Predicting Functional Outcomes After Above Knee Amputation for Infected Total Knee Arthroplasty

Abstract

Background: Above knee amputation (AKA) is a rare, but serious, complication of total knee arthroplasty with relatively poor functional outcomes. The purpose of this study was to identify the factors predicting ambulatory status after AKA for periprosthetic joint infection of the knee and to elucidate the effects of this procedure on general health outcomes.

Methods: Patients who underwent AKA after an infected total knee arthroplasty between 2009 and 2014 at a single institution (n = 53) were retrospectively reviewed. Patients were followed for an average of 29 ± 18 months postoperatively or until death (n = 10). The primary outcome variable was ambulatory status at a minimum of 1-year follow-up. Secondary outcomes were Veterans RAND-12 (VR-12) scores. Demographics, surgical history, and complications were collected by chart review and/or telephone interview. Multiple regression modeling was used to identify predictors of better ambulatory status following AKA.

Results: Following AKA, 47% patients were nonambulatory, 28% were home ambulators, and 26% were community ambulators. The ambulatory status did not significantly worsen with AKA (P = .961). Male gender (P = .002), preoperative community ambulatory status (P = .030), and absence of persistent phantom pain (P = .016) were independent predictors of better ambulation. The VR-12 scores improved with AKA (physical, P < .001; mental, P = .368), with higher mental scores seen in elderly patients served with AKA (P = .015).

Conclusions: Overall, functional outcomes did not worsen following AKA compared to preoperative status. Gender, preoperative ambulatory status, and phantom pain affect postoperative ambulatory status. These data provide information to council patients regarding postoperative expectations when this procedure is required.

Keywords: amputation; complication; infection; outcomes; predictors; total knee arthroplasty.