Mei Lin Tay: Investigating mechanisms of failure for unicompartmental knee replacements

Knee arthroplasty can improve quality of life for patients with end-stage knee osteoarthritis (OA). The need for knee arthroplasty has increased due to an ageing population and increasing obesity. The majority of patients have disease isolated to one compartment and are eligible for a unicompartmental (partial) knee arthroplasty (UKA) instead of total knee arthroplasty (TKA). UKA has advantages over TKA including cost-effectiveness, fewer complications and faster recovery; however UKAs have higher revision rates and consequently lower surgeon usage. A better understanding of the reasons for UKA failure is needed for improved clinical outcomes. We aimed to identify reasons for failure of medial UKAs, and to examine differences by implant types and time.

A systematic review was performed by searching MedLine, EMBASE, CINAHL and Cochrane databases between 2000 and 2020. A retrospective audit of UKA outcomes was conducted using data from the New Zealand Joint Registry combined with electronic patient notes from four large centres (Auckland, Counties Manukau, Canterbury and Waitematā District Health Boards) between 2000 and 2017 (n=2196).

A total of 24 cohort studies were identified in the literature review. The most common indications for UKA revision were aseptic loosening (24%) and OA progression (30%). The retrospective audit showed 2100 medial UKAs were performed between January 2000 and December 2017 with a 93.4% implant survival rate. Reasons for revision in our patient cohort mirrored those found in the systematic review. Early failures were due to infection, bearing dislocation and fractures, whereas late-term failures were due to osteoarthritis progression in the unreplaced compartment. Biologically, both aseptic loosening and osteoarthritis progression are associated with inflammation in surrounding tissues. Further research will focus on investigating the role of underlying inflammatory mechanisms in UKA patient outcomes.

This poster was uploaded for the SGS Research Showcase 2021.