Is there a correlation between outcomes after hip arthroscopy for femoroacetabular impingement syndrome and patient cortical bone thickness?

In order to determine the associations between age, sex, cortical bone thickness (CBT), and outcomes following hip arthroscopy for FAIS, a retrospective study of patients undergoing hip arthroscopy for FAIS from a single institution from 2012 to 2014 was performed. Based on preoperative radiographs, femoral cortical index (FCI) and femoral canal-to-calcar ratio (FCC) were used as measures of CBT and used to classify patients using the Dorr classification. Linear and logistic regression was used to determine whether CBT was predictive of 2-year patient reported outoutcomes. Patients were stratified by sex and age (<45 or =45 years old) to determine whether variables were potential effect modifiers on the association between outcomes and CBT. A total of 108 patients were included in the study, with 27 patients in each of the following groups: females <45, females =45, males <45, and males =45 years. The results showed that at 2-year follow-up, all groups demonstrated significant improvements in reported outcomes (HOS-ADL, HOS-SS, and mHHS) (p<0.001). Females =45 scored significantly worse than other groups on all scores (p<0.05 for all). Chi-square test for trend showed a linear by linear association between Dorr classification type and gender/age group (p=0.018). Analysis of the whole study population showed a linear association between FCC and HOS-ADL and mHHS scores. However, CBT measures were not predictive of achieving MCID. In conclusion, patients undergoing hip arthroscopy for FAIS, older female patients had the worst patient-reported outcomes and lowest CBT measures. Furthermore, FCC is independently associated with the HOS-ADL and mHHS. LEVEL OF EVIDENCE: Retrospective comparative study, Level III. WHAT IS KNOWN ABOUT THE SUBJECT: Among patients undergoing hip arthroscopy for FAIS, female patients over the age of 45 have been reported to be at risk for inferior post-operative outcomes. Meanwhile, this patient population is also the most at risk for deteriorating CBT. WHAT THIS STUDY ADDS TO EXISTING KNOWLEDGE: This study demonstrates that female patients with FAIS over the age of 45 have inferior CBT indices than their male and younger-aged counterparts. Furthermore, this study presents an association between the FCC and 2-year patient-reported outcome measures, suggesting that CBT characterization may withhold prognostic value.