Short-term Squatting Mechanics After Arthroscopic Treatment for Femoroacetabular Impingement in Adolescents

Femoroacetabular impingement (FAI) results from overcoverage of the acetabulum or excess bone on the femoral head-neck junction, which may cause pain or discomfort with repetitive hip flexion. Previous studies have reported adaptations in squat mechanics in individuals with FAI compared with controls, but to our knowledge, there has been little research exploring pre- to postoperative deviations in adolescents.

(1) Does surgical treatment result in measurable improvements in maximum squat depth? (2) Does surgical intervention alter the individual's balance control strategy during squatting? (3) Are there kinematic changes at specific movement milestones within the squat cycle after surgery? (4) Does the overall squat strategy, encompassing the entire movement, exhibit postoperative changes?

A retrospective analysis was conducted of patients enrolled between February 2016 and July 2023 in a large prospective study evaluating lower extremity biomechanical outcomes after various hip surgeries. Sixty hips were identified meeting specific criteria: (1) absence of neurological or syndromic abnormalities, (2) diagnosis of symptomatic idiopathic FAI through radiographic assessment, (3) scheduled for arthroscopic hip preservation surgery performed by one orthopaedic surgeon, and (4) tested in our motion capture lab before surgery. Of the 60, patients with bilateral symptomatic FAI were excluded as were those who had undergone previous surgical treatment, leaving 43 patients. In all, 79% (34 of 43) of patients completed the target squat that was analyzed in this study, and 65% (22 of 34) of patients completed the same task at their postoperative visit 8 to 16 months after surgery. Sagittal plane segment and joint angles as well as foot progression angle were analyzed across the squat cycle at four key movement milestones: maximum squat depth, preoperative maximum squat depth, maximum pelvic tilt, and maximum hip flexion. Pelvic tilt and hip flexion were plotted versus squat depth and versus each other throughout the squat task with the area between the descent and ascent curves calculated to quantify motion in the sagittal plane.

Median (range) maximum squat depth (preoperative 27 [13 to 38] versus postoperative 28 [17 to 40], median difference 1 [95% CI 1 to 5]; p = 0.02) increased postoperatively. Balance control strategies showed minimal changes, as the only notable difference was increased trunk flexion during the postoperative squat (preoperative 44 [6 to 65] versus postoperative 47 [18 to 74], median difference 3 [95% CI 1 to 13]; p = 0.01). Increased knee flexion was observed at both the maximum squat depth (preoperative 112 [71 to 135] versus postoperative 117 [78 to 144], median difference 5 [95% CI -1 to 14]; p = 0.02) and maximum hip flexion (preoperative 112 [71 to 132] versus postoperative 117 [78 to 144], median difference 5 [95% CI -1 to 14]; p = 0.02) positions. Pelvic tilt, hip flexion, and foot progression angles demonstrated no differences at the maximum squat depth, maximum pelvic tilt, or maximum hip flexion positions during the squat. Median (range) sagittal plane ROM increased for the trunk (preoperative 43 [16 to 66] versus postoperative 52 [25 to 75], median difference 9 [95% CI 2 to 16]; p = 0.01), pelvis (preoperative 24 [13 to 37] versus postoperative 27 [15 to 44], median difference 3 [95% CI 1 to 7]; p = 0.02), hip (preoperative 98 [76 to 116] versus postoperative 103 [89 to 130], median difference 5 [95% CI 0 to 8]; p = 0.046), and knee (preoperative 112 [73 to 141] versus postoperative 124 [87 to 152], median difference 12 [95% CI 3 to 15]; p = 0.02).

Based on these findings, the squat task could be used as a functional tool for clinicians to quickly assess a patient's abilities before and after surgical treatment. Future research should explore longitudinal studies to assess biomechanical changes over time and to consider whether standardized postoperative rehabilitation in adolescents alters the squat pattern for patients with FAI.

Level III, therapeutic study.