Introduction: Staphylococcal bacteria, especially the coagulase negative Staphylococci, are responsible for the majority of orthopaedic device related infection. These infections are sub acute, and may not present for months or years following surgery. The virulence of these bacteria is related to their ability to form biofilm, a protective slime which allows them to survive the effects of the host immune system and antimicrobial therapy. Treatment of biofilm based infection almost always necessitates removal of the implant.

Recent work has identified environmental stimuli which induce biofilm formation in Staphylococci. These include stressors such as high temperature, high osmolarity, anaerobiosis, nutrient depletion, salt, ethanol and subinhibitory concentrations of certain antimicrobial drugs. Given the ability of these bacteria to survive the “respiratory burst” from the cells of the mononuclear-macrophage system, we hypothesised that oxidative stress may be one such promoter of biofilm formation by Staphylococci.

Methods and Materials: Staphylococcus epidermidis CSF41498 and Staphylococcus aureus RN422O were selected for study as these are known biofilm forming organisms. Hydrogen peroxide (H₂O₂) was used as an oxidizing agent.

Bacteria were incubated for 24 hours at 37°C in Brain-Heart Infusion (BHI, Oxoid) containing progressively weaker concentrations of H₂O₂ to determine a Minimal Inhibitory Concentration (M.I.C.) for the representative strains. Bacterial viability was assessed by measuring the optical density of the incubated culture using a cell density meter (Ultraspec 10, Amersham Biosciences).

The bacteria were then grown as a biofilm on a 96 well microtitre plate (Nunc) in the presence of subinhibitory concentrations of H₂O₂, using pure BHI as a control. Semiquantative determination of biofilm formation was performed by washing the plates, staining the adherent cells with crystal violet, and measuring the light absorbance of the adherent stained cells at 492 nm using a Multiskan plate reader (Flow Laboratories).

Results: The M.I.C. of H₂O₂ was 18 mM for both Staphylococcus epidermidis CSF41498 and Staphylococcus aureus RN422O. Concentrations of H₂O₂ of 16 mM and below had no normal bacterial growth and replication.

There was no difference in biofilm formation by Staphylococcus epidermidis csf41498 in the presence of 15 mM H₂O₂ when compared to that of the control. However, H₂O₂ had a significant inhibitory effect on biofilm formation by Staphylococcus aureus RN422O, even at a concentration well below the M.I.C.

Conclusion: We conclude that oxidative stress may have an antibiofilm action on certain Staphylococcal species, which is independent from its bactericidal effect, and which is manifest at a concentration below the M.I.C. for that species.

First described in 1910, Legg Calve Perthes disease is considered to be a complication of osteonecrosis of the femoral head-affecting children between the ages of 2 and 12. Treatment has centred on containment, surgical and non-surgical in the hope that keeping the femoral head covered by acetabulum that it will remodel and maintain congruency with the acetabulum. We know from previous studies that deformities of the femoral head increase the risk of development of arthritis in later life and that the shape of the femoral head is the only alterable parameter in the development of this early onset arthritis.

During the natural history of the disease, once the central part of the femoral head collapses the integrity of the femoral head is reliant on the support of the lateral and medial columns. These columns then collapse altering the shape of the femoral head. We induced LCPD in the femoral heads of twenty skeletally immature rabbits and buttressed the central column of the femoral head in twelve. These treated rabbits had cement, bone graft or bone paste inserted through a drill hole that extended into the centre of the femoral head. The rabbits were then recovered and x-rayed at six weeks. All the rabbits had evidence of varying degrees of head collapse radiologically. Once the rabbits reach skeletal maturity in March, they will be euthanised and their femoral heads examined histologically and radiologically to determine the effects of central column enhancement by each of the three substances.

The aim of this study is to evaluate the effectiveness of the application of vibration, during the femoral cementation, as a cementing technique.

It has been demonstrated that when vibration of a constant frequency was utilised, flow of low viscosity cement increased with vibration of increasing amplitude up to a particular acceleration. Above this acceleration there was little additional benefit. It has also been shown that when constant amplitude was used the flow increase was uniform over a wide frequency range, eventually falling off over a particular frequency. These results prove that the flow of orthopaedic bone cement is significantly affected by mechanical vibration of the receiving structure. It is our hypothesis that vibration promotes the ingress of bone cement into cancellous bone.

The effect of mechanical vibration in the frequency range 0–500 Hz on the cadaveric human femur has been assessed in the past. It was found that when the bone was fixed at both ends, its resonant frequency was markedly affected by end loading and damping. If the conditions of the experiment were designed to simulate the condition of the femur when prepared for a total hip replacement, it was found that the bone did not resonate but behaved in a mass-like mode. The significance of this observation is that in the event of vibration being applied to enhance the penetration of orthopaedic bone cement, the movement induced in the bone will be proportional to the force applied regardless of frequency.

Introduction: The meniscus plays an important role in protecting the articular surfaces of the tibia and femur from excessive wear due to aberrant forces across the knee joint. While the biochemical changes associated with cartilage and meniscal wear have been well documented, little data exists in the literature describing the ultrastructural events associated with such a degenerative process.

Aim: To develop an in vivo model to evaluate the effects of joint incongruity on meniscal wear.

Materials and Methods: Six New Zealand White rabbits underwent an arthrotomy of the right knee joint. A sagittal osteotomy of the medial femoral condyle was then performed on four of these animals while the remaining two served as controls. Post operatively all animals were allowed to mobilise ad librium and were sacrificed after 20 weeks. The medial meniscus was harvested and processed for electron microscopy by routine methods. Survey light microscopy sections (1um) were examined and adjacent ultra-thin sections (50nm) were assessed in an electron microscope at magnifications from 1,500 to 30,000.

Results: On gross examination of the menisci there was no evidence of any significant wear. Neither was there noticeable damage on light microscopy. There was no significant difference in the numbers of chondrocytes and fibroblasts in the superior and inferior surfaces of both control and test samples, indicating a lack of cellular response in the test specimens. On electron microscopy, the superficial electron dense layer was markedly attenuated in test subjects (control 246 – 305 nm, test 109 – 167nm). The superior surfaces of two test samples were markedly roughened, while chondral fragments were noted in craters on the surface. Numerous cystic lesions were present within the superficial collagen stroma of test subjects. Interestingly cleavage planes were noted in the superior and inferior aspects of one of the four test subjects. No difference in collagen fibril diameter was observed between control and test subjects.

Discussion: These results represent the early stages of meniscal degeneration. The process appears to one of microfibrillation, with degeneration occurring within the bundles of collagen fibrils rather than within the substance of the fibrils themselves. The absence of a healing response suggests that this is an intractable process, a finding which accords well with findings in the clinical setting.

Management of symptomatic residual acetabular dysplasia in adolescence and early adulthood remains a major therapeutic challenge. At our unit the two senior authors review all patients preoperatively and simultaneously perform each procedure. In the four years from 1998 forty-three Bernese osteotomies were performed in 40 patients with residual acetabular dysplasia. The mean average age at surgery was 21 years (range 12 – 43 years) and there were 34 female patients. The indication for surgery was symptomatic hip dysplasia (all idiopathic but for one male with a history of slipped capital femoral epiphysis) presenting with pain and restricted ambulation. 4 patients had previous surgery on the affected hip (2 Salter’s osteotomy, one Shelf procedure and one proximal femoral osteotomy). 27.5% of patients had symptomatic bilateral disease. 42% of patients had Severin class IV or V dysplasia at presentation. 100% of patients had preservation of the hip joint at last follow-up evaluation (mean 2.4 years), with excellent results in 82%, an average post-operative Harris hip score of 96, and an average d’Aubigne hip score of 16.1. The mean post-operative improvements in radiographic measures were as follows: Anterior centre edge angle +19.4°, Lateral centre angle +25.8°, Acetabular Index – 10.7°. Head to Ischial distance – 7.3mm. Surgical operative time decreased from 128 minutes to 43 minutes from the first to the most recent case. Average blood loss has reduced from 1850mls to 420mls over the four years experience. Predonation of 2 units of blood requested from all patients with baseline hemoglobin of > 12g/dl. When combined with intraopera-tive cell salvage the need for transfusion of homologous blood has been eliminated. All complications occurred in the first 9 patients: (one major – iliac vein injury requiring no further treatment; four moderate – lateral cutaneous nerve injuries; four minor – asymptomatic heterotopic ossification). Our experience confirms that the Ganz periacetabular osteotomy is an efficacious procedure for the treatment of the residually dysplastic hip, providing excellent clinical results, where early intervention is the key to improved outcome. It is a technically demanding procedure with a significant early learning curve and we believe that a two

Introduction: This retrospective study examined the clinical characteristics, radiological findings, management, and functional outcome in 34 rehabilitated patients who presented with traumatic central cord syndrome.

Methods: Between 1994 and 2004 a total of 34 patients with central cord syndrome were admitted to the National Spinal Injuries Unit. There were 29 men and 5 women. The mean age was 56.1 years (15 to 88). The mean follow up time was 4.9 years. Patients were divided into three groups by age, < 50 years (10 patients), 50–70 years (16 patients), and > 70 years (8 patients). The American Spinal Injury Association (ASIA) system recorded the motor and sensory scores, of upper and lower limbs, on admission, discharge and during rehabilitation. Patients underwent radiological investigation that included plain film, CT, and MRI of the cervical spine.

Results: The mechanism of injury was a fall in 58.8%, road traffic accident in 35.2% and other in 6%. Alcohol was a contributing factor in 32.4% of cases. Seven patients had a spinal fracture. The cervical spine was involved in 5 cases with the remaining 2 cases involving the thoracic spine. Seventy percent of patients received intravenous steroids. Over half (53%) of the patients had some degree of cervical spondylosis while cord changes were seen in almost all of the patients (79.4%). In the majority of cases (70.4%) the affected level was C3/4. Disc herniation was present in one third of cases (33.2%). The mean upper limb ASIA score on admission was 7.6, on discharge was 12.4 and at follow up was 20.2. A similar pattern was also observed in the lower limb with scores of 12.1, 13.7, and 20.5 respectively. Sensory loss also improved with time. 88.2% of those admitted required urinary catheterization, with 23.5% being discharged to the National Rehabilitation Hospital with a catheter in situ. Surgical decompression was performed in 7 cases. The remainder of patients wore a Miami-J cervical collar.

Conclusion: As was shown in the original paper by Schneider et al (1954), hyperextension of a degenerative cervical spine was the predominant mechanism of injury. The return of lower limb function precedes that of upper limb, with autonomic function recovering in the majority of cases.

Discussion: In this study patients in the younger age groups had better recovery of function and had fewer complications. The original paper by Schneider et al. stated that conservative treatment was most appropriate, however, in this review surgery was performed in specific cases such as those with cord compression secondary to disc herniation. Alcohol was a significant contributing factor.

Introduction: Recent data from the UK suggests that the incidence of osteomyelitis in the paediatric population is declining. However, the incidence in the Scandic countries has risen in the late eighties and nineties. We undertook to examine the epidemiology of osteomyelitis presenting to a paediatric teaching hospital in an Irish urban setting.

Patients and Methods: We undertook a retrospective review to identify patients admitted over a twenty-five year period with a diagnosis of osteomyelitis. Patients were identified from hospital records, theatre log-books and a departmental database. Demographic data was collected, as were details of the infected bony structure, treatment required and organism cultured.

Results: A total of 291 patients were admitted over a twenty-four year period, from 1977 to 2000.

A marked reduction in osteomyelitis was noted over the twenty-four year incidence of the study. In addition, a shift in the causative organism was noted from an incidence of H Influenzae in the 70’s of up to 30%, to less than 5% in the 90’s. The treatment regime changed markedly over the course of the study period, with a significantly reduced duration of hospital stay reflecting the move away from protracted periods of hospitalisation.

Conclusion: A marked fall in osteomyelitis has occurred in the paediatric population. This may be due to improved living conditions and the introduction of H Influenzae vaccinations. The duration of hospital stay has declined markedly and the introduction of newer imaging modalities has aided diagnosis, allowing early aggressive intervention. However, as osteomyelitis is becoming increasingly rare, a higher index of suspicion is required, particularly from non-specialists who are more likely to be the first to encounter these patients.

Introduction: The magnitude of the initial chondral injury and the residual articular step-off are amongst prognostic factors implicated in outcome following intra-articular fractures. The alignment of an intra-articular fracture line may be an as yet unrecognised prognostic variable.

Hypothesis: That fractures in the coronal plane of the medial femoral condyle result in worse outcomes than those in the sagittal plane.

Aim: To compare the effect of displaced intra-articular osteotomies (ie simulating fractures fixed in an incongruent position) of the medial femoral condyle – in one group performed in the sagittal plane, in the other in the coronal plane.

Materials and Methods: The study was conducted in two arms: in vitro and in vivo.

In vitro study: A pneumo-electric rig was designed and built. Ten freshly harvested porcine knee joints underwent osteotomy (test specimens: 5 sagittal, 5 coronal). 5 control specimens underwent no osteotomy. Specimens were mounted on the rig and subjected to cyclical flexion and extension under load (40,000 cycles over 11 hours). Transarticular pressure measurements were performed before and after testing. Surface roughness was measured following testing using laser interferometry.

In vivo study: Three groups (A to C), each comprising 15 New Zealand white rabbits were utilised. Rabbits from each group were consigned to a control (5), coronal osteotomy (5) or sagittal osteotomy (5) group. Rabbits in group A were sacrificed at 3 weeks (early outcome), group B at 10 weeks (immediate) and group C at 20 weeks (long term). The knee was then harvested en bloc and prepared for light microscopy. A further 10 specimens underwent electron microscopy of the medial meniscus.

Results:

In vitro study: A significant difference in loading patterns was noted between the sagittal, coronal and control groups. Specimens from the sagittal group sustained significantly more wear on the apposing medial tibial articular surface (p=0.04), with the meniscus having a protective effect on the underlying articular surface.

In vivo study: Light microscopy confirmed degenerative changes in the apposing tibial articular cartilage, being more marked in sagittal specimens. On the femoral side of the knee, the healing response of the femoral osteotomy was significantly better in sagittal test specimens than coronal (p< 0.05).

Conclusion: In contrast to the hypothesis, sagittal femoral step-offs gave rise to more tibial wear. This can be explained by the short duration of exposure of the coronal incongruity to the apposing joint during the flexion extension cycle. The sagittal step-off was constantly exposed, giving rise to persistently elevated tibial joint loading pressures opposite the high side of the step-off.

In contrast, the coronal femoral osteotomies had a worse healing response. The alignment of the fracture line perpendicular to the plane of motion of the joint exposes the repair tissue within it to increased shear and tensile stresses. This may play a negative role in the repair of these coronal defects when compared to sagittal osteotomies, which are relatively protected from the high transarticular pressures and showed a greater tendency to remodel their articular surface.

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.

Aims: Developmental dysplasia of the hip (DDH) is a common paediatric orthopaedic problem. Open reduction and debridement of the hip joint in neonates is necessary to ensure a congruent reduction in some patients. Despite advances in the treatment of DDH, the various surgical approaches are not without limitations and risks. The purpose of this study was: (a) to design a suitable animal model of DDH for the purpose of designing and evaluating hip arthroscopy, (b) to document the pathoanatomy of the dysplastic hip arthroscopically and (c) to deþne the methodology of performing hip arthroscopy in neonates with DDH. Methods: A novel model of producing hip dysplasia in large white cross piglets has been created. 4-week-old piglets undergo surgical þxation of the knee by retrograde passage of a 3.5mm diameter steinmann pin. After free ambulation, progressive hip dysplasia is produced. We have monitored the development of hip dysplasia at 4 and 6 weeks post þxation by plain radiographs, MRI and Hip Arthroscopy using a 2.7mm diameter arthroscope. Results: We have successfully produced hip dysplasia in an animal model of comparable size and anatomy to that seen in infants. Hip arthroscopy was performed in 20 animals. Documentation of a lax capsule, elongated ligamentum teres and pulvinar has been made. In addition arthroscopic debridement of the joint has been performed. We believe that arthroscopic debridement of the impediments to reduction in DDH is possible using the techniques learned from this model.

Aims: The aim of this study was to investigate the ability of control and degenerate human nucleus pulposis to respond to an exogenous proinßammatory stimulus. Methods: Disc material from patients undergoing surgery for scoliosis, sciatica and low back pain was cultured under basal and lipopolysaccharride (LPS) stimulated conditions using a serumless technique. Levels of IL-1β, TNFα, LTB4, GM-CSF, IL-6, IL-8, MCP-1, PGE2, bFGF and TGFβ-1 in the media were estimated using commercially available enzyme linked immunoabsorbent assay kits. Results: Neither basal nor LPS stimulated control nucleus pulposis (NP) produced detectable levels of IL-1β, TNFα, LTB4 or GM-CSF. LPS induced a significant increase in scoliotic disc IL-8 production, p< .02. LPS induced signiþcant increases in degenerate disc IL-6, IL-8 and PGE2 production, p< .01, p< .001 and p< .005 respectively. LPS signiþcantly increased degenerate disc IL-6, IL-8 and PGE2 production compared to LPS stimulated scoliotic disc, p< .05, p< .02 and p< .003 respectively. Conclusions: Human nucleus pulposus can react to a pro-inßammatory stimulus by secreting IL-6, IL-8 and PGE2, suggesting that the NP may actively participate in the genesis of chemical radiculitis and dis-cogenic back pain.

Management of symptomatic residual acetabular dysplasia in adolescence and early adulthood remains a major therapeutic challenge. At our unit the two senior authors review all patients preoperatively and simultaneously perform each procedure. In the four years from 1998 forty-three Bernese osteotomies were performed in 40 patients with residual acetabular dysplasia. The mean average age at surgery was 21 years (range 12 – 43 years) and there were 34 female patients. The indication for surgery was symptomatic hip dysplasia (all idiopathic but for one male with a history of slipped capital femoral epiphysis) presenting with pain and restricted ambulation. 4 patients had previous surgery on the affected hip (2 Salter’s osteotomy, one Shelf procedure and one proximal femoral osteotomy). 27.5% of patients had symptomatic bilateral disease. 42% of patients had Severin class IV or V dysplasia at presentation. 100% of patients had preservation of the hip joint at last follow-up evaluation (mean 2.4 years), with excellent results in 82%, an average post-operative Harris hip score of 96, and an average d’Aubigne hip score of 16.1. The mean post-operative improvements in radiographic measures were as follows: Anterior centre edge angle +19.4°, Lateral centre angle +25.8°, Acetabular Index – 10.7°. Head to Ischial distance – 7.3mm. Surgical operative time decreased from 128 minutes to 43 minutes from the first to the most recent case. Average blood loss has reduced from 1850mls to 420mls over the four years experience. Predonation of 2 units of blood requested from all patients with baseline hemoglobin of > 12g/dl. When combined with intraoperative cell salvage the need for transfusion of homologous blood has been eliminated. All complications occurred in the first 9 patients: (one major – iliac vein injury requiring no further treatment; four moderate – lateral cutaneous nerve injuries; four minor – asymptomatic heterotopic ossification). Our experience confirms that the Ganz peri-acetabular osteotomy is an efficacious procedure for the treatment of the residually dysplastic hip, providing excellent clinical results, where early intervention is the key to improved outcome. It is a technically demanding procedure with a significant early learning curve and we believe that a two-surgeon approach is invaluable to the management of these difficult cases.

Introduction: Outcome following intra-articular fractures is dependent on a myriad of variables, including the extent of the initial osteochondral and soft tissue injury. In the clinical setting it is impossible to control such variables, and studies are largely confined to radiographic and outcome based assessments. Therefore the effect of fracture line orientation has not been widely examined. Theoretically an incongruent intra-articular fracture results in a “low” side that is relatively unloaded, at the expense of a “high” side exposed to increased loads. Furthermore the orientation of the fracture may give rise to a narrow or broad swathe of wear on the opposing articular surface.

Aim: To evaluate the effect of an incongruent intra-articular fracture of the medial femoral condyle on subsequent loading and wear patterns, using an in vitro model.

Materials and Methods: 15 porcine stifle (knee) joints were harvested within three hours of death. Three groups of five joints were evaluated. Group S underwent a sagittal osteotomy of the medical femoral condyle that was then fixed in an incongruent position. In Group C the osteotomy was performed in the coronal plane. The third group acted as a control group and had no oseotomy performed. In all cases great care was taken to prevent injury to the menisci, articular surfaces and Ligamentous structures. The size of the step-off was documented using a contour-mapping machine (CMN). In addition the surface roughness of the femoral condyles was documented using a laser interferometry device (UBM, Germany). The specimen was mounted on a custom-made electro-pneumatic rig, and pressure mapping of the articular surfaces performed with pressure sensitive film (SPI, New Jersey, USA). Following mapping, each specimen underwent 10,000 cycles of flexion and extension over a three-hour period. When testing was complete, pressure mapping was again performed, the size of the step-off re-measured using the CNM, and surface roughness of the menisci, femoral condyles and tibial plateau assessed. Data was restored on a laptop for subsequent statistical analysis.

Results: Pressure mapping documented an unloaded area on the low side of the step-off in both Group C and S. This extended up to 8mm, and was mirrored by an area of increased load on the high side. Following testing, the area exposed to altered loads on both the high and low side of the osteotomy had diminished. On ANOVA testing the uncovered tibial articular surfaces in test subjects were significantly rougher than control specimens, though no difference was noted between Groups C and S (Mean Ra value GC: 101.83+22.78, GS: 93.52+17.89, ns. vs. Con 53.45+25.8,p< 0.05). Meniscal surface roughness was greater in the test groups, though this did not reach statistical significance. No significant difference in femoral condyle surface roughness was noted following testing. Nor was any difference noted in surface roughness in the submeniscal areas of the tibial articular surface.

Discussion: The displaced femoral osteotomy resulted in an area of increased wear on the opposing tibial articular surface. However no significant difference was noted between the coronal and sagittal group. It is probable that the menisci negated the effect of fracture line orientation. We suggest that they minimized secondary articular damage by decreasing the area of direct tibiofemoral contact. Furthermore the elasticity of the menisci, in addition to their ability to move in the anteroposterior plane further decreased stress transmission between joint surfaces. Further studies will be performed on the hip joint to determine the effect of articular incongruity in the absence of such a fibrocartilage buffer.

Introduction: Subject to recent literature citing a reduction in ankle range of motion predisposing to ankle fractures in children, we decided prospectively to analyse the passive range of motion in children presenting to our fracture clinic with simple distal radial metaphyseal fractures treated conservatively in cast.

The range of motion was assessed by two observers, and measured using a goniometer in 80 patients. (42 radial fractures and 38 controls) The controls were recruited from children presenting with lower limb injuries and with no prior history of an upper limb injury or neuromuscular condition. The fractures were as a result of simple falls onto the outstretched hand with definite radiological and clinical findings. The range of motion in the contralateral limb was assessed. Both groups showed an equal distribution of dominant and non-dominant limbs.

Results: Both groups were well matched with an average age of 10 and 10.3 years fracture group and control group respectively, and gender 55% male fracture group and 52.5% control group. The m injured group showed a passive range of motion of 1680, whereas the control group showed a higher range of motion of 1820, a difference of 140 (p< . 005 student t-test). A third blinded independent observer of 20 children assessed Intra and interobserver error, and no observer was noted to have higher or lower readings.

Conclusion: Children with radial fractures have a lower passive range of motion of their wrists than Controls. This may contribute to the aetiology of wrist fractures in a paediatric population. An possible explanation may be as cited in original work that children who sustain fractures have less mobility around their joints due to reduced elasticity in their musculoskeletal framework. Simple passive stretching of fracture prone joints should therefore be advised.

Background: Developmental dysplasia of the hip (DDH) is a common paediatric orthopaedic problem. Open reduction and debridement of the hip joint in neonates is necessary to ensure a congruent reduction in some patients. Despite advances in the treatment of DDH, the various surgical approaches are not without limitations and risks. The development of hip arthroscopy is a new science, which we believe could be applied to the treatment of DDH.

Aims: To date there have been no reports in the literature of the use of hip arthroscopy in either the neonatal hip or in infantile hips with DDH. The purpose of this study was: (a) to design a suitable animal model of DDH for the purpose of designing and evaluating hip arthroscopy, (b) to document the pathoanatomy of the dysplastic hip arthroscopically and (c) to define the methodology of performing hip arthroscopy in neonates with DDH.

Method: A novel model of producing hip dysplasia in large white cross piglets has been created. 4-week-old piglets undergo surgical fixation of the knee by retrograde passage of a 3.5mm diameter steinmann pin. After free ambulation, progressive hip dysplasia is produced. We have monitored the development of hip dysplasia at 4 and 6 weeks post fixation by plain radiographs, MRI and Hip Arthroscopy using a 2.7mm diameter arthro-scope.

Results: We have successfully produced hip dysplasia in an animal model of comparable size and anatomy to that seen in infants. Hip arthroscopy was performed in 20 animals. Documentation of a lax capsule, elongated ligamentum teres and pulvinar has been made. In addition arthroscopic debridement of the joint has been performed. We believe that arthroscopic debridement of the impediments to reduction in DDH is possible using the techniques learned from this model.

Introduction: Elucidation of the exact cause of adolescent idiopathic scoliosis (AIS) remains an elusive goal. The intervertebral disc is one of the many areas that have been investigated in an effort to find a cause for this condition. We hypothesize that a qualitative change in the orientation of collagen fibers in the annular layers of the disc could cause the deformity seen in AIS. This paper presents a mathematical model of such a change and how it could produce appropriate deforming forces. Hypothesis: In the normal disc the collagen fibers are obliquely orientated. Fibers in adjacent lamellae are orientated in opposing directions. This means that as forces are transmitted from a compressed nucleus to the annular fibers there is no net force tending to rotate one vertebra with respect to its neighbour. If there is a preponderance of fibers running in one direction as the nucleus is compressed there will be a net resultant force perpendicular to the long axis of the spine tending to produce an intervertebral rotation. This intervertebral rotation, applied to successive spinal segments will cause a scoliotic deformity.

Model: The highly oriented structure of the AF suggests the utility of an explicit representation of the collagen fibres and their mechanical contribution to disc function. In our study we have considered two groups of fibres, representing the clockwise and counter clockwise fibres in the disc. The AF is considered as a continuum containing two populations of fibres assumes to be of equal density and uniform distribution within an isotropic material as originally described by Spencer. Nuclear compression as a result of growth was modelled as a tendency to produce increased intervertebral separation of spinal segments and examined whether the resultant transformation that leads to a scoliotic pattern of deformity. Based on anatomical data from literature the positions of the 12 nodes that represent the thoracic vertebrae are applied to the model. The three-dimensional location of each vertebral body is defined. We store the coordinates of thoracic vertebrae in a three-dimensional matrix. In the present study in order to involve the translation operation in our transformation, we have used the homogeneous transformation matrix or Denavit & Hartenberg matrix.

In the present model for the initial set of transformations the reference axis is chosen to be the lowest vertebral axis (T-12) and remains unchanged throughout the transformation. All elements of the spine above the reference axis are transformed (translated and rotated). After completion of this iteration and storing the values for the origin coordinate and vector values in the next level of the matrix, the next reference axis is chosen. For the second axis everything above the axis will be transformed in the same way with the current axis and the one preceding it remaining unchanged. Therefore for each transformation a new reference axis is taken and the transformations are applied to all vectors and origins above it leaving all elements preceding it unchanged by the transformation.

Results: The first part of the model shows that rotational displacement increases linearly with changes in the fibre ratio. Rotational displacement on the other hand occurs independently of distraction of the vertebral bodies. When the rotational displacement is applied to a series of segments it produces alterations of curvature in the three planes. Specifically it produces a lateral curvature in the coronal plane and a hypokyphotic curvature in the saggital plane. The magnitude of these displacements varies with the imbalance in fibre ratio. Discussion: The proposed changes in annular fiber orientation have been modeled using accepted mathematical methods. These changes will produce an intervertebral rotation whose magnitude depends on the degree of fiber imbalance akin to that seen in AIS. When the displacements produced by this rotation being applied to a series of segments is modeled, it will produce a three dimensional deformity similar to that seen in AIS. Ongoing histological studies are being performed to see if the proposed imbalance can be identified in patients with AIS. Such a fiber orientation anomaly may be genetically determined by some fashion of directional sense gene and may be the aetiological basis for AIS.

Recently there has been considerable interest in the role of inflammatory mediator production by herniated degenerate discs. Modic has described MR endplate changes which have an inflammatory appearance and have been linked with discogenic back pain. To date there has been no biomechanical investigation of discs with associated Modic changes.

The aim of this study is to determine if degenerate discs with associated Modic changes have higher levels of pro-inflammatory mediator production than those without Modic changes.

Intervertebral disc tissue was obtained from 52 patients undergoing spinal surgery for sciatica [40] and discogram proven discogenic low back pain [12]. The tissue was cultured and the medium analysed for interleukin-6, interleukin-8 and prostaglandin E2 using an enzyme linked immunoabsorbetn assay method. Preoperative MR images of the patients were examined by a double blinded radiologist to determine the Modic status of the cultured disc level.

Forty percent of patients undergoing surgery for discogenic low back pain had a Modic 1 change compared to only 12.5% of patients undergoing surgery for sciatica [p< .05] There was a statistically significant difference between levels of IL-6, IL-8 and PGE2 production by both the Modic1 [M1] and Modic2 [M2] groups compared to the Modic negative [NEG] group. IL-6:NEGvM1 p< .001, NEG v M2 p< .05, IL-8: NEG v M1 p< .01, NEG v M2 p> .05, PGE2: NEG v M1 p< 01, NEG v M2 p< .05.

Modic changes have been associated with positive provocative discography by a number of authors. Pain generation requires the presence of nerves and hyperalgsia inducing mediators. Both IL-8 and PGE2 are known to induce hyperalgesia. The fact that Modic changes are associated with high levels of production of these mediators supports their role as an objective marker of discogenic low back pain.

Cement is still in common usage in primary and revision arthroplasty surgery. Infection rates in cemented arthroplasties ranges from 1–4% and poses a huge problem for the revision arthroplasty surgeon. Infection in septic implants is biofilm based and almost completely resistant to conventional anti-microbial therapy. Recent papers have questioned the efficacy of using gentamicin-loaded cement in arthroplasty as staphylococcus aureus biofilms will develop on same. The focus of this study was to investigate the efficacy of antibiotic loaded cement in preventing initial bacterial adhesion and subsequent development of a bacterial biofilm in vitro.

Three cements Simplex unloaded, Simplex with erythromycin and Simplex with tobramycin were mixed in a conventional manner, ie vacuum hand mixing in sterile conditions and then injected into pre-moulded PTFE coated cylinder moulds yielding 8 cylinders in each group. The cement cylinders were then removed and exposed to a known pathogenic strain of staphylococcus aureus ATCC—29213-NCTC 12973 in solution 3x10⁶ Colony forming units CFH/ml) for 15 minutes. The cylinders were then removed and cultured for 24 hours at 37°C in RPMI with Glutamine. Cylinders were then removed and subjected to rinsing in PBS to remove any non-adherent bacteria. Cylinders were then sonicated at 50 Hz in Ringer’s solution and adherent biofilms were serially log diluted and plated on Columbia blood agar. Colonies were counted manually. Control cylinders of unloaded cement showed 120,000 CFU/cm² of adherent bacteria whereas loaded cement erythromycin and tobramycin showed 500 and 80 CFU/cm² respectively (p< .0005 Student t-test).

This study shows that loaded cement does not prevent biofilm adhesion in its initial reversible stages whereas unloaded cement does not. This is important since most infected implants are infected at time of primary operation and cements anti-bacterial role beyond the first 48 hours remains questionable, when inflammatory encapsulation of the implant begins. We would therefore question the usage of unloaded cement in primary arthroplasty surgery.

Metallic implants are used frequently in the operative repair of joints and fractures in orthopaedic surgery. Orthopaedic implant infection is chronic and biofilm based. Present treatment focuses on removing the infective substratum and implant surgically as well as prolonged anti-microbial therapy. Biofilms are up to 500 times more resistant than planktonic strains of bacterial flora to antibiotics. Silver coatings on polymers and nylon (catheters, heart valve cuffs, burn dressings) have shown inhibition of this biofilm formation in its adhesion stage. Our aim was to deposit effective, minute, antibacterial layers of silver on orthopaedic stainless steel and titanium K-wires and to investigate the effect of these coatings when exposed to Staphylococcus Aureus biofilms in an in vitro and in vivo environment.

Combining magnetron sputtering with a neutral atom beam (Saddle Field) plasma source at 10⁻⁴ mbar in argon gas at temperatures of 60°C, a silver coating of 99.9% purity was deposited onto stainless steel and titanium orthopaedic K-wires. Coating thickness measurements were obtained using glancing angle x-ray diffraction of glass slides coated adjacent to wires. Magnetron parameters were modified to produce varying thickness of silver. Adhesiveness was examined using Rockwell punch tests. Silver leaching experiments were carried out in phosphate buffered saline at 37°C for 48 hours and using inductive coupled plasma spectrometry to assess leached silver ions. Surface microscopy visualised physical changes in the coatings.

Biofilm adhesion was determined by exposing wires to Staphylococcus Aureus ATCC 29213 – NCTC 12973 for 15 minutes to allow biofilm initiation and adhesion. Wires were then culturing for 24 hours at 37°C in RPMI. Subsequently, wires were sonicated at 50Hz in ringer’s solution and gently vortexed to dislodge biofilm. Sonicate was plated out by log dilution method on Columbia blood agar plates. Bacterial colonies were then counted and changes expressed in log factors.

K-wires were coated with 1 to 50 nm of silver by running the magnetron sputtering at low currents. These coatings showed excellent adhesive properties within the 48 hours exposed with only 3.7% of silver leaching in buffered saline. The silver coated stainless steel wires showed a log 2.31 fold reduction in biofilm formation as compared to control wires (p< .001), Student t-test), the silver coated titanium wires showed a log reduction of 2.06, (p< .001, Student t-test). Animal studies demonstrated enormous difficulty in reproducing biofilm formation and showed a 0.49 log fold reduction in the titanium group when exposed to Staph Aureus (p< .01, Student t-test), the other groups showed no statistically significant reduction.

We have perfected a method of depositing tiny layers of anti-bacterial silver onto stainless steel and titanium, which is anti-infective in vitro but not in vivo. Further studies involving other metal coatings such as platinum and copper are warranted.

Introduction: While the incidence of infection associated with hip and knee prosthesis is low, with the increasing number of arthroplasties being carried out, the total number of such cases is increasing. Also increasing is the number of multi-resistant organisms. These factors have raised questions regarding the optimal antibiotic impregnated cement for use in both spacers and in cemented revisions.

While gentamycin, erythromycin, cefotaxime and vanomycin have a proven record as effective thermostatic antibiotics, newer antibiotics teicoplanin (although used in clinical practice) are as yet untested.

Aim: To investigate the effectiveness of teicoplanin impregnated cement against a Staph Aureus.

Method: A pure culture of Staphlococcus Aureus with known antibiotic sensitivities was obtained. Six batches of Palacos cement were mixed without under sterile conditions. One batch contained cement alone. The other 5 batches were mixed with one of gentamycin, vancomycin, erythromycin, cefotaxime and teicoplanin.

Group 1: A pure culture of over 60 colonies was grown on 5 Columbian blood agar plates. A 1cm spherical sample of each batch of the cement was placed on each plate at regular intervals and allowed to heat and harden.

Group 2: A further 1cm spherical ball of cement from each batch were placed on a further 5 blood agar plates which were then inoculated with the Staph Aureus and the cement was allowed to heat and harden.

Group 3: 24 hours later, the cement was placed on a further 5 blood agar plates which were then inoculated with the Staph Aureus.

Results: Group 1: None of the cement groups had any effect on the established colonies of Staph Aureus.

Groups 2 & 3: The cement without antibiotic had no effect on the growth of the antibiotic even when allowed to heat on the plate. All the other groups including the teicoplanin impregnated cement both initially and after 24 hours, caused a zone of inhibition, ie prevented bacterial growth.

Conclusion:

Heat alone did not affect the growth of the bacteria.