Aims: After Total Hip Replacement (THR), bearing surface pistoning during the gait cycle can affect wear rates. This ‘micro-separation’ has been shown clinically by video-fluoroscopy to be greater with a Metal-on-Polyethylene (MOP) bearing than a Metal-on-Metal (MOM) one. In this study, we quantified the suction forces that these bearings generate during the swing phase of the gait cycle as a result of interfacial tension from the thin fluid film present at the bearing surface. Methods: We used a servo-hydraulic universal testing machine with 250N load cell and programmed a sinusoidal waveform that could vary the loads and frequencies applied to MOP or MOM bearings submerged in 25% serum. We measured the bearing separation (±1μm) at tensile loads of 10N to 100N lasting 0.1s to 0.5s per 1Hz cycle.

Results: MOM bearings resisted tensile loads of up to 35N when applied for 0.1s to 0.5s of the simulated gait cycle. Bearing separation was measured at a maximum of 198 microns. Above 50N, the MOM bearing was unable to prevent separation occurring even when applied for only 0.1s of the simulated gait cycle (p< 0.001). The MOP bearing could not resist separation at any of the applied tensile loads (p< 0.0001).

Conclusions: The suction-fit of the MOM bearing used in this study is insufficient to prevent bearing separation due to gravity (110N). However, it may reduce the total bearing separation distance by delaying the time point at which separation occurs during the finite period of the swing phase (< 0.5s) during the gait cycle. This effect is crucially dependent upon the bearing clearance, bearing diameter, weight of the leg, speed of walking and soft tissue tension around the hip. This ultimately relies upon prosthetic design, patient selection and surgical technique.

Aims: Metal-on-Metal (MOM) bearings for Total Hip Arthroplasty (THA) are known to elevate the serum concentrations of metal ions, raising concern about possible long-term side-effects. One potential modifier of ion release is the bearing diameter used. Resurfacing MOM bearings have a large surface area available for corrosion, 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.

Methods: In this study, we measured the serum cobalt and chromium levels from 22 large diameter MOM resurfacing arthroplasties (Cormet2000 & Birmingham Hip Resurfacing) and compared them to 22 THA (Ultima) with a bearing diameter of 28 mm. Patients were prospectively matched for activity level, weight and date after surgery. All were at least 6 months after surgery.

Results: At a median of 16 months (range 7 to 56) after resurfacing arthroplasty, we found the median serum cobalt and chromium levels to be 38 nmol/l (14 to 44) and 53 nmol/l (23 to 165) respectively. Both these figures were significantly greater than the levels after 28 mm MOM THA, which were 22 nmol/l (15 to 87, p=0.021) and 19 nmol/l (2 to 58, p< 0.001) for cobalt and chromium respectively.

Conclusions: As the upper limit of normal in patients without implants is typically 5 nmol/l, both groups had significantly raised metal ion levels, albeit at a relatively short median follow-up period. Large diameter MOM bearings resulted in a greater systemic release of cobalt and chromium ions than did small diameter bearings. This may be of relevance for potential long-term side-effects. It is not known to what extent this difference is due to corrosion of the component surfaces or of the wear particles produced.

The purpose of the project was to develop a questionnaire for completion by patients with elbow pathologies which is short and practical, internally consistent, valid, responsive and sensitive to changes of clinical importance.

The first, pilot phase included 43 patients who each completed a 19 item questionnaire relating to elbow function. The 19 ADLs produced a total scale Cronbach Alpha of 0.96., two different groups of ADLs were identified by multivariate analysis. Group 1 consisted of ADLs requiring moderate to high isometric loading and Group 2 of ADLs requiring high flexion. From the 19 items the best 10 which represented both groups were selected. A summary score was used to create the Wrightington Elbow Disability Score (WEDS).

In the second phase 89 patients completed the new WEDS form, reliability studies produced a Cronbach’s alpha value of 0.91. Internal validity of the groups of ADLs all correlated at p< 0.001 level with strength (Group1) and flexion (Group 2). A sub set of 40 patients undergoing total elbow arthroplasty were assessed for sensitivity to change in disability, the WEDS indicated a significant improvement at the p< 0.001. Convergent validity was demonstrated by the correlation with the ASES-e score at p< 0.001 level. The WEDS was significantly correlated with the ASES-e but not the DASH score.

Our study confirms that the WEDS questionnaire which is short and practical, is internally consistent, valid, responsive and sensitive to changes of clinical importance.

Background: The necessity for radiographic follow up of infants with hip clicks and normal ultrasound is not clear.

Materials and methods: Infants referred to a paediatric hip clinic whose sole risk factor for DDH was a soft tissue hip click who had a normal ultrasound scan on initial assessment were identified. A follow up six month AP pelvis radiograph was assessed and acetabular index(A.I), position of femoral ossific nucleus and Shen-ton’s line measured. Infants with rotated pelvis Xrays were excluded. Inter-observer variability for acetabular index was measured and dysplasia defined according to Tonnis.

Results: 171 infants (193 clicking hips) met the criteria for inclusion. 48 male and 109 female with unilateral clicks (57 right, 64 left) and 36 bilateral clicks. 10 were excluded due to rotation of the AP pelvis Xray. Inter-observer error for A.I. was 4°. All A.I. were within normal ranges. Shenton’s line was unbroken and all hips were located.

Conclusion: In this study infants with soft tissue hip clicks and a normal ultrasound scan on initial assessment had a normal Xray at six months.

Clinical screening aims to identify and treat infants with neonatal hip instability in order to reduce the risk of subsequent hip displacement but risks failures of diagnosis and treatment (abduction splinting) and potential iatrogenic effects. The Hip Trial aims to assess the clinical effectiveness of ultrasound (US) imaging compared to clinical assessment alone to guide the further management of infants with clinical hip instability.

Infants with clinical hip instability confirmed by a second senior doctor were recruited from 33 UK centres and randomised to standardised US hip examination at age 2–8 weeks [US group: n=314] or clinical assessment alone [no ultrasound (NU) group: n=315. ] Primary outcomes by two years were hip X-ray appearances, operative treatment, abduction, splinting and walking. Analysis was ‘intention to treat’.

Key prognostic factors were similar between the randomised groups. Protocol compliance was high (90% US; 92% NU). X-ray information was available for 91% by 12–14 months and 85% by two years. Fewer children in the US group had abduction splinting in the first two years (RR 0. 78; 95% CI 0. 65–0. 94; p=0. 01). Operative treatment was required by 21 US (6. 7%) and 25 NU (7. 9%) infants (RR 0. 84; 95% CI 0. 48–1. 47. ) By two years, subluxation, dislocation, acetabular dysplasia or avascular necrosis were identified on X-ray on one or both hips of 21 US and 21 NU children (RR 1. 00; 95% CI 0. 56 – 1. 80. ) One US and 4 NU children were not walking by two years (RR 0. 25; exact 95% CI 0. 03–2. 53; p=0. 37)

The use of US imaging in infants with screen-detected clinical hip instability allows abduction splinting rates to be reduced, and is not associated with an increase in abnormal hip development or higher rates of operative treatment by two years of age.

Between June 1988 and December 1997, 332 babies with 546 dysplastic hips were treated in the Pavlik harness for primary Developmental Dysplasia (DDH) as a product of the Southampton selective screening program. Each was managed by a strict protocol including ultrasonic monitoring of treatment within the harness. The group was prospectively studied over a mean duration of 6. 5 years (SD=2. 7y) with 89. 1% follow-up. The Acetabular Index (AI) and Centre-Edge angle of Wiberg (CEA) were measured on annual radiographs to determine the natural history of hip development following treatment in the Pavilik harness. These were compared to published normal values.

We observed a failed reduction rate of 15. 2% of all complete hip dislocations; these required alternative surgical treatment. The development of those hips of infants successfully treated in the harness showed no significant difference from the normal values of Acetabular Index for female left hips, after eighteen months of age. Of those dysplastic hips that were successfully reduced in the harness; 2. 4% exhibited persisting significant late dysplasia (CEA< 20°) and 0.2% demonstrated persistent severe late dysplasia (CEA< 15 °) All such cases could be identified at sixty months. Dysplasia was clinically deemed sufficient to merit innominate osteotomy in 0. 9% dysplastic hips treated. Avascular necrosis was noted in 1% of hips treated in the harness.

We conclude that using our protocol, successful initial treatment of DDH with the Pavlik harness appears to revert the natural history of hip development to that of the normal population. We recommend that regular radiographic surveillance up to 60 months of age constitutes safe and effective practice.

Differentiating cases of aseptic loosening of total hip arthroplasty (THA) from loosening due to low-grade infection can often be difficult. It is possible that some cases of ‘aseptic’ loosening may be related to unidentified bacterial infection.

Using Polymerase Chain Reaction (PCR), this study attempted to identify the frequency with which bacterial DNA could be observed at revision arthroplasty for what was considered ‘aseptic’ loosening.

All revision cases had to fulfil strict criteria to be considered aseptically loose In all cases operative specimens from the synovial fluid, synovium, femoral and acetabular membranes where possible were sent for analysis by histology, bacteriology and by PCR to identify the presence of the 16S bacterial ribosomal fraction, an indicator of bacterial DNA. Ten bacteria per millilitre of tissue/fluid were the threshold for detection. As a control for environmental contamination, specimens from primary THA were also sent for analysis in the same manner as revisions.

The identification of bacterial DNA in at least one sample from a patient was considered a positive case result.

45 revision THA were identified over a 3-year period (1998–2001). From those 45 revision cases, 163 specimens were sent for analysis by PCR. These specimens were compared to the control group of 34 primary THA from which 91 specimens were sent for analysis by PCR. When analysed by specimens positive by PCR, bacterial DNA was identified in 55 of 163 specimens sent from the 45 revision THA. This compared with 21 of 91 specimens positive by PCR sent from the 34 primary THA (p=0. 07).

When analysed by cases positive by PCR, bacterial DNA was identified in 29 of 45 revision THA and in 8 of 34 primary THA (p< 0. 001).

PCR is a sensitive test for detecting infection in revision THA. Results from the primary THA cases would suggest there is at least a 23% false positive rate even with negative bacterial culture. The increased frequency with which bacterial DNA has been identified in ‘aseptically’ loose revision THAs, however, is unlikely to be due solely to environmental contamination. These results may have relevance for our interpretation and understanding of aseptic loosening as well for the diagnosis of prosthetic infection.

The objective of this study was to compare the wear mode of 100 Mrad PE cups run in a hip simulator to retrieved 100 Mrad PE cups, and to evaluate the efficacy of the PE wear model.

15 In-vitro PE cups: 3 each 0,2.5.50,100 and 150 Mrad (9 channel hip simulator, 6.2 million cycle duration, physiological load profile by Paul, 2000N maximum load at 1Hz using 30% bovine serum). 5 Retrieved PE cups: three SOM cups (Mizuho Medical Instrument Co., COP alloy 28 mm head)-0 Mrad after 8 years of clinical use, two 100 Mrad cups after 15 years of clinical use, two T28 PE 2.5 Mrad cups (Zimmer): 18 years and 13 years of clinical use. The cups were examined using a SEM (Philip XL30 FEG) for wear scar locations and PE wear-topography.

Original machine marks were observed in the weight-bearing areas of the highly cross-linked in-vitro PE. No machine marks were observed for the 0 and 2.5 Mrad in-vitro cups and none were seen in any of the retrieved cups. The formation of more nodules and fibrils in the 0Mrad cups compared to the extensivley cross-linked cups (in-vitro and retrieved) was striking. The frequency of occurrence and length of the fibrils and nodules was dependent on the dose of gamma irradiation. More ripples were formed in the 2.5 Mrad and higher cups compared to the non-irradiated cups (in-vitro and retrieved). The in-vitro cups formed more ripples than the retrieved cups. In general, the SEM features for in-vitro Mrad cups appeared similar to those of the retrieved Mrad cups.

The in-vitro Mrad cups accurately reflected the conditions of the artificial joint in living body. Therefore, comparisons of retrieved PE cups with simulator PE cups appeared to be a very powerful research tool.

(2) SEM observation demonstrated far less wear damage in the extensively cross-linked cups than in the non-extensively cross-linked PE. Thus the extensive cross-linked PE cups appeared to be a significant improvement over conventional PE cups in terms of wear resistance.

Programmed cell death (PCD) contributes to the pathogenesis of many diseases including osteoarthritis. The principal method is apoptosis that has a well-defined and very characteristic morphology and biochemistry.

The aim of the present study was examine whether the mechanism of cell death in OA chondrocytes was classical apoptosis.

Rat thymocytes were used as controls since these cells are known to undergo classical apoptosis. Human OA cartilage was obtained from femoral head of patients (50 – 80 years) who were undergoing joint replacement surgery. Pieces of OA samples were processed into paraffin and sections incubated with the following antibodies: M3O, an antibody that recognizes the cleavage of cytokeratin 18 by caspases; annexin V, which recognizes phosphatidylserine “flip-flop” that occurs early in the apoptotic process; bcl-2, a protein whose presence protects apoptosis and c-myc, a transcription factor thought to be associated with apoptosis. To induce apoptosis, some samples were incubated with etoposide and staurosporine.

In sections of thymus we noticed the presence of numerous apoptotic bodies. The number increased when the tissue was treated with etoposide and staurosporine. Some thymocytes were immunopositive for M3O and annexin V, and the number of positive cells increased when treated for 2h with etoposide. Chondrocytes of the articular cartilage showed chromatin condensation and many vacuoles but no fragmentation into apoptotic bodies, even when treated with etoposide or staurosporine. The OA chondrocytes were immunonegative for M3O and annexin-V, even after incubation with etoposide and staurosporine. With respect to c-myc and bcl-2, both non-weight bearing and weight-bearing areas in OA sample showed more positive cells then the thymus. More chondrocytes stained for c-myc in the superficial zone of the articular cartilage in the non-weight bearing, while in the weight-bearing areas it was more in the intermediate zone. On the other hand, there were no differences in the distribution of the cells stained for bcl-2 in the articular cartilage. It is known that some events like the phosphatidylserine flip, caspase activation and apoptotic bodies fragmentation occur quickly during apoptosis, so may be difficult to detect.

The results suggest that some features of classical apoptosis, such as phosphatidylserine flip,caspase activation and apoptotic bodies formation did not take place in OA cartilage. It is known that the molecular machinery for apoptosis is not always present in tissues that are undergoing programmed cell death, which seems to be case for OA chondrocytes.

Background: Metal-on-metal (MOM) bearing surfaces with low diametric clearance possess a surface tension that prevents easy separation of the surfaces when lubricated. Potentially this ‘suction-fit’ may increase the torque required for dislocation. This study assessed the protective role of a MOM bearing surface as a single risk factor for dislocation.

Method: Prospective data was recorded on a series of 229 patients undergoing 249 primary THR for osteoarthritis. From 1993–8, patients under 70 years old were routinely given a 28mm ceramic-on-polyethylene (COP) bearing surface. Due to a high dislocation rate (see results below), an alternative was sought (1998–2001) and a 28mm metal-on-metal (MOM) bearing system chosen. For all cases in both groups, the acetabulum was uncemented with a modular 10° posterior lip insert allowing the same primary arc range (Duraloc/PFC/ Ultima, Johnson & Johnson). The cemented femoral component was the same in all cases (Ultima). All operations were performed by the same surgeon using the posterior approach. Variables in patient and prosthesis factors were compared. Statistical analysis was performed by the Chi-square and student’s t-test where appropriate.

Results: We identified 140 THR in 129 patients who received a COP bearing and 109 THR in 100 patients who received a MOM bearing. Nine of 140 (6.4%) COP bearings dislocated within 3 months of surgery compared to 1 of 109 (0.9%) in the MOM group (p=0.028). No significant differences were identified between groups when comparing factors relating to the patient or prosthesis.

Discussion: This study has shown a high dislocation rate for a COP bearing that was reduced to a low dislocation rate by changing the bearing surface to a MOM design. A potential mechanism for this may be the ‘suction fit’ from the surface tension of the low clearance, high tolerance that the metal-on-metal bearing possesses, requiring increased torque to dislocate during impingement.

The formation of biomimetic environments using scaffolds containing cell recognition sequence and osteo-inductive factors in combination with bone cells offers tremendous potential for bone and cartilage regeneration. In tissues, collagen forms the scaffold by mediating the flux of chemical and mechanical stimuli. Recently, a synthetic 15-residue peptide P-15, related biologically to the active domain of type I collagen, has been found to promote attachment and the osteoblast phenotype of human dermal fibroblasts and periodontal ligament fibroblasts on particulate anorganic bone mineral (ABM). The aim of this study was to exam the ability of the collagen peptide, P-15, to promote human osteoprogenitor attachment, proliferation and differentiation on cell culture surfaces and 3-D scaffolds.

Selected human bone marrow cells were cultured on particulate microporous anorganic bone mineral (‘pure ‘ hydroxyapatite based on x-ray diffraction standard JCPDS9-432) phase and polygalactin vicryl mesh adsorbed with or without P-15 in basal or osteogenic conditions. Cell adhesion, spreading and patterning were examined by light and confocal microscopy following incorporation of cell tracker green and ethidium homodimer fluorescent labels. Osteoprogenitor proliferation and differentiation was assessed by DNA content and alkaline phosphatase specific activity. Growth and differentiation on 3-D ABM structures were examined by confocal and scanning electron microscopy (SEM).

P-15 promoted human osteoprogenitor cell attachment and patterning on particulate bovine anorganic bone mineral phase and polygalactin vicryl mesh over 5–24 hours compared to culture on ABM and vicryl mesh alone as observed by photomicroscopy. Increased alkaline phosphatase specific activity was enhanced following culture on P-15 adsorbed matrices as recognized by enhanced expression of alkaline phosphatase, type I collagen, osteocalcin and cfba-1. The presence of mineralised bone matrix and extensive cell ingrowth and cellular bridging between 3-D ABM matrices and polygalactin vicryl mesh adsorbed with P-15 was observed by confocal microscopy and alizarin red staining. SEM confirmed the 3-D structure of newly formed cell constructs and cellular ingrowth on and between the P-15 modified inorganic bone mineral materials. Negligible cell growth was observed on ABM alone or polygalactin vicryl mesh alone.

These observations demonstrate that the synthetic 15-residue collagen peptide, P-15, when adsorbed to ABM or polygalactin vicryl mesh, can stimulate human osteoprogenitor attachment and spreading. They also demonstrated that P-15 coupled 3-D matrices stimulate human osteoprogenitor differentiation and materialisation. The studies indicate that a synthetic analogue of collagen provides a biomimetic environment supportive for cell differentiation and tissue regeneration and indicate a potential for the use of extracellular matrix cue in the development of biomimetic environments for bone tissue engineering.

Purpose: To describe the characteristic examination findings post whiplash injury of relevance to the shoulder surgeon and an injection test, which can be used to abolish these signs and distinguish neck from shoulder pathology.

5A large amount has been written about whiplash injuries of the neck, but many of these patients are often referred to shoulder units for assessment either acutely or years after the accident because of continuing symptoms. Although neck pain is the commonest complaint tenderness on examination is sided and within the trapezius muscle in virtually all cases. Pain referred to the shoulder is also reported in 36 – 67% whilst interscapular pain occurs in 20 – 72%, depending on the time from injury.

We have reviewed a personal series of the senior author of over 700 cases. The consistent finding in these patients is tenderness localised to a specific part of the trapezius in the base of the neck, which is sided. Tenderness on the same side is also present along the vertebral border of the scapula to its lower pole in over 90%, provided the scapula is protracted. A further finding in some patients is a high arc of pain on abducting the arm, thus simulating an acromioclavicular joint problem, but in these cases the pain is localised to the trapezius. These findings are in addition to those of the neck, which may show some restricted movement due to pain.

The trapezius tenderness can be abolished by the injection of local anaesthetic into the trigger spot at the base of the neck (whiplash injection test), which also resolves most of the above signs and allows further assessment of the shoulder without the referred pain from the injected area.

Conclusions: Shoulder examination in patients who have suffered whiplash injuries is often difficult due to referred pain. Knowledge of the signs specifically due to the whiplash injury is required so that shoulder pathology is not assumed. A new whiplash injection test not previously described has been found very useful in abolishing the whiplash signs to enable accurate shoulder assessment in our practice.

Ex vivo gene transfer of osteogenic factors into multipotential stem cells offers potentially important therapeutic implications in a variety of musculoskeletal diseases. One possible approach is the development of a cellular vehicle, namely bone morphogenetic protein (BMP)-producing bone marrow cells, created using adenoviral gene transfer. These transduced cells provide local delivery of BMP for bone formation. The aims of this study were to study the feasibility of gene transfer to human bone osteoprogenitor cells, using adenoviral vectors. Specifically, the aims were to study the efficacy of transduction with an adenoviral vector expressing BMP-2 and then to determine the ability of the transduced cells to produce active BMP-2 and to generate bone ex vivo.

Primary human bone marrow osteoprogenitor cells were expanded in culture and infected with AxCALacZ, a replication-deficient adenoviral vector carrying the E. coli lacZ gene, with a range of multiplicity of infection (MOI) of 6.25 to100. Transduced cells showed positive staining for β-galactosidase using X-Gal with an efficiency close to 100%. Uninfected cells showed no β-galactosidase activity. Efficiency was independent from MOI, however cells infected at the lower MOIs expressed lower levels of β-galactosidase. Following confirmation that primary bone marrow cells could be infected by adenoviral constructs, additional osteoprogenitors were infected with AxCAOBMP-2, a vector carrying the human BMP-2 gene, at a multiplicity of infection of 10–20. In order to determine BMP-2 activity, conditioned media from bone marrow cells expressing BMP-2 was added to promyoblast C₂C₁₂ cells. The promyoblast C₂C₁₂ cells are exquisitely sensitive to BMP-2 with induction of alkaline phosphatase activity (ED₅₀ 20 nM) in a dose-dependant manner. Alkaline phosphatase activity was induced following culture with conditioned media from BMP-2 expressing cells, in a dose dependant manner, confirming successful secretion of active BMP-2. Immunohistochemical staining for alka- line phosphatase in C₂C₁₂ cells also confirmed the bio-chemical observations. Media from uninfected control human bone marrow cells failed to produce a similar effect. The concentration of BMP-2 in the media was estimated to be 5–10 nM/10⁷ cells.

To examine whether adenoviral transfection affected the osteoblast phenotype and their ability to mineralise in vitro, adenovirally-transduced bone marrow cells expressing BMP-2 were seeded onto poly(-lactic acid co÷glycolic acid) (75:25) porous scaffolds (provided by K. Shakesheff and S. Howdle; Nottingham University) and cultured for up to 6 weeks. Expression of alkaline phosphatase activity, type I collagen formation, as well as the synthesis of osteoblast stimulating factor-1 confirmed bone cell differentiation and maintenance of the osteoblast phenotype in extended culture for up to 6 weeks.

These results indicate the ability to deliver active BMP-2 using human bone marrow osteoprogenitor cells following adenoviral infection. The maintenance of osteoblast phenotype in extended culture and generation of mineralised 3-D scaffolds containing such constructs offers a realistic approach to tissue engineer bone for orthopaedic applications.

The growth plates of rapidly growing animals have been studied extensively. Nevertheless, several questions remain unanswered, partly because many events happen simultaneously, especially at the vascular front. Terminal chondrocytes are thought to undergo programmed cell death, but the fate of the cell remnants remains unclear. Are the dying cells released into the vascular space and phagocytosed by macrophages, as one would expect for apoptosis? Or are the cells eliminated prior to opening of the lacunae, leaving empty lacunae? Do all terminal chondrocytes die or do some become bone-forming cells? Rodents maintain a growth plate into old age, long after longitudinal growth has ceased. These stationary growth plates have several features not found in the growth plates of rapidly growing animals and closer study of these features may provide answers to the above questions. Femurs and tibiae from 4–16 week-old and 62–80 week-old rats were decalcified, processed into paraffin, and the morphological changes were documented.

Between 4–16 weeks, the heights of the growth plates decreased due to loss of the large hypertrophic chondrocytes, but the various zones were still present. In the aged rats, the growth plates were identifiable as a narrow cartilaginous band with some short columns of inactive cells. The vascular front was irregular, the narrow spicules of primary spongiosa were absent and the much thicker spicules, which are normally seen in secondary spongiosa, directly abutted to the cartilage. Horizontal apposition of bone matrix onto the cartilage edge was frequently present. In addition, the following features were noted. 1) Acellular areas: Nearly all growth plates contained regions of cartilage from which all cells and their lacunae had disappeared. In some cases, these acellular regions stretched from the reserve zone to the vascular front and even persisted as a relatively wide core within the spicules of spongiosa, indicating increased resistance of acellular cartilage to resorption. The absence of cells or cell debris was consistent with an autophagic mode of cell death and subsequent collapse of the lacunae. 2) Remodelling within the growth plate; in some growth plates, large regions of growth plate cartilage had been resorbed and new bone had been laid down in a pattern similar to the remodelling of cortical bone. This suggested that the normal resistance of cartilage to vascular invasion had been lost locally, but was maintained in adjacent non-remodelled regions. 3) Trans-differentiation of chondrocytes to bone-forming cells; extensive new medullary bone formation was noted in the diaphysis of approximately 30% of the aged rats, suggesting that they had received an (unknown) osteogenic stimulus. In these rats, bone matrix was identifiable inside chondrocytic lacunae, and spreading beyond the confines of the lacunae, thus directly replacing growth plate cartilage with bone matrix.

The results suggest that i) chondrocytes are capable of self-elimination, perhaps by a mechanism similar to the autophagic cell death that occurs during insect metamorphosis; ii) resorption of cartilage and vascular invasion requires the presence of the viable chondrocytes; and iii) chondrocytes have the capacity to transdifferentiate to bone-forming cells, but only do so when receiving an increased osteogenic stimulus.

The ossific nucleus in Developmental Dysplasia of the Hip. A study of relative ossific nuceus size in hips treated in the Pavlik harness and its predictive value in treatment outcome.

Purpose

To assess the value of measuring relative ossific nucleus (ON) size difference in Developmental Dysplasia of the hip (DDH) as a potential predictor of outcome of hips treated in the Pavlik Harness.

Study Design

Prospective study of all unilateral cases (n=68) of DDH identified in Southampton by dynamic ultrasound and treated in a Pavlik harness studying changes in relative ON size and acetabular indices over a mean follow up period of 3.6 years.

Results

All cases responding to the Pavlik harness showed a progressive correction of ON size difference. Initial ON size difference was not associated with any difference in acetabular index at the date of last follow-up. Ultrasound grading of dysplasia did not affect the rate of normalisation of ON size difference.

Conclusion and clinical relevance

In patients responding to treatment of DDH in a Pavlik harness, ON size difference was not found to be a useful prognostic indicator of outcome.

Cohort studies in humans have suggested that the peak bone mass attained at skeletal maturity may be programmed in utero. To investigate which aspects of bone development might be influenced in utero, we utilised a rat model of maternal protein insufficiency, which has previously been used to demonstrate the fetal origin of adult hypertension. In rodents, a growth plate remains present throughout life, even after longitudinal growth ceases. Generally, the height of the growth plate is related to the rate of bone growth. Fast growing bones have maximal height growth plates, and as bone growth slows down the height decreases until it remains stationary.

The aim of this study was to compare the morphology of long bones in aged rats that had been subjected to protein insufficiency in utero with that of controls. Rat dams were fed either an 18% casein control diet or a 9% casein low protein diet from conception until the end of pregnancy. The offspring were fed a normal diet until death (~72 weeks), when bone density was measured by dual energy X-ray absorptiometry (DEXA) and the tibiae and femurs were processed for histology.

The offspring of rats from the low protein group had a significantly lower bone mass, as assessed by DEXA. The major differences in bone structure were found in the growth plates, which were very irregular without the usual zones of resting, proliferating and hypertrophic chondrocytes. A number of unusual cellular events were noted to have taken place subsequent to cessation of growth, including: a) elimination of all chondrocytes in a number of regions, resulting in vast acellular areas; b) formation of chondroid bone and/or transdifferentiation of chondrocytes to bone-forming cells in other regions; c) partial resorption of those latter regions while the acellular regions were not resorbed; d) ‘horizontal’ apposition of bone against a smooth metaphyseal edge of the growth plate.

To compare the growth plates from the low and high protein groups semi-quantitatively, the degrees of the above features were scored. In addition, the heights of the growth plates were were assessed by two independent measurements. In the low protein group, the height of the growth plate were found to be significantly greater (p< 0.001). Additionally, the growth plates from this group of animals were observed to be more irregular with regards to all the features outlined above.

These findings are consistent with the hypothesis that growth trajectory and bone mass are programmed in early life. The increased height of the growth plate in animals undernourished in utero may reflect the cessation of growth at an earlier age. The increased irregularity of the growth plate in this group of animals may infer an earlier onset of age-related changes within the growth cartilage.

From a cohort of 110 idiopathic clubfeet, 26 feet in 18 children requiring surgery for severe relapse have been studied. Surgery was comprised of a lateral column shortening procedure (Lichtblau) plus or minus a plantarmedial release. Surgery was staged to avoid wound complications.

Pre-operatively, feet were prospectively categorised into one of four grades according to a system reported by Dimeglio. Children were reviewed on two subsequent occasions. At review, feet were again graded. In addition, appearance and functional outcome was analysed and included an assessment of gait, activity and functional limitation.

Three children were lost to follow-up, leaving 22 feet in seven male and eight female patients available for review. The mean age at surgery was 43 months (23–82). The mean time from surgery to first and second reviews was 35 and 56 months, respectively.

There was a significant improvement in grading at first review compared to pre-operative grading (Wilcoxon signed ranks test). Although there remained a significant improvement in grading at second review compared to the preoperative grading, there was a significant reduction in the number of feet in which grading had improved when compared to first review.

There was no significant change in function between the two post-operative reviews (Chi-square tests), with the majority of children experiencing little functional limitation. There were no wound complications.

Relapse surgery, involving a lateral column shortening procedure for severe clubfoot, results in a significant initial improvement when assessed using a grading system. This improvement in grading subsequently decreases over time. However, the functional outcome in such cases remains favourable.

Introduction: Aseptic loosening of THR has a multifactorial aetiology. Differentiating such cases from loosening due to low-grade infection can often be difficult. It is possible that at least some cases of ‘aseptic’ loosening may be related to unidentified bacterial infection. This study attempted to identify the frequency with which bacterial DNA could be observed in the periprosthetic membrane and synovial fluid of patients undergoing revision surgery for what was considered ‘aseptic’ loosening.

Methods: Specimens from 39 revision and 31 primary hip replacements were obtained. The latter were used as a control for environmental contamination. All revision THR cases were investigated pre-operatively for infection by CRP, ESR, WCC, Gallium Scan. Operative specimens were analysed by bacteriological culture as well as by PCR to identify the presence of the 16S bacterial ribosomal fraction. Results were analysed by Chi square test.

Results: By PCR, bacterial DNA was identified in 22 of 39 revision hip surgery specimens and 6 of 31 primary hip replacement specimens (p=0.002). By culture none of these specimens had any bacterial growth.

Conclusions: The increased frequency with which bacterial DNA has been identified in ‘aseptically’ loose revision THR is unlikely to be due solely to environmental contamination although this remains a concern. These results may have relevance for our interpretation and understanding of aseptic loosening as well for the diagnosis of prosthetic infection.

This study investigated the relationship between histological, clinical and radiological features of aseptically loose total joint replacements (TJRs) and synovial fluid levels of interleukin (IL)-1b, IL-6, IL-8 and IL-10.

Tissue and synovial fluid samples were retrieved from patients undergoing primary (hip; n=15: knee; n=13), or revision of aseptically loose TJRs (hip; n=14: knee; n=9). The presence of inflammatory cells, blood vessels and wear debris in the tissue were assessed on a relative scale. Revision TJRs were assessed for sepsis, migration of the implant, gross loosening and the degree of radiolucency. Cytokine levels in the synovial fluid samples were determined by ELISA.

All cytokines were increased in synovial fluid from revision TJRs compared to primary replacements, as were the degree of macrophage and giant cell infiltration (p< 0.01). There was a significant positive correlation between the presence of macrophages and giant cells with the levels of IL-1b, IL-8 and IL-10 (p< 0.05) but not IL-6.

The amount of wear debris was related to the presence of macrophages and giant cells (p< 0.01) but not to any of the cytokines.

There were no relationships between any of the clinical parameters and the presence of wear debris or the levels of any cytokine with the exception of IL-6 and gross loosening (p< 0.01). Similarly there were no differences between hips and knees for any of the parameters except IL-6, for which higher levels were found in hips (p< 0.05).

The results suggest that macrophages and giant cells are responsible for the majority of IL-1b, IL-8 and IL-10 production but another cell type is contributing to IL-6 production. Furthermore, IL-6 does not fit the pattern of the other cytokines as it is upregulated in hip joints compared to knees and correlates with the presence of gross loosening. This may suggest a unique role for IL-6 that requires further investigation.