Introduction and Objective

Postoperative management regimes vary following open reduction and internal fixation of unstable ankle fractures. There is an evolving understanding that poorer outcomes could be associated with non-weight bearing protocols and immobilisation. Traditional non-weight bearing cast immobilisation may prevent loss of fixation, and this practice continues in many centres. The aim of this systematic review and meta-analysis is to compare the complication rate and functional outcomes of early weight-bearing (EWB) versus late weight-bearing (LWB) following open reduction and internal fixation of ankle fractures.

The aim of this study is to investigate whether MoM implants result in more chromosome aberrations and increased blood metal ions postoperatively whe compared to MoP implants.

MoM arthroplasties are being inserted in increasing numbers of younger patients due to the increased durability and reduced requirements for revision in these implants. Recent studies have raised many concerns over possible genotoxicity of MoM implants.

This is a prospective study of patients who have undergone elective total hip replacement, they were selected and then randomised into two groups. Group A received a MoP implant and group B received a MoM implant. Patients are reviewed pre-operatively (control group), at 3 months, 6 months, 1 year and 2 years post-operatively. On each occasion blood tests are taken to quantify metal ion levels (chromium, cobalt, titanium, nickel and vanadium) using HR-ICPMS method and chromosome aberrations in T lymphocytes using 24 colour fluorescent in situ hydridisation (FISH).

51 patients have been recruited to date, 23 of whom had MoP prosthesis and 28 a MoM. 47 of these had their 1 year follow-up with blood analysis and 38 have had 2 year follow up. There appeared to be a bedding period for both MoM and MoP groups, with an increase in metal ion release. The blood concentration of chromium, cobalt and titanium rise significantly in the MoM group at the 2 year stage. Chromosome aberrations occurred in both groups. Both the MoM and MoP groups showed increase frequency of aneuploidy aberrations and structural damage. The greatest increase in metal ion levels occurred at the 1 to 2 year interval corresponding to significant rise in chromosome aberrations.

Preliminary results of this study show that the levels of chromium, cobalt and titanium are significantly higher in the MoM group compared to the MoP group. This corresponds to increases in chromosome aberrations in the groups with increases in structural chromosome damage after two years.

It is generally accepted that there is a high rate of local recurrence following surgical excision of chordoma of the sacrum, even if the margins of excision appear clear. There is uncertainty as to whether the addition of postoperative radiotherapy may decrease the risk of local recurrence, particularly if there are close or involved margins. We aimed to determine the effect of conventional radiotherapy, in the post-operative setting, on the effect of local recurrence, metastases and patient survival in a multi-centre study.

The aim of this study is to investigate whether Metal-on-Metal (MoM) implants result in more chromosome aberrations and increased blood metal ions post-operatively when compared to Metal-on-Polyethylene (MoP) implants. Metal-on-metal arthroplasties are being inserted in increasing numbers of younger patients due to the increased durability and reduced requirement for revision in these implants. Recent studies have raised many concerns over possible genotoxicity of MoM implants. This is a prospective study of patients who have undergone elective total hip replacement, they were selected and then randomised into two groups. Group A received a MoP implant and group B received a MoM implant. Patients are reviewed pre-operatively (control group), at 3 months, 6 months, 1 year and 2 years post-operatively. On each occasion blood tests are taken to quantify metal ion levels (chromium, cobalt, titanium, nickel and vanadium) using HR-ICPMS method and chromosome aberrations in T lymphocytes using 24 colour fluorescent in situ hybridisation (FISH). 53 patients have been recruited to date. 24 of whom had MoP prosthesis and 29 a MoM. 37 of these have had their one year follow-up with blood analysis and 14 have had 2 year follow up. Cobalt and chromium concentration increased during the first 6 months in both MoM and MoP groups, in the MoM group the chromium levels were twice that of MoP group and 12x that of the preoperative samples. Chromosome aberrations occurred in both groups. At 6 months both the MoM and MoP groups showed increase frequency of aneuploidy aberrations with further increases after one year. Structural damage in the form of translocations occurred in the MoM group after one year, but not in the MoP group, by two years there was a profound increase in translocations Preliminary results of this study show that the levels of chromium and cobalt are significantly higher in the MoM group compared to the MoP group. This corresponds to increases in chromosome aberrations in the groups with increases in structural chromosome damage after two years.

In 2002 the UK government in its attempt to reduce long total joint arthroplasty waiting lists, arranged for local councils via NHS trusts to send patients abroad for their surgery. In theory it was a win-win situation where pressures upon surgeons were reduced, trusts could reach government targets and of course, patients got their operation with a bonus holiday! Unfortunately, it was not until patients had returned from their surgery that problems with this method of waiting list reduction were realised. The majority of patients were discharged after only one check up and often had very little in the way of post operative physiotherapy. A few presented to our clinic with more serious complaints with two cases eventually requiring revision surgery.

We undertook a case-control study looking at an age and sex matched group of patients who underwent total knee arthroplasty, Group A (Belgium) and Group B (Local Institution) during the same time period from November 2003 to November 2004. We compared their Oxford knee score (OKS), Knee society score (KSS) and SF12 physical and mental component scores.

Introduction

We discuss the use of the SMILES (Stanmore Modular Individualised Lower Extremity System) in salvage revision knee surgery and review the medium-long term results of 42 cases.

Metal-on-metal arthroplasties are being inserted in increasing numbers of younger patients due to the increased durability and reduced requirement for revision in these implants. Recent studies have raised many concerns over possible genotoxicity of MoM implants. This is a prospective study of patients who have undergone elective total hip replacement, they were selected and then randomised into two groups. Group A received a MoP implant and group B received a MoM implant. Patients are reviewed pre-operatively (control group), at 3 months, 6 months, 1 year and 2 years post-operatively. On each occasion blood tests are taken to quantify metal ion levels (chromium, cobalt, titanium, nickel and vanadium) using HR-ICPMS method and chromosome aberrations in T lymphocytes using 24 colour fluorescent in situ hybridisation (FISH).

Fiffty three patients have been recruited to date, 24 of whom had MoP prosthesis and 29 a MoM. 25 of these have had their one-year follow-up with blood analysis. Cobalt and chromium concentration increased during the first 6 months in both MoM and MoP groups, in the MoM group the chromium levels were twice that of MoP group and 12x that of the preoperative samples. There was no difference with the levels of titanium, nickel and vanadium. Chromosome aberrations occurred in both groups. At 6 months both the MoM and MoP groups showed increase frequency of aneuploidy aberrations with further increases after one year. Structural damage in the form of translocations occurred in the MoM group after one year, but not in the MoP group.

Preliminary results of this study show that the levels of chromium and cobalt are significantly higher in the MoM group compared to the MoP group. This corresponds to increases in chromosome aberrations between the groups particularly in translocations present in the MoM group at 1 year.

Introduction: Primary or secondary bone tumours of the distal tibia are uncommon. Before the development of endoprostheses in the 1970’s, the primary treatment for these was below knee amputation. Limb salvage is now possible without adversely affecting survival largely due to improvements in chemotherapy. We report the clinical and functional outcome of six patients who underwent limb salvage with endoprosthetic reconstruction of the distal tibia and ankle joint for malignancy.

Methods: Retrospective review of all patients who underwent limb salvage with endoprosthetic reconstruction of the distal tibia and ankle joint at our institution. Data was collected from the bone tumour database, medical records, imaging studies, clinic reviews and individual structured patient questionnaires. MSTS and TESS scores were used to assess functional outcome.

Results: Six patients underwent distal tibial replacement for malignant bone tumours of the distal tibia. There were 4 males and 2 females with a mean age of 31.2 years (range 13 to 68) and mean follow-up of 35 months (range 13 to 76). One patient died of non-neoplastic disease at 76 months. Two patients had Ewings sarcoma, two had osteosarcoma, one had malignant fibrous histiocytoma and one had adamantinoma.

No patient had metastases at presentation and no patient developed local recurrence or distant metastases post-operatively. Four patients developed infection, for which two required below knee amputation and two suppressive antibiotics. Hardware failure was seen in one patient with infection which was managed by below knee amputation. One patient required sub-talar fusion and calcaneal osteotomy for persistent ankle pain.

A child who underwent the procedure age 13 developed a 5 cm leg-length discrepancy once skeletally-mature. Mean MSTS and TESS scores for the three patients who still had a functioning endoprosthesis were 77% and 79% respectively.

Conclusion: Limb salvage with distal tibial combined with ankle joint replacement can be used as an alternative to below knee amputation in patients with bone tumours of the distal tibia. Due to the difficulties in achieving adequate soft tissue cover, patients should be counselled regarding the high potential complication rate which can lead to significant morbidity, functional deficit and further surgical intervention.

Introduction: Metal-on-metal arthroplasties are being used for their increased durability and reduced requirement for revision. Previous data reports that metal-on-metal bearing surfaces release three times more cobolt and chromium ions than metal-on-polyethelene hip replacements. Data also suggests that these metal ions can cause DNA damage.

Method: A prospective study of patients (aged 60–80), meeting exclusion criteria were selected and randomised to metal-on-metal or metal-on-polyethylene articulation. Patients were reviewed preoperatively (control model) and at 3 months, 6 months and one year postoperatively. On each occasion blood tests were taken to quantify metal ion levels (chromium, cobalt, nickel, vanadium and titanium) and chromosome aberrations in T lymphocytes using 24 colour fluorescent in situ hybridization (FISH).

Results: The number of chromosome aberrations increased with time; in particular there was a statistically significant increase in aneuploidy after one year, there was also an increase in chromosome translocations. There was a similar increase in blood concentration of metal ions over this same time period which proved significant. Higher levels of metal ions were seen in the metal-on-metal group when compared with the metal-on-polyethylene.

Conclusion: This study has highlighted the effects of metal ions on chromosome replication in particular causing aneuploidy aberrations. This provides evidence of the short-term effects of metal-on-metal arthroplasty but further research needs to be undertaken to assess long-term risk and also the risk associated to other cell lines.

Introduction: Initial results for the management of osteochondral defects with both ACI-C and MACI have been encouraging, showing significant clinical improvement. This single-centre study set out to determine any significant difference in outcomes between ACI-C and MACI.

Aim: Reporting three year follow up of clinical and arthroscopic assessment of prospective analysis of ACI-C and MACI used in the management of symptomatic, full-thickness chondral and osteochondral defects in the knee.

Method: Following assessment arthroscopy and harvesting of chondrocytes for culture, patients were randomised into the ACI-C or MACI arm and underwent their respective procedures one month later. In ACI-C a covered technique is employed using a porcine-derived type I/III collagen membrane sutured in place; MACI requires cultured autologous chondrocytes to be seeded in a bi-layered type I/III collagen membrane which is glued into position. An arthroscopy was performed at 12 and 24 months postprocedure to assess graft coverage and biopsies taken to determine extent of hyaline, mixed and fibro-cartilage proliferation.

Results: 102 patients underwent either ACI-C (44) or MACI (58) with an average age of 33.6 (14–52). Mean Cincinnati knee rating scores recorded prior to assessment arthroscopy for ACI-C: 45.2 (10 – 94) and MACI: 45.5 (10 – 90) showed improvement at follow up with 63% of patients in the ACI-C group scoring good or excellent at three years, and 60% in the MACI group. ICRS arthroscopy scores were good or excellent in 91.4% of ACI-C and 76.1% of MACI patients at 24 months. Biopsies of the transplants at 24 months revealed proliferation of hyaline and mixed cartilage (hyaline and fibro-cartilage) in 48.6% of the ACI-C and 30.5% of the MACI patients.

Conclusion: Results to date suggest significant clinical and arthroscopic improvement following ACI-C and MACI, with evidence of proliferation of hyaline cartilage at the transplant site. Limited differences are noted between the outcomes of the two techniques.

Introduction: The use of custom made CAD-CAM femoral stems in primary Total Hip Replacement allows preservation of valuable bone stock in anatomically challenging femora whilst optimising biomechanics and improving function. The custom prosthesis design and manufacturing process is carried out with the aid of computed tomography (CT), a system of tomographic image processing, a Computer–Aided Design (CAD) system and a Computer–Aided Manufacturing (CAM) system.

Aim: To report seven year minimum follow up of a custom made and designed femoral component used in total hip replacement, focusing on clinical and radiographic evidence of failure.

Methods: Patients who had an uncemented total hip arthroplasty, by one of the two senior authors, with a CAD-CAM hip between February 1993 and February 2000 were retrospectively studied. An independent observer evaluated all patients radiologically using Engh’s criteria of osteointegration and clinically using Harris and Oxford Hip Scores.

Results: 85 patients (47 male, 38 female) (102hips) underwent THA for a variety of reasons between February 1993 and February 2000. Average age was 53.7 (25.4–91.5). Average follow up was 9.3 years (7–15). The aetiologies for THA were: Developmental Dysplasia of Hip (22 hips), Osteoarthritis (25), Slipped Upper Femoral Epiphysis (3), Skeletal Dysplasia (11), Trauma (9), Perthe’s Disease (6), Avascular Necrosis (14), Tumour (4) and other (8). At last follow up 4 hips had been revised: 2 for aseptic loosening, 1 for deep infection and 1 for excessive acetabular cup liner wear. 84 patients were evaluated (one deceased from unrelated causes). Average Harris Hip Score was 81 (range 53–96). Average Oxford Hip Score was 24 (range15–43). A full set of x-rays was available for 73 patients and when evaluated all were radiographically stable. Endosteal bone formation or spots welds were present on all 73 of the x-rays. Radiolucent lines at the bone-implant interface were present on 7/73 x-rays but did not correlate with clinical problems. There was no evidence of bone pedestal formation.

Conclusions: Clinical results are good to excellent with little radiographic evidence of failure. CAD-CAM hips can be safely and reliably used for a variety of aetiologies with predictable result at least up to seven years postoperatively.

Introduction: Total femoral endoprosthetic replacement can be used as an alternative to hip disarticulation following extensive tumour excision or in cases of more severe bone loss. To date there have been no long term studies on the oncological and functional outcome of patients who have had this procedure for malignant bone disease. We report our experience of over 25 years employing this procedure using a custom-made and modular total femoral endoprosthetic replacement.

Methods: This is a retrospective, single centre study of 27 patients who underwent consecutive total femoral replacement as a primary procedure between 1978 and 2005. Information was collected from the bone tumour database, medical records and clinic review. Outcome was assessed using the Musculoskeletal Tumour Society (MSTS) rating score, the Harris Hip Score (HHS) and the Oxford Knee Score (OKS).

Results: There were 15 males and 12 females, with a mean age of 30 years (5 to 65). The overall mean follow-up was 4.3 years (1 to 16.4) for all patients, 9.1 years (1 to 16.4) for the 7 patients who were alive at the time of this review, and 2.6 years (1 to 13) for the 20 patients who had died. 24 patients had primary malignant bone tumours of the femur and 3 had metastatic disease from a known primary elsewhere. 3 patients developed local recurrence, 1 patient developed new lung metastases. Mean MSTS score was 63% (19/30), mean HHS was 68/100 and mean OKS was 34/48.

Discussion: Total femoral replacement can be an effective alternative to hip disarticulation in patients with malignant bone disease. Good functional outcomes can be achieved without compromising survival.

Introduction: We report our experience with use of the SMILES prosthesis in primary knee arthroplasty.

Methods: The Stanmore Modular Individualised Lower Extremity System (SMILES prosthesis) has been shown to be effective in complex revision knee surgery. It incorporates a rotating hinge platform knee joint and can overcome the major problems of bone loss and ligamentous laxity.

38 patients (41 knees) who received a primary SMILES knee prosthesis by one of the senior authors between 1990 and 2006 were retrospectively studied. Knee function was assessed pre and post-operatively using the Oxford knee score (0–48 scoring system) and the Knee Society Score. Patients receiving surgery for tumours were excluded. The main indications for primary SMILES were bone loss and ligamentous laxity.

Results: The minimum follow-up was 18 months with a mean of 5 years (1–17). The mean age of the patients was 57.7 years (23–86); 15 of the patients were male. The indications for surgery were trauma (12), osteoarthritis with deficient medial collateral ligament (8), polio (7), rheumatoid arthritis (5), epiphyseal dysplasia (4), achondroplasia (2), avascular necrosis (1), osteogenesis imperfecta (1) and ankylosing spondylitis (1).

2 patients died and 5 were lost to follow-up. 2 patients required revision surgery (one for infection and one for re-bushing). Post-operative complications included peroneal nerve palsy (1) and DVT (1). The mean Oxford knee score improved from 9 pre-op to 44 post-op, and the mean knee society score improved from 24 pre-op to 71 post-op. The average range of motion was 57 degrees pre-op and 88 degrees post-op.

Conclusion: We conclude that the SMILES prosthesis offers significant improvement in clinician and patient assessed outcome scores in complex primary knee arthroplasty. The cost compares favourably with other designs and its use is well established.

This study explored differences in the early pattern of recovery for self-report (pain and physical function subscales of the Western Ontario and McMaster Universities Osteoarthritis Index) and physical performance measures (six minute walk and timed up and go test) in patients following arthroplasty. Using hierarchical linear modeling, different patterns of recovery and predictors of change were observed. The physical function subscale did not detect the early deterioration in physical function that was detected by the performance measures. Different important clinical information can be learned from performance measures, supporting the use of both types of measures when monitoring decline and recovery.

To explore differences in the pattern of recovery for self-report and physical performance measures in patients following total hip (THA) and knee (TKA) arthroplasty.

Different patterns of recovery and predictors of change were observed for the pain and physical function subscales of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the performance measures. The physical function subscale did not detect the early deterioration in physical function demonstrated by the six minute walk (6MWT) and timed up and go (TUG) tests.

WOMAC scores are commonly used to monitor changes in pain and physical function both pre and post-operatively. Failure of the physical function sub-scale to detect decline in physical function experienced post-operatively suggests that the WOMAC may not always accurately reflect physical function.

The postoperative predicted scores for the WOMAC either exceeded or met the preoperative scores within one to two weeks compared to seven to eight weeks with the performance measures. The performance measure models contained a greater number of predictors than the WOMAC subscale models.

One hundred and fifty-two patients (mean age 63.8 ± 10.2 years) who underwent THA and TKA were assessed at several points over the first four postoperative months. Average growth curves for the WOMAC, 6MWT and TUG were characterized using hierarchical linear modeling. Predictors of recovery were sequentially modeled after validation of the basic developmental models.

Differences in models and the time point at which preoperative scores are met suggest that different information is being learned from self-report and physical performance measures.

Funding: This research was not supported by funding from a commercial party. It was supported by a grant from the Orthopaedic & Arthritic Foundation.

Introduction: Distal femoral varus osteotomy (DFVO) has been advocated as the treatment of choice for lateral compartment osteoarthritis associated with a valgus knee in the young population in order to delay the need for total knee arthroplasty (TKA). The aim of this study was to evaluate the long-term results of DFVO for the valgus osteoarthritic knee.

Methods: A retrospective analysis was performed on 38consecutive patients (40 knees) who underwent a DFVO between 1984 and 2001. Two patients (2 knees) were lost to follow-up. Mean follow up was 123 months (range 39 to 245 months). Peri-operative documentation was evaluated for etiology, pre-operative functional and subjective impairment, intra-operative technical difficulties or complications, early and late post-operative complications and post-operative functional and subjective outcomes.

Results: At the time of the most recent follow-up, 24 knees had good or excellent result, 3 knees had a fair result and 3 had poor results. The remaining 8 knees were converted to a total knee arthroplasty. The mean Knee Society objective score improved from 18 (range, 0–74) to 87.2 (range, 50–100) and the mean Knee Society function score improved from 54 (range, 0–100) to 85.6 (range, 40–100). The ten-year survival rate of DFVO was 82% (95% confidence interval, 75%–89%) and the fifteen-year survival rate was 45% (95% confidence interval, 33%–57%).

Discussion: With proper patient selection, DFVO is a reliable procedure for the treatment of the valgus osteoarthritic knee. This procedure delays the need for further surgical procedures, such as TKA, with good results.

Introduction and Aims: A growing number of studies suggest worse pre-operative functional status is associated with worse outcome in terms of both function and pain after total hip (THA) and knee (TKA) arthroplasty. A gap in these studies, however, is the lack of physical performance measures to validate the self-reported findings.

Method: Using a repeated measures design, 152 subjects with endstage osteoarthritis were assessed at multiple points over the first four post-operative months. Outcome measures included the six-minute walk test (6MWT), timed up and go test (TUG), and the pain and physical function subscales of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Average growth curves and individual variations in the pattern were characterised using hierarchical linear modelling. Following validation of the basic developmental models, predictors of recovery were sequentially modelled. Gender, baseline pre-operative function, site of replacement, age, additional outpatient rehabilitation, and number of co-morbidities were investigated as predictors.

Results: In the models explored, a second-degree polynomial growth term provided a reasonable fit for the data over the study interval. Baseline pre-operative score was a significant predictor (p< .001) in all of the models. A significant interaction (p< .0005) was observed between the growth parameter (weeks post-surgery) and baseline pre-operative score for the 6MWT. Patients with better pre-operative scores are predicted to improve their 6MWT distances faster. Although gender was a significant predictor (p< .0005) of TUG and 6MWT performance at one week post-operatively (women slower), it was not a predictor in the WOMAC models. No significant interaction was observed between the growth parameter and gender in either of the 6MWT or TUG models. Site of replacement (hip or knee) was a significant predictor (p< .001) of one-week scores in all of the models except for the WOMAC physical function subscale. In both performance measure models, the average growth curves demonstrate that patients post-THA are predicted to start with worse function, however, their growth rates are faster over the studied interval. Co-morbidities, age and additional outpatient rehabilitation were not explanatory variables for any of the models.

Conclusions: Performance measurement demonstrated that women started with worse function than men one week after surgery, but thereafter had similar rates of improvement. The importance of pre-operative function as a predictor of post-operative recovery cannot be overlooked. Patient and surgeon’s expectations of outcome need to take pre-operative function into account.

Introduction and Aims: With the current trend to minimally invasive techniques for total hip (THA) and knee arthroplasty (TKA), an understanding of early functional recovery for traditional surgical approaches is required for outcome comparison. Patterns of recovery for self-report and physical performance measures were therefore explored during the early post-operative period.

Method: One hundred and fifty-two patients were assessed pre-operatively and several times over the first four post-operative months. The pain and physical function subscales of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the six-minute walk (6MWT) and timed up and go test (TUG) were used as outcome measures. Hierarchical linear modelling was used to characterise the average pattern of recovery for each measure. Model development began with a parameter that estimated the patients’ self-reported or actual measured function at one week postoperatively and a parameter that estimated the patients’ rate of change for every week thereafter.

Results: Sixty-nine subjects underwent THA and 83 underwent TKA with a mean age of 63.8 + 10.2 years. Different patterns of recovery and predictors of change were observed for the WOMAC subscales and physical performance measures. The growth models for the performance measures were more complex, including more predictors and interaction terms. The model for the physical function subscale was the simplest. In addition to the growth parameters and the intercept, baseline function was the only other model parameter influencing the estimated score at one week. A striking difference between the WOMAC and performance measure growth curves concerned the point at which pre-operative scores are predicted to be met. The predicted scores for the WOMAC subscales either reach or exceed the pre-operative scores at one to two weeks post-surgery in comparison to the 6MWT and TUG, which do not reach these levels until six to eight weeks post-surgery. It would appear that the physical function subscale of the WOMAC does not reflect the early deterioration that occurs in physical function. The predicted growth curves for the TUG confirm its usefulness as a physical function measure only in the early recovery period, as a ceiling effect occurred around 10 weeks.

Conclusion: The physical function subscale of the WOMAC may not always accurately reflect physical function. Using only self-report measures to compare traditional surgical approaches to minimally invasive techniques might miss significant differences in recovery of physical function. Using both physical performance and self-report measures to monitor early recovery is recommended.

Introduction Wear particle induced osteolysis is regarded as the main reason for aseptic loosening of hip replacements. Crosslinked polyethylene show extremely low wear in lab studies and is routinely used today, though with very little clinical testing. We report wear, migration and function for uncemented cups with a crosslinked poly.

Methods Twelve hips in 12 patients with mean age of 70 years were operated with uncemented cups (Reflection), cemented stems and metal heads. Five Mrad cross linked liners annealed below melt temperature were used in all hips (XLPE, Smith & Nephew). Tantalum markers were inserted in liners and acetabular bone for RSA measurements and migration and wear measured over two years. The result was compared to matched controls from a study of 80 cups with the same implant and non cross linked poly, operated by the same surgeon. X-rays, WOMAC and Sf-36 were performed pre-operatively and at two years.

Results The mean proximal head penetration at two months was 0.09 mm. This was thought to be mainly due to the creep of the polyethylene and was equal to “normal” poly. At the one year follow-up the mean proximal wear had increased with 0.02 mm and at two years 0.03 mm. This compares with the 0.33 mm recorded for the old poly (p=0.001, Mann Whitney U test.). The cups migrated 0.2 mm proximally and showed a normal migration profile, comparable to the cups with non cross-linked poly. The accuracy of measuring proximal wear, in this study, was found to be 0.07 mm (95% CI). No differences in radiolucent lines or clinical scores were found.

Conclusions The first two years proximal wear was 0.03 mm compared to the 0.33 mm found for non crosslinked poly. This is a reduction with 90% which certainly looks promising.