Static and dynamic pelvic kinematics after one-stage bilateral or unilateral total hip arthroplasty

Introduction: The pelvis rotates simultaneously around both hips along sagittal, frontal and transversal planes and its kinematics change in patients after total hip arthroplasty (THA). Consequently, it is reasonable to expect different pelvic kinematic profiles in bilateral or unilateral THA. Therefore, the aim of this study was to compare pelvic kinematics in patients with bilateral or unilateral THA. Methods: 40 patients undergoing bilateral (n = 20) or unilateral (n = 20) THA were evaluated for pelvic kinematics during standing and walking tasks using an optoelectronic system. Mean pelvic orientation was assessed during standing, whereas the Gait Variable Score (GVS), maximum and minimum peaks, range and values of pelvic tilt, obliquity and rotation during Heel-Strike and Toe-Off phases of gait cycle were calculated during walking. Data were collected the day before and at seven days after surgery. Results: At baseline, no between-group differences were found. At 7 days, GVS for pelvic tilt (p = 0.029) and rotation (p = 0.046) were closer to normative data in bilateral patients, who also revealed lower maximum peak of anterior tilt (p = 0.013) and lower range of pelvic tilt during gait (p = 0.031) with respect to unilateral cases. No between-group differences were found for pelvic orientation during standing at any time-point. Conclusions: Bilateral patients revealed more physiological pelvic kinematics than unilateral cases. These findings underline the advantage of patients undergoing 1-stage bilateral THA and may be helpful in selecting personalised rehabilitative approaches.