During a retrospective case note analysis, a significant difference was found in prosthesis survival, between two cohorts of patients who underwent different total knee replacements. The first cohort included 70 patients who underwent Kinemax Plus total knee replacement, the second cohort included 58 patients who underwent PFC Total Knee replacement. All patients were under the care of one Consultant Orthopaedic Surgeon. Interestingly, the Kinemax Plus cohort was found to have a higher rate of revision compared to the PFC cohort. A detailed comparison was carried out between the two groups to identify any obvious cause for the disparity. The two cohorts were found to be well matched with respect to age, sex, ASA grade, underlying pathology and operative technique. Median follow up being 6 years and 5 years for the Kinemax Plus and PFC groups respectively. There were 11 failed prostheses in the Kinemax Plus cohort, 7 undergoing revision with the remaining 4 patients offered revision but unwilling to have surgery. Wear of the polyethylene tibial insert was the most obvious finding at revision, present in six of the seven revisions. 97% of the Kinemax Plus Prostheses were intact at 5 years but by 8 years only 87% were intact. There were no revisions performed in the PFC cohort. Post-operative x-ray analysis was undertaken to rule out prosthesis malalignment as a cause for the increased failure rate. The coronal alignment of the prostheses (CAK) was calculated and all post operative x-rays were within the normal limits of 4-10 degrees. Analysis of the explanted Kinemax Plus polyethylene liners was undertaken. In six cases, the polyethylene bearing surfaces displayed severe surface and subsurface delamination. This suggests massive fatigue and fatigue wear. Only one implant showed localised delamination. These findings suggest the hypothesis of weak polyethylene particle interface strength

224 patients from the Cardiff and Vale NHS Trust who had total knee replacements at the NHS Treatment Centre in Weston-Super-Mare by surgeons from overseas appeared to have significantly worse results than those recorded in the published literature. We wished to establish whether a group of patients treated in the same hospital with the same prosthesis at a similar time by local NHS orthopaedic surgeons in substantive posts would have a similar outcome.

Follow-up of all 214 patients (223 knee replacements) treated in 2004 was conducted with questionnaires, clinical review and x-ray assessment. In cases of no response, contact was made with GPs to establish the outcome of the surgery.

The outcome of all patients was known and of the 125 knee replacements available for clinical review at six years (mean), 119 cases (96%) achieved satisfactory coronal alignment with reference to the published literature. There were six revisions, five for loosening and one for malalignment. The cumulative survival rate for re-operation at six years was 97.2% (95% confidence interval 95.2 to 99.1).

This study shows that the results of total knee replacement performed by a group of NHS orthopaedic surgeons were comparable with other institutions and were significantly better than those reported from the NHS Treatment Centre in Weston-Super-Mare, using the same facilities and implant over the same period of time. This work supports previous recommendations for single surgeon supervision of the patient pathway and appropriate follow-up procedures.

Pseudo-patella baja (PPB) describes narrowing of the distance between the patella and the tibia without shortening of the PT and occurs following Total Knee Arthroplasty (TKA), where the tibial prosthesis plus insert are thicker than the resected tibia. Soft tissue balancing is an important factor in the success of TKA, but if extensive may necessitate the use of thicker tibial inserts with the risk of creating a PPB. Patients who undergo extensive soft tissue releases during TKA, with resultant use of thicker tibial inserts will develop a PPB, with increased risk of patella pathology. 506 patients aged 40-90 years underwent 526 Kinemax TKAs, performed by 7 surgeons in 5 centres between 1999 and 2002. The extent of soft tissue releases and the thickness of tibial inserts were recorded. Pre- and post-operative lateral radiographs were measured by an independent observer, using the Caton-Deshamps method to assess patella position. The patients were assessed using the Oxford Knee Score and the American Knee Society Clinical Rating System, with a minimum follow-up of 12 months. 1. TKA surgery creates a Pseudo-Patella Baja. Excluding patients with a pre-operative patella baja, PPB was introduced into 26.7% of patients. (p=0.000). 2. The incidence of pseudo-patella baja increased with the extent of soft tissue release; Minimal, Moderate or Extensive. (p=0.000). 3. The incidence of pseudo-patella-baja increased with increases in insert thickness. Three groups were identified: Inserts 8 mm, inserts 10-12mm, and inserts 15-22 mm. (p=0.035). There was no correlation between the incidence of PPB and changes in clinical or functional outcome, as measured using the OKS and AKSS. Pseudo-patella baja occurs in 26% of all patients following TKA, and in 46% of patients in whom extensive soft tissue releases have been performed and/or large tibial inserts have been used. At 12 months, no detrimental outcomes were attributable to the incidence of pseudo-patella baja

We aimed to identify whether patients in lower socioeconomic groups had worse function prior to total knee arthroplasty and to establish whether these patients had worse post-operative outcome following total knee arthroplasty. Data were obtained from the Kinemax outcome study, a prospective observational study of 974 patients undergoing primary total knee arthroplasty for osteoarthritis. The study was undertaken in thirteen centres, four in the United States, six in the United Kingdom, two in Australia and one in Canada. Pre-operative data were collected within six weeks of surgery and patients were followed for two years post-operatively. Pre-operative details of the patient's demographics, socioeconomic status (education and income), height, weight and co-morbid conditions were obtained. The WOMAC and SF-36 scores were also obtained. Multivariate regression was utilised to analyse the association between socioeconomic status and the patient's pre-operative scores and post-operative outcome. During the analysis, we were able to control for variables that have previously been shown to effect pre-operative scores and post-operative outcome. Patients with a lower income had a significantly worse pre-operative WOMAC pain (p=0.021) and function score (p=0.039) than those with higher incomes. However, income did not have a significant impact on outcome except for WOMAC Pain at 12-months (p=0.014). At all the other post-operative assessment times, there was no correlation between income and WOMAC Pain and WOMAC Function. Level of education did not correlate with pre-operative scores or with outcome at any time during follow-up. This study demonstrates that across all four countries, patients with lower incomes appear to have a greater need for total knee arthroplasty. However, level of income and educational status did not appear to affect the final outcome following total knee arthroplasty. Patients with lower incomes appear able to compensate for their worse pre-operative score and obtain similar outcomes post-operatively