The Association of α Angle on Disease Severity in Adolescent Femoroacetabular Impingement

Background: Femoroacetabular Impingement (FAI) is a common cause of hip pain in adolescent patients. Clinical exam and radiographic markers, such as α angle and lateral center edge angle (LCEA), are commonly used to aid in the diagnosis of this condition. The purpose of this study was to correlate preoperative α angle and LCEA with preoperative symptoms, intraoperative findings, and preoperative and postoperative patient reported outcomes (PROs) in the adolescent patient.

Methods: A retrospective analysis of prospectively collected data was conducted for all patients who underwent operative intervention for FAI at an academic institution over an 11-year period. Preoperative imaging was obtained and measured for LCEA and α angle. PROs (modified Harris Hip Score, Hip Disability and Osteoarthritis Outcome Score, and UCLA score) were collected preoperatively, as well as 1, 2, and 5 years postoperatively. Operative intervention was either open surgical hip dislocation or arthroscopic, and intraoperative disease was graded using the Beck Classification system. Patients with minimum 1-year follow-up were included in statistical analysis.

Results: There were 86 hips (64 female hips) included with an average age of 16.3 years (range, 10.4 to 20.5 y), with an average of 37 months of follow-up. There was no correlation between severity of preoperative symptoms or difference between pre and postoperative PROs for both α angle and LCEA. Overall, significant improvement was noted in modified Harris Hip Score, Hip Disability and Osteoarthritis Outcome Score, and UCLA Score (P<0.001 for each). Independent of preoperative symptoms, increased α angle correlated with more severe intraoperative labral disease (P<0.001), and longer length of labral tear (Corr 0.295, P<0.01). Femoral head and acetabular articular cartilage damage did not correlate with α angle or LCEA, nor did overall severity of disease.

Conclusions: In adolescent patients with FAI, increased α angle was found to significantly correlate with labral pathology, including increased length of tear and severity of disease, irrespective of preoperative symptoms or postoperative patient reported outcomes.

Level of evidence: Level III-retrospective.