Failure mechanisms of unicompartmental knee replacement: the impact of changes in operative technique and component design

Reliable unicompartmental knee replacement requires knowledge of the common failure mechanisms of this type of arthroplasty. The problem in the past has been loosening of components because of design flaws and technical failure. Whereas recent reports are very encouraging in terms of clinical results and enhanced durability of unicompartmental replacements, the current study confirms the observation that nonparallel orientation of femoral and tibial components is common and may produce excessive polyethylene wear and clinical failure. Newer unicompartmental designs with meniscal bearings may be the answer to this problem.