EP8.34 External Validation of the THA-10 Score for Predicting Long-Term Conversion to Total Hip Arthroplasty After Hip Arthroscopy

Abstract

Abstract Background The THA-10 Score is a risk stratification tool to help predict 10-year conversion to total hip arthroplasty (THA) following hip arthroscopy (HA) for femoroacetabular impingement (FAI). It is intuitive that the score demonstrated predictive accuracy on the original cohort utilized to create the metric. However, external validation has not yet been conducted. The purpose of the present study was to externally validate the THA-10 Score using a large single-institution cohort with long-term follow-up. Methods A retrospective review was conducted of patients who underwent primary HA with labral repair and capsular repair between 2011 and 2015. Inclusion criteria required a minimum of 10-year follow-up. Exclusion criteria included revision surgery, Tonnis grade ≥2, lateral center-edge angle <18°, or periacetabular osteotomy. The THA-10 Score was calculated by assigning points for body mass index (BMI) ≥25 kg/m2 (1 point), Tonnis grade 1 (1 point), age ≥47 years (2 points), and high-grade (Outerbridge grade 3 or 4) acetabular and femoral head chondral defects (3 points each). Discrimination was assessed using receiver operating characteristic (ROC) analysis and calibration was evaluated using the Brier score. Results The final cohort consisted of 215 patients (74.0% female, mean age 33.6 ± 13.0 years, mean BMI 26.9 ± 6.4 kg/m2). At a mean follow-up of 11.1 years (range 10.0-13.9 years), 23 patients (10.7%) underwent conversion to THA. The THA-10 Score demonstrated sufficient discrimination with an area under the curve (AUC) of 0.763. Calibration analysis demonstrated a Brier score of 0.078 with a p-value of 0.115, which is consistent with appropriate model calibration. Patients with THA-10 Scores ≥4 had 10.4-times greater odds of conversion to THA compared to those with scores <4 (p<0.001). Conclusions The THA-10 Score demonstrated sufficient discrimination and appropriate calibration for predicting 10-year THA conversion after HA for FAI. These findings support the use of the THA-10 Score as a counseling and risk-stratification tool in patients undergoing HA.