DEFINITION

The subscapularis is one of four muscles making up the rotator cuff. Tears can result from chronic attenuation secondary to age or overuse, but more commonly, they result from trauma.

Subscapularis tears commonly occur after a fall on the outstretched arm, traction injuries resulting in a strong external rotation force applied to the arm, or an anterior shoulder dislocation. A subscapularis tear is the most common complication after a shoulder dislocation in patients older than 40 years of age.

Many tears affect only the upper tendinous portion of the insertion. Other injuries result in a complete tear of the tendinous and muscular portions of the insertion.

Subscapularis tears are often missed early in the course of treatment. Tears older than about 6 months are usually not reparable because of atrophy and degeneration of the muscle, necessitating a pectoralis major muscle transfer.

 

 

ANATOMY

 

The subscapularis muscle (FIG 1A) arises from the deep, volar surface of the scapular body (the subscapular fossa) and inserts on the lesser tuberosity. The upper two-thirds of the insertion are tendinous and the lower third is a muscular insertion.

 

 

The anterior humeral circumflex artery courses laterally along the demarcation between the tendinous and muscular portions of the muscle.

 

Tears of the subscapularis differ from tears of the other rotator cuff muscles in that there is often an intact soft tissue sleeve across the front of the shoulder with the torn tendon retracted medially within this “sheath.” This is in contrast to tears of the supraspinatus and infraspinatus that typically leave exposed humeral head. The remaining soft tissue over the anterior humeral head after a subscapularis tear can be mistaken for an intact or partially torn tendon.

 

 

 

FIG 1 • A. Anterior view of the subscapularis muscle. B. Clavicular and sternal heads of the pectoralis muscle.

 

 

The pectoralis major muscle is composed of two major heads: sternal and clavicular (FIG 1B).

 

 

The clavicular head originates from the medial third of the clavicle. The sternal head originates from the manubrium, the upper two-thirds of the sternum, and ribs 2 to 4. The muscle courses laterally to insert on the lateral lip of the biceps groove.

 

The sternal head lies deep to the clavicular head, forming the posterior lamina, and inserts slightly superior to the clavicular head. The clavicular head forms the anterior lamina. The laminae are usually continuous inferiorly.

 

Some of the deep muscular fibers from the inferior aspect of the pectoralis major muscle course toward and insert on the more proximal or superior aspect of the muscle insertion. These inferior to superior directed fibers tend to make the muscle “flip” when it is released. The superior corner should be tagged to assist with orientation when used for the transfer.

 

The mean width of the pectoralis major insertion is 5.7 cm (range, 4.8 to 6.5 cm).7 The undersurface of the insertion has a broad tendinous insertion, whereas the anterior surface is primarily muscular; only the most distal insertion is tendinous.

 

The pectoralis major muscle is innervated by the medial and lateral pectoral nerves, which arise from the medial and lateral cords of the brachial plexus, respectively.

 

 

The medial pectoral nerve enters the pectoralis major muscle about 11.9 cm (range, 9.0 to 14.5 cm) from the humeral insertion and 2.0 cm from the inferior edge of the muscle.7

 

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The lateral pectoral nerve enters the pectoralis major muscle at a mean of 12.5 cm (range, 10.0 to 14.9 cm) from the insertion.7

 

The musculocutaneous nerve arises from the lateral cord of the brachial plexus and enters the conjoint tendon an average of 6.1 cm (range, 3.5 to 10 cm) from the coracoid (95% confidence interval, 3.1 to 9.1 cm).7

 

In some patients, a proximal branch enters the conjoint tendon proximal to the main branch of the musculocutaneous nerve. The function of this proximal branch is not known. It is likely innervated to the coracobrachialis, and its release has little clinical effect.

 

PATHOGENESIS

 

Subscapularis tears result from the following:

 

 

Anterior shoulder dislocations

 

 

Traction injuries to the arm with extension and external rotation forces to the arm Rarely, chronic attenuation from age and overuse

 

Possible relationship to coracoid impingement

 

The subscapularis muscle is particularly prone to atrophy and degeneration after a tear. With complete, retracted tears of the muscle, there is a window of opportunity for about 6 months when a primary repair can be performed. Beyond that time point, the muscle is increasingly difficult to mobilize and repair is under substantial tension, leading to early failure.

NATURAL HISTORY

 

 

Subscapularis tears can result in pain, loss of motion, and loss of strength in the affected shoulder. Failure to recognize the injury can result in a delay in treatment and possibly an irreparable tear.

 

An untreated rotator cuff tear can lead to progressive loss of function, stiffness, and possibly arthritis. Loss of the subscapularis may result in dynamic proximal migration of the humeral head with arm elevation that can eventually become static elevation and lead to rotator cuff tear arthropathy.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Lift-off test: The patient will not be able to lift the hand off the back if the subscapularis is deficient.

 

Abdominal compression test: With a tear, the patient will not be able to maintain the elbow anterior to the plane of the body and will flex the wrist or hand will release from the abdomen.

 

Bear hug test: The patient places the hand on top of the opposite shoulder. The examiner lifts the hand off the shoulder against patient's resistance. Weakness suggests a subscapularis tear.

 

Range-of-motion testing: A subscapularis tear will result in increased external rotation with the arm at the side and a “softer” end point.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

A standard shoulder series of radiographs comprising a shoulder anteroposterior (AP) view, a true scapular AP view, an axillary view, and a scapular Y view is obtained to rule out fractures, arthritis, or other injury.

 

 

A subscapularis tear may result in proximal migration of the humeral head relative to the glenoid, depending on the degree of tear and involvement of other rotator cuff muscles.

 

In the absence of a subscapularis tear, slight anterior subluxation of the humeral head may be noted on the axillary view.

 

A magnetic resonance imaging (MRI) will reveal the tear and is also helpful in assessing the degree of retraction, atrophy, and fatty degeneration of the subscapularis muscle. The proximal portion of the long head of the biceps tendon becomes unstable from the intertubercular groove when the subscapularis tears. An MRI may demonstrate a dislocated or subluxed biceps tendon.

 

A computed tomography (CT) arthrogram is an alternative to an MRI.

 

Subscapularis tears can be diagnosed with ultrasound if performed by a competent, experienced ultrasonographer. Ultrasound is very sensitive for biceps tendon subluxation or dislocation from the groove.1

 

DIFFERENTIAL DIAGNOSIS

Supraspinatus tears Infraspinatus tears Biceps tendon pathology Anterior instability

Rotator cuff insufficiency secondary to neurologic etiology

 

 

NONOPERATIVE MANAGEMENT

 

Physical therapy focusing on strengthening the intact rotator cuff muscles can be beneficial to maximize the function of remaining musculature.

 

 

Range-of-motion exercises focus on any areas of loss of motion or capsular contracture.

 

Rotator cuff strengthening with the use of light-resistance Therabands at waist level is an effective initial exercise. Progression to higher resistance exercises is as tolerated.

 

Cortisone injections may give some temporary pain relief but are unlikely to result in permanent resolution of symptoms.

 

Nonsteroidal anti-inflammatory medication may be helpful for pain relief of mild to moderate pain.

 

SURGICAL MANAGEMENT

 

An attempt is made at the time of surgery to repair the native subscapularis. Within reasonable limits, the subscapularis is mobilized by releasing the surrounding soft tissues. Even a partial repair is recommended in conjunction with a pectoralis major transfer.

 

 

Surrounding soft tissues include the rotator interval and coracohumeral ligament, the anterior capsule of the shoulder (middle and inferior glenohumeral ligaments), and superficial soft tissue adhesions deep to the coracoid and conjoint tendon.

 

The subscapularis differs from the other rotator cuff muscles in that it has a fascial sleeve that remains attached to the lesser tuberosity and covers the anterior humeral head. This is in contrast to the other rotator cuff muscles, which leave exposed greater tuberosity and cartilage without soft tissue coverage. This material is easily mistaken for an intact subscapularis, emphasizing the significance of preoperative evaluation and a high index of suspicion.

 

Preoperative Planning

 

Patient history, physical examination, and all imaging studies are reviewed. A soft tissue imaging study such as MRI or ultrasound of the rotator cuff is a necessity.

 

 

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Plain films should be assessed for proximal migration, anterior subluxation, and deformity secondary to trauma and arthritis. An MRI is useful for assessing the condition of the subscapularis. A high degree of retraction and degeneration of the muscle is highly suggestive of a chronic, irreparable tear that will necessitate a pectoralis major muscle transfer.

 

Subscapularis tears result in instability of the long head of the biceps tendon with medial subluxation into the joint. The surgeon should be prepared to perform a biceps tenotomy or tenodesis of the tendon if it has not already ruptured from chronic, attritional changes.

 

Associated tears of the other rotator cuff muscles are addressed concurrently. Isolated arthritic lesions are débrided, as is degenerative labral fraying or tear.

 

Positioning

 

The pectoralis major transfer is most easily performed with the patient in the beach-chair position. The head of the bed or positioning device is elevated about 60 degrees. The head is secured to avoid cervical injury. The arm is prepared and draped free and held in a commercially available arm holder that allows flexible arm

positioning.6

Approach

 

Several different variations of the pectoralis major transfer have been described.

 

 

 

Wirth and Rockwood9 described a split pectoralis major muscle transfer superficial to the coracoid. Resch and colleagues8 described a split pectoralis major transfer deep to the coracoid.

 

Jost and colleagues5 and Gerber and associates4 recommended transfer of the whole pectoralis major muscle superficial to the coracoid.

 

Gerber and associates4 described transfer of the sternal head of the pectoralis major with or without the teres major tendon.

 

The procedure can be performed through a deltopectoral or anterior axillary incision.

 

 

The deltopectoral incision allows a more extensile approach and is recommended in revision cases.

 

The anterior axillary incision from the coracoid to the anterior axillary crease is useful in primary cases in smaller patients.

 

Both incisions use the deltopectoral interval for deep exposure.

 

TECHNIQUES

• Split Pectoralis Major Muscle Transfer

The deltopectoral interval is identified. The cephalic vein is usually retracted laterally with the deltoid. The subdeltoid and subacromial spaces are released of adhesions.

Regardless of technique, the native subscapularis is examined and mobilized to its full extent. If repair is not possible, a muscle transfer is performed.

The superior 2.5 to 3 cm of the pectoralis major insertion is identified along the lateral edge of the biceps groove. This contains portions of both the anterior and posterior laminae. The identified portion of the pectoralis major insertion is released sharply from its insertion. Care is taken to avoid injury to the long head of the biceps tendon, which lies directly under the insertion in this case. The distal tendon is tagged with three or four stay sutures.

 

 

 

 

TECH FIG 1 • A. The medial pectoral nerve (arrow) arises from the medial cord of the brachial plexus and enters the pectoralis major muscle 6 to 8 cm medial to the muscle insertion. Thus, medial dissection and mobilization is limited to 6 to 8 cm to avoid denervating the muscle. B. The superior half of the pectoralis major insertion is freed from the humerus and mobilized. This half is transferred to the humeral head and secured in a small bone trough with drill holes for the sutures.

 

 

Tension is applied to the stay sutures to facilitate the muscle split of the pectoralis major muscle. Muscle dissection is performed bluntly in a medial direction at the inferior portion of the split to mobilize the superior muscle for transfer. Dissection should be limited to 6 to 8 cm to preserve the medial pectoral nerve (TECH FIG 1A).

 

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The humerus is rotated internally to expose the greater tuberosity and humeral shaft lateral to the biceps groove. An osteotome or burr is used to make a bone trough measuring 5 × 25 mm oriented in a vertical position for reinsertion of the transferred pectoralis muscle.

 

Three or four holes are drilled just lateral to the edge of the trough and a curved awl is used to connect the drill holes to the trough (TECH FIG 1B).

 

The sutures in the tendon are passed into the trough and out through the drill holes. Tension is placed on the sutures, bringing the tendon into the trough. The sutures are then tied over the bone bridges between the holes, securing the tendon.

 

A biceps tenotomy or tenodesis is performed as needed.

• Subcoracoid Muscle Transfer of the Sternal or Clavicular Head

   

  A deltopectoral incision and approach are used (TECH FIG 2A).

   

  The tendon of the pectoralis major insertion is exposed along its full length (TECH FIG 2B).

   

  The superior half to two-thirds of the clavicular head is detached from the humerus. The muscle fibers corresponding to the detached section of the tendon are split or separated from the remaining muscle using blunt dissection in a medial direction. The blunt dissection is performed between the sternal and clavicular heads so that only the clavicular head muscle is released and preserved for the transfer (TECH FIG 2C). The muscle fibers of the sternal portion that course into the proximal portion of the muscle are transected.

   

   

   

  TECH FIG 2 • A. This cadaveric dissection illustrates the deltopectoral approach (black arrow, pectoralis major; white arrow, deltoid). The incision should be long enough to allow adequate exposure of the pectoralis major and the proximal humerus for reattachment. B. Cadaveric dissection illustrating the pectoralis major and its insertion (arrow). C. The pectoralis major has two heads: the superficial clavicular head (white arrow) and the deeper sternal head (black arrow). In this photo, the insertion has been released and is reflected medially. (continued)

   

   

  In muscular individuals, the sternal head alone can be used for the transfer. The most proximal insertion of the pectoralis major is made of the sternal head. The deeper surface is tendinous. The heads can be separated by blunt medial dissection and the clavicular portion left intact. Preservation of the clavicular

  head is advantageous in patients concerned with cosmesis.

   

  The space between the medial border of the conjoint tendon and the pectoralis minor is gently dissected bluntly. The musculocutaneous nerve and its entry into the conjoint tendon are identified. The space deep to the conjoint tendon and

   

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  superficial to the musculocutaneous nerve is developed for the muscle transfer (TECH FIG 2D).

   

   

   

   

  TECH FIG 2 • (continued) D. To avoid injury to the musculocutaneous nerve, it should be identified as part of the surgical procedure for a subcoracoid transfer. The muscle should be transferred deep to the conjoint tendon (black arrow) and superficial to the nerve (white arrow). E. The pectoralis major muscle (white arrow) is transferred deep to the conjoint tendon (black arrow), laterally to the greater tuberosity.

  F. Intraoperative photo of a right shoulder with a pectoralis major transfer secured to the greater tuberosity. White arrow, biceps; black arrow, conjoint tendon.

   

   

  Stay sutures are attached to the distal pectoralis major tendon. The sutures are grasped with a curved forceps and passed deep to the conjoint tendon and superficial to the musculocutaneous nerve, advancing the muscle to the greater tuberosity (TECH FIG 2E).

   

  The tendon is attached to the lesser tuberosity with transosseous nonabsorbable sutures. In very large individuals with substantial muscle mass, the muscle may need to be debulked to facilitate tension-free passage deep to the coracoid (TECH FIG 2F).

   

  The transferred muscle is reattached using anchors or transosseous sutures.

• Whole Pectoralis Muscle Transfer

   

  The deltopectoral approach is identical to that described earlier.

   

  An attempt is made to mobilize and repair the subscapularis. Releases are performed at the rotator interval, the base of the coracoid, the brachial plexus, and the subscapularis fossa. A partial repair is performed if possible.

   

  The entire tendon of the pectoralis major tendon is exposed and released from its insertion of the humerus.

   

  Three nonabsorbable sutures are passed through the tendon using a modified Mason-Allen technique.

   

  The muscle and tendon is mobilized and brought over (superficial) the coracoid to the medial aspect of the greater tuberosity where it is secured using anchor fixation or to a bone trough (TECH FIG 3).

   

  If a bone trough is used, the sutures are routed through the trough and the knots are tied over a small titanium plate to prevent suture pullout. The uppermost corner of the tendon is sutured to the anterolateral supraspinatus. Care is taken not to overtighten the rotator interval.

   

   

   

  TECH FIG 3 • The whole pectoralis major muscle is released from its insertion on the humerus and transferred and secured to the humeral head using anchor fixation or a bone trough with tunnels.

   

   

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• Split Pectoralis Major and Teres Major Tendon Transfer

   

  Setup and exposure are as described earlier.

   

  The plane between the sternal and clavicular heads is located and developed. The sternal head is sharply released from the humerus. Nonabsorbable sutures (no. 2) are placed in the tendon in Mason-Allen fashion.

   

  The sternal head is mobilized and pulled underneath the clavicular head to the lesser tuberosity where it is secured (TECH FIG 4A). The transfer is superficial to the coracoid process and should be tight but

  allow 30 degrees of external rotation.

   

  If the subscapularis tear is completely irreparable, the authors recommend combining this transfer with the teres major muscle.

   

   

   

  TECH FIG 4 • A. This transfer uses the sternal head of the pectoralis major muscle. It is released and mobilized underneath the clavicular head to the lesser tuberosity. B. The teres major muscle is released from its insertion on the humerus and transferred along with the sternal head of the pectoralis major to the lesser tuberosity. The teres major inserts deep to the latissimus dorsi, which is reattached in its anatomic position.

   

   

  To expose the teres major, the arm is externally rotated.

   

  The latissimus dorsi insertion is located and the superior and inferior aspects are demarcated. The latissimus is released, leaving a cuff of tissue laterally for repair.

   

  The teres major insertion is deep to the latissimus. The teres major is tagged and released. Often, the muscle must be released from confluence with the latissimus.

   

  The axillary nerve and posterior humeral circumflex artery lie at the superior border of the teres major muscle. The radial nerve and brachial artery are in close approximation to the inferior border of the teres major.

   

  Finally, the teres major is transferred to the inferior portion of the lesser tuberosity where it is secured with nonabsorbable sutures (TECH FIG 4B).

   

  PEARLS AND PITFALLS   P.3687
  		Indications

  • Subscapularis tears are often missed, resulting in a delayed diagnosis.

   

  • Elderly patients with generalized atrophy should be considered for a whole muscle transfer, whereas more muscular individuals are better candidates for split or sternal head transfers.

 

Pectoralis major muscle detachment and mobilization

• Mobilization of the muscle should not proceed greater than 8 cm from the insertion in order to protect the pectoral nerves.

• In whole muscle transfers, the medial pectoral nerve can enter the muscle within 1.2 cm of the inferior edge.

• Muscle split is performed bluntly.

   

  Subcoracoid transfer of the pectoralis major muscle

• The musculocutaneous nerve and its proximal branches are at risk.

• The musculocutaneous nerve is identified.

• Transferred muscle should course deep to the conjoint tendon and superficial to the nerve to avoid excessive traction and neurapraxia.

• Scar in revision cases can make this dissection difficult; an intraoperative nerve stimulator may help identify structures of the brachial plexus if necessary.

 

Fixation problems ▪ Mason-Allen or Krackow sutures are used to grasp the tendon securely.

 

Orientation ▪ Before release of the muscle, the superior corner is tagged to keep muscle in its anatomic orientation (some inferior muscle fibers course to the superior insertion, so the muscle tends to flip after release).

 

POSTOPERATIVE CARE

 

A drain should always be used because release and transfer of the pectoralis major muscle6 results in dead space, and hematoma formation is common.

 

The operative arm is placed in a sling postoperatively. Passive exercises are started on postoperative day 1.

 

The surgeon should evaluate tension on the transfer intraoperatively before closure to determine the limits of external rotation during early rehabilitation.

 

 

Forward elevation is performed in internal rotation or neutral rotation to minimize tension on the transfer. Active internal rotation and extension are avoided for 6 weeks.

 

Active-assisted and active range-of-motion exercises are started 6 weeks after surgery. Resistance exercises commence as tolerated thereafter. No internal rotation resistance exercises are recommended until 12 weeks postoperatively.

 

OUTCOMES

Jost and associates5 reported a series of 30 transfers in 28 patients. Twelve had isolated subscapularis tears and 18 had concomitant supraspinatus-infraspinatus tears. The mean relative Constant score improved from 47% to 70% at an average of 32 months of follow-up. Thirteen patients were very

 

 

satisfied, 10 patients were satisfied, 2 patients were disappointed, and 3 patients were dissatisfied.

Resch and colleagues8 reported on a series of 12 patients with a subcoracoid transfer. The Constant score increased from 26.9% to 67.1%. Nine assessed their final result as good or excellent, three as fair, and none as poor. Four unstable shoulders were stable at the average of 28 months of follow-up.

Wirth and Rockwood9 reported a series of 13 patients. Seven had a pectoralis major transfer and six had a pectoralis minor transfer. Ten of the 13 were satisfied, but the results were not separated between the patients with the pectoralis major and minor transfers.

Galatz and associates2 reported on the subcoracoid pectoralis major transfer in 14 patients as a salvage procedure for iatrogenic anterior superior instability. Nine of the 14 had satisfactory results in terms of pain relief, but the functional results are not as predictable for this particular indication.

Gerber and colleagues4 reported a combination of sternal head and sternal head plus teres major transfers. In the sternal head patients, 9 of 11 had pain relief. Two had a rupture that required revision. In the sternal head plus teres major group, seven of nine patients had pain relief. One had a rupture discovered at the time of revision surgery (fusion). Final American Shoulder and Elbow Surgeons (ASES) scores were 61 in the sternal group and 55 in the sternal plus teres group.

Gavriilidis and colleagues3 reported on 15 patients who had a subcoracoid pectoralis major transfer for anterior superior tears (subscapularis and supraspinatus/infraspinatus). The Constant score increased from 51.7 to 68.1, with improvements in pain and activities of daily living. Range-of-motion increase was not statistically significant; however, preoperative elevation was 145 degrees.

In all series, most of the patients had had surgery before the transfer, and in most cases, a pectoralis major transfer was performed for revision purposes. This has dramatic implications on outcome.

 

COMPLICATIONS

Musculocutaneous nerve injury Pectoral nerve injury

Fixation failure

Mechanical impingement with the coracoid, either deep or superficial to the conjoint tendon

 

 

REFERENCES

1. Armstrong A, Teefey SA, Wu T, et al. The efficacy of ultrasound in the diagnosis of long head of the biceps tendon pathology. J Shoulder Elbow Surg 2006;15:7-11.

    

    

2. Galatz LM, Connor PM, Calfee RP, et al. Pectoralis major transfer for anterior-superior subluxation in massive rotator cuff insufficiency. J Shoulder Elbow Surg 2003;12:1-5.

    

    

3. Gavriilidis I, Kircher J, Magosch P, et al. Pectoralis major transfer for the treatment of irreparable anterosuperior rotator cuff tears. Int Orthop 2010;34(5):689-694.

    

    

4. Gerber A, Clavert P, Millett PJ, et al. Split pectoralis major and teres major tendon transfers for reconstruction of irreparable tears of the subscapularis. Tech Shoulder Elbow Surg 2004;5:5-12.

    

    

5. Jost B, Puskas GJ, Lustenberger A, et al. Outcome of pectoralis major transfer for the treatment of irreparable subscapularis tears. J Bone Joint Surg Am 2003;85A:1944-1951.

    

    

6. Klepps S, Galatz LM, Yamaguchi K. Subcoracoid pectoralis major transfer: a salvage procedure for irreparable subscapularis deficiency. Tech Shoulder Elbow Surg 2001;2:92-99.

    

    

7. Klepps SJ, Goldfarb C, Flatow E, et al. Anatomic evaluation of the subcoracoid pectoralis major transfer in human cadavers. J Shoulder Elbow Surg 2001;10:453-459.

    

    

8. Resch H, Povacz P, Ritter E, et al. Transfer of the pectoralis major muscle for the treatment of irreparable rupture of the subscapularis tendon. J Bone Joint Surg Am 2000;82:372-382.

    

    

9. Wirth MA, Rockwood CA Jr. Operative treatment of irreparable rupture of the subscapularis. J Bone Joint Surg Am 1997;79A:722-731.