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

Introduction: We compared the 12-months 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 thirty-seven individuals with FAI syndrome who received biomechanical assessment before and 12-months following either arthroscopic surgery (n = 17) or physiotherapist-led care (Personalised 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 to their respective baseline (mean increase across stride, arthroscopy: 0.97 BW [95% CI 0.49, 1.46] p < .001; PHT: 1.05 BW [95% CI 0.68, 1.43] p < .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 to baseline, while hip extensors made smaller contributions.

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