Effects of Arthroscopic Surgery and Non-Surgical Therapy on Hip Contact Forces in Femoroacetabular Impingement Syndrome.

Introduction: We compared the 12-month effects of arthroscopic surgery and physiotherapist-led care for femoroacetabular impingement (FAI) syndrome on the time-varying magnitude of hip contact force and muscle contributions to hip contact force during walking.

Methods: Secondary analysis was performed on 37 individuals with FAI syndrome who received biomechanical assessment before and 12 months after either arthroscopic surgery (n = 17) or physiotherapist-led care (personalized hip therapy [PHT]) (n = 20). At both time points, three-dimensional whole-body motions, ground reaction forces, and surface electromyograms (n = 14) were acquired during overground walking. A neuromusculoskeletal model was used to determine hip contact force and muscle contributions to hip contact force. Two-way repeated measures analyses of variance, implemented through statistical parametric mapping, were used to assess interactions between, and main effects of, treatment (arthroscopy vs PHT) and time (baseline vs follow-up) on time-varying magnitude of hip contact force and muscle contributions to hip contact force. Effects were reported as mean differences (normalized to bodyweight, BW) with 95% confidence intervals [95% CI, lower, upper bound].

Results: For both treatment groups, hip contact force was larger at 12 months compared with their respective baseline value (mean increase across stride, arthroscopy: 0.97 BW [95% CI, 0.49-1.46] P < 0.001; PHT: 1.05 BW [95% CI, 0.68-1.43] P < 0.001); however, no interaction effects were found. For both treatment groups, hip flexor, adductor, and abductor muscle groups made greater contributions to hip contact force after 12 months compared with baseline, whereas hip extensors made smaller contributions.

Conclusions: Compared with baseline, both treatments resulted in 12-month increases in hip contact force during walking caused by larger flexor, adductor, and abductor muscle forces. At 12 months, hip contact force magnitude remained different from normative values reported for healthy individuals, indicating that neither treatment fully restored hip biomechanics.