Results of Revision Surgery and Causes of Unstable Total Knee Arthroplasty

Over the past two decades primary total knee arthroplasty (TKA) has proven to be a highly successful operation, with survivorship rates approaching 95 % after a 15-year follow-up period.1) However, the results of revision TKA over the same period have been less encouraging. Failure rates in a range of 11 % to 60 % have been reported after a generally shorter follow-up interval.2,3) The poor results of TKA have been attributed to multiple factors, including size mismatching,3-5) ligamentous instability or soft tissue incompetence,3-6) pain of an unclear etiology,7) loosening8) and infection,5,9) and extensor mechanism problems.6,8) Background: The aim of this study was to evaluate causes of unstable total knee arthroplasty and results of revision surgery. Methods: We retrospectively reviewed 24 knees that underwent a revision arthroplasty for unstable total knee arthroplasty. The average follow-up period was 33.8 months. We classified the instability and analyzed the treatment results according to its cause. Stress radiographs, postoperative component position, and joint level were measured. Clinical outcomes were assessed using th