Pectoralis major muscle transfer for irreparable rupture of the Subscapularis and supraspinatus tendon
Authors: H. Resch, M. Tauber
References: SECEC 2005, Rome
1. Chronic isolated rupture of the Subscapularis tendon
2. Chronic rupture of Subscapularis and supraspinatus tendon.
Confirmation of the clinical diagnosis of anterior or anterior-superior tendon defect is performed by means of an MRI. This imaging technique also informs about the size of the tear, retraction of the tendons and the degenerative status of the attached muscles.
The operation is performed with the patient in general anaesthesia and in a beach chair position. In case of an isolated rupture of the Subscapularis tendon the deltopectoral approach is used only. In case of a two tendon tear an additional classic superior rotator cuff approach is needed. The deltopectoral approach is used to expose the conjoined tendon, the tendon of the pectoralis major, and the anterior surface of the humeral head. In case of a two tendon tear the long head of the biceps is tenotomized and the distal portion is sutured to the intertubercular groove.
The tendon of the pectoralis major muscle is exposed all over its full length at the humerus. Depending on the size of the defect the superior half (isolated rupture of the Subscapularis) or two thirds (rupture of Subscapularis and supraspinatus) of the tendon is detached from the humerus. This is routinely performed by detaching the tendon together with a bone chip by means of a chisel. The muscle fibres corresponding to the detached section of the tendon are split mainly by blunt dissection over a length of approximately 10 cm working from the insertion medially. In case only the superior half of the tendon is taken some of the muscle fibres of the inferior sternal and abdominal portion that radiate from dorsal into the proximal part of the tendon have to be transsected in order to take only the clavicular and proximal sternal portion for the transfer. In case the proximal two thirds are taken only some of the fibres from the abdominal portion have to be transsected, whereas most of them remain attached to the tendon i.e. most of the abdominal and inferior sternal portion is used for the transfer.
The space between the pectoralis minor muscle and the conjoined tendon is entered, and the area behind the conjoined tendon is exposed with use of the index fingers of both hands. Then the musculocutaneous nerve is located in the depth and also its entrance into the muscle is identified visually by raising the medial edge of the conjoined tendon with two pointed hooks. The average distance between the tip of the coracoid process and the entrance if the nerve is 5.3 cm (2 to 11 cm). It can happen that the interval is too small. In case of a two tendon tear the transferred muscle is not only bigger but also abdominal part is still attached to the tendon causing tension on the nerve by its direction. Therefore, in this group of patients the interval has to be checked very carefully and has to be enlarged in case of doubts.
In case the interval between the nerve and the conjoined tendon seem too small the entrance of the nerve can easily be shifted downward a few cm by splitting bluntly the muscle fibres with the scissors as the nerve just runs downward within the muscle.
The stay sutures attached to the tendon of the pectoralis muscle are grasped with curved forceps, the muscle is advanced behind the conjoined tendon but in front of the musculocutaneous nerve, and the tendon is attached to the lesser tuberosity in case of isolated rupture of the Subscapularis or to the greater and lesser tuberosity in case of a two tendon tear. A residual defect on the posterior side is left open. Attachment is performed by the use of transosseous nonabsorbable number-1 sutures.
There was only one complication. This was a transient weakness of the biceps brachii muscle in one of our early cases with a two tendon tear. After four days the muscle had regained its full strength. Caused by this experience in almost all following cases with an anterior superior two tendon tear the interval was checked very carefully and was enlarged in almost all cases to be on the save side.
The shoulder is immobilised in a sling for four weeks (stable fixation due to the bone chip), and passive range of motion exercises for abduction, flexion, and internal rotation are begun on the first postoperative day. After four weeks, active range of motion exercises are begun in all planes including external rotation. After twelve weeks, full loading is permitted.