EP1.5 Acetabular Labral Height is Associated with Increased Hip Distractive Stability o tthe Hip: An In Vivo Analysis on Exam Under Anesthesia

Abstract Purpose: The purpose of this study was to examine the relationship of acetabular labral size, measured on magnetic resonance imaging (MRI), with resistance to early axial distraction prior to hip arthroscopy. The authors hypothesized that larger labral sizes would be associated with decreased distraction distances. Method: Patients undergoing primary hip arthroscopy for the treatment of femoroacetabular impingement (FAI) syndrome were reviewed for study inclusion. Inclusion criteria were: 1) appropriate hip MRI and 2) completion of the study traction protocol, which consisted of fluoroscopic images taken at traction intervals of 12.5 pounds from 0 to 100 pounds of axial traction on a post-free traction table prior to surgical intervention. Distraction distance was calculated as the difference of the joint space at each traction interval and the joint space at zero pounds of traction. Labral size was measured on MRI sagittal reformats in the 1:30 o’clock region. Individuals were stratified into two groups, larger labrum and smaller labrum, based on a 6mm cutoff. Descriptive statistics and independent samples t-tests were utilized for analysis, with an alpha of <0.05. Results: Forty-three patients were included. Labral height was <6 mm in 19 (44%) patients and ≥6 mm in 24 (56%) patients. There were no statistical differences between groups regarding age, sex, BMI, alpha angle on frog leg lateral radiographs, or lateral center edge angle on anteroposterior radiographs (p>0.05). The larger labrum group was found to have decreased distraction distances compared to individuals in the smaller Labrum group at traction intervals of 62.5 pounds(1.43±2.34mm vs 3.33±3.37mm; p=0.035), 87.5 pounds (4.22±3.46mm vs 6.59±3.25mm; p=0.028), and 100 pounds (5.30±3.76mm vs 8.28±2.77mm; p=0.006). Conclusions: Larger labrum size on MRI is associated with increased resistance to axial distraction on an exam under anesthesia prior to hip arthroscopy in the primary setting for the treatment of FAI. Clinically, this may be utilized to predict intraoperative distractibility, while also providing important considerations regarding labral size during augmentation and reconstructive procedures. Level of Evidence: IV, Case series