The "bridging sign": a MR finding for combined full-thickness tears of the subscapularis tendon and the supraspinatus tendon

Abstract

Background: In daily practice, we discovered one of the secondary magnetic resonance (MR) findings of the subscapularis (SSC) tendon tear, the "bridging sign", which has not been previously described.

Purpose: To describe the "bridging sign" on shoulder MR imaging and its radiological and clinical significance in patients with SSC tendon tear.

Material and methods: Twenty-nine patients who had undergone shoulder arthroscopy and had full-thickness tear of the subscapularis tendon were enrolled. The medical records of the 29 patients were retrospectively reviewed for the duration of shoulder pain, rotator cuff tears, and associated arthroscopic findings: biceps tendon abnormality and superior glenoid labral tear. Then, preoperative shoulder MR images were retrospectively reviewed for the presence or absence of the "bridging sign" and associated MR findings: periarticular fluid and fatty atrophy of the supraspinatus and subscapularis muscles. The type of rotator cuff tear associated with the "bridging sign" was assessed and the sensitivity, specificity, and accuracy of the "bridging sign" for the diagnosis of a certain type of rotator cuff tear were calculated. Associated arthroscopic and MR findings and mean duration of the shoulder pain between the patients with and without the "bridging sign" were compared.

Results: The "bridging sign" was seen in 17 of 29 patients and corresponded to a complex of the torn and superomedially retracted subscapularis tendon, coracohumeral ligament, and superior glenohumeral ligament, adhered to the anterior margin of the torn supraspinatus (SSP) tendon on arthroscopy. All patients with the "bridging sign" had combined full-thickness tear (FTT) of the cranial 1/2 portion of the subscapularis tendon and anterior 1/2 portion of the SSP tendon. The sensitivity, specificity, and accuracy of the "bridging sign" for the diagnosis of combined FTTs of the SSC tendon and anterior portion of the SSP tendon were 81.0%, 100%, and 86.2%, respectively. The patients with the "bridging sign" had longer duration of shoulder pain and more frequent associated arthroscopic and MR findings than the patients without the "bridging sign".

Conclusion: The "bridging sign" is a highly specific finding for combined full-thickness tears of the subscapularis tendon and anterior portion of the supraspinatus tendon, associated with more chronic shoulder pain and more sever rotator cuff tear.