The subscapularis is one of four tendons that comprise the Rotator Cuff and functions as an internal rotator of the humerus. Although most often found in combination with tears of the supraspinatous and possibly the infraspinatous tendon, it may also be torn in isolation. Initially, prior to the advent of arthroscopy and MRI, it was believed the incidence of pathology of the subscap was 4%; however, more recent studies put it at nearly 30%. Multiple tests have been described to detect tears or dysfunction of this muscle-tendon unit, most notably the Lift-Off Test, the Belly-Press Test, and the Bear-Hug Test.
The Lift-Off Test described by Gerber in 1991 demonstrates weakness of the subscapularis at the limit of the amplitude of contraction of the muscle when the arm is fully extended and internally rotated. This is performed by having the patient place the dorsum of the hand on lower lumbar region and then asking the patient to lift the arm off of the lumbar area. A positive test is when a patient is unable to lift the hand off the lumbar region. Care needs to be used in making sure the patient is not simply extending the elbow during this test. Another obstacle of this exam is that many patients with cuff pathology have intense pain when attempting this maneuver.
A variation of the exam is the Internal Rotation Lag Sign (IRLS) as described by Hertel. Here the patient’s arm is positioned in maximal internal rotation with the dorsum of the hand on the lumbar region. The arm is lifted off the lumbar area and asked by the examiner to hold his arm in this position. A positive sign is when the patient cannot tolerate this position and the arm lags from the starting position or falls back down to the lumbar area. This exam may also be compromised by pain in this position as the proximal humerus rolls under the coraco-acromial arch.
In an attempt to evaluate the subscapularis tendon without causing pain, the Belly Press Test was described by Gerber. Here the patient is asked to press the palm of the hand against the abdomen while trying to keep the arm in maximal internal rotation. If active internal rotation is strong, the elbow will be maintained in front of the trunk in the sagittal plane. If the subscapularis strength is poor, the maximal internal rotated position cannot be maintained and the elbow drops behind the trunk and is interpreted as a positive test. In a positive belly-press test the patient will try and apply pressure on the abdomen by extending the shoulder with the elbow by the side-the so-called Napoleon Sign.
The Bear-Hug Test is performed by placing the palm, with the fingers extended, on top of the contralateral shoulder. The elbow is elevated and anterior to the body. The patient is asked to hold that position while the examiner tries to externally rotate the arm with a force applied perpendicular to the forearm. A test is considered positive if the patient cannot resist external rotation.
References
Gerber C, Krushell RJ. Isolated tears of the subscapularis muscle. Clinical features in sixteen cases. J Bone Joint Surg Br 1991;73:389-394.
Hertel R, Ballmer FT, Lambert SM Gerber C. Lag sign in the diagnosis of rotator cuff rupture. J Shoulder Elbow Surg 1996;5:307-313.
Gerber C, Hersche O, Farron A. Isolated rupture of the subscapularis tendon. Results of operative repair. J Bone Joint Surg Am 1996;78:1015-1023.
Scheibel M, Magosch P, Pritsch M, Lichtenberg S, Habermeyer P. The Belly-Off Sign: A new clinical diagnostic Sign for Subscapularis Lesions 2005;21:1229-1235.
