations. In 9 cases the compression was by the ligamentum flavum and in 2 at the foramen. Of the eleven cases operated on 9 had complete relief of symptoms and 2 were unchanged.

Conclusions: MRI scans do not show a cause for sciatica in all patients as it is not a dynamic test. In the presence of a normal MRI scan, NRI’s should be performed.

L Ng N Chaudhary P Sell

Study Design: A randomized, double blind controlled trial.

Objectives: Various studies have examined the therapeutic value of peri-radicular infiltration using treatment agents consisting of local anaesthetic and corticosteroids for radicular pain. The main objective is to determine the treatment effect of corticosteroids in peri-radicular infiltration for radicular pain. We also examined prognostic factors in relation to the outcome of the procedure.

Subjects: Eligible patients with radicular pain who had unilateral symptoms who failed conservative management were randomised for a single injection with bupivicaine and methylprednisolone (b+s) or bupivicaine (b) only.

Outcome measures: Oswestry Disability Index (ODI), Visual Analogue Score (VAS) for back pain and leg pain, claudication walking distance and patient’s subjective level of satisfaction of the outcome.

Results: We recruited 43 patients in the b+s group and 43 patients in the b only group. The follow up rate is 100%. There is no statistically significant difference in the outcome measures between the groups at 3 months (change of the ODI [p=0.7], change in VAS [back pain, p=0.68; leg pain, p=0.94], change in walking distance [p=0.7]). No statistical difference in the change in VAS score between stenotic group and disc herniation group at 3 months. Further subgroup analysis also showed no difference in the outcome between contained and non-contained herniation group.

Conclusion: Clinical improvement occurs in both groups of patients. Corticosteroid did not provide additional benefit.

L Ng S Tafazal P Sell

Study design: Prospective cohort study.

Objective: Despite wide acceptance of decompression surgery for spinal stenosis, the reported success rates remain variable. Our aim is to investigate the value of various predictors of functional outcome in patients undergoing primary lumbar decompression surgery secondary to degenerative spinal stenosis.

Subjects: Eligible patients who had primary posterior lumbar decompression surgery for degenerative spinal stenosis with follow up for 2 years.

Outcome measures: Oswestry Disability index (ODI), Low Back Outcome Score (LBOS), Visual Analogue Score (VAS), claudication walking distance and patient’s subjective assessment of the outcome of the surgery.

Results: Ninety-nine patients who had primary lumbar decompression surgery were recruited between July 1994 and December 2001. The follow up rate was 100% at one year and 76% at two years. There is a statistical significant association between duration of symptoms and the change in ODI, change in LBOS, change in VAS and change in walking distance both at one year and two years follow up. One-way analysis of variance also showed that the groups of patients with symptoms less than 33 months have a much better functional outcome at two years follow up. We have not found modified somatic perception score, modified zung depression score and gender to influence the outcome of the surgery.

Conclusion: This study indicates that patients with a prolonged duration of symptoms have a less favourable functional outcome. Patient’s satisfaction is greatest if surgery occurs within 33 months.

Full Access
G C Mclorinan M G Mcmullan A Mcdowell JV Glenn E A Cooke N Eames A H Hamilton P Nolan S Patrick

Study Design: In a prospective study, intervertebral disc material from 64 patients undergoing discectomy for sciatica and 23 control patients was analysed for the presence of bacteria.

Objective: There have been many theories postulated as to the pathogenesis of back pain and sciatica. Possible inflammatory or auto-immune aetiologies have been suggested. Stirling et al (2001) suggested a possible link between sciatica and bacterial infection by demonstrating the presence of bacteria in disc material from 19 of 36 patients with severe sciatica. Previously, we developed methods for improved detection of bacterial infection associated with failed hip implants (Tunney et al 1999).These techniques have now been applied to the detection of bacteria in intervertebral discs from patients with sciatica.

Outcome Measures: Bacterial culture and non-culture immunofluorescence microscopy, using specific monoclonal antibodies, were applied to intervertebral disc material for the detection of bacterial infection. The results were also compared with functional scores before and after surgery.

Results: This study found that 20% (n=13) of patients suffering from sciatica had culture-positive disc material compared to 9% (n=2) of controls. The anaerobe Propionibacterium acnes was the predominant bacterium isolated in both case and control groups. Bacteria were also identified in skin, wound tissue and wound washings in some patients.

Conclusions: We are unable to demonstrate an association between sciatica and infection (p=0.335). This study suggests that bacteria detected in retrieved disc material may result from skin contamination during surgery.

F.A. Carroll S.M. Cockshott S. Mulay P. Carter I. Agorastides B.H. Pennie

Study Design: A prospective cohort study of patients undergoing surgery for prolapsed intervertebral disc.

Objective: To assess a patient’s ability to recall information discussed pre-operatively at the time of informed consent six weeks following surgery.

Subjects: Sixty-one consecutive patients undergoing discectomy for prolapsed intervertebral disc with follow up six weeks after surgery.

Outcome measures: Patients were assessed, using a pre-prepared questionnaire, to establish their understanding of disc surgery prior to signing a consent form. All information on the questionnaire had previously been given to the patient at the time of being put on the waiting list via a copy of the clinic letter to the general practitioner. If patients were unable to complete the questionnaire, they were then tutored using visual aids such as posters and models until they were able to answer the questions correctly. The consent form was then signed. Six weeks following surgery, patients were then asked the same questionnaire to establish their ability to recall the information discussed pre-operatively about disc surgery.

Results: Prior to tutoring, 20 % of patients were unable to recall that their symptoms were due to disc pathology and that surgery to remove the disc would relieve their symptoms. They were also unable to recall the success rate of surgery. Following surgery, only half of this group of patients could recall these facts. Only 32% of patients were able to recall two or more risk factors of surgery prior to tutoring. This improved to 45% following surgery. Pre- and post-operative questionnaire scores were analysed using a paired t-test. There was no statistical improvement in questionnaire scores long term following tutoring.

Conclusion: In this group of patients, extensive tutoring with the use of visual aids as an adjunct, does not statistically improve their ability to recall important information about surgery for prolapsed intervertebral disc and the risks associated with it.

Z.H. Dailiana S.E. Varitimidis N. Rigopoulos M. Hantes T. Karachalios K.N. Malizos

Introduction: Suppurative conditions in closed cavities/tunnels require surgical drainage and irrigation for elimination of infection. The purpose of this study is to evaluate the pattern of extension of infections in hand compartments and the necessity for intraoperative and continuous postoperative catheter irrigation.

Material and Methods: Compartmental infections of the hand and wrist (CIHW) were diagnosed in 42 consecutive patients involving the flexor tendon sheaths (pyogenic flexor tenosynovitis) (28); the tip (3); the carpal tunnel (2); or extended to multiple compartments including the above mentioned and the thenar, midpalmar, web and Parona’s (9). Three patients had diabetes mellitus, 2 suffered from bites, 15 had penetrating injuries and 7 were working with animals or meat products. Fifteen were previously treated in other centers. After meticulous clinical evaluation to define all the involved compartments, all patients were treated with drainage of the respective compartments, sheath irrigation and appropriate antibiotics, whereas continuous postoperative catheter irrigation was used in 24. Hand therapy started the third postoperative day.

Results: Mean follow-up time was 20 months. The most common pathogen was S. aureus (14 patients) whereas cultures were negative in 15. Three patients received additional fungal treatment. Results were excellent or very good in 25 hands and good in 12 regaining full or near full ROM. Recurrence of infection in 4 (that were initially treated inadequately in other centers or had intraoperative sheath irrigation without postoperative continuous irrigation) necessitated a revision of the procedure with extensive debridement and continuous postoperative irrigation. Finally, 1 patient developed complex regional pain syndrome.

Conclusions: A high index of suspicion and profound knowledge of the anatomy is essential for early diagnosis and prompt surgical treatment of CIHW. Initially «benign» infections often extend in multiple compartments of the hand as a result of inadequate initial treatment. Intraoperative irrigation is not always adequate for the resolution of infection, especially in neglected cases or cases with underlying conditions. Early surgical debridement of all the involved compartments in combination to continuous postoperative irrigation, administration of appropriate antibiotics and precocious onset of hand therapy is the treatment of choice for these potentially debilitating, infectious conditions of the hand.

T. Kälicke J. Schierholz U. Schlegel G. Printzen D. Seybold M. Köller G. Muhr S. Arens

Introduction: Since the establishment of osteosynthesis as the treatment of choice for bone fractures, the issues relating to complications and their prophylaxis have become a major topic of scientific discussion and research in the field of traumatology. Infection of the bone and soft tissue represents one major complication that arises after the implantation of osteosynthetic material at the fracture site. The treatment of these infections is often time-consuming and involves repeated, extensive surgical interventions. The aim of this study was to acquire information about the effect of an antibacterial and biodegradable poly-L-lactide (PLLA) coated titanium plate osteosynthesis on local infection resistance.

Material and Methods: We compared infection rates in white New Zealand rabbits after titanium plate osteosynthesis of the tibia with or without antibacterial coating after local percutaneous bacterial inoculations at different concentrations (2x105–2xlO8):

group I (n=12):uncoated titanium plate,

group II (n=12): PLLA coated titanium plate,

group III (n=12): titanium plate coated with PLLA + 3% Rifampicin and 7% Fusidic acid, group IV (n= 12): titanium plate coated with PLLA + 2% Octenidin und 8% Irgasan.

The plate, the contaminated soft tissues and the underlying bone were removed under sterile conditions after 28 days and quantitatively evaluated for bacterial growth. A stepwise experimental design with an “up-and-down” dosage technique was used to adjust the bacterial challenge in the area of the ID50 (50% infection dose). Statistical evaluation of the differences between the infection rates of both groups was performed using the two-sided Fisher exact test (p< 0.05).

Results: The overall infection rate was 50%. For group I and II the infection rate was both 83% (10 of 12 animals). In group III and IV with antibacterial coating the infection rate was both 17% (2 of 12 animals). The ID50 in the antibacterial coated groups III and IV was recorded as lxl108 CFU, whereas the ID50 values in the groups I and II without antibacterial coating were a hundred times lower at lxl106 CFU, respectively. The difference between the groups with and without antibacterial coating was statistically significant (p=0.033).

Conclusions: Using an antibacterial biodegradable PLLA coating on titanium plates, a significant reduction of infection rate in a canine infection model could be demonstrated. For the first time we were able to show, under standardized and reproducable conditions, that an antiseptic coating leads to the same reduction in infection rate as an antibiotic coating. Taking the problem of antibiotic-induced bacterial resistance into consideration, we thus regard the antiseptic coating, which shows the same level of effectiveness, as advantageous.

C. Wagner T. Bernschneider A. Wentzensen V. Heppert G.M. Hänsch

Introduction: Posttraumatic osteitis is a localised inflammatory process leading to tissue destruction and eventually osteolysis. The molecular mechanisms underlying the disease progress are not yet fully understood. In a previous study we demonstrated infiltration of polymorphonuclear neutrophils (PMN) into the site of infection; the PMN were highly activated as seen by upregulation of the activation-associated surface receptors CD14 and CD64. In this study we analysed the superoxide generation by the infiltrated PMN as possible pathomechanism of the local tissue destruction.

Material and Methods: Ten patients with device-associated osteomyelitis requiring surgery were recruited into the study. When removing the infected implant the site was rinsed intraoperatively. The leukocytes were recovered, then activation-associated surface receptors were determined by cytofluorometry as was superoxide generation by reduction of cytochrome C.

Results: 1–2 x 107 leukocytes were recovered from the «lavage» fluid; 80 to 90% were identified as PMN. The PMN were highly activated as seen by an upregulation of CD14 and CD64, and a concomitant downregulation of the selectin CD62L. In response to phorbol ester (PMA) the superoxide production of the infiltrated PMN was enhanced when compared to peripheral PMN of the same patient. The infiltrated PMN, but not the PMN of the peripheral blood, responded to the bacterial peptide f-Met-Leu-Phe (f-MLP) with superoxide production, indicating an enhanced responsiveness of the cells. The underlying molecular mechanisms were analysed in vitro using PMN of healthy donors: only the induction of superoxide production by f-MLP, but not by PMA, required a «priming» of the cells, for example by low doses of lipoploysaccharide (LPS) or cytokines (e.g. TNFa, IL-8).

Conclusions: In posttraumatic osteomyelitis PMN infiltrate the infected site; they are locally activated as seen by an upregulation of the appropriate receptors and by “priming” for superoxide generation. Priming of local PMN could on one hand potentiate the bactericidal activity, on the other hand contribute to tissue destruction. The occurrence of viable bacteria and activated «armed» PMN at the same site points to an esacpe mechanism, possibly due to biofilm formation. Due to their cytotoxic and proteolytic potential PMN might participate in local tissue destruction and osteolysis.

F.M. Jaberi1 M.A. Erfani1 M. Nicfar1 N. Tanideh2 B. Gramizadeh3

Introduction: Despite the present routine treatment of septic arthritis with antibacterial agents, articular damage is persistent and frequently leads to loss of joint function. The aim of this study was to assess the effect of intra-articular corticosteroid added to systemic antibiotics in the treatment of experimental staphylococcal knee joint infection in rabbits.

Material and Methods: Thirty rabbits were injected in their knees by staphylococcus aureus. The rabbits were divided into 3 equal groups. In group A, rabbits received no treatment. In group B, rabbits were treated with systemic antibiotics alone. Group C, received systemic antibiotics and intra-articular corticosteroid. After 16 days animals were killed and the knee joint X-Ray as well as histopathological-histochemical parameters were assessed.

Results: All rabbits survived the experiment; the treated groups (B, C) had better histopathological-histochemical scores in comparison with the untreated group (A). Group C had significantly better scores in joint sections in comparison with group B (mean SD=6.7 ± 2.3 v 4.0 ± 2.4, P= 0.019). Lower damage in the former group was expressed in lesser clustering of chondrocytes, proteoglycan depletion, and severity of synovitis. Radiological soft tissue scoring was significantly better in group C in comparison with group B. Three peri-articular abcesses were observed in group C but none in group B.

Conclusion: Addition of intra-articularly administered corticosteroid to antibiotic treatment of septic arthritis improved histopathological-histochemical parameters in this experimental setting, although on account of the clinical observation of three cases with peri-articular abcesses in this group, caution is warranted in the interpretation of these results.

V. Alt T. Bechert P. Steinrücke P. Seidel E. Dingeldein E. Domann R. Schnettler

Infections in total joint arthroplasty, particularly with multiresistant bacteria, are a serious problem. A new nanoparticulate silver cement had previously shown good biocompatibility combined with good in vitro antimicrobial activity against multiresistant bacteria.

The purpose of the current study was to evaluate the antibacterial activity of nanoparticulate silver cement against biofilm-building methicillin-resistant S. aureus (MRSA) in a rabbit model and to compare it to that of gentamicin-loaded cement.

Gentamicin cement or nanoparticulate silver bone cement was injected into the proximal half of one femur in 10 animals, respectively. Before hardening of the cement 107 or 108 colony forming units of MRSA with high gentamicin resistance were inoculated at the cement bone interface in 5 rabbits of each group. The animals were euthanized after 14 days and both the cement adjacent bone and the cement itself were studied using microbiological and histological methods. Infection was defined as positive culture growth from the bone and/or cement samples.

Infections rates were 100% for the gentamicin group (10 of 10 animals had infection) and 30% for the NanoSilver group (3 of 10 animals). Thus, nanoparticulate silver bone cement significantly reduced infection rates by 70%.

Nanoparticulate silver cement exhibited good antimicrobial activity in the prophylaxis of cement-related infections with MRSA and is therefore a promising alternative in total joint arthroplasty.

J.C. Messina C.L. Romanò R. Chiapparino M. Gallazzi M. Castellani G.P. Garbagna E. Meani

Introduction: Reports about the usefulness of FDG-PET in detecting infections were few in the last years but are greatly increasing in number in the recent years. The interest for this method is related to the demonstration that FDG uptake is increased in cells with elevated glycolitic activity as neoplastic cells, neutrophils, activated macrophages, probably bacteria. As far as a neoplasm is excluded, FDG uptake is increased in inflammatory sites. This study was done to test the possible use of this method in painful total hip-replacement diagnosis.

Materials and methods: A prospective study on 24 patients (33 hip arthroplasties) affected by painful total hip replacement was conducted. All patient has blood test, X-ray examinations of hips and chest, Ultrasound scan, cultures from sinus tract or hip aspiration, Tc99m MDC bone scan (SPECT), FDG-PET. Areas of uptake were evaluated and compared. Fifteen patients were operated on (9 two-stage revisions, debridements), during operation cultures were repeated and bone biopsy were done at the sites of icreased PET uptake. Bone and soft tissue debridement was specifically performed on site of PET uptake with maximal preservation of bone stock.

Results: Infected hips were 20. Infection was demonstrated by positive culture and positive biopsy in all cases. Sensibility and specificity of PET were respectively 100% and 92%. The study of tracers uptake showed that these are complementary and give different information. All patients who were operated on were reviewed with a mean follow up of 7 months (range 3 months-15 months ). The nine patients who had revision were free of infection at follow-up.

Discussion: from our experience PET is easy to perform, has an excellent sensibility and good specificity and can be placed at the end point of the flow-chart for diagnosis of total hip replacement infection (preceeded in any case by standard X-Rays and bone scan). Moreover PET scan could be useful in pre-operative planning of revision surgery as it has better anatomical definition than traditional scans and may allows surgeon to localize on three planes infected bone and soft tissues. Therefore at the moment this tool has high costs so should be used in selected cases. Its real usefulness in revision surgery has to be confirmed by a longer follow-up of treated cases.

H. Kohler F. Heppert A. Wentzensen (D)

Introduction: The osteitis of the tibia still is a common problem in orthopaedic surgery. Long lasting treatment time and possible recurrent infections bring a lot of medical and social problems to the patient. We compared in this study a group being treated in the conventional way by bone grafting the defect with another group, which had an Ilizarov procedure to find out, which method brings better results for the patient.

Material and Methods: Each group consisted of 65 patients about the same age. The follow up time was averaged 7.5 years. The size of the defect was in the conventional group 2.5 cm in the Ilizarov group 6.4 cm. Patients were classified to the Cierny Mader Classifications in both groups. Each patient was examined at the time of follow up clinically and radiologically. Special topics were: Pain, job, social activity etc. Scores were evaluated using SF 36. More than this, a questionnaire was handed out to each patient which was filled out after the investigation and was mailed back from home, not to influence the patient during the investigation. These dates were scored by Nottingham Health Profile.

Results: Healing time with the Ilisarov group was longer on the total way, but related to 1 cm defect shorter. Time of hospitalization, number of operations were very similar in both groups. There were more leg length discrepancies and axis deviations in the Ilizarov group. Refering to the job 67% of the Ilizarov group, but only 48% of the conventional group returned to their original profession. Life quality (SF 36 and Nottingham Health Profile) testing was better in the Ilizarov group too. Recurrent infection was seen in the conventional group in 13.8%, in the Ilizarov group only in 9% including the pin track Osteitis. A recurrent infection in the callus distraction group was seen only in 1 case.

Conclusions: Ilizarov treated patients show better long tenn results, even if they are classified B-type hosts, according to the Cierny Mader Classification. They return earlier to work and demonstrate better life quality results. In future these results might even be better, if axis deviations and leg length discrepancies could be minimized. With host B patients the conventional treatment should not be favoured, Ilizarov procedure brings better results too.

V. Alt P. Steinrücke T. Bechert P. Seidel E. Domann R. Schnettler

Introduction: Deep periprosthetic infections are infrequent but devastating situations in total joint arthroplasty. During the last years the total number and the percentage of total joint infections with multiresistant bacteria has increased. The aim of this study was to investigate the antimicrobial activity of a new bone cement loaded with nanoparticulate silver against bacteria with different antibiotic resistance.

Material and Methods: An in vitro proliferation test was used to test antimicrobial properties of 1% nanoparticulate silver bone cement, gentamicin-loaded, tobramycin-loaded and plain bone cement. This in vitro testing method consisted of two incubation steps. During the first step the tested bacteria could adhere to the bone cement surface. In the second step bacteria either seeded out of vital daughter cells in case of no antimicrobial effect of the cement or were killed by the antibacterial properties of the cement. Seeding out of daughter cells was detected by a microplate reading system resulting in specific time proliferation curves. Several staphylococci and gram-negative strains with different resistance profiles against methicillin, tobramycin, and gentamicin were tested including MRSA and MRSE.

Results: 1% nanoparticulate silver bone cement showed bactericidal effect against all tested strains, including MRSA and MRSE. Gentamicin and tobramycin cement was not effective against bacteria with high resistance level against the respective antibiotic. Plain bone cement was not effective against any strain.

Conclusion: 1% nanoparticulate silver bone cement exhibited excellent antibacterial properties that could not be reached by gentamicin or tobramycin-loaded cement. Good activity against MRSA could also already be shown in a first animal trial. If further in vivo investigations confirm these promising results nanoparticulate silver bone cement is a new alternative for prophylaxis in total joint arthroplasty.

F.M. Jaberi G.H. Shahcheraghi M.A. Erfani M. Ahadzadeh

Background/objective: Although several prospective trials have shown the efficacy of sequential intravenous followed by oral antimicrobial regimen in treatment of bone and joint infections, considerable uncertainty exists about ideal antibiotic regimen and optimal duration of antibiotic therapy.

The aim of this study was to demonstrate that short course antibiotic therapy combined with surgical drainage and followed by oral antibiotic therapy is quite adequate and suggested a scoring system as a comfortable and reliable tool to adjust the route of drug administration.

Methods: Thirty-three cases of acute hematogenous bone or joint infection were randomly treated with short term (7 days for joint infection, l0 days for bone infection) or a long-term (14 days and 21 days, respectively) intravenous antibiotics after surgical drainage. The treatment outcome was measured through a detailed scoring system that included the ability to eradicate infection, the functional status of the limb, and the radiological appearance of the bone and joint.

Criteria for discontinuation of parenteral antibiotic Scoring criteriapoints

Clinical evaluation

A: improved active motion of the joint: l

B: Painless active motion of the joint: 2

C: improvement in A & B:3

Radiological findings

A: progressive osteolysis ormultifocal involvement: 0

B: absence of the above findings*: 1

Laboratory evaluation

A: drop of 50.00/mm3 in WBC count or return to normal range (5.000–10.000 /mni3): 0.5

B: drop in ESR of 30 mm/hr or return to level of 30 mm/hr or less: 0.5

Total score: 5

*Pure periosteal elevation received a score of 1.

Patients with a score > or equal to 4 would be switched to oral antibiotic.

Results: The average follow up was 19 months. The scoring system had the following results: Infection was eradicated in both groups. Radiological scoring for septic arthritis was full for both groups and had a non-significant difference P> 0.05 between the 2 groups for osteomyelitis.

The mean functional scoring between the short-term group and long-term group were similar P> 0.05.

Overall, excellent or good results were achieved in both groups. No fair or poor results were observed. The average hospital cost for a patient in long-term group was twice that of a patient in short-term group.

Conclusion: It is concluded that for bone or joint infection in children who have received appropriate and early surgical treatment, intravenous antibiotics given for 7 days in joint infections and 10 days in bone infections, followed by 4 weeks of oral antibiotics, is an adequate treatment.

A decision on prolonging the duration of parenteral antibiotics should be based on a combination of clear clinical, laboratory, and radiographic criteria, such us the scoring system presented in this article.

Salfl Cosimo F. Da Rin M. Ciotti F. Centofanti A. Prantera M.A. Rosa

Introduction: SCC is a rare but well-known complication of chronic osteomyelitis since 1835, with an incidence from 0.5 to 2.3%. Amputation has generally been the treatment of choice; in selected Patients, Limb-salvage procedures have been employed 28 cases are presented here.

Materials and Methods: From 1975 to 2000, 4089 Patients with ostemyelitis were admitted to our service. SCC was present or arising in 28 cases: they were all middle aged males, except one woman. Mean age was 56.6 yrs, range 40–72. Clinical data were pointed out, and in all of them single or multiple biopsy was performed.

Results: All the cases were affected by SCC in the lower limb: tibia was the main site 20, followed by hip (2), foot (2), femur (4). Bone infection was born over 40 yrs. before (range 21–57). Patients were painfree up to 51 years. From worsening symptoms to admission, time was about 9 months (1–24). 19/28 cases came with wide leg ulcers, the rest with one discharging sinus or more (up to 8). In 6 cases pathological fracture was observed. Microbiological yields were not significant.

13 cases were transferred to Bone Tumors Centers: 10 of them were lost at F.U. Among those who underwent amputation: in two of them, local recurrence was observed, and one deceased after two years. Another Patient deceased for non-related heart problems.

Conclusions: In chronic osteomyelitis relapses are frequent, malignancy rare. If clinical changes in lower limb are observed, (pain, increased discharge, fethor, enlarging ulcer), SCC must be suspected. Early diagnosis is vital: biopsy should be wide, deep, multifocal, including the marrow space. Amputation is the treatment of choice. Metastases occur in 18 months; prognosis after 3 yrs from surgery is good.

Aetiology is still unknown: there is no evidence for an initiating factor. About favouring conditions ( inflammation, lower limb,) data are not clear enough.

In limb preserving surgery, our experience suggests one-stage procedures, avoiding to re-create chronic inflammation near the site of cancer.

A. Moroni C. Faldini F. Pegreffi A. Hoang-Kim S. Giannini

Introduction: Deterioration of bone-pin interface, causing pin loosening and infection, is a major cause of postoperative complications following external fixation. This paper presents the results obtained using hydroxyapatite (HA)-coated pins in various bone types, such as osteoporotic bone.

Materials And Methods; In an animal study comparing HA-coated and standard pins, pin insertion and extraction torque were measured. Subsequently, a clinical study compared insertion, extraction torque and pin-tract infection rate of standard and HA-coated pins implanted in healthy and osteoporotic bone.

Results: hi the animal study, mean final insertion torque was 4360±1050Nmm in the standard group and 3420 ± 676 Nmm in the HA-coated group. Mean extraction torque was 253 ± 175 Nmm in the standard group and 3360 ± 1260 Nmm in the HA-coated group (p = 0.002). In the clinical study on healthy bone, the mean insertion torque was 4130 ± 2160 Nmm in the standard group and 3440 ± 1930 Nmm in the HA-coated group (p = 0.03). The mean extraction torque was 1470 ± 1700 Nmm in the standard group and 5130 ± 2300 Nmm in the HA-coated group (p < 0.001). There were 33 pin-tract infections in the standard group and 20 pin-tract infections in the HA-coated group (p < 0.05, power 0.9). The standard pin group had a mean extraction torque of 730 (0–5500) Nmm in the infected pin-tracks and 2110 (0–7000) Nmm in the uninfected pin-tracts (p < 0.0001). The HA-coated group had a mean extraction torque of 5310 (1000–8000) Nmm in the infected pin-tracts and 5080 (0–8000) Nmm in the uninfected pin tracts (NS). In the clinical study on osteoporotic bone, mean final insertion torque was 461 ± 254 Nmm in the standard group and 331 ± 175Nmm in the HA-coated group (p = 0.01). Mean extraction torque was 191 ± 154 Nmm in the standard group and 600 ± 214 Nmm in the HA-coated group (p < 0.0005). Pin infection rate was greater in the standard group (p < 0.05).

Conclusion: There was no deterioration of the bone-pin interface strength (measured by torque resistance at the time of pin extraction) with HA-coated pins. The improved strength of fixation of the HA-coated pins was associated with a lower incidence of pin-tract infection.

A.J. Van Der Borden H.C. Van Der Mei H.J. Busscher

Introduction: Biomaterial implants in the human body constitute passive surfaces that are prone to bacterial adhesion as the on-set of biomaterials-associated infection. Antibiotic treatment of infected biomaterial implants is little successful clinically, because the biofilm-mode of growth protects the adhering organisms. Percutaneous implants, such as bone screws used in orthopedics or dental implants, constitute a special class of implants with infection rates exceeding the infection rate of deep body implants by far. Especially fixation frames, used in orthopedic surgery for the treatment of complicated fractures, inevitably become infected during the course of a treatment.

The aim of this study is to determine whether it is possible to stimulate bacterial detachment from surgical stainless steel and decrease the viability of the remaining adhering bacteria using block currents. Method: Bacteria were allowed to adhere from a flowing suspension of high ionic strength in a parallel plate flow chamber, after which the suspension was replaced by a bacterium free solution with 10 mM potassium phosphate buffer. Block currents of 15, 60 and 100 ìA with different frequencies (0.1 to 2 Hz) and duty cycles (5 to 50%) were applied to induce bacterial detachment.

Results: Initial detachment rate increased with increasing frequency and duty cycle, namely from 0 to 3700 cm−2s−1. The total detachment percentage for block currents of 100 ìA with 25% to 50% duty cycle and frequencies as of 0.5 Hz are similar for all conditions. The detachment percentage in this range amounts on average 76%, whereas DC currents around 100 ìA have an average of 60%, which was found to be significant lower (p=0.03).

The killing capacity of these current series can be up to two log scales depending on the current.

Conclusion: Current induced detachment of Staphylococcus epidermidis from surgical stainless steel seems very effective, especially for a 100 ìA, 50% duty cycle and 2 Hz block current. The viability of the remaining adhering bacteria decreased with 2 log scales. Clinically this could mean another way of preventing and curing pin tract infection.

U. Randel F. Kutscha-Lissberg M. Wick

Introduction: Septic glenohumeral destruction is one of the most feared complications after operative fracture care. Unlike for other joints resection arthroplasty is not a possible alternative form of treatment. Our aim in this study was to assess the long-term results of shoulder arthrodesis in 15 patients after septic joint destruction.

Patients and Methods: Between 1978 and 1998 septic arthrodesis of the shoulder was performed in 15 patients. There were four women and 11 men with a mean age of 51.9 years. All patients were asked to return for clinical evaluation in June 2002. Three had died from unrelated causes and one from abroad had been lost for follow up. The outcome was evaluated according to the modified functional score of Hawkins and Neer and David, Makowski and Muhr. We recorded the complications, further operations, alterations in working habits, pain and patient satisfaction.

Results: The mean follow up was 8.3 years (3 to 14y). 3.8 (1 to 14) previous procedures had been performed. The entire 11 pat. were limited using their arm behind their backs. None was able to perform toilet hygiene and only one patient was able to reach his back pocket. Function at the level of the head in order to shave or to comb hair was difficult for the most, whereas nine patients were able to work at waist level. Eight were able to put on shoes and socks. Four were able to climb a ladder. All had had pain before surgery. On visual analogue scale, the mean preoperative level of pain was 7.9 and 3.3 after fusion. Complications occurred in 5 patients. 3 had persistent infection and failure of bony fusion requiring further surgery, one patient with persisting infection denied surgical interventions, one sinus tract healed after hardware removal.

Conclusion: The outcome depends on the individual patient and the indication for arthrodesis. To our knowledge, this is the first study which has investigated the long term results after arthrodesis indicated by septic joint destruction. Heavy tobacco misuse and a high number of previous procedures could be identified as risk factors for persisting of infection, persisting pain and failure of bony fusion with statistical significance.

A. Fontana

Hip septic arthritis requires prompt surgical decompression. The aim of this study is to evaluate the advantages and effectiveness of hip arthroscopy in alternative to arthrotomy.

Since 1996, 6 children affected by hip septic arthritis were treated by arthroscopy. The mean follow up was 7.5 years (8–7 years), 2 patients were female and 4 male, the mean age was 6.5 years (from 4 to 8).

Time from onset of symptoms to operative treatment ranged from 24 h to 4 days. The surgical procedure was performed with the patient in the supine position and the leg in slight traction, by means of a sopratrocanteri c portal. A standard 4.5 mm arthroscope with a 70° optics was used. A sample or articular fluid was harvested for bacteriological and gram stain examination. The joint was then washed out with 8–10 litres of saline solution. No drain was left inside and all the patients were treated by a guided antibiotic therapy post-op.

In all cases a grossly purulent fluid was aspirated. In 3 cases the gram stain showed a S. Aureus as responsible of the infection. No complications were attributable to the arthroscopy in the intra and post-op period. ESR, PCR and WBC count normalized after 3 days post-op in all cases. The mean period of hospitalisation was 8 days (from 5 to 13), the mean time of full recovery was 17 days (from 15 to 20). At 7 years of follow-up no recurrence was reported and the clinical evaluation showed no pain and no functional restriction of the operated hip.

Early surgical drainage is the main treatment for septic arthritis of the hip. Hip arthroscopy allows to completely remove the purulent fluid from the inside of the hip joint, by means of a large volume lavage and direct suction. Hip arthroscopy demonstrated to be an excellent alternative to arthrotomy for treatment of septic arthritis in children old enough to be safely arthroscoped, with a significantly less morbidity.

C.L. Romanò E. Meani D. Romanò E. Usellini

Introduction: In 1995 we started using, at the G. Pini Orthopaedic Istitute of Milano, a system for bone healing stimulation based on low intensity pulsed ultrasound. Advantages of the method are: home therapy (20 minutes per day); no side effects, even in the presence of metallic devices or infection; ease of use. Indications of low intensità pulsed ultrasound are bone healing after fresh frarctures, in which a significant bone healing accelation can be observed, delayed and non-unions. We share our experience in a challenging field of application: septic non-unions.

Materials and methods: We retrospectively evaluated 30 patients, treated from 1996 to 2003, affected by septic non-unions (a fracture that, in the presence of infection, did not show any significant increase in callus formation at 8 months from the time of fracture). The patients had a mean 1.7 ± 2 previous failed intervention. Patients were treated, in the absence of other medical or surgical treatment (excluding antibiotic therapy), with low intensity pulsed ultrasound (EXOGEN S.A.F.H.S. or, since year 2002, IGEA F.A.S.T.). The treatment was applied, after the necessary instructions, directly from the patient, at home, 20 minutes per day. Failures of the treatment were considered need for further surgery to stimulate bone healing, persistence of non-union at follow-up. Exclusion criteria included: evident instability of the synthesis, soft tissue loss and bone exposure, wide bone loss (> 2 cm).

Results: 24 bone healing (86 %), 4 failures (need for surgery), 2 treatment discontinuation. Mean treatment duration: 123 ± 43 days (minimum 90, maximum 240 days). No side effects local or general were observed. In 18 cases a bone debridment and/or hardware removal intervention had been performed after bone healing. At follow-up, 28 patients are free from infection, while two showed infection recurrence.

Conclusions: Low intensity pulsed ultrasound is an effective options in the treatment of septic non-unions, without side effects. An accurate indication and patient selection provide an advantageous cost/benefit ratio.

L.B Stolle M. Arpi P. Holmberg-Jørgensen P. Riegels-Nielsen J. Keller

Objectives: Antimicrobial agents exert their effect inside the interstitial space, which is the site of many infections. Recently, microdialysis was applied to cortical and cancellous bone for the evaluation of gentamicin. The principle of microdialysis is to introduce a semipermeable membrane into bone and perfuse it with liquid, thus enabling dynamic measurements to be made.

The aim of this investigation was to measure pharmacokinetics of a Gentacoll sponge in bone tissue by microdialysis.

Materials and Methods: Nine pigs were randomized to either wet or dry application of a Gentacoll sponge (10cm* 10cm) into the bone marrow of tibia. Two catheters were inserted into cancellous bone tissue, one 1 cm (MD1cm) and one 2 cm (MD2cm) apart from the aimed location of the sponge. Then, the Gentacoll sponge was implanted. Wet application was defined as; the sponge was wetted in 2 mL. blood. Dry application was defined as usual surgical procedure. Concentrations of gentamicin were measured in serum and microdialysates on an Abbott Drug Analyser. Data presented are median (range). A rank sum test was performed for statistical analysis. A p-value below 0,05 was considered significant..AUC describes the total amount of gentamicin that passed though the tissue.

Results: The AUC6h, serum wet was 92 (72–129) and AUC6h, serum dry was 196 (142–626) mg*minute/L (P=0.02). The Cpeak, wet-group was 120 mg/L (33–585) and Cpeak, dry-group 178 mg/L(59–1294), (P=0.31). The overall (n=9) AUCMD1cm was 24431 mg*minute/L (5.155–152.855) and similar the AUCMD2cm 13759 mg*minute/L (6.351–74.573) (P=0,25). The Cpeak, MD 1cm was 106 (41–354) (P=0.21). was 209 (33–1294) and Cpeak, MD 2cm

Conclusions: This first study applied microdialysis for pharmacokinetic measurements of a local implant. The distribution of local applied antibiotics into bone tissue is difficult to measure. The small sample size precludes a detailed analysis, but previous found variation on the distribution of gentamicin from a Gentacoll sponge is reproduced in this work. It seems that neither application nor distance had impact on the initial pharmacokinetic of Gentacoll in bone tissue.

V. Heppert

Introduction: If you loose the talus, especially in infection cases, you have a problem. Literature says, that in a lot of cases you should amputate. We analysed 17 cases, being transferred to our hospital with a non-union an 12 own cases. The question was: What ca you do, to get an acceptable result. An analysis of the mistakes was tried to achieve.

Material and Method: 29 cases were analysed in this retrospective study. In 27 cases an infection situation was found. In 2 cases a vascular disturbance of the talus, avascular necrosis, was found. We analysed the stabilization method, the length of non weight bearing and the personal compliance of the patient. We found patients being stabilized with a nail, an external fixator of AO or Ilisarov Fixator.

Results: In about 68% of the non-union cases too early weight bearing therapy according to mobilization of the joints occurred. In 32% a cancellous bone graft didn’t take place. Shortening of the leg > 4 cm happened in 69%.

Discussion: The problem of stabilization of this anatomical area is well known. The anatomy itself brings problems. But the surgeons opinion, to make a very early functional treatment possible, is contraproductive in these cases. Leave the implant much longer than you would think, start weight bearing only after 6 weeks and you can get reasonable results. Callus distraction solves the problem of leg length discrepany. During that time, lasting longer than the arthrodesis, the bone heals. Leave the fixator for the whole time in situ and you will get an acceptable result for the patient. More than that, make an additional arthrodesis between the tibia and the Naviculare bone. Our own results demonstrate a success rate of 80% in these desperate cases.

G.T. Ensing J.G.E. Hendriks J.E. Jongsma J.R. Van Horn H.C. Van der Mei H.J. Busscher

Introduction: Local drug delivery yields higher gentamicin concentrations than can be safely achieved with systemic application. Unfortunately, both for beads as well as for bone cements, a sharp drop in release follows high initial gentamicin release. Aim of this study is to compare the effects of pulsed ultrasound on the release of gentamicin from antibiotic-loaded beads and bone cements. Mercury intrusion porosimetry is carried out to compare the pore size distribution in both materials before and after antibiotic release.

Materials and Methods: Ultrasound: Gentamicin release from three brands of gentamicin-loaded bone cement (CMW 1, Palamed G and Palacos R-G) and Septopal gentamicin-loaded beads was measured after 18 h of exposure in PBS to an ultrasonic field of 46.5 kHz in a 1:3 duty cycle with a peak intensity of 500 mW/cm2 at the sample position. Ultrasound experiments were performed for 18h in 9-fold on bone cement and in 6-fold on beads. Samples not exposed to ultrasound were used as controls. The gentamicin release was measured with fluorescence polarisation immunoassay. Gentamicin release from insonated and control groups was compared using a two-tailed Student’s t test for independent samples.

Mercury intrusion porosimetry: In order to mimic bone cement and beads after prolonged stay in the human body (i.e. after initial release of the loaded gentamicin) samples were immersed for four and two weeks, in PBS. Immersed and not-immersed samples were compared.

Results: Pulsed ultrasound significantly enhanced gentamicin release from gentamicin-loaded beads, whereas gentamicin release from the gentamicin-loaded bone cements was not significantly enhanced. Mercury intrusion porosimetry revealed a rise in pores between 0.1 and 0.01 um in beads after gentamicin release, while in bone cements no increase in the number of pores before and after antibiotic release was found.

Conclusions: Ultrasound increases gentamicin release from antibiotic-loaded acrylic beads by 15%. Development of pores coincides with increased gentamicin release by ultrasound for beads. Application of ultrasound could optimise usage of an (antibiotic) reservoir in local drug delivery systems to treat bone and soft tissue infections more effectively.

M.A. Catagni R. Cattaneo L. Lovisetti

Introduction: The bone defects in the long bones are traumatic as a consequence of open fractures or resections due to infection or necrotic nonunion. A devitalised bone with no nutrition or vascularity is liable to an infection, with extension proportional to the size of the necrotic bone. To be sure to eliminate the infection and the nonunion it is necessary to perform open surgery and remove the necrotic and infected segments thoroughly, and then proceed to osteosynthesis and internal transport after osteotomy.

Material and Methods: From 1981 to 2002 203 cases were treated with the Ilizarov Method. The previous treatment given before the patients came to our center was as follows: 1) in tibial nonunion intramedullary nail 17%; 2) in femoral nonunion plates 46%, monoaxial external fixator 42%, intramedullary nail 10%, circular external fixator 4%; 3) humerus nonunion Ender 3%, plates 81%, intramedullary nail 16%; 4) forearm nonunion plates 80%, wires and cast 20%. Our treatment was resection of the infected bone segment and then bifocal internal transport in 162 patients, threefocal convergent transport in 41, or threefocal tandem transport. If the resection does not exceed 4–5 cm. it is possible to perform immediate shortening, first by placing the resection stumps in contact and compression, and then by performing bifocal transport. The bifocal method consists of resection and proximal or distal metaphyseal osteotomy and then internal transport of the free bone segment bringing it into contact with the stump where the resection was performed. In the threefocal convergent method, after resection, two osteotomies are performed, one proximal and the other one distal, and the two bone segments are made to converge on the resection site. In the threefocal tandem method, after resection on a clear-cut proximal or distal infection, the osteotomies are performed on the same bone segment with double level transport. The good result is conditioned by satisfying regeneration in the site of the osteotomies. The rhythm of transport is purely individual and proportional to the patient’s age, and ranges from 1 to ¼ mm a day. In case of hypotrophy of the regenerated bone, concertina manoeuvring becomes necessary, that is shortening and subsequent distraction of the transport segments.

Results: According to these techniques we attained both consolidation and elimination of the infection in 181 cases, that is 89%.

Conclusions: In infectious nonunion healing cannot be possibly achieved through antibiotic therapy, so the only resolving action is the eradication of the necrotic-septic site and then its resection. The consequent limb shortening is compensated, in the Ilizarov Method, by internal transport of the healthy bone segment. Our results are good for cases, and the infection is eliminated in any case.

J.K. Koort T.J Mäkinen E. Suokas M. Veiranto J. Jalava J. Knuuti P. Törmälä H.T. Aro

Introduction: Drug delivery systems (DDSs) using resorbable materials have been developed for local therapy of adult osteomyelitis. An ideal DDS would provide controlled release of antibiotic for an extended period and have an osteoconductive component for spontaneous restoration of bone stock.

Materials and Methods: The developed DDS consisted of three components: poly(DL)-lactide (PDLLA), ciprofloxacin (AB) and bioactive glass (BG) as the osteoconductive component. Based on in vitro studies, the composite provides a long-lasting release (> 3 months) of the ciprofloxacin at therapeutic levels. The localized osteomyelitis model (Stage IIIA) was applied in adult male New Zealand white rabbits (n=30). A cortical bone window was drilled in the proximal tibial metaphysis and filled with bone cement. 0.1 ml of Staphylococcus aureus lxl05 1/ml was injected into the defect. Infection was allowed to develop for two weeks, when the bone cement was surgically removed (debridement) and osteomyelitis was confirmed by positive bacteriology. In treated experimental animals, antibiotic containing composite (AB-PDLLA-BG) was impacted into the infected medullary space. In untreated infection control group, the infected the medullary space was subjected only to surgical debridement. In sham-treated control group, the infected medullary space was filled with a composite without antibiotic (PDLLA-BG). In the negative control group, the injection of bacterial suspension was replaced by saline injection. The treatment response was evaluated by FDG-PET and pQCT at 3 and 6 weeks. Concentration of ciprofloxacin was also measured from bone tissue. The statistical significance of the differences was calculated using paired t-test and one-way ANOVA with Tukey t-test.

Results: Before infection treatment, 96% of the animals had positive bacterial cultures, while none of the negative control group had positive cultures. At sacrifice, all animals in untreated and sham-treated control groups had culture positive infection, while all bone cultures were negative in treated animals. However, three treated animals had culture positive soft-tissue infection. In untreated infection control group, the FDG uptake was increased many-fold compared with the negative control group both at 3 and 6 weeks. The treatment with AB-PDLLA-BG significantly decreased the FDG uptake and the difference was highly significant (p=0.013) compared the untreated animals. Based on pQCT imaging, the cortical defect healing was faster in treated and negative control animals than in untreated and sham-treated groups. In treated animals, the local therapy resulted in high bone concentration of ciprofloxacin.

Conclusions: The current experiment confirmed by collaborative results of both bacteriologic, FDG-PET and pQCT studies that the local infection therapy by the selected antibiotic composite was successful in bone eradication of Staphylococcus aureus pathogen.

J. Wodtke S. Luck J.F. Loehr

Introduction: Periprosthetic infection is still the most severe complication in THA. In spite of vigorous efforts over the last decades the problem has not been Solved nor minimized. Standardised procedures for prophylaxis and treatment have long been established. Reported results reach into the mid 80% but did not improve remarkably in the last ten years. Our latest follow-up reveals a success rate of 88.6%. A close analysis of the involved unsatisfying cases will help to improve future results.

Material and Methods: 105 consecutive one stage exchanges of THA for periprosthetic infection in 1996 were investigated after 7 years through questionnaire, telephone interview and clinical examination. An overall success rate of 88.6% was found and the failures were analysed. Criteria like age, co morbidities, ASA, duration of infection anamnesis, number of infection related interventions, lab-findings, local findings like fistulas, x-ray rating, operation time, surgeon, complication postoperative and the bacteria involved were compared.

Results: In general it shows that the most desolate cases in all categories line up for a primary failure. The ASA rating is remarkably higher and local findings like fistulas are present in nearly all patients. The bacteria involved are staphylococci in 70%. Over 50% had a combination of two or more pathogens and two patients showed an additional pathogen in the samples taken during the operation. The pattern of the involved bacteria is remarkably severe. But there are also three cases where no sign of higher risk or lower chances could be detected.

Conclusions: Knowing about causes of failure in the specific one stage exchange situation does lead to adaptation in the concept of treatment for those specific cases. With successful application, better results through individual therapy-concepts will be possible.

C. Faber H. Stallmann D. Lyaruu U. Joosten C. von Eiff A. van Nieuw Amerongen P. Wuisman

Introduction: Antimicrobial peptides (AMP) are a novel class of antimicrobial agents effective against among others MRSA in vitro. Previously, we reported the release of AMP Dhvar-5 and hLF1-11 from different bone cements(1,4). In this study we investigated the efficacy of calcium phosphate cement (Calcibon®) loaded with hLF1-11 for the treatment of MRSA osteomyelitis in vivo.

Materials and Methods: Osteomyelitis was induced in 14 rabbits by MRSA, as described by Norden et al.(2) After 3 weeks all animals were treated by a thorough local debridement and subsequent filling of the tibial cavity with Calcibon® bone cement. Six control animals received Calcibon® without additives and 8 animals received Calcibon® loaded with 50 mg hLFl-11 per g cement powder. Treatment outcome was analyzed by microbiology, radiology and histology after 3 weeks follow-up.

Results: The results are shown in table 1. The number of CFU per gram of bone were significantly lower in the 50 mg hLFl-11 group (median 3.0x103 CFU/g bone) compared to the control group (median 3.5xl06 CFU/g bone).

Conclusion: This study demonstrates that hLFl-11 has the ability to cure an existing MRSA osteomyelitis in 5 out of 8 animals. The data suggest that the antimicrobial peptide, hLFl-11 in Calcibon® is able to treat osteomyelitis in vivo.

A. Bruno F. Carola F. Carnelli P. Orlando G. Santoro A. Spini

Introduction: Discomfort and pain are common but unspecific symptoms in orthopaedic prosthetics. The majority of these symptoms are secondary to mechanical failure or loosening, while only a small proportion is related to infection. The differentiation between synovitis, loosening or infection is important for a correct therapeutical management, but it is often difficult using noninvasive techniques.

Positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose (FDG) has evolved from a research imaging modality to a clinical practice for the assessment of malignancies. FDG, a nonspecific tracer of increased intracellular glucose metabolism, has been found to accumulate not only in malignant cells but also in infection and inflammation foci.

Aim of the study was to evaluate the usefulness of FDG PET scan in patients with joint replacement.

Materials and Methods: In this study we describe PET findings in 33 patients (age 42–88 yrs.) with hips (n. 16) and knees (n. 17) prostheses who had a complete operative and/or clinical follow-up; 42.5% had a pattern of mobilization. All patients underwent PET scan 60 minutes after i.v. injection of 185 MBq of 18F-FDG (transmission-emission, 3D acquisition). PET tomograms were evaluated by nuclear physicians without knowledge of the clinical diagnosis by visual interpretation, which was graded on a four-point scale according with common clinical classification (0 = normal pattern: not significant locoregional uptake; 1 = synovitis: synovial localized uptake; 2 = prosthesis loosening: synovial and soft tissues uptake; 3 = prosthesis infection: synovial, soft and bone tissues diffuse uptake).

Results: The results will be discussed in detail and correlated with clinical findings. The diagnostic value of PET, in terms of sensitivity, specificity and accuracy was compared with traditional radionuclear techniques (dynamic bone scan, 99mTc-labelled granulocytes).

Conclusion: We underline a good correlation between PET and clinical pattern (88% of cases). Particularly PET was able to correctly differentiate the prostheses loosening in the 100% of cases without infection and in the 77% of patients with infectious disease suggesting its usefulness in clinical practice also for detecting only inflammatory tissue such as synovitis. Moreover, the capability of PET to quantificate the inflammatory activity could be useful in the monitoring of the therapy. Further evaluation in a large group of patients is indicated.

Z. Dailiana N. Rigopoulos S. Varitimidis A. Damdounis T. Karachalios K.N. Malizos

Introduction: Osteomyelitis and septic arthritis (SA) below the elbow are severe conditions affecting the function and viability of the hand. Factors predisposing to these conditions and parameters affecting prognosis are emphasized.

Material and Methods: In a 4 years period, 16 patients with SA (4) or osteomyelitis (12) were treated in a University Orthopaedic Department providing care to a rural population of 1.000.000, Nine had history of trauma in unhygienic environment, 3 had immunodeficiency and in 4 osteomyelitis was iatrogenic [previous fixation of fractures (3) and vein catheterization (1)]. SA was located in the wrist (2) and thumb joints (2) and osteomyelitis involved the radius (3), ulna (1), metacarpals (3) and phalanges (5). Ten patients received oral antibiotics in other centers. The mean delay from onset of symptoms to referral to our center was 22 days. Apart of antibiotics administration, surgical treatment included debridement and irrigation for SA and excision of necrotic bone, stabilization (external fixators), use of antibiotic beads and secondary bridging with bone graft for osteomyelitis. Additional procedures (amputations, arthrodesis) were also required in some cases.

Results: Cultures were positive in 9 of 16 cases [Staph. aureus (5) and enterobacter cloacae (3)]. Patients underwent multiple procedures (mean: 3.8) and 4 underwent amputation of a digit (2) and hand (2) due to the rapid extension of infection threatening and finally taking the lives of 2 elderly and immunosuppressed patients. Mean follow-up period of the 12 surviving and non-amputated patients was 18 months. Union was accomplished in all cases. Functional results were excellent or very good in 10 of 12 patients and good in 2 patients. All patients were satisfied and returned to their previous occupations.

Conclusions: Osteomyelitis and SA below the elbow was frequent in population living in unhygienic environment or working with soil. All cases received medical treatment with delay. Immunosuppressing conditions favored the extension of infection and threatened patients lives. Delay in treatment in combination to immunosuppression resulted to significant morbidity. Early treatment including surgical drainage, thorough debridement and antibiotic administration is necessary for elimination of skeletal infection and salvage of the hand and patients life.

A. Gasbarrini G. Barbanti Bròdano E. Bertoldi M. Commessatti F. De Iure F. Gonella L. Mirabile M. Russo S. Terzi S. Boriani

Introduction: Purpose of this study is to evaluate retrospectively 61 cases of spinal infections, unrelated to previous spinal surgical treatment. We included patients with drug addiction. Objective of this study is to analyze the results of treatment using a diagnostic and therapeutic algorithm. This procedure may allow a systematic and comprehensive approach to the diagnosis and management of vertebral osteomyelitis. For instance, despite advances in imaging, this pathology is easily missed and treatment is often delayed.

Materials and Methods: We reviewed 61 patients aged 15–83 (average 52y) treated between January 1997 and March 2001. All patients received plain radiographs, gadolinium enhanced magnetic resonance imaging, Ga-67 and Tc-99 scintigraphy. A total of 36 patients underwent CT- guided fine-needle aspiration biopsy: the coltures of spinal specimen were positive in 47% (17/36) of cases. Blood coltures were positive in 65% (13/20).

Results: Staphylococcus Aureus was the main organism followed by Mycobacterium Tubercolosis and Staphylococcus Epidermidis. All patients received intravenous antibiotics. Neurologic impairment was present in 13 (26%) patients who underwent surgery. All patients with paresis recovered completely after surgical decompression (100%). Patients with nonsurgical spondylodiscitis were treated with bed rest and bracing. They reported residual back pain not frequently 22% (8/36) than patients treated surgically 38% (5/13).

Conclusions: the outcome of patients with vertebral osteomyelitis in general is favourable when appropriate treatment is picked even if vertebral osteomyelitis is a rare condition and because of this often overlooked initially. Delay in diagnosis may results in spine impairment, more hospitalisation time and more cost. We suggest diagnostic and therapeutic criteria in order to simplify the treatment.

G. Gualdrini G. Dolci A. Bassi A. Hamad A. Giunti

Introduction: morcelized defatted bone-Bank graft (MOD-B) has been employed in 249 patients for different diseases in Rizzoli Institute from 1998 to 2002. 82 hip revisions, 51 spine fusions, 50 osteolitic bone cavities, 47 non-unions). Good results obtained with MOD-B have been the reason for different researches of his properties like an antibiotic carrier and, in the same time, a particular new bone graft.

Material and Methods:

MOD-B with antibiotic powder and PMMA Cylinders (A-MB-C) have been placed in saline solution and plasma for 4 weeks, compared with cylinders made with PMMA and antibiotic.

The mechanical resistance of A-MB-C to compressive test has been performed subsequently.

About biocompatibility, A-MB-C were implanted in sheep’s Ilium. After 3 moths an histologic evaluation has been performed.


The MOD-B + antibiotic + PMMA have released the higher quantity of antibiotic for all the 4 weeks.

The A-MB-C resistance has been of 13.6 MPa, the same resistance of cancellous bone in the man’s femur.

The histological result with a fluoroscopic microscope has been an osteogenesis in the full section of the cylinders.

Conclusions: morcelized defatted bone-Bank graft is an important opportunity to restore bone loss lesions but, with a septic situation, it is not so easy obtain good results. A very important goal would be to have a graft with good antibiotic deliver system, good mechanical compressive strength and the potential capacity to become new living bone.

A. Hernandez X. Flores N. Joshi L. Metta J. Nardi

Introduction: Fusion of the knee joint should be the last option for salvage of infected total knee arthroplasty (TKA). Although knee arthrodesis implies lost of function, it is a successful treatment in eradicating the infection and in decreasing pain.

External fixation compression devices have been an excellent method for gaining fusion but, there is no documentation about its ability for obtaining adequate limb alignment with a stable fusion of the knee joint.

Material and Methods: We have retrospectively reviewed the results of knee arthrodesis after infection of TKA using an anteriorly placed unilateral external fixator. In addition, we have assessed patient self-satisfaction.

Postoperative radiographs have been evaluated to digitally measure loss of femoral and tibial bone stock using Engh radiological classification. Moreover, we have quantified tibiofemoral alignment and the section of bony fusion. Fusion of the knee joint was assessed with CT. Patients were interviewed and pain was graded using a Visual Analog Scale (VAS) and self-satisfaction as well as current health status using the 12-item social function survey form (SF12).

Results: From 1992 to 2003, 52 arthrodeses were done for treatment of infected TKA. The average age was 71 years (range, 37–83 years). Type III bone defect according with Engh classification, in femur and/or in tibia, was present in 50% of the patients. The average postoperative tibiofemoral alignment was 1.2° (SD 3.79). The mean time to fusion was 11.26 months (range, 3–30 months). Time to fusion was statistical related with severe bone loss and with the tibiofemoral contact section. The average score according VAS was 1.6 (SD 2.60).

Conclusions: Knee arthrodesis using a monolateral external fixator for infected TKA is an effective method to control infection as well as to obtain knee fusion and pain relief. Severe bone loss, frequently present in infected TKA, was found to be the most relevant factor in achieving tibiofemoral union. The individual clinical result according to SF12 shows a lower quality of life both for physical and mental components compare with general population.

R. Orani C. Salfi G. Caterino F. Centofanti D. D’Antona E. Campatila

Introduction: Treatment of infected non union of the lower limb has many possibilities. A new one, the Expandable Nailing System (ENS), already employed in traumatology, is presented here.

Materials and Methods: Between June 2001 and Dec.2003, 119 Patients with an infected non union of the long bones of the lower limbs (98 tibias, 21 femurs) were treated in our osteomyelitis centre. Most of the cases were men (87%), mean age was 38.4 years. Follow-up was min 5 months, max 23 (8.7 ave.)

ENS was used for 28 cases (25.4%). Other surgical techniques, were the Ilizarov apparatus (41 cases, 34.4%), the Grosse-Kempf locked nail (18.4%), fibular osteotomy (11%) the retrograde nail (5%), others (6%). ENS is indicated in:

3 – non unions with focuses at least 5cm. From epiphysis.

2)- serious soft tissue and bone cortical damage.

3)- failure of previous treatment.

3 – hypertrophie non unions where infection is reduced /absent and ESR is negative.

ENS is not indicated in the following conditions:

focus near the epiphysis;

severe bone loss;

atrophic non-unions ;

3 – active stage of the infection.

In spite of point 4, the Authors used it in 5 cases with active osteomyelitis that could not be treated otherwise.

Results: Many cases are still undergoing treatment. Recovery times are generally shorter compared to traditional Grosse-Kempff Nails and Ilizarov. Bone healing is physiological and refractures after removal have not occurred in the few nails removed. Two Patients underwent re-operation, one for a nail failure, the second for a wrong choice in the first operation. Nail breakages occurred in 4 cases (3 tibias, 1 femur). There were 3 re-infections, all among the 6 patients operated with an active form.

Conclusions: ENS is a more sophisticated nailing system, less aggressive, that reduces X-ray exposure, blood loss, surgical time. This nail offers the advantage of a dynamic GKN, controlling torsion with longitudinal bars, but with a relative weakness especially for femurs. The learning curve is brief, but without a guide-wire more care is needed. The cost is high.

F. Termaat P. Raijmakers P. Patka F. Bakker H. Haarman

Introduction: A variety of diagnostic imaging techniques is available for excluding or confirming chronic osteomyelitis(COM).

Aim of the study was to determine the accuracy of current imaging modalities, radiography, MRT, CT, leukocyte (LS), bone (BS), and Galium (Ga) scintigraphy, and FDG-PET, for diagnosing COM.

Materials and methods: Systematic review and meta-analysis of the literature for clinical studies on COM evaluating diagnostic imaging modalities by a comprehensive search of the Mediine, Embase, and Current Contents databases. The value of each imaging technique was studied through its sensitivity and specificity compared to histology / culture / clinical follow-up.

Results: In total 23 clinical studies were included, describing the diagnostic accuracy of 39 imaging modalities: Radiography (2), MRI (4), CT (1), BS (5), LS (13), Ga (1), combined BS-LS (5), combined BS-Ga (3), combined LS-Ga (1), and FDG-PET (4). A high diagnostic accuracy of FDG-PET was found for detecting COM in the central and peripheral skeleton. Subgroup analyses revealed that LS is more accurate for detecting peripheral localizations of COM than for central localizations of COM.

Conclusions: The available diagnostic studies for COM are characterized by a low methodological quality. Despite, FDG-PET demonstrated to be an important new imaging technique with a high diagnostic accuracy and has the potential advantage for quantitative assessment on surgical treatment of COM.

P.G. Scotton L. Cesaris M. Collodel U. De Nicola A. Vaglia

Introduction: The purpose of this study is the evaluation of the role of combination chemotherapy with rifampin in the treatment of Staphylococcus-infected arthroplasties, without removal of the implants. The study started on July 1997 and is still open today. The enrolled patients refused surgical operation or were not eligible for it.

Material and Methods: we examined patients with hip or knee infected arthroplasties. The hip prostheses infections were treated with an oral therapy for 6 months, while the knee prostheses infections were treated for 9 months. Follow up was extended to two years. Cure should be defined as the absence of clinical, radiological and biological evidence of infection after two years, but we also considered the clinical success at one year as the study is still open, so that not all the patients finished the two-years follow-up, and more, no relapses had been observed after one year of follow-up.

Results: 42 patients with an arthroplatsy infection (16 knee prostheses and 26 hip prostheses due to Staphilococcus spp (23 S aureus and 19 SCN) were enrolled in our study; the middle age was 69.4. 27 of 42 patients treated with rifampin were examined at one year follow up; no relapses had been observed after one year of follow-up. Rifampin was used in combination with: ciprofloxacin (n° 16), TMP/SMX (n° 10) or fusidic acid (n° l).

The success rate after 1 year was of 81.5% (22 of 27 patients): 90% success rate for methicillin-resistant Staphilococci (9/10) and 76.5% for methicillin-susceptible Staphilococci (13/17). The patients with infection due to S. aureus had a success rate of 83.3% (10/12). whereas for infections due to SCN was 80% (12/15). The success rate for hip prostheses infection was of 83.3% (15/18) and 77.8% (7/9) for knee prostheses infection. The overall success rate after two years of follow up today is 77% (17/22), two patients dead because of cancer.

Conclusions: the long-term treatment with rifampin combination appears to be a satisfactory choice for patients that can’t be eligible for surgical revision or that refuse it.

B.A.S. Knobben Y. Engelsma D. Neur H.C. van der Mei H.J. Busscher J.R. van Horn

Introduction: One of the primary complications in total hip and knee arthroplasty is infection. One of the major risk factors for deep periprosthetic infection is wound infection. This alone is associated with a substantial morbidity-increase which, in turn, increases hospital admittance time and therefore adds significant costs to the healthcare system. The aim of this study is to determine whether contamination of instruments used during primary insertion of a prosthesis, can be considered an early indicator for the occurrence of prolonged wound discharge. Early antibiotic treatment could then prevent this and decrease hospital admittance time and costs to the health care system.

Material and Methods: During 121 procedures, swabs were taken from the first unused broach at the beginning and at the end of the procedure. Removed material from the bone (acetabulum and femur in the hip joint; femur and tibia in case of the knee joint) was tested for contamination as well. During 50 procedures a control swab was taken. The patients on the ward were also monitored to find out whether prolonged wound discharge occurred and to see after how many days the patients were discharged.

Results: In 46 cases (38%) at least one culture showed microbial growth. In the other 75, there was no growth at all. If one of the cultures is positive, there is a 52% risk of prolonged wound discharge. Ifall cultures are negative, this risk is reduced to 13% (Chi-square: PO.001). Patients with a positive peroperative culture have to remain in the hospital for an additional 2.4 days (T-test: P-0.001).

Conclusion: Peroperative culturing during primary insertion of a knee or hip prosthesis, provides a reliable tool to predict postoperative duration of wound discharge and hospital-admittance time.

T.M. Frangen S. Aren F. Kutscha-Lissberg U. Hebler C. Wingenfeld T. Kälicke G. Muhr

Introduction: Infection following arthroplasty is a rare but significant and threatening complication. The incidence is about 2%. Treatment of an infected joint replacement may be demanding, time consuming and expensive. The aim was to evaluate the average cost of an infected arthroplastic in our own department under the given reimbursement system in Germany.

Material and Methods: During 3 month 20 consecutive cases of infected joint refered to our institution were monitored for treatment costs and final reimbursement by the health insurances.

Results: In 65% of the included cases the amount of reimbursement by the health insurance organisations did not cover the costs of the treatment in our department. The amount of financial loss in total was 48.142 € with more than 9.000 € in some cases.

Conclusions: For the treating institution there is a risk of substantial financial losses due to inadequate reimbursement. Calculated on the basis of ~ 150.000 implanted joint protheses / a, an infection rate of 2% and treatment costs of ~50.000 € / infected case the economic burden is an estimated 150 million € / a in Germany. This amount should justifie a sound evaluation of costs related to infection in arthroplasty, which should be the effort of the health insurance organisations. Additionally specific research in the field of infection prevention must be sponsored. The system of reimbursement should be adeaquately adopted and corrected.

G.N. Jukema C.Y. Wong P. Steenvoorde J.T. v Dissel

Background: The experimental use of maggots (sterile larvae of Lucilia sericata) can prevent the amputation of an extremity in case of severe infection after trauma injury. Maggots destroy bacteria by secreting enzymes such as tryptase, peptidase and lipase. An alkaline environment is created by the secretion of allantoin, ammonia and calcium carbonate, which reduces bacterial growth and stimulates new formation of granulation tissue.

Material and Methods: In the period 4.1999–12.2003 42 patients (mean age 54 yrs (25–83), were included in cur prospective study for maggot treatment of severe infections after trauma (Osteomyelitis n=26, lower leg 13x, femur 6x, pelvis 4x, upper extremity 3x), necrotizing fasciitis n=7, soft tissue infection n=3, gangrene n-3, ulcus cruris n=3). Maggots were applied to the wound in a polyvinyl alcohol bag (Biobag) and were replaced every 3–4 days.

Results: The mean duration of treatment was 32,1 days (n~37) for the patients who had received one continuous treatment and 62,2 days if more treatments were applied (n=5). The average number of biobag changes per patient was 11.5 (range 4–30); the average number of maggots applied per patient was 863 (range 80–6840). In only 1 patient with osteomyelitis a lower leg amputation was necessary (1/26=3.8%) although in almost patients there was severe (multiple) co morbidity.

Conclusion: In our study the experimental use of maggots could reduce the amputation rate of limbs in case of severe infections after trauma. Our laboratory research investigations with analysis of the secreting enzymes of maggots will be presented to support that this «ancient» method has a place in modern traumatology to diminish invalidating amputations.

J. Correl

Introduction: Even most severe foot deformities can be treated with the Ilizarov method (IM). In the last 17 years the IM was used in more than 200 feet. 11 of these feet had a severe chronic Osteomyelitis of the foot. In one case the osteomyelitis lasted more than 21 years. With traditional methods these feet cannot be healed, but often must be amputated.

Material and method: AH 11 feet had a type 4 classification according to Dimeglio. All feet have been treated unsuccessfully up to ten times and more before. In one foot necrotic bone was sequestrated regularly. Our operation consisted in all cases in one step only: the Ilizarov ring fixator was put to the foot and the lower leg according to the deformity. No necrectomy was done. An open wedge osteotomy was done if necessary. Postoperatively the feet were gradually distracted and kept in orthograde position. Antibiotics were given as a single shot intraoperatively only.

Results: During the time of correction in all cases secernation stopped without any further treatment. In all cases the osteomyelitis became clinically inapparent. Even serology became normal. The feet could be kept in normal position. The patients were able to walk even longer distances. All became pain free. Mean follow-up is 3 years and 7 months (6 months-15 years).

Complications: In 4 feet a 2nd procedure with resection of subcutaneous bone spurs was necessary. Not a single case became worse or developed a sepsis.

Discussion: We could show that even long lasting cases of severe osteomyelitis of the foot can be treated successfully with the IM. It is most important to correct the deformity. No skin flap or muscle transfer is necessary to improve the condition. The IM should be the treatment of choice in severely involved cases with osteomyelitis and chronic ulceration, especially in patients with neuropathic osteomyelitis, e.g. spina bifida.

P.C. Jutte S.R. Rutgers R. van Altena J.R. van Horn

Introduction: Data on intralesional concentrations of modern anti-tuberculosis drugs isoniazid (H), rifampin (R) and pyrazinamid (Z) in tuberculous pleural effusions and psoas abscesses are scarce. Insight into drug penetration is important since subtherapeutic drug concentrations may result in the selection of a resistant bacterial population and lead to treatment failure.

Material and Methods: Intralesional concentrations were measured 2 hours after drug administration in 6 patients with pleural effusions, and 10 with psoas abscesses.

Results: Concentrations were variable. The same range was found for pleural effusions and psoas abscesses. Concentrations were below MIC values in none of 15 patients for H, in 2 of 13 for R, and in 8 of 9 for Z. Cmax:MIC ratio was always > 4 for H, in 4 of 13 for R, and in none of 9 for Z. In 5:8 patients receiving all 3 drugs both R and Z had Cmax:MIC ratios < 4, indicating subtherapeutic drug levels.

Conclusion: Intralesional drug concentrations of isoniazid (H), rifampin (R), and pyrazinamid (Z) were variable. The same range was found for pleural effusions and psoas abscesses. Cmax:MIC ratio for H was always sufficient, for R in most cases below the desired ratio, and for Z on average 10 times too low. In 5 of 8 patients receiving all 3 drugs, both R and Z had Cmax:MIC ratios below 4, indicating intralesional subtherapeutic drug levels for R and Z. This local monotherapy with H may result in the selection of a resistant bacterial population and lead to failure of treatment. Drainage as additional therapy seems indicated.

M. Rottman J.-N. Martin P. Gaudin A. Lortat-Jacob J.L. Gaillard P. Piriou

Introduction: The emergence of multidrug resistant Gram negative bacilli susceptible to hardly any beta lactam compound has led to infections close to a therapeutic dead end. In such circumstances, Imipenem-cilastatin (I-C) is often the only remaining therapeutic option. We report our experience with the prolonged administration of high-doses of I-C in the treatment of osteoarticular infections with bacteria resistant to other beta-lactam agents (or 4l generation cephalosporins in 14 cases).

Materials and methods: Our retrospective study over 7 years included 29 patients with septic arthritis (n=3) continuous osteitis (n=6), septic non-union(n=12) and prosthetic joint infections (n=8). Treatment included an extensive surgical debridement and post-operative combination antibiotherapy with intravenous I-C and aminoside (54%) and/or fluoroquinolones (46%) and/or fosfomycin (29%). Associated microorganisms requiring yet additional antimicrobial agents were associated in 17 (59%) cases. I-C was maintained for an average of 46 days (extremes 21–90), at an average dose of 3,8g/day (extremes 2–6). The bacteria warranting I-C were cephalosporinase hyperproducing Enterobacter cloacae (38%), extended spectrum beta-lactamases producing enterobacteria (31%), Pseudomonas aeruginosa (21%) and/or Acinetobacter baumanii (21%).

Results: Early outcome was favorable in 24 patients (82%). Two patients relapsed with the bacteria requiring I-C. Three failed to negate succion fluid cultures : one was discharged with no change in his condition, one agreed to a leg amputation and the third died of candidemic septic shock in SICU with drainage fluid still bactériologie ally positive. Repeated secondary colonization and systemic infection with yeasts led to a monitoring of yeast load. Per os amphotencin B and immediate treatment of urinary colonization prevented further systemic dissemination of candical infections. No other tolerance incidents were noted. Acquired resistance occurred only once in a P. aeruginosa isolate while Imipenem-cilastatin was chosen to cover an ESBL producing Escherichia coli. Secondary treatment with ceftazidime was then successful in eradicating P. aeruginosa.

Conclusion: I-C has been widely used for the treatment of mixed flora infections as a wide spectrum antibiotic.

We report good tolerance of high posology long term administration in documented osteoarticular indications if yeast colonization is properly monitored, and eradication rates are comparable to those reported in infections with susceptible bacteria.

L. Pizzoli L. Renzi Brivio F.M. Lavini

Introduction: Septic non unions are rare and often occurs after an open fracture but they might arise after an inappropriate surgical or medical treatment. Different techniques can be used for the treatment. External fixation has many advantages over other techniques particularly when bone reconstruction and/or plastic surgery are indicated although sometimes more than one surgery is necessary to restore ideal biological and mechanical conditions for healing.

Material and Methods: The authors present their experience in the treatment of 38 septic non unions using a protocol which differentiates the diagnostic and therapeutic approach. External fixation can be used as a single procedure or associated to other surgical procedures in relation to the type and diffusion of the infection.

Results: Bone healing and infection eradication have been obtained in 92% of the cases (35 pts). We had 3 secondary amputations (8%). In the first series of patients screw removal and replacement, for pin track infections, occurred in 40% of the cases while this percentage decreased to 4.3% when HA- coated screws were used.

Conclusions: The treatment of septic non-unions needs a multidisciplinary approach to treat properly both non union and infection of bone and soft tissues. Internal fixation remains a procedure at risk because of the high rate of infection recurrence. External fixation is instead still the safer and more versatile surgical option to treat these pathologies. It nevertheless requests strict diagnostic and therapeutic protocols and a good postoperative organisation in order to shorten the healing time and to minimise the complications.

X. Flores N. Joshi A. Hernández L. Mella J. Nardi

Introduction: From 1972–2003, 205 arthroplasties of infected hips were performed in the Musculoskeletal Infectious Disease Unit of our hospital. Using as a basis the outcome for conventional one-and two-stage hip replacement with cemented implants and antibiotics performed in these patients, we designed a new two-stage hip replacement protocol using «personalized» solid spacers and non-cemented components.

Material and Methods: A total of 44 patients were treated with our protocol. Patient characteristics are described, as well as an elevated incidence of associated disease, the causative microorganisms, and therapy provided. Most of the cases had failed other treatment methods. Strict application of the protocol implied:

Previous identification of the infective microorganism

First-stage surgery including radical debridement and placement of «personalized» spacers.

Specific antibiotic treatment during three months.

Second-stage surgery including second debridement, withdrawal of the spacers, collection of samples for microbiologic and histologic study (including intraoperative PMN study). Implantation of prosthesis without use of cement.

Results: Reactivation of infection occurred in only one case. The patient was cured with antibiotic administration. The remaining patients remained free of infection for a mean follow up period of 64.54 months (19.77–86.63 months). The septic process was erradicated in 96% of cases. Five-year implant survival was 100%.


Cement with antibiotics is not essential for prosthesis reimplantation when replacement is performed in two-stage.

Outcome in patients treated according to this protocol is equal or superior to that of other technique options (eradication of the septic process for a mean of more than 5 years).

Prosthesis survival results justify the exclusion of cement for reimplantation.

F. Kutscha-Lissberg U. Hebler G. Muhr S. Arens

Introduction: Knee arthrodesis is a well-recognized salvage procedure in patients with septic destruction of the knee joint. If fusion can be achieved, it offers the opportunity for a stable lower limb and eradication of infection, but at the expense of knee motion. However, knee arthrodesis in this setting may be difficult to achieve because of poor bone stock, persistent infection and soft tissue compromise. In this study we present clinical and radiological results after knee fusion as well as an algorithm according to different surgical techniques (hybrid external fixator (HEF), antegrad compression nail (ACN) and modular cement less titanium rod (MCR)) and types of soft tissue damages and bone loss caused by infection

Patients and Methods: Between 10/2000 and 10/2002 in 37 patients knee arthrodesis was indicated after septic joint destruction. In 23 Pat. (67.0 y, 19.4–88,8 y) septic failure of total knee arthroplasty (TKA)caused severe bone loss and soft tissue damage. Because solid bony fusion was not to be expected weight bearing capability was restored by the use of MCR in a second stage procedure, using a PMMA Gentamycin spacer for eradication. In 14 Pat. (54.3 y, 23.l–87.7 y) remaining bone stock indicated direct fusion. In 10 of these cases HEF was used (6x primary joint infection, 3x septic failure of TKA, lx infected osteosynthesis). 2 pat. denied written consent for HEF, another 2 pat. had infected ipsilaterale midshaft femor-and/or tibia non unions. Because of these we used the ACN.

Results: In 5 pat. (21.7%) treated with MCR 1,4 revision procedures were indicated to eradicate infection before the implantation of MCR. Recurrence of infection after implantation occurred in 13% (n=3): 2 pat. were treated non surgically, lx amputation had to be done. No radiological signs for implant loosening were seen. HEF was removed after 15 weeks (12–18w) on average. 5 revision procedures were necessary in HEF cases (lx Pin-, lx ring exchange, lx sequestrectomy after pintractinfection,)- hi 2 cases the procedure was changed to MCR because of a non-union. Using the ACN we saw a 100% fusion rate, in one case the sinus tract persisted. The check up examinations were done 8,7 month (2,4–22,4mo) after arthrodesis procedure. 82,6% of pat. after MCR, 100% after HEF- and ACN-had full weight bearing capability. Eradication of infection was achieved in 86,9% (n=20) after MCR, in 70% (n=7) after HEF and in 75% (n=3) after ACN. In all 3 groups soft tissue reconstruction by flap surgery was indicated in 20%.

Conclusion: HEF is indicated when bone loss allows bony fusion. Failure occurred when bone defects were underestimated ort he fixator was removed before the 14th week. MCR can be used when eradication of infection is success and because of bone defects direct fusion is not possible. When eradication is not possible and bone stock makes the fusion reliable the ACN can be used under ongoing infection. ACN is also used when HEF is not recommended by the patient or because of mechanical reasons (floating knee).

C. Gigante A. Borgo G. Perrone S. Bonaga S. Turra

Introduction: In temperate places pyomyositis is very uncommon in children and adolescents. West European and North American Literature about is relatively poor (104 articles from 1998 to nowadays and most of these papers are case-rep orts). S. Aureus is the etiologic agent in 90% of cases. Muscle of the thighs and hips are the most frequent localisation and severe complications are observed in 10% of cases.

Material and Methods: We reviewed all patients affected by primary pyomyositis and admitted in our Department from 1995 to nowadays. Age, sex, history and clinical findings, general and local risk factors were reported. X-rays, Ultrasonography, MRI, Scintigraphy, Haematological investigation and culture were considered in order to state the imaging and laboratory findings of the disease.

Result: Pyomyositis was diagnosed in three males, aged 11, 13 and 16. There was no evidence of medical or familiar risk factors. Soleus, Otturatorius and Psoas muscles were respectively involved. In all cases fever, local signs of inflammation and pain, neutrophylic leukocytosis, increased ESR and CRP levels were present. Blood culture was positive in one case. Standard X-Rays were normal in all cases. Ultrasound scan, RMI and Scintigraphy were positive but non-specific in all cases. 2 cases underwent to surgical drainage and a 3 weeks antibiotic therapy; 1 case resolved performing only medical treatment (5 weeks of antibiotic). All patients showed complete clinical, haematological, and RMI recovered without reliquates.

Conclusions: Pyomyositis is uncommon in temperate climate and it may be easy misdiagnosed at the onset. In our patients the mean time from onset of symptoms to diagnosis was 10 days. History and clinical examination might be evocative, but there are no pathognomonic haematological or radiological findings so that diagnosis is often the result of extensive and wide considerations. Pyomyositis should be suspected in any unclear septic condition of the musculoskeletal apparatus. High index of suspicion, prompt diagnosis, and early treatment can prevent complications and allow the recovery of this potentially life-threatening disease.

F. Lazzaro S. Mapelli S. Bastoni

Introduction: Infection following major orthopaedic oncological surgery is a serious complication and every precaution should be taken to avoid it.

One potential source of infection is the biopsy procedure, particularly when is carried out of a referring centre. In fact up to 30 per cent of patients with soft tissues problems following a biopsy is reported. As an infected biopsy may make subsequent limb preservation surgery impractical, the greatest care should be taken in carrying out the biopsy.

The implantation of foreign materials (prostheses, grafts, acrilic cement, metallic devices, etc) as the duration of the surgical procedure, intraoperative bleeding, possible deep haematomas, presence of drains, increase the risk of infection. Also the importance of haematogenous spread from other sites of infection to joint pros-thesis is well estabilished.

Materials and methods: In this paper the Authors present their experience regarding septic complications after orthopaedic oncologie surgery. From 1988 to 2002, 143 patients underwent a major surgery for the treatment of skeletal neoplasms (wide resection and reconstruction employing modular or composite prostheses, osteoarticular or intercalary allografts, acrylic cement and osteosynthesis devices, major spinal surgery, internal hemipelvectomy, etc).

Results: The patients were followed-up to detect the presence of a septic complication. Also patient’s files were revised to evaluate paramethers related to infection as bleeding, duration of surgery, postoperative fever, neutropenia, ESR and CRP, antibiotic prophylaxis, etc. The overall infection rate was approximately to 15 per cent.

Conclusions: Immunosuppression from previous chemotherapy may predispose the patient to infection which may be occult, but which must be diligently sought.

It has to be also emphasized that if at any stage the patient has had local radiotherapy, the tissues may be fibrosed and avascular and unable to combat local infection effectively.

The Authors retain that the infection after major orthopaedic oncologie surgery could represent a serious threat to the implant and to the limb. The importance of meticolous asepsis practised at every stage has to be emphasized, together with prolonged use of prophylactic antibiotic, specially in immunosuppressed patients or chemotherapy.

P. Costigliola A. Andollina A. Maso G. Bertoni A. Borrelli D. Tigani F. Chiodo

Introduction: The aim of study was to evaluate the prevalence of microbiological isolates obtained from patients admitted to a 308-bed university-affiliated adult and children orthopaedic hospital of northern Italy (with more than 16.000 admissions per year), during a three year period (2000–2002), and, to analyze modifications during this period with regard to the prevalence of methicillin-resistant staphylococci strains.

Material and Methods: A retrospective study was conducted using laboratory records from 2000 to 2002 (2003 in progress) concerning bacterial and yeast isolates from all specimens sent to microbiological laboratory for culture. The specimens came from 8 surgical, 1 intensive care, 1 oncologie and 1 physiotherapy wards and included samples taken at surgical intervention, as like as at patient bed. Antimicrobial susceptibility testing results were also collected. All data were stored in an electronic database for statistical analysis.

Results: Between 2000 and 2002 a total of 8302 clinical specimens have been cultured and they yielded to 2978 isolates from 2653 positive samples. The prevalence of positive cultures form 24.8% in 2000 to 36.7% in 2002 and the isolated organisms are shown in table 1. Gram positive bacteria represent more than 70% of isolates and staphylococci are the most common organism (almost 50%). Staphylococcus epidermidis and other coagulase-negative staphylococci prevalence raised during the period 2000–2002 (respectively 25.4% to 33.4%, and 3.3% to 6.5%). Methicillin resistance rate resulted, 27.1% to 34.9% for Staphylococcus aureus, 37.6% to 28% for Staphylococcus epidermidis, and 33.3% to 42.1% for other coagulase-negative staphylococci. No difference in methicillin sensitivity was found between staphylococci isolated from surgical sites and other samples (urine, blood, sputum, throat swab).

Conclusions: Knowledge of the local epidemiology of pathogens in a surgical/orthopaedic hospital is critical in formulating policies on infection control. Amongst these rules the choice of antibiotic prophylaxis should be taken after analysis of bacteria prevalence and their antibiotic sensitivity.

S. Mapelli E. Usellini L. Odoni E. Meani

Introduction: The problems of the differential diagnosis (d.d.) between musculoskeletal infections and tumours are generally uncommon because both pathologies are quite rare. This is not the experience at the G. Pini Orthopaedic Institute where there are two Units specialized on bone infections and bone tumours and their clinicians often consult each other for difficult cases.

Material and Methods: On the basis of this experience, the A.A. revised clinical and radiological criteria of d.d. between acute or chronic osteomyelitis and different histotypes of musculoskeletal tumours. In particular they examined the type and the course of the symptoms, the laboratory data, the site of the lesions and the characteristics of the imaging, both for bone damages and for soft tissues invasion. Afterwards they compared this revision whit the experience of the cases consulted each other.

Results: D.d. of acute osteomyelitis include Ewing sarcoma, Osteosarcoma and Eosinofilìe granuloma, especially in children; d.d. of chronic and deep lesions (axial skeleton) in adults include lymphoma and metastasis; in the epiphysis d.d. can involve also benign lesions. This work allowed the A.A. to identify some guidelines that they consider suitable. Time, possibilities and limits of the imaging techniques like bone scans, CT and MRI are outlined, likewise time and types of direct examination of the lesions by puncture or biopsy, that was necessary in many cases, are proposed.

Conclusions: The A.A. think that these personal guidelines can help them to face easier, in the future, the difficult cases, minimizing both diagnostics and therapeutics delays and mistakes.

Luca Lazzarini Fausto de Lalla

Introduction: Antibiotic prophylaxis is a standard practice in prosthetic orthopaedic surgery. In total knee arthroplasty (TKA), several surgeons routinarily use a tourniquet to interrupt the blood circulation of the leg to be operated. The penetration of systemically given antibiotics is reduced by the tourniquet. To avoid this problem, some authors administered the antibiotic in a leg vein, after tourniquet inflation, to enhance antibiotic penetration in the operative field. We reviewed the available literature about the use of regional prophylaxis in TKA.

Materials and methods: The medical literature was seeked by means of the PubMed (National Library of Medicine, Washington, USA) research engine. The keywords «prophylaxis», «knee» «arthroplasty», «regional» were used in various combinations.

Results: In 1990, Hoddinott et Al. compared the bone and fat penetration of two cephalosporins (cefaman-dole and cefuroxime) given either by the systemic and the regional route, and found the concentrations after regional administration significantly higher.

A similar result was confirmed by Field et Al. in 1992.

In 1993, de Lalla et Al. compared the systemic administration of 800 mg teicoplanin with the regional administration of 400 mg teicoplanin, and found higher levels of drug in the tissues of the operative field after regional administration.

In 2000, the same authors enrolled 205 prostheses in a clinical trial to assess the efficacy of the regional prophylaxis with 400 mg teicoplanin, and did not record any prosthetic infection.

In 2001, Lazzarini et Al. reviewed 217 patients who received regional prophylaxis with 400 mg teicoplanin for TKA, and found 8 (2.9%) surgical site infections, mostly occurring in patients with previous TKA.

In 2003, Lazzarini et Al. compared the tissue levels of teicoplanin after systemic administration of 800 mg and after the regional administration of 200 mg. The tissue levels after regional administration were still higher than those after systemic administration.

Conclusion: There is a good evidence for the use of regional prophylaxis when a tourniquet is used for TKA.

M. Graf L. Özokyay S. Ahrens F. Kutscha-Lissberg

Introduction: Although more than 30 different surgical procedures to achieve solid ankle fusion were described, after septic joint destruction or ongoing infection external fixation is preferred. In 1999 the referring institution reported on 45 cases with internal (screw) fixation and additional external fixation [1]. Later on we used hybrid external fixation including transfixation of the midfoot [2]. Since range of motion of the middle and forefoot is of great importance for limb function we designed a prospective study to compare fusion rate and limb function after ankle fusion without foot or midfoot transfixation.

Patients and Methods: Between 9/2000 and 2/2002 18 patients with septic ankle destruction were admitted for ankle fusion. 10 patients were treated with a fine wire ring fixator using 2 full rings in the tibia and one 5/8 shaped ring in the calcaneus and talus. Compression was applicated only between the distal tibia and the talus. Every 14 days the wires were retensioned. 8 patients were treated with a titanium compression nail in an antegrad technique. All operations were done by one surgeon. 14 patients had a posttraumatic osteitis complicated in 6 cases by polyneurophathy and in two cases previous fusion failed. 4 patients suffered from diabetic polyneuropathy, 2 of them with ongoing infection. In both techniques weight bearing was allowed after 3 weeks.

Results: External fixator was removed 16 weeks after operation on average (14w–18w). Solid fusion was achieved in 16 cases (88%). In 3 patients the fistula persisted in one of them fusion failed. Dynamic pedobarography showed better results in patients without fixation of the subtalar joint. (Compression nail)

Conclusion: The study showed similar fusion rates compared with surgical procedures including transfixation of the whole foot. Range of motion of the not fused joints of the foot was better because early physioptherapy was performed. The fixation of the fore and mid foot is not necessary to achieve solid fusion by increased stability.

P.G. Scotton L. Cesaris M. Collodel U. De Nicola A. Vaglia A

Introduction: We studied from July 1997 infected hip and knee arthroplasties treated with only antimicrobial therapy without removal of the implants. The patients enrolled were not eligible for surgical operation or refused it. We tried to understand the role of this kind of therapy for the infections at stage I, II and III.

Material and Methods: We evaluated patients with hip or knee infected arthroplasties at stage I, II and III, respectively: an early infection (2–4 weeks after the prosthesis implantation), a chronic infection that appears more than one month after the operation and an hematogenous infection. The prosthetic hip infections were treated with an oral therapy for 6 months, while the prosthetic knee infections were treated for 9 months. Follow up examinations were conducted regularly for two years

Results: We observed 35 patients from July 1997: 15 with an infection at stage I, 17 at stage II: and 3 at stage III. In 23 patients the prosthesis affected was the hip, while in 12 patients it was the knee. The infections were due in most cases to Staphylococci (85.7%), while in 4 patients (3 cases of hematogenous infection) the pathogens isolated were Gram negative bacteria and 1 infection was due to Clostridium perfrigens. Only in 9 (25.6%) patients was performed a debridement before the beginning of the medical therapy. The overall success rate at one year of follow up was 72.7% (24/33), the success for the patients in stage I was 86.6%(13/15), in stage II 60% (9/15) and for stage III was 66.6% (2/3).

Conclusions: In patients with arthroplasty infection at stage I and III a long-term antimicrobial treatment, without the implant removal, could be a good chance, especially when the pathogen isolated is a S. aureus or a S. coagulase negative. As we expected the success rate for infection at stage II was the lower that we observed between all the prosthetic joint infection, treated with the only antimicrobial therapy. The gold standard for the treatment of stage II should be prosthesis revision (1 or 2 stages); but in our study we enrolled patients not eligible for surgical operation, because of severe clinical conditions, or patients that refused it. With these results we cannot recommend the medical therapy alone, but we can use it as a salvage therapy. As for the infections at stage I and III, no relapse had been observed after one year of follow up; we think that, especially for infections at stage II, a one-year follow up could be sufficient for the identification of the relapses.

S. Navarro J.M. Madrigal F. Najarro F. Santos R. Pérez F. Huesa S. Rodriguez F. Romero-Candau

Introduction: To introduce a unit of bone and joint infections and to show the first result after a-two-year clinic experience.

Material and Methods: The bone and joint infections represent the most fearsome difficulty for surgeons. In order to deal with this kind of patient a multidiciplinary team work is required. In our Health Centre, in the year 2001, it has been made up a unit, directed by an Orthopedic surgeon, Head doctor of the Centre, and which is formed by two more Orthopedic surgeons; belonging the first one to the unit of plastic surgery and the second to the infection commission; furthermore, there is a specialist in internal medicine, a specialist in family and community medicine, a specialist in rehabilitation, a specialist in laboratory and clinic analysis and a nurse. Five beds of restricted entry and a monographic consult are also available. The way of work consists of two-day-a-week combined visists to floors and a weekly clinic session. Outpatients are seen by Orhtopedic surgeons of the unit, the internist doctor, the rehabilitators in their everyday consults and the monographic consult of the enfermary. Patients who are admitted in the unit are affected with bone and joint infection: Only exceptionally, patients in need of hospital isolation and with tissue infections caused by germs, are admitted; namely, Acinetobacter baumannii, Staphylococcus methicillm-resistant.

Results: Results of the unit after two-year clinic experience are presented:

We have treated a total of 82 patients, 78 of them where men and 4 women, between 18 and 58 years old. Most of the patients were included in, first in the 40–50 (21 patients) and second in the 30-40 (26 patients) years-old range. Out of the 82 patients, 64 had ostheomyelitis, 10 arthritis and 8 soft tissue infection. The first localization for the ostheomyelitis has been in tibia (30 cases) and in femur (8 cases). The etiology is distributed in: 32 infections after osteosynthesis and 27 after an open fracture. The germs mostly isolated were Gram positives: Staphylococcus coagula negatives (21), staphylococcus methicillin-sensitive(14) y enterococcus (5); Gram negatives: Pseudomona aeruginosa (14), Serratia (3), Enterobacter (2).

Conclusions: In our opinion a unit of bone and joint infections as a multidiciplinary medical team work improves the clinic quality.

M. Buttaro R. Valentini F. Piccaluga

Introduction: Maximum effort should be taken during surgical debridement of an infected hip arthroplasty to remove all implants and cement, as also granulation, devitalized and necrotic tissue. Nevertheless, this process is sometimes technically demanding, risky for bone stock and prolongs the procedure. Residual unremoved polymethylmethacrylate (PMMA) after the resection of infected prosthetic components constitutes a controversial issue.

Material and Methods: We analyzed 10 patients with infected total hip prosthesis that had been previously treated with resection arthroplasty and antibiotics who presented persistent infection with residual cement. In 9 patients, surgical debridement with resection of all the PMMA was performed, and adequate intravenous antibiotics were administered. One patient refused surgical treatment, but accepted antibiotics.

Results: At an average 4 (1–18) years follow-up, 8 patients evolved with no signs or symptoms of recurrent infection. One severely immunodeficient patient died 2 years after the removal of residual cement for reasons other than his hip with an intermitent fistula. The patient who refused surgical treatment continues to have an active sinus 4 years after first consultation.

Conclusions: Residual cement could be responsible for chronic infection. Resection arthroplasty as part of the treatment of an infected hip arthroplasty must be precise and thorough, and all devitalized or foreign material must be removed.

Giuliana Carrega Giovanni Riccio Clemente Sandrone

Background: In recent years there has been an increase in the insertion of prosthetic devices in orthopaedics. In spite of improvements in surgical techniques and antibiotic prophylaxis, the absolute number of infectious complications is high. Infections have a negative impact in patient’s quality of life and have high costs of management.

Patients and Methods: Retrospective analysis of diagnosis, aetiology, and therapy of prosthetic devices infections observed from 1985 to 1999 in the operative unit for diagnosis and treatment of Infections in orthopaedics of Ospedale S. Corona- Pietra Ligure (SV).

Results: During the study period, 251 patients with infected hip prosthesis and 133 with infected knee prosthesis had been treated. Diagnosis of infection was made by means of clinical features supported by x-ray, MRI, CT scan, ultrasonography and radio-nuclide scan. Aetiology was established by microbiological culture and histology. The majority of cases were single agent infections due to Gram-positives, especially S. aureus and S epidermidis, isolated in 41% of hip and 53% of knee prosthesis infection, while P. aeruginosa represented the most frequently isolated Gram-negative (3% in hip prosthesis and 10.6 % in kne prosthesis).

Polymicrobial infections (with constant presence of S. aureus and/or S. epidermidis) accounted for 8% of hip and 7% of knee prosthesis infections. Treatment was represented by prolonged antibiotic administration (at least 8 weeks) associated with surgical debridment inacute infections, and two-stage exchange in chronic infections. In 23 hip infections in patients in poor clinical conditions or in suspected persistence of latent infection a new prosthesis was not replaced and Girdlestone’s hip arthroplasty was performed.

Conclusions: Gram-positives are the main cause of orthopaedic infections but Gram-negatives, especially P aeruginosa, are often isolated. The treatment must necessarily be combined: antibiotic therapy and surgical treatment. Only in presence of optimal conditions a new prosthesis can be replaced.

A.J. Swieringa N.J.A. Tulp M.J.H.M. Wolfhagen

Introduction: The results of total hip arthroplasty are in general very good. One of the factors with a negative influence on the outcome is an infection of the prosthesis. The prevalence of an acute post-operative infection is in the Netherlands in the range of 0.5 up to 2.0%. Different types of treatment are advised in the literature.

Methods and Material: In 1997 we started to treat all the acute infected THA according a protocol of open surgical debridement, pulsative irrigation, application of several gentamicin loaded sponges and starting directly post-operative an antibiotic combination therapy of flucloxacillin and rifampin. The antibiotic therapy was adjusted to the cultures taken during the operation and continued till 3 months after the debridement.

From Mars 1997 till July 2003 we subsequent included 32 patients, 26 with a minimal follow-up of 2 years are presented in this study. We evaluated the results of the treatment prospectively. The inflammatory parameters; C-reactive protein, erythrocyte sedimentation rate and white blood cell count (before and after debridement) The Harris Hip Score and radiograms were monitored multiple times.

Results: The mean onset of infection symptoms till surgical debridement was ldays (range 0–15). All had high-elevated infection parameters and in all cases we found positive tissue cultures. 15 Times a Staphylococcus aureus was found, 5 times a Enterobacter cloacae, twice a Streptococcus, once a Pseudomonas, once a Klebsiella and once a peptostreptococcus. The average follow-up was 46 months (range 24–74).

In 23 patients the infection did not re-appear. The C-reactive protein normalised from a mean of 103 (2–320) to lower than 5 at 2 years, the erythrocyte sedimentation rate from 72 (14–120) to lower than 10. The white blood cell count was not elevated.

In none of the cases radiological signs of loosening was found and the mean HHS was 88 (75–96) points.

However in 3 patients the infection did re-occur: once after 2.5 months with the same bacterium as the first infection, a Streptococcus, again treated with a surgical debridement. At present she is clinical free of infection at a follow up of 2 years. The 2 other re-infections occurred respectively after 9 and 10 months, once after a surgical treatment of a jaw abscess and once after an episode of diverticulitis. The cultures derived other bacteria, a streptococcus and an E. coli, than the first infection, both a Staphylococcus aureus. In both cases a two-stage revision was the choice of treatment.

Conclusion: Finally 24 of the 26 acute infected hip arthroplasties were free of infection at 2 years follow-up. Surgical debridement and three months of antibiotics gave a good clinical result and a very low recurrent rate of the infection.

M.V. Loraas I. Skr̊mm G. Bukholm

Introduction: Besides having various health consequences for the patients, post-operative wound infections following orthopaedic surgery increase health costs, often markedly. Optimal estimates of such costs require accurate incidence data over a prolonged period.

The test group: Five hundreds and eighty consecutive patients undergoing orthopaedic surgery during the period May 1st 1998 to December 31st 1999 were studied. They underwent either of the following procedures: total primary hip replacement; total primary knee replacement; operations for trochanter-major fracture (using Hip Compression Screw); ankle fractures.

Methods: The basic cost of the 580 operations was estimated from the aggregated costs of diagnosed related groups (DRG)-costs, applying only major codes. Patients who had to be re-admitted later because of wound infections during 1999 were studied and their secondary, wound-infection related costs was estimated from the aggregated DRG-costs during these hospitalisations.

Results: A total of 47 of the 580 patients had a diagnosis of a post-operative wound infection, 14 were deep and 33 were superficial infections; 15 were readmitted for their infections. The additional days of hospitalisation for these re-admissions totaled 270 hospital days with an aggregated cost of 230.000.- Euro, compared to 3.000.000.- Euro for all 580 operations (fig. l shows graphically expenses caused by post operative wound infections as a fraction of the total cost).

Discussion: Additional hospital costs related to postoperative wound infections amounted to 7% of the total hospital costs over a period of 20 months. Additional expenses not counted are those related to insurance compensations, sick leave compensations, expenses related to doctor visits and visits to out patient departments besides expenses related to additional nursing at home. Added to strict economic calculations are less easily calculable, short or prolonged reductions in quality of life. It is emphasized that post-operative wound infections after orthopaedic surgery represent a major cause for additional health expenses and reductions in quality of life.

T. Stock A. Wulke D. Frank B. Jansen

Introduction: Survivorship of total joint replacement is limited by infection or mechanical failure. While acute infection is obvious low grade infection is sometimes difficult to prove.

Regarding to the literature the management in revision surgery I terms of differentiate between septic and aseptic loosening is still a matter of debate.

Material and Methods: From 1997 to 2004 we investigated 228 revision total knee replacements prospectively as far as bacterial colonisation is concerned. If there was pre- or intraoperative evidence of infection the loosening was quoted as septic. So 40 two stage revision in cases of suspicion and 188 one stage revision had been performed.

Specimen of joint fluid, of membranes from the metal-cement a