Increased Labral Height is Associated with Greater Distractive Stability of the Hip: An In Vivo Analysis.

Abstract

Purpose: To examine the relationship of labral height measured on magnetic resonance imaging (MRI) and resistance to axial distraction in patients with femoroacetabular impingement (FAI) syndrome.

Methods: Patients who underwent primary hip arthroscopy for FAI syndrome between March 2020 and August 2020 were enrolled in the study traction protocol. Prior to any operative instrumentation, fluoroscopic images were taken of the native hip joint at 12.5 lb intervals between 0-100 lbs of axial traction on a postless traction table. Distraction was calculated as the difference between the total joint space at each traction interval and the baseline joint space. Labral height was measured on MRI sagittal reformats at approximately 1:30 on the acetabular clockface by a musculoskeletal fellowship-trained radiologist who was blinded to the traction data. Descriptive statistics, independent samples t-tests, Pearson chi-square tests, and Fisher's exact tests were utilized in analysis.

Results: Forty-three hips in 42 patients were included. Labral height was <6 mm in 19 (44%) patients and ≥6 mm in 24 (56%) patients. No statistically significant differences in age, sex, body mass index, alpha angle, Tönnis grade, lateral center edge angle, Beighton score, or presence of labral tears were observed between patients with <6 and ≥6 mm of labral height (P > 0.05). A greater percentage of patients with a labral height <6 mm broke their suction seal relative to patients with a labral height of ≥6 mm at 62.5 lbs (42% v. 4%; P=0.003) and 100 lbs (95% v. 67%; p=0.027).

Level of evidence: III, retrospective cohort study CONCLUSIONS: Anterosuperior labral height ≥6 mm is associated with increased resistance to axial distraction on an exam under anesthesia in patients undergoing primary hip arthroscopy for FAI syndrome.