Purpose: We describe a new clinical sign for subscapularis lesions that we call the belly-off sign and compare its diagnostic value with standard subscapularis tests (the lift-off test, internal rotation lag sign, and belly-press test/Napoleon sign) in cases of different types of subscapularis lesions. The belly-off sign represents the inability of the patient to maintain the palm of the hand attached to the abdomen with the arm passively brought into flexion and internal rotation.
Type of study: Case series.
Methods: This descriptive and explorative study included 60 patients (mean age, 55.3 years) with clinical, surgical, and/or magnetic resonance imaging-confirmed evidence of isolated or combined lesions of the subscapularis musculotendinous unit. In all patients, a complete physical shoulder examination was performed and the results were compared with the intraoperative and magnetic resonance imaging findings.
Results: The belly-off sign appeared to be more reliable than any other diagnostic test or sign in detecting isolated partial tears of the subscapularis tendon (group I), combined partial subscapularis and complete supraspinatus tendon tears (group II), and postoperative subscapularis insufficiency with mild atrophy of the upper aspect of the subscapularis muscle (group VII). In cases of complete/near complete subscapularis tears with or without supraspinatus and infraspinatus tendon tears (groups IV, V, and VI), the belly-off sign appeared to be as reliable as the belly-press test, internal rotation lag sign, and lift-off test. For assessing partial subscapularis tendon tears and insufficient external rotators (group III), the belly-off sign was less reliable than any other diagnostic test or sign.
Conclusions: The belly-off sign represents a promising new clinical diagnostic sign for subscapularis lesions. In particular, subtle lesions of the upper subscapularis tendon and postoperative subscapularis insufficiencies can be detected by the belly-off sign in cases of intact external rotators. In cases of an advanced lack of external rotators, the belly-off sign becomes negative and loses its diagnostic value. We therefore conclude that the belly-off sign is attributable to an unbalanced transverse force couple with overwhelming of the external rotators of the shoulder.
Level of evidence: Level IV, case series with no, or historical, control group.