RADIAL MR ARTHROGRAPHY USING T2*-WEIGHTED IMAGES WITH SALINE FOR DIAGNOSIS OF TORN ACETABULAR LABRUM

Abstract

Objectives: During the past decade, acetabular labrum injury has been increasingly recognized as a cause of hip joint pain. Currently, T1-weited MR arthrography (MRa) with gadolinium is the most popular diagnostic imaging technique used for direct detection of acetabular labrum injury. However, the intra-articular injection of gadolinium is not a procedure approved in Japan. We have conducted radial MRa using T2*-weighted images with saline instead. The purpose of this report was to evaluate the sensitivity, specificity, and accuracy of T2*-weighted MRa with saline for the diagnosis of acetabular labrum injury.

Methods: Between November 2005 and March 2007, thirty-two hip joints of 30 patients (8 joints of 7 males and 24 joints of 23 females) aged between 13 and 81 (mean; 58) years at the time of study, who underwent MR arthrogram and hip arthroscopy were studied.

Prior to performing T2*-weighted MRa, a mixture of 5ml of 2% lidocaine chloride, 5ml of 64% iotrolan, and 15ml of saline was injected under fluoroscopy guidance injected into the hip joint. T2*-weighted MRa was conducted using a 1.5-tesla magnet and local surface coil in radial slices perpendicular to the labral rim, at 15-degree intervals. Radial sequences were operated at T2*-weighted images, Gradient echo method, TR of500ms, TE of 20ms, flip angle of 30 degrees, slice thickness of 5 mm, and FOV of 180 mm.

On the MRa, acetabular labrum tear was diagnosed when inflow of contrast medium (high intensity) was observed continuous with the joint space at the base of acetabular labrum.

Hip arthroscopy was conducted in the supine position by the standard three portal methods. The results of T2*-weighted MRa were compared with arthroscopic findings to calculate the sensitivity, specificity and accuracy of T2*-weighted MRa.

Results: On T2*-weighted MRa, acetabular labrum tear was observed in 17 joints, and no abnormalities in 15 joints. From arthroscopic findings, acetabular labrum tear was observed in 20 joints, and no acetabular labrum abnormalities in 12 joints. Comparing the two methods, the T2*-weighted MRa results were true positive in 17 joints, true negative in 12 joints, and false negative in 3 joints. Therefore, MRa had a sensitivity of 85%, specificity of 100%, and accuracy of 90.6%.

Discussion: MRa has become the standard imaging technique for the diagnosis of acetabular labrum tear. The sensitivity was reported to range from 63 to 100%, specificity from 44 to 75%, and precision from 63 to 94%.

Our results showed that this method provides sensitivity, specificity and accuracy that approach conventional MRa, demonstrating that radial T2* weighted MRa is a useful imaging technique for the diagnosis of acetabular labrum pathology.

Conclusions: We recommend T2*-weighted MRa with saline for the diagnosis of acetabular labrum injury.