Outcomes After Revision Total Knee Arthroplasty for Isolated Flexion Instability Compared to Flexion Instability and Concomitant Arthrofibrosis.

Abstract

Flexion instability (FI) after total knee arthroplasty (TKA) is a leading cause of early failure and is typically associated with increased early flexion, pain, swelling, and subjective instability. However, there is a subset of patients who have symptomatic FI with concomitant arthrofibrosis (FI + A). This study compared outcomes in revision TKA cases performed for isolated FI to those performed for FI + A. A retrospective review was performed on 115 patients who were revised for FI and 20 patients who were revised for FI + A. The surgical technique emphasized the established principles and surgical algorithms for FI. Clinical data and patient-reported outcome measures (PROMs) were evaluated. The two groups did not differ by demographics (P ≥ 0.207), mean follow-up (P = 0.462), or comorbidities (P ≥ 0.358); however, the FI group had a higher prevalence of uncontrolled depression (28 versus 5%, P = 0.026), although it was not associated with outcomes (P ≥ 0.434). The two groups did not differ by radiographic metrics (P ≥ 0.117) or PROMs at the latest follow-up or in the change from pre-revision baseline PROMs (P ≥ 0.186). The FI + A group had a greater increase in knee range of motion (ROM) from the pre-revision baseline compared to the FI group (22.5 versus 2.2 degrees, P = 0.015). However, the FI group obtained a higher absolute post-revision ROM (116 versus 103 degrees, P = 0.016). This study demonstrated no difference in outcomes after revision TKA comparing patients who were revised for FI + A to those revised for isolated FI. However, the FI + A group gained a clinically relevant improvement in post-revision ROM and benefited from revision TKA. Further study is warranted to understand the challenging and often multifactorial diagnosis of FI with concomitant arthrofibrosis. III.