Subchondral drilling for chondral flaps reduces the risk of total hip arthroplasty in femoroacetabular impingement surgery at minimum five years follow-up

Introduction: The best treatment of acetabular chondral flaps during surgery for femoroacetabular impingement (FAI) is unknown. We asked if subchondral drilling improves clinical and radiographic outcome and if there are factors predicting failure. Methods: We treated 79 patients with symptomatic FAI and acetabular chondral flaps with surgical hip dislocation between January 2000 and December 2007. Exclusion of all patients with previous hip pathology or trauma resulted in 62 patients (80 hips). The chondral flap was slightly debrided in 43 patients/51 hips (control group). In 28 patients/29 hips (study group), additional osseous drilling was performed. 4 patients (5 hips, 6%) were lost to follow-up. Mean follow-up was 9 years (5-13 years). The groups did not differ in demographic data, radiographic parameters or follow-up. Clinical outcome was assessed with the Merle d'Aubigne score, modified Harris Hip Score and University of California Los Angeles activity score and progression of osteoarthritis with the Tonnis grade. Results: No patient underwent conversion to total hip arthroplasty (THA) in the drilling group compared to 7 patients (8 hips, 16%) in the control group (p = 0.005); in the remaining hips, clinical scores and progression of Tonnis grade did not differ. Increased acetabular coverage, age and body mass index were univariate predictive factors for conversion to THA. No drilling was as an independent predictive factor for conversion to THA (hazard ratio 58.07, p = 0.009). Conclusion: Subchondral drilling under acetabular chondral flaps during surgical treatment of FAI is an effective procedure to reduce the rate of conversion to THA.