Dr. Ebraheim’s educational animated video describes the condition and treatment of subscapularis tendon rupture, the signs and symptoms, etiology, anatomy, diagnosis, and the treatment.
The subscapularis muscle is a large muscle that originates on the anterior surface of the scapula and lies in front of the shoulder. The subscapularis muscle is the largest of four rotator cuff muscles and it provides about 50% of the total cuff strength. The subscapularis muscle inserts into the lesser tuberosity, while the other rotator cuff muscles have an insertion into the greater tuberosity. The biceps tendon lies in the groove and is held in place by the transverse humeral ligament.
Ultrasound examination
Usually the probe is placed transversely over the bicipital groove to identify the groove and the biceps tendon while the arm is in a neutral position. The arm is then externally rotated to view the subscapularis tendon.
Function of the subscapularis muscle is internal rotation and acts as a dynamic stabilizer of the humeral head.
The subscapularis muscles is supplied by the upper and lower subscapular nerve. The upper and lower subscapular nerves originate from the posterior cord of the brachial plexus.
Causes
•Anterior shoulder dislocation.
•A fall on an outstretched arm during abduction is usually the mechanism of injury.
•May occur following anterior shoulder surgery
•In traumatic situations a subscapularis tendon avulsion can be associated with avulsion of the lesser tuberosity.
•A subscapularis tear may be associated with a rotator cuff tear.
Tears are rare and can be either chronic or acute. Patient will have pain, anterior shoulder swelling, decreased range of motion and weakness of internal rotation. Patient will also have an increase in passive external rotation.
Diagnosis of a subscapularis tear could be difficult and may be missed. With complete rupture of the subscapularis tendon, the transverse humeral ligament will become torn, causing medial dislocation of the biceps tendon from its groove.
Clinical diagnostic tests for subscapularis tendon rupture.
Liftoff test
The patient places the hand behind their back at the lumbar level and lifts the hand away from the back with an intact subscapularis tendon. If the patient is unable to lift the handoff of the lower back, then a tear of the subscapularis tendonis suspected.
Liftoff lag test.
The examiner will hold the patient’s hand away from the back at the lumbar region and let go. Patient will be unable to keep the hand away from the back if the tendon is torn.
Belly press test
The patient presses the palm of the hand against the abdomen with the wrist in a neutral position. This is an example of an intact subscapularis tendon. A positive sign for the bellypress test occurs if the patient is unable to press his belly without wrist volar flexion or the elbow falling posteriorly.
Bellyoff test
The shoulder is placed in flexion and maximum internal rotation. The examiner positions the patients hand on the belly while holding the flexed elbow. If the tendon is ruptured the patient will not be able to maintain this position and the hand will lift off of the abdomen when the examiner let go.
Tear can be diagnosed by MRI or ultrasound.
Treatment
Complete tear
Surgical repair. Repair may be either open or arthroscopic. Biceps tenodesis during repair is associated with improved outcomes. Biceps tenodesis is usually done if the biceps is involved in the process, otherwise subluxation of the biceps will stress and fail the repair.
For Chronic muscle tear, Pectoral major muscle transfer is the procedure of choice.