Abstract

BACKGROUND: Appropriate gait function is an important determinant of the outcome of total hip arthroplasty and relies on appropriate joint motion and muscle activity. The purpose of this study was to test the hypothesis that 6-month postoperative dynamic joint range of motion, time-distance measures and muscle activity in the operated limb in patients undergoing total hip arthroplasty differ from preoperative levels and are more similar to those observed postoperatively in the contralateral limb and in healthy subjects. METHODS: Basic time-distance gait measurements, knee and hip kinematics and electromyographic activity from eight hip muscles were obtained preoperatively and 6 months postoperatively in 52 patients undergoing total hip arthroplasty and in 24 age-matched healthy subjects during treadmill walking. FINDINGS: Postoperative dynamic hip range of motion for the operated limb (confidence interval differences [-3.9°; -2.3°]) and postoperative knee range of motion for both limbs (operated: [-8.4°; -5.6°]; contralateral: [-8.1°; -5.3°]) in patients with total hip arthroplasty were significantly lower than values for the control subjects (P<0.001). Postoperative gait in patients with total hip arthroplasty was more symmetric than preoperative gait. Preoperative and postoperative electromyographic intensities were higher in patients with total hip arthroplasty than values for the control subjects (P<0.001), and patients had different EMG patterns compared to the control group. INTERPRETATION: Pre- and postoperative differences not only in hip but also in knee kinematics emphasize the importance of evaluating the dynamic outcome of total hip arthroplasty by assessing joint motion of all lower extremity joints in both legs. Verf.-Referat