Does a third condyle TKA restore normal gait kinematics in varus knees? In vivo knee kinematic analysis.

INTRODUCTION: Patients with knee osteoarthritis tend to modify spatial and temporal parameters during walking to reduce the pain. Total knee arthroplasty (TKA) is considered the gold standard treatment for end-stage knee osteoarthritis. However, reduced physical function of the knee is partly, but apparently not fully, remedied by surgery. The purpose of this study was to investigate the in vivo, three dimensional knee kinematics during gait at the patients with knee osteoarthritis and the influence of "third condyle" psoterior stabilized (PS) total knee arthroplasty on restoration of normal kinematics.

MATERIALS AND METHODS: Twenty patients with medial knee osteoarthritis and a control group with age-matched subjects were prospectively collected for this study. The same group of 20 patients were re-assessed 10 months after total knee arthroplasty with "third condyle" PS prosthesis. All subjects were assessed with a 3D, optoelectric knee assessement device, while walking on a treadmill at a self-selected speed. For each participant, knee flexion-extension, abduction-adduction, internal-external rotation and anterior-posterior displacement, were calculated.

RESULTS: The range of flexion/extension was improved significantly (39.9° ± 5.5° vs 44.8° ± 5.1°, p < 0.05) after TKA but it still remained lower than control group (6.9° ± 5.5° vs 2.2° ± 3.9°, p < 0.05). The range of motion in internal-external rotation did not change pre- and post-arthroplasty, but remained lower than the matched control group (6.7° ± 2.4° vs 9.3° ± 2.4, p < 0.05). The maximum posterior displacement during swing phase was significantly higher at post-arthroplasty group comparing with control group (-9.5 ± 2.2 vs -5.7 ± 3 mm, p < 0.05).

CONCLUSION: Following "third condyle" PS-TKA, patients had better clinical, spatiotemporal and kinematic parameters. Despite improvements, the knee kinematics during gait in TKA group differed from healthy control group. TKA group had a lower extension lower range of axial rotation and an increased tibial posterior displacement.