Kinematic and neuromuscular changes in patient with preoperative knee fixed flexion deformity (FFD) before and after total knee arthroplasty (TKA)

Abstract

Introduction: FFD are common in osteoarthritic knees. Residual FFD after TKA have been associated with poorer functional outcomes. Muscle co-contraction, Quadriceps-Hamstrings, is one of the factors potentially associated with residual FFD after TKA. This study aimed to review the changes in static, dynamic knee kinematics and electromyography (EMG) before and after TKA in patients with preoperative FFD. Methodology: 13 patients (age 73.5±8.7;13 females) with preoperative FFD (14.6±4.3°) with full correction of FFD during TKA were included. Data on knee kinematics and gait analysis were measured before TKA, and at 6 weeks, 3 months and 6 months postoperatively. The primary outcome measures are knee range at static and dynamic conditions, and co-contraction index (CCI) (Rectus Femoris-medial Hamstrings) measured by EMG. Results and Analysis: In static assessment, knee FFD was statistically significantly improved (16.4±6.9° (preop) to 0.6±1.7° (6 month), p=0.000). In gait analysis, knee flexion angle during mid-stance and terminal stance were reduced (43.8%, p=0.027;47.2%, p=0.041) at 6 months after TKA. However, patient still had 13.5±8.2° and 12.1±9.3° of residual knee extension lag during mid-stance and terminal stance. CCI was 34.5±7.4 pre-operatively. It persisted during 3 months follow up (31.3±9.3) but reduced after 6 months (27.0±10.6). Discussion and Conclusion: Patients showed improving in passive knee extension range, but still had residual knee extension lag during walking, and muscle co-contraction still persisted 3 months postoperatively. Neuromuscular re-education emphasis on reduction in co-contraction may be considered to enhance recovery, and to prevent recurrence FFD.