Surgery for Femoroacetabular Impingement in Skeletally Immature Patients: Radiographic and Clinical Analysis

OBJECTIVES: The improved recognition of symptomatic femoroacetabular impingement (FAI) has lead to an emphasis of early diagnosis and treatment in the adolescent population. The purpose of this study was to evaluate the radiographic and clinical outcomes in patients with open physes that underwent hip arthroscopy for the treatment of symptomatic FAI. Additionally, we describe the three-dimensional (3D) pathomorphology in this unique population. METHODS: We retrospectively reviewed 39 hips (28 patients; 75% male) with a mean age 15.8 years (range, 12.8-19.3 years) with FAI, who additionally demonstrated open physes on pre-operative radiographs. Radiographic parameters included the lateral center edge (LCE), Tonnis angle, AP and lateral alpha angle and head-neck offset ratio (HNOr). Each patient also underwent a pre-operative CT scan, which was utilized for the evaluation for femoral and acetabular measurements and simulated range of motion (ROM) to impingement. Preoperative and post-operative functions were evaluated prospectively using the modified Harris Hip Score (mHHS) and pain on a visual analogue scale (VAS). All patients participated in organized athletics and 50% were in multiple sports year round. RESULTS: All patients (100%) within this cohort had open femoral neck and iliac crest physis. The ischial tuberosity and greater trochanteric physes were open in 95% and 54% of the hips respectively. Although there was no significant difference between pre-operative and post-operative LCE and Tonnis angles, the alpha angle and HNOr were significantly improved (39.7° vs. 61.7°; p<0.001 and 0.19 vs. 0.17; p<0.001). Mean femoral version was 17.6°±7.4°, while the acetabular version at the 1:30 and 3:00 positions were 1.0°±6.7° and 14.0°±4.1°. The mean maximum alpha angle was 72.0°±12.1° and was located on average at the 1:15 position. Simulated ROM to bony impingement was 121.6°±12.1° for flexion, 33.8°±13.3° for internal rotation in 90 degrees of flexion. Mean follow-up was 18.6 months (range, 6.3 - 55.8 months). There was a mean 23.0-point improvement in the mHHS (pre-operative 69.4, post-operative 92.4; p<0.001) and a mean decrease of 3.5 points in the VAS for pain (pre-operative 5.2, post-operative 1.7; p<0.001). 93% percent of patients returned to their preinjury level of sports participation and did not feel limited by their hip. Multivariate analysis demonstrated that a greater pre-operative LCEA correlated with a greater change in the mHHS score (r=0.374, p=0.038). Similarly, a greater pre-operative AP alpha angle and change in the AP alpha angle also correlated with a greater change in the VAS pain score (r=0.411, p=0.038 and r=0.426,p=0.019, respectively). No major complications were noted, but 3 hips (2 patients) underwent revision hip arthroscopy during the follow-up period secondary to further development of cam-type FAI. There were no cases physeal growth arrest, growth disturbance, avascular necrosis. CONCLUSION: The arthroscopic approach for the treatment of FAI in adolescents with open physes is a safe and effective and has a high return to sports rate. Risk for recurrent FAI in the presence of open growth plates was noted. Young, highly athletic adolescent patients with a larger FAI pathomorphology demonstrate the most predictable improvement in clinical outcomes after arthroscopicy.