[Isolated lesions of the subscapularis muscle. Apropos of 21 cases].

PURPOSE OF THE STUDY: The goal of this retrospective study is to describe the different anatomic lesions of the subscapularis and to precise the diagnostic value of the clinical and imaging tests.

MATERIAL: Twenty-one cases of isolated tear of the subscapularis were operated on between 1989 and 1992. Affecting both sex, this lesion happens in younger patients than the rotator cuff tear concerning supra or infra-spinatus. The onset was most often traumatic but not specific. Four patients had no traumatic history.

RESULTS

In 16 cases, the complaint was an unspecific chronic painful shoulder. The Jobe test was positive in 12 cases. The lift-off test was positive in 9 cases. Arthrography showed extravasation of dye into the subacromial bursa in 11 cases. Subscapularis lesion was suspected with the presence of dye spot on the lesser tuberosity on the A.P. view in external rotation (18 cases). Arthro-CT-scan was diagnostic in 12 cases, revealing dye spot touching the lesser tuberosity. At surgery, 3 types of lesions were found: complete ruptures or ruptures concerning the superior two-thirds of the tendon and letting intact the inferior muscular third (15 cases): partial superior lesions (5 cases) and a muscular tear of the inferior two-thirds. The long head of the biceps was dislocated in 5 cases, subluxated in 5 cases, ruptured in 3 cases and normal in 8 cases.

DISCUSSION: The mechanisms of these lesions are probably different. The most common mechanism is traumatic but 4 patients had no traumatic injury. Degenerative changes of the tendon or subcoracoid impingement are also evocated. Arthrography permits a good screening but arthro-CT-scan is the most accurate to detect the lesion. Presence of dye touching the lesser tuberosity is a specific sign of the subscapularis lesion.