Abstract
Introduction
Symptomatic instability following total knee arthroplasty (TKA) is a leading cause of early failure. Despite numerous reports on instability, standardized diagnostic and treatment protocols for these patients continue to remain unclear. Most reports recommend component revision as the preferred treatment, because of poor outcomes and high failure rates associated with isolated tibial polyethylene insert exchange (ITPIE). However, modern implant systems and standardized protocols may potentially change this teaching.
Methods
We performed an IRB-approved, retrospective review of 90 consecutive patients with minimum 2 years follow-up who underwent revision TKA for instability by one of four arthroplasty surgeons at a single institution. Mean age was 62.0 years (range, 41 to 83 years), and 73% of patients were women. Charts were reviewed for relevant preoperative clinical and physical exam findings, as well as pertinent intraoperative findings. Radiographs were analyzed for femoral and tibial component positioning. Pre- and post-operative Knee Society Scores (KSS) were calculated.
Results
Mean follow-up was 3.7 years. Using standardized criteria, 40% of patients were treated with ITPIE while 60% underwent revision of one or both components. In those treated with ITPIE, mean increase in polyethylene thickness was 4.4mm; level of constraint was also increased whenever allowed by the primary implants (47% of ITPIE cases). Total arc of motion improved from 117° to 123°. There were significant postoperative improvements in both KSS knee (48.4 to 82.6) and function (49.0 to 81.0) scores. Subgroup analysis demonstrated no significant differences in motion or KSS between those treated with ITPIE versus revision of one or both components. Combined failure rates were 19.4% in the ITPIE group versus 18.5% in the component revision group (p = 1.00).
Conclusions
Using an algorithmic approach to patients with instability following TKA, symptoms and function can reliably be improved. Contrary to conventional teaching, ITPIE can be an effective strategy at addressing instability symptoms when specific preoperative and intraoperative criteria can be fulfilled.
