The conversion rate to total hip arthroplasty after hip arthroscopy in patients with femoroacetabular impingement syndrome is 8% and is affected by older age, cam morphology and osteoarthritis

PURPOSE: Patients with femoroacetabular impingement syndrome (FAIS) may experience persistent hip problems following arthroscopic surgery, with some patients requiring total hip arthroplasty (THA). Therefore, the purpose was (1) to investigate the proportion of THA conversion in a large national Danish cohort of patients with FAIS who had previously undergone hip arthroscopy. (2) To investigate factors that might affect time to conversion. (3) To describe patient-reported outcomes after THA.

METHODS: Patients aged 18 years or above registered with arthroscopic surgery for FAIS between January 2012 and November 2023 in the Danish Hip Arthroscopy Registry (DHAR). Eligible patients were invited to participate in an online survey. If they responded 'yes' to the entry question 'Have you had total hip arthroplasty?', they were asked to complete the Copenhagen Hip and Groin Outcome Score (HAGOS), the Hip Osteoarthritis Outcome Score (0-100 scores, 100 being no problems), the Hip Specific Sports Scale, and Patient Acceptable Symptom State. To perform survival analysis, a Kaplan-Meier method was used to estimate cumulative all-cause conversion to THA. A Cox regression model was fitted after examining proportional-hazards assumptions to examine predictor variables on conversion to THA.

RESULTS: A total of 5109 patients were eligible and invited for the survey. Of which, 2383 (46.6%) responded; 406 patients had received THA at a median of 4.2 [2.1; 7.0] years after hip arthroscopy. Regarding HAGOS, patients (N = 199) treated with THA reported mild pain (75 [55; 93] points) and problems with daily activities (70 [40; 90] points) and moderate problems with sports activities (53 [28; 81] points) and hip-related quality of life (50 [30; 80] points), 56% participated in sports activities and 62% reported an acceptable symptom state.

CONCLUSIONS: A low number of conversions to THA (8%) was observed. Older age decreased lateral joint space width, Tönnis grade > 0, higher alpha angle and femoral cartilage pathology were associated with conversion to THA.

LEVEL OF EVIDENCE: Level II, retrospective study.