Predictors of Inferior Outcomes Following Hip Arthroscopy for Femoroacetabular Impingement

Abstract

Objectives:Hip arthroscopy for femoroacetabular impingement (FAI) provides reliable pain relief and functional improvement in the majority of patients. Although a small percentage of patients will go on to subsequent revision hip arthroscopy or conversion to arthroplasty, some patients will also have inferior clinical outcome without revision surgery. The purpose of this study is to identify clinical and radiographic characteristics predictive of inferior outcomes 2-years following hip arthroscopy for FAI.Methods:A clinical repository containing patients undergoing primary hip arthroscopy for femoroacetabular impingement (FAI) between 1/1/2012-1/1/2014 with a minimum follow up of two years was queried to include patients in this study. Operative procedures generally included labral debridement and repair, acetabular rim trimming, femoral osteochondroplasty and capsular plication. The primary outcome measure was the Hip Outcome Score Activities of Daily Living (HOS-ADL) questionnaire. Secondary outcome measures included the Hip Outcome Score Sports Subscale (HOS-SS) and modified Harris Hip Score (MHHS). Patients requiring revision hip arthroscopy or hip arthroplasty were excluded from this study. Patients were organized into superior and inferior outcome groups based on the top and bottom quartiles of the postoperative HOS-ADL score. Demographic, preoperative, intraoperative and postoperative variables between these groups were compared to identify predictors for inferior outcomes using bivariate and multivariate analyses.Results:Of 482 patients undergoing hip arthroscopy for FAI there was two year outcome data for 392 patients (81.5%) with an average follow up of 2.3 ± 0.6 years. The superior group contained 98 patients with an HOS-ADL score of 97.06 or higher while the inferior group contained 98 patients with an HOS-ADL score of 80.5 or lower. Patients in the superior outcome group were younger (30.7 ± 12.8 vs 38.0 ± 11.8 p<0.001) with a lower BMI (24.1 ± 4.1 vs. 26.5 ± 5.1 p=0.005) and higher preoperative average joint space width (4.2 ± 0.5 mm vs. 3.7 ± 0.4 mm; p=0.009) and lower Tonnis grade (p<0.001; Table 1). Patients in the inferior outcome group also had a higher incidence of smoking (p=0.005), workers compensation claims (p=0.04) and prior psychiatric history (p=0.007). A stepwise multivariate logistic regression analysis revealed that older age (p=0.00674), higher BMI (p=0.02629), and smoking (p=0.01863) were independent predictive factors of inferior outcome (Table 1). Both groups demonstrated significant improvements in HOS-ADL, and MHHS scores, however the inferior outcome group did not have significantly improved HOS-SS scores (p=0.06).Table 1:Demographic and radiographic differences between superior and inferior outcome groups following hip arthroscopy for Femoroacetabular Impingement Inferior OutcomeSuperior OutcomepAge38.0 ± 11.830.7 ± 12.8 <0.0001 Tonnis Grade > 019 (22%)1 (1.1%) <0.0001 Postoperative Alpha Angle42.3 ± 4.438.4 ± 3.7 0.001 BMI26.5 ± 5.124.1 ± 4.1 0.005 Smoking14(14%)3 (3%) 0.005 Preoperative Joint Space (mm)4.2 ± 0.543.75 ± 0.41 0.009 Psychiatric History27 (28%)12(12%) 0.02 Workers Compensation8(8.4%)2 (2.0%) 0.04 Spine History18 (19%)11(11%)0.16Gender (%F)60(61%)55 (56%)0.47Postoperative LCEA29.4 ± 4.530.1 ± 4.00.56Preoperative LCEA32.54 ± 5.732.16 ± 0.530.62Preoperative Alpha Angle61.5 ± 10.361.2 ± 9.30.83Conclusion:Older age, higher BMI, and smoking were independent predictors of inferior clinical outcomes at 2-years following hip arthroscopy for FAI, although both superior and inferior outcome groups experienced significantly improved clinical outcome scores. In addition, lower preoperative joint space, workers compensation status, and psychiatric history were significant factors for inferior outcomes on bivariate analysis. These factors can be considered in preoperative patient counseling about the expected outcome of hip arthroscopy for FAI.