Usefulness of Unenhanced MRI and MR Arthrography of the Shoulder in Detection of Unstable Labral Tears.

OBJECTIVE: Shoulder surgeons commonly intervene to repair unstable labral tears (tears that displace with patient movement). Surgeons can detect unstable tears at surgery. It is difficult to be certain if a tear is unstable from a static MR image. This study reports the comparative benefits of using unenhanced MRI and MR arthrography together to detect unstable labral tears.

MATERIALS AND METHODS: One hundred fifty consecutive unenhanced shoulder MRI and MR arthrography examinations performed on the same patients were reviewed retrospectively by consensus reading of two musculoskeletal radiologists. Both unenhanced MRI and MR arthrography were performed on each patient on the same day. Labral tears were assessed. It was also determined if there was any difference in position of the labral tear between unenhanced MR images and MR arthrograms. A change in position of 4 mm or more between unenhanced MR images and MR arthrograms was considered indicative of an unstable tear. All patients proceeded to arthroscopy.

RESULTS: Of these 150 patients, 94 had superior labral anterior-to-posterior (SLAP) tears, 53 had posterior labral tears, and 42 had anterior labral tears on MRI. All lesions described on MRI were described on arthroscopy. Twenty-three SLAP tears, 16 posterior labral tears, and 17 anterior labral tears showed a change in the position of the labral tear when comparing unenhanced MR images versus MR arthrograms of 4 mm or more. All of these labral tears were considered unstable by the surgeon, and all of these patients had surgical tacking performed. The other labral tears showed motion on unenhanced MR images and MR arthrograms of less than 4 mm. All of these tears except for three were considered stable on arthroscopic examination. There were five SLAP tears, three anterior labral tears, and four posterior labral tears seen on arthroscopy that were not seen on unenhanced MRI or MR arthrography. The tears not seen on unenhanced MRI or MR arthrography were considered stable at arthroscopy.

CONCLUSION: In this study, unenhanced MRI and MR arthrography of the shoulder was useful in diagnosing unstable labral tears in 23 patients with SLAP tears, 16 patients with posterior labral tears, and 17 patients with anterior labral tears. This information was useful in surgical planning. Of 133 tears that moved less than 4 mm on unenhanced MR images and MR arthrograms, 130 were considered stable on arthroscopy.