Comparison of Standard Hip MR Arthrographic Imaging Planes and Sequences for Detection of Arthroscopically Proven Labral Tear

Abstract

The purpose of this study was to compare multiple imaging planes and two pulse sequences for detection of arthroscopically proven labral tears. From March 2004 through June 2007, acetabular labral tear was diagnosed at hip arthroscopy of 189 patients. Preoperative MR arthrography of the affected hip was performed on 144 patients at our institution. These MR arthrograms were retrospectively reviewed by a musculoskeletal fellow and two musculoskeletal radiologists. The sequences used were coronal T1-weighted with fat saturation, coronal T2-weighted with fat saturation, sagittal T1-weighted with fat saturation, axial oblique T1-weighted with fat saturation, sagittal oblique T1-weighted with fat saturation, and axial T1-weighted. Using consensus, the reviewers evaluated images obtained with each sequence for the presence of a tear, number of slices on which a tear was seen, and the signal intensity of the tear. Among the 144 tears, 97.2% were identified as definitely present on images obtained with at least one of the sequences. The axial oblique sequence had the highest individual detection rate (85.0%). The detection rates for the sagittal T1-weighted (74.6%), coronal T1-weighted (67.4%), and coronal T2-weighted (63.6%) sequences were intermediate. Detection rates with the axial T1-weighted (29.9%) and sagittal oblique (18.2%) sequences were low. With the combination of three sequences (coronal T2-weighted with fat saturation, axial oblique T1-weighted with fat saturation, and sagittal T1-weighted with fat saturation), 95.8% of the 144 tears were identified as definitely present. Twenty-eight percent of tears had a signal intensity less than that of gadolinium or fluid. Imaging in the axial oblique plane has the highest rate of detection of acetabular labral tears. More than 95% of tears were identified with the use of three imaging planes. Signal intensity within a tear does not have to be equal to that of gadolinium or fluid to confirm the diagnosis of labral tear.