Pectoralis Major Tendon Transfer for Subscapularis Insufficiency: An Operative Technique

Video Transcript

This is our technique of a pectoralis major tendon (PMT) transfer for subscapularis insufficiency.

Here are our disclosures.

This is the overview of our presentation.

A 41-year-old man with chronic anterior shoulder instability previously treated with an open Bankart repair, posterior labral repair, who also had an untreated reverse humeral avulsion of the glenohumeral capsule presented to our clinic with a chief complaint of anterior shoulder instability when lifting objects. He failed nonoperative management.

On physical examination, he had normal bulk and tone. His full active and passive range of motion was globally limited due to pain. Importantly, the patient had apprehension with anterior translation with abduction and external rotation at 90°. He had rotator cuff weakness with 3 plus out of 5 strength in the subscapularis with a positive bear hug and belly press maneuver, but his supraspinatus and infraspinatus had full 5 out of 5 strength. He also had a 2 plus sulcus sign without dissipation during external rotation. He was otherwise neurovascularly intact.

Our patient’s sagittal T1 magnetic resonance imaging (MRI) is depicted in the left image here showing severe subscapularis muscle atrophy and fatty infiltration as shown with the blue arrow. The white marbling of fat within the subscapularis muscle belly is a classic sign of a chronic muscle injury. The image on the right is a sagittal T2 fat suppressed with contrast MRI image which shows the subscapularis detached from the humerus inferiorly, labeled with an orange arrow.

Operative treatment for PMT transfer is indicated for subscap insufficiency not amenable to repair, which causes pain and limited function.^1,4,6 An operative patient is typically a younger and active individual with an intact posterosuperior rotator cuff. The deltoid and the rest of the rotator cuff need to be intact to provide posterior stability. The patient also should have minimal glenohumeral joint arthritic changes.^1,4,6 A PMT transfer is contraindicated in patients with deltoid injury or denervation, or an irreparable posterosuperior rotator cuff.

In older patients with concomitant advanced glenohumeral arthritis, a tendon transfer is not an appropriate treatment selection, but a reverse total shoulder arthroplasty could be considered in those patients. In addition, elderly, low functioning or patients with underlying medical conditions making them poor surgical candidates should not be treated operatively.^1,4,6 Alternative treatments include anterior capsule reconstruction and double-row subscap repair. ⁵ Given the chronicity of injury and degree of fatty atrophy within the subscap muscle belly, we deemed his subscap and anterior capsule was not sufficient for repair, and thus, our patient would be best served with a PMT transfer.

To set up for this surgery, the patient was positioned in the beach-chair position with a dynamic limb positioner. We used the open deltopectoral approach, a standard workhorse approach to the shoulder, to create the construct shown in this diagram. We want to isolate the pec tendon, pass it deep to the conjoined tendon of the coracobrachialis and short head of the biceps, and then anchor the pec tendon to the anatomic footprint of the subscap on the lesser tuberosity.

Before we get into the surgery, let’s take a quick pause here to review the anatomy of the proximal humerus. This video shows the PMT inserting on the lateral aspect of the bicipital groove. The teres major and latissimus dorsi come from posterior and wrap around the humerus medially to attach on the medial aspect of the bicipital grove. We’ll have to isolate the pec tendon to move it to the subscap footprint on the lesser tuberosity. ²

We started with a standard delto-pec incision. Full-thickness flaps were created, and the deltopectoral interval was divided. The cephalic vein was identified, then dissected free, and taken laterally. Our dissection continued as we identified the short head of the biceps in relation to the coracoid process, and retracted the biceps medially. The long head of the biceps was identified and tagged with suture. We then proceeded to dissect down to the subscapularis and coracoid with conjoined tendon.^2,3

The PMT was identified and dissected free. It was subsequently mobilized with suturetape, and this was tagged, passed inferior to the conjoined tendon, and transferred to the lesser tuberosity for reapproximation. We then prepared the humerus for a 5.5-mm anchor placed in the lesser tuberosity.

The biceps tendon, which was previously secured with suturetape, is secured to the same anchor with additional mattress sutures. This is the final structure showing the tendon transfer, biceps tenodesis, and reapproximated subscapularis fixated to the cortical anchor. ⁴ The transferred PMT is shown with the Army-Navy retractor on the left. We confirmed stability and then proceeded to close.

Now, let’s jump to the cadaver laboratory for a closer look. We started here with the same deltopectoral incision with the pec medial and inferior and the deltoid superior and lateral. We then dissected down to find the axillary nerve, shown at the tip of the scissors. ² We found the conjoined tendon inserted on the coracoid and cleared it of adhesions. We then identified the muscle belly of the pec major and the intermuscular septum separating the sternal and clavicular heads, and followed it to the tendinous insertion on the humerus. We elevated the confluent pec tendon superiorly and laterally to expose the clavicular portion of the tendon, as it lies most inferiorly and closest to the humerus. We then took care to free only the sternal head of the pec tendon while leaving the clavicular head attached. We then dissected the septum of the tendon to free the sternal head.

This is a picture of the pec tendon with the 2 heads separated. The sternal head is labeled “S,” and the clavicular head is labeled “C.” After isolating the sternal head of the tendon, we passed suture with a Krakow stitch. We then passed the sternal head of pec tendon deep to the clavicular head of the pec and deep to the conjoined tendon, and approximated it to the lesser tuberosity.^2,3

There are many potential complications that can occur with this procedure. One potential adverse outcome is injury to the musculocutaneous nerve, so careful dissection and identification near the conjoined tendon are essential.^1,2 In addition, cortical anchor loosening is a potential complication, but this risk can be mitigated with accurate sizing of the drill hole and adequate bone quality determined by patient selection. Infection is a risk with any open surgical procedure, so proper sterile technique should be performed. Finally, because we are performing an open procedure, arthrofibrosis can occur. For that reason, it is important to focus on range of motion, with formal physical therapy involvement.

There is variation within rehabilitation protocols depending on the patient, but for this particular patient, we utilized a 5-phase approach over the course of 12 months, broken down into a series of several weeks. ⁴ Initially, the patient is restricted to strict immobilization in a sling with a 4-inch abduction pillow, which places the shoulder in internal rotation. After 2 weeks, the patient can begin passive range of motion as tolerated, with progressive gentle pendulum exercises under the supervision of a physical therapist. After 6 weeks, the sling is discontinued, and the patient can progress to active and passive range of motion as tolerated. Progressive light isometric and stretching exercises are also started at this time and advanced as tolerated. At 12 weeks, the patient will typically have full active and passive range of motion. At this time, light internal rotation against resistance can be started. Ultimately, at 6 months, the patient is focused on advancing functional capacity, and they may return to unrestricted activity when cleared by the surgeon. ⁴

To look at PMT transfers in the literature, this is a review of 8 studies assessing outcomes of pectoralis major transfer for subscapularis insufficiency published in 2014 by Nelson and Colleagues. ³ The article categorized outcomes based on the patient’s underlying subscapular pathology. They found that patients with an isolated subscapularis insufficiency had the best outcomes after a PMT transfer. Patients had a significant increase in constant score, range of motion, and strength in internal rotation. Those who underwent PMT transfer in the setting of subscap insufficiency with a concomitant multitendon rotator cuff tear had moderate improvement with a significant increase in constant score and range of motion.

However, persistent instability and anterior subluxation reduced patient satisfaction. The final group examined were those who received a PMT transfer for subscap insufficiency after a shoulder arthroplasty. These patients saw the least benefit to the procedure, as they had no significant improvement in constant score or postoperative pain.

This second article published in 2017 by Moroder and colleagues evaluated 22 patients who underwent PMT transfer for subscapularis insufficiency at a 10-year follow-up. ² Their results showed the patient’s constant score remained significantly improved and similar to the short-term score. Their results also showed that the simple shoulder test and the visual analog scale for pain score followed a similar pattern, with long-term scores similar to short-term postoperative scores. However, they did report that long-term strength on internal rotation and range of motion significantly decreased at long-term follow-up, matching strength and range of motion scores similar to before the surgery.

Discrepancies between long-term stability and range of motion outcomes could be due to the nonphysiologic forces of the transferred pec tendon that does not restore native shoulder kinematics. Overall, most patients were satisfied at 10-year follow-up.

These are our references.

Thank you.