There is ongoing debate on the benefits of fixed versus mobile bearing Unicompartmental Knee Replacement (UKR). We report the results from a randomised controlled trial comparing fixed and mobile bearing of the same UKR prosthesis. Forty patients were randomized to receive identical femoral components and either a fixed or mobile bearing tibial component. At 6.5 years follow-up 37% of the mobile bearing design had been revised and 14% for the fixed bearing design. The main reasons for revision were pain and loosening. These results were compared with data from The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) that show a cumulative percent revision of 24.2% for the mobile bearing Preservation UKR at 6.5 years. All locally explanted mobile bearings were examined microscopically, and 83% demonstrated significant backside wear. Constraint on the undersurface of the bearing coupled with a congruent upper surface may have contributed to the excessive revision rate. This is the first randomised controlled trial examining mobile and fixed variations of the same UKR prosthesis and shows this design of UKR with the mobile bearing has an unacceptably high revision rate and patients with this knee design should be closely monitored.

Aims

To report the rate of early revision (within two years) after shoulder arthroplasty and identify any patient, disease or prosthesis factors that may be associated with these early failures.

Introduction: In recent years some countries have shown increasing interest and use of unicompartmental knee arthroplasty (UKA). Several studies have reported increasing use of UKA for osteoarthritis in younger patients with low revision rates. The aim of this study was to determine the outcome of UKA by combining two national databases containing prospectively collected data.

Method: Over 50 000 UKA procedures were analyzed to determine the cumulative percentage revision (CPR). Any reason for revision was used as the end point. The analysis was stratified according to age, gender and type of prosthesis to determine outcomes in patients younger than 65 years

Result: In this study both countries showed declining use of UKA in terms of the proportion of knee replacement procedures and of absolute numbers undertaken per year. The seven year CPR of UKA in patients younger than 65 years was 16.2%, and at 10 years was 17.5%. No significant difference was found between gender, however outcome did vary depending on the type of prosthesis used.

Conclusion: This study reports the outcomes from the two largest databases of UKA. Within 10 years of UKA a substantial number of revisions were seen in patients younger than 65 years, with varying results depending on the type of prosthesis used.

Introduction and aims: The extent of primary total hip and knee replacement revisions in the first 2 weeks following surgery is unknown. This study reports the incidence and reasons for revision of primary total hip and knee replacements within that period.

Method: Data was obtained from the Australian Orthopaedic Association National Joint Replacement Registry (AOA NJRR). The AOA NJRR began data collection in September 1999, becoming national during 2002. This is an analysis of patients whose conventional primary total hip and/or primary total knee replacement and subsequent revision are recorded by the AOA NJRR with a procedure date on or before the 31st December 2006. Patient demographics, method of fixation used in the primary procedure as well as reasons for revision, and type of revision (major or minor) were analysed.

Results: The analysis involved 104,234 conventional primary THR and 134,799 primary TKR. There were 286 revisions (0.27%) of primary THRs and 102 revisions (0.076%) of primary TKRs in the first 2 weeks following surgery. The risk of revision was significantly higher for THR than TKR (P< 0.0001).

Dislocation (44.1%) was the main reason for revision of primary THR in the first 2 weeks after surgery followed by fracture (26.8%) and loosening (16%). The main reason for revision of primary TKR was infection (39%) followed by loosening (18%) and fracture (8.6%).

Most revisions of primary THRs in the first 2 weeks were major (66.4%). When only one major component was revised it was mainly the femoral stem (32.9% of all revisions). Almost all of these were cementless (94.7%). When a revision of a primary TKR occurred the majority were minor (69.6%) (p< 0.001). The insert (64.7% of all revisions) was the main component revised.

Risk factors associated with primary THR revision include a diagnosis of developmental dysplasia (P=0.030) and cementless procedures had a significantly higher risk of revision than either cemented (P< 0.0001) or hybrid (P< 0.0001) procedures. We did not identify any risk factors associated with primary TKR in the first 2 weeks following surgery.

Conclusions: The number of revisions of primary THR and TKR within the first 2 weeks of surgery remains small with approximately 1.6 per 1,000 procedures revised. The risk of revision was significantly greater for THR than TKR. Surgical technique was the main reason for revision of primary THR and infection for primary TKR.