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

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.