Abstract
INTRODUCTION
Cadaveric studies have reported damage to the direct head of rectus femoris and tensor fascia lata muscles with direct anterior approach(DAA) and to the abductors, external rotators with posterior approach(PA). The aim of this prospective study was to evaluate differences in hip muscle strength recovery between DAA and posterior approach (PA) THA.
METHODS
Patients with unilateral hip osteoarthritis undergoing THA at a single institution from January 2011 to October 2011 were enrolled. All DAA THA's were performed by one surgeon, and all PA THA's were performed by another surgeon with similar design of components, pain management and rehabilitation protocols. Hip muscle strength was measured with a handheld dynamometer in all planes by a single observer preoperatively, at 6 weeks, 3 months and 6 months. Functional recovery was assessed with the motor component of Functional Independence Measure, UCLA activity score, Harris hip score, SF-12 score.
RESULTS
There were 30 patients (15 per group) with similar age, sex, BMI and preoperative functional scores. There was a significant difference between groups in ER strength recovery pattern(p=0.04) with greater mean deficit in PA group from preoperative to 6 weeks(37%), 3 months (28%) and 6 months (25%); whereas DAA group demonstrated 3% mean deficit at 6 weeks, 2% mean improvement at 3 months and 10% mean improvement at 6 months from preoperative values. Flexion strength decreased in DAA group by a mean of 10% at 6 weeks(p=0.07) but improved at 3 months by a mean of 12% as compared to preoperative values. There were no differences in recovery pattern of other hip movements between groups. Functional recovery scores between groups were similar.
DISCUSSION
Both DAA and PA THA offer similar recovery in hip muscle strength up to 6 months with exceptions of ER strength deficit in PA group and a trend to flexion strength deficit at 6 weeks in DAA group.
