Differential Effect of Total Knee Arthroplasty on Valgus and Varus Knee Biomechanics During Gait

Abstract

Background: Total knee arthroplasty and its relation to gait abduction or adduction moment has not been fully described.

Methods: Gait analysis was performed on 25 patients (27 knees) preoperatively, 6 months and 1 year after total knee arthroplasty. Reflective markers were placed on the lower extremity, and motion data were collected at 60 Hz using 6 infrared cameras. Ground reaction forces were recorded at 960 Hz with a force plate. Stance phase was divided into braking and propulsive phases. Coronal knee angles and moments were calculated. Repeated-measures analysis of variance was used to compare frontal plane knee impulse over time and between the braking and propulsive phases of stance.

Results: In varus knees, static alignment was corrected from 2.2° varus to 3.3° valgus and in valgus knees from 15.2° valgus to 2.7° valgus (P < .010). Braking phase adduction impulse decreased from 0.145 to 0.111 at 6 months but increased to 0.126 Nm/kg s (P > .05) at 1 year. Propulsive phase impulse changed from 0.129 to 0.085 and persisted at 1 year. Impulse changed from 0.01 (abduction) to 0.11 Nm/kg s (adduction) at 6 months and persisted (P = .01).

Conclusion: Restoration of anatomic alignment and soft tissue balancing changes the lateral loading conditions of valgus knees. Both cases, between 6 months and 1 year, increased peak moment.

Keywords: gait; knee arthroplasty; knee biomechanics; total knee arthroplasty; valgus; varus.