FP4.9 Hip Arthroscopy for Femoroacetabular Impingement Syndrome Restores Kinematics to the Contralateral Side by One Year after Surgery

Background: Femoroacetabular impingement syndrome (FAIS) is common in athletes, yet little is understood about the effect of biomechanics and how they alter after hip arthroscopy. This study aimed to assess the impact of hip arthroscopy on biomechanical function in patients with femoroacetabular impingement syndrome (FAIS) during gait, stair ascent and descent.

Hypothesis: We hypothesized that symptomatic FAIS hips would exhibit decreased motion preoperatively compared to contralateral hips, but that these differences would be corrected postoperatively and that these changes would correlate to improvements in patient-reported outcome measures (PROMs).

Methods: Ten patients undergoing hip arthroscopy for FAIS were included and completed PROMs as well as kinematic assessment at baseline and 1-year post operatively. 3D motion tracking was performed using a 10-camera system while performing gait, stair ascent and descent. Joint kinematics were calculated in the sagittal, coronal, and transverse planes for the symptomatic and contralateral side. Peak and valley angles for each joint during each task were compared between limbs using linear mixed effects models. Significant changes in kinematics were corelated to PROMs.

Results: Preoperatively, the symptomatic hip demonstrated significant deficits in gait and stair ascent compared to the contralateral hip. One year postoperatively, significant improvements in kinematics were found with the operative hip returning to similar levels in gait, stair ascent and stair descent compared to the contralateral hip. During gait, hip kinematics improved compared to before surgery with respect to increased flexion (+7.7°, SD 7.3°), abduction (+2.4°, SD 3.2°), and external rotation (ER) (+3.0°, SD 4.9°) (p<0.01). During stair ascent hip abduction (+2.8°, SD 1.7°), and ER (+2.8°, SD 5.7°), were significantly improved (p<0.01). During stair descent, hip flexion (+2.5°, SD 6.4°), extension (+3.9°, SD 8.3°), abduction (+2.3°, SD 2.6°), and ER (+4.8°, SD 4.3°), were significantly improved (p<0.01). Significant improvements were seen in patient reported outcomes, but these did not correlate to hip kinematics.

Conclusion: Hip arthroscopy for FAIS restores hip flexion, abduction, and external rotation during dynamic tasks such as gait, stair ascent and descent to comparable states as the contralateral limb. Additionally, patients report significant improvement in function and pain at one-year post-operatively.

Clinical Relevance Hip arthroscopy for FAIS is effective at restoring function of the affected limb to that of the contralateral limb during dynamic tasks like walking and stair ascent.