Patients with Borderline Hip Dysplasia Undergoing Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome Demonstrate Lower Outcome Scores but Comparable Survivorship to Non-Dysplastic Controls: A Propensity-Matched Study with Minimum 10-Year Follow-up
Authors: Chapman Reagan , Larson Jordan , Fenn Thomas , Beals Corey , Nho Shane 
Published: February 2024

Background: Patients with borderline hip dysplasia (BHD) have demonstrated similar outcomes following primary hip arthroscopy for femoroacetabular impingement syndrome (FAIS) compared to equivalent patients without dysplasia at short- and mid-term follow-up. However, outcomes in these groups have not yet been compared at long-term follow-up. Objectives: To compare long-term clinical outcomes following primary hip arthroscopy for FAIS between patients with BHD and non-dysplastic matched controls. Methods: A retrospective review was conducted of patients who underwent primary hip arthroscopy for FAIS from January 2012 through February 2013. Patients with BHD, defined as a lateral center edge angle (LCEA) between 18° and 25°, were propensity matched in a 1:3 ratio by sex, age, and body mass index (BMI) to non-dysplastic controls. Preoperative and postoperative radiographs were assessed. Patient-reported outcomes (PROs) were collected preoperatively and 10 years postoperatively, and achievement rates of Minimal Clinically Important Difference (MCID) and Patient-Acceptable Symptom State (PASS) were calculated. PRO measures included the Hip Outcome Score Activities of Daily Living (HOS-ADL) and Sports-Specific (HOS-SS) subscales, modified Harris Hip Score (mHHS), 12-item international Hip Outcome Tool (iHOT-12), and Visual Analog Scales (VAS) for Pain and Satisfaction. Gross survivorship was assessed using Kaplan-Meier curves. PROs, MCID and PASS achievement rates, and survivorship were compared between groups. Results: Twenty-eight patients with BHD (71.4% female; age: 30.8 ± 10.8 years, BMI: 24.2 ± 3.9 kg/m2) were matched to 84 controls (66.7% female, age: 34.4 ± 10.5 years, BMI: 24.9 ± 5.1 kg/m2; p ≥ 0.135). Mean follow-up was 10.3 ± 0.3 years. There were no significant differences between groups in any demographic characteristics, radiographic measurements, or intraoperative findings (p ≥ 0.096), except pre- and post-operative LCEA and Tönnis angle, which were lower and higher, respectively, among BHD patients (p < 0.001). Both groups demonstrated significant improvement in all PROs between the preoperative and 10-year postoperative time points (p < 0.001 for all). Preoperative, 10-year postoperative, and magnitude of change (delta) in PRO scores were similar between groups for all measures (p ≥ 0.072), except 10-year postoperative HOS-SS (BHD: 62.9 ± 31.9 vs. Controls: 80.1 ± 26.0, p = 0.030) and change in VAS Pain (BHD: -34.2 ± 27.2 vs. Controls: -48.5 ± 26.1, p = 0.047). Rates of MCID achievement were similar between groups for all PRO measures, but rates of PASS achievement were significantly lower among BHD patients for HOS-ADL (BHD: 39.1% vs. Controls: 77.4%, p = 0.002), HOS-SS (BHD: 45.5% vs. Controls: 84.7%, p = 0.001), and VAS Pain (BHD: 50.0% vs. Controls: 78.5%, p = 0.015). There was no difference in reoperation rate between groups (BHD: 14.3% vs. Controls: 17.9%, p = 0.778). Kaplan-Meier survival analysis demonstrated comparable gross survivorship at long-term follow-up (p = 0.645). Conclusions: Patients with BHD undergoing primary hip arthroscopy for FAIS demonstrated significantly lower sports-specific PRO scores than propensity-matched controls at 10-year follow-up, with a trend toward significantly worse scores for measures assessing activities of daily living, pain, and satisfaction. Rates of MCID achievement were similar between groups, but BHD patients demonstrated lower rates of PASS achievement for the majority of PRO measures. However, patients with BHD had similar long-term hip survivorship compared to controls, with no significant differences in rates of revision hip arthroscopy or conversion to total hip arthroplasty.