Preoperative and Postoperative Lower-Extremity Joint and Pelvic Kinematics During Maximal Squatting of Patients with Cam Femoro-Acetabular Impingement

Background: Understanding how the function of the lower extremity joints during everyday movements following surgery to treat cam femoro-acetabular impingement is essential to assess whether surgical intervention effectively restores the normal biomechanics of the hip. The purpose of this study was to compare preoperative and postoperative lower-extremity joint and pelvic angular displacements during maximal depth squatting of patients with unilateral symptomatic cam femoro-acetabular impingement. Methods: Ten participants were compared with respect to their preoperative and postoperative test results. The participants were between eighteen and fifty years of age and had a positive impingement test and visible cam deformity on anteroposterior and Dunn view radiographs. Postoperative testing for each participant occurred between eight and thirty-two months following surgical intervention. Three-dimensional lower-limb joint and pelvic kinematics of participants were collected during maximal depth squats. Results: Postoperatively, participants squatted to a greater mean maximal depth than they did preoperatively. Postoperative knee flexion and ankle dorsiflexion angles of the affected extremity at maximal depth were significantly greater than preoperative values. The postoperative sum of all joint angles of the affected limb at maximal squat depth was significantly larger than the preoperative sum. No significant differences were detected between the preoperative and postoperative measurements of the patients with cam impingement with respect to the kinematics of the affected hip at maximal squat depth, the pelvic angular displacements at maximal squat depth, or the overall pelvic range of motion during maximal deep squatting (p > 0.05). Conclusions: The squat performance improved postoperatively, likely because of the combined effects of increased knee and ankle angles as well as a greater acetabular opening and thus reduced anterior femoral head coverage, allowing increased posterior pelvic pitch during the descent phase of the squat.