Outcome of a Fixed-Bearing all-polyethylene unicompartmental tibial tray: A 12-year Joint Registry Follow-Up study

Aims This study aims to evaluate the long-term durability of a unicompartmental knee arthroplasty (UKA) implant using a fixed-bearing all-polyethylene tibial tray with a Cobalt-Chromium (Co-Cr) femoral condyle, stratified by patient age. It also aims to compare implant survivorship between inlay and onlay tibial implantation techniques. Methods Data from the New Zealand Joint Registry (NZJR) was used to evaluate survival of Smith & Nephew Genesis II ® UKA performed between February 2000 and December 2011 in which two different tibial implant techniques (inlay and onlay) were used. The primary endpoint was revision surgery. Results At a minimum follow-up of 10 years, 57 revisions were performed at an average of 6.6 years from index surgery. The revision rate per 100 component years was 1.29 (CI: 0.97 – 1.66), with a significant difference between the over-75 years cohort compared with the under-65 cohort, in favour of the older cohort ( p < 0.05). There was a significant difference in survival between inlay and onlay techniques, in favour of the inlay technique ( p < 0.05). Conclusion Fixed-bearing all-polyethylene tibial UKA show acceptable outcomes at an average 12-year follow-up, especially in elderly patients and use of inlay tibial tray implantation technique.