Steven Milos and Allen Deutsch
DEFINITION
Subscapularis tears are less common than supraspinatus or infraspinatus tears. They occur in 2% to 8% of rotator cuff tears and are often missed.5,12
Subscapularis tears can be.
Isolated tears (partial or complete)
Partial-thickness tears
Anterosuperior (involving the supraspinatus)
Rotator interval lesions (with associated biceps tendon injury)
There is a high association of concomitant biceps tendon pathology.12,18
ANATOMY
The subscapularis is innervated by the upper and lower subscapular nerves (C5–C8). Its origin is at the subscapularis fossa, and the upper two thirds inserts onto the lesser tuberosity, while the inferior third inserts onto the humeral metaphysis.
The subscapularis is the strongest of the rotator cuff muscles. It acts to internally rotate the humerus along with the teres major, latissimus dorsi, and pectoralis major muscles. It resists anterior and inferior translation of the humeral head.10,17
The upper fibers of the subscapularis and the anterior fibers of the supraspinatus contribute to the rotator interval as well as the transverse humeral ligament.
The coracohumeral ligament is the roof of the rotator interval and blends with the supraspinatus and subscapularis. The coracohumeral ligament and the superior glenohumeral ligament are the primary stabilizers of the biceps.2
The biceps muscle is innervated by the musculocutaneous nerve (C5–C6). It is composed of a long head, which originates from the supraglenoid tubercle, and a short head, which originates from the coracoid process. Both heads insert onto the bicipital tuberosity of the radius and the ulnar fascia of the forearm.
The long head of the biceps tendon provides superior shoulder stability when the arm is abducted. It also provides posterior shoulder stability when the arm is in midranges of elevation.14,21
The coracoid is located just anterior to the superior border of the subscapularis. It projects laterally, anteriorly, and inferiorly toward the glenoid.
The subcoracoid bursa does not communicate with the glenohumeral joint but can communicate with the subacromial bursa.
PATHOGENESIS
In the young patient, subscapularis tears occur as a result of trauma. The typical mechanisms include hyperextension of an externally rotated arm or forced external rotation of an adducted arm.5,8
In older patients a tear is typically degenerative in nature, although it may be the result of a glenohumeral dislocation or other trauma.13,15,16
Frequently, there is associated long head of the biceps pathology. This may include tenosynovitis, subluxation, dislocation, degeneration, or complete rupture.12,19
Subcoracoid impingement may also be a cause of subscapularis tendon tears.
NATURAL HISTORY
Isolated subscapularis tendon ruptures are relatively rare. Subscapularis tears are often associated with tears of the supraspinatus and infraspinatus.
One study found that subscapularis tears occur in 8% of rotator cuff tears.7
An MRI study was performed on 2167 patients with rotator cuff tears.12
2% of the patients had subscapularis tendon tears.
27% of those tears were partial-thickness tears and 73% were full-thickness tears.
One study found a high correlation between subscapularis tendon tears and medial biceps subluxation, biceps tendinopathy, superior labral pathology, and fluid within the subscapular recess or the subcoracoid space.12,18
The above-listed MRI study found that 25 of the 45 patients with subscapularis tendon tears had associated biceps pathology.
PHYSICAL FINDINGS
Patients with complete tears of the subscapularis have increased passive external rotation compared with the unaffected shoulder.
Several muscles contribute to internal rotation of the shoulder, including the pectoralis major, latissimus dorsi, and teres major, and can compensate for loss of the subscapularis.
Passive external rotation: Increased passive external rotation may indicate a complete rupture of the subscapularis.
Passive forward flexion, external rotation, and internal rotation: Limited passive range of motion is indicative of adhesive capsulitis.
Active forward flexion: Limited active forward flexion is indicative of a possible large rotator cuff tear.
The lift-off test isolates the subscapularis muscle. Inability to lift the hand off the back is a positive test.
Internal rotation lag sign11 : The examiner measures the lag between maximal internal rotation and the amount the patient can maintain. A positive sign shows increased sensitivity over the classic lift-off test.
Belly press (Napoleon test)8 : A positive test is the inability to bring the elbow forward. An intermediate test is the ability to bring the elbow forward partially. A positive test indicates a complete rupture, while an intermediate test indicates a partial tear of the subscapularis.
The bear hug test1 : If the examiner is able to lift the hand off the shoulder, then the patient likely has a partial or complete tear of the upper subscapularis tendon. This is perhaps the most sensitive test for a subscapularis tear.
Coracoid impingement6 : Reproduction of pain or a painful click indicates a positive test. A positive test indicates impingement of the coracoid onto the subscapularis.
Speed’s test4 : If the maneuver produces pain or tenderness, the test is positive, which may indicate bicipital pathology, although the test is not specific.
Yerguson test22 : The patient will experience pain as the biceps tendon subluxes out of the groove with a positive test; this indicates biceps instability.
Pain may inhibit a patient from maneuvering the arm behind the body into the lift-off position, thereby preventing assessment.
A complete rupture of the long head of the biceps tendon will result in an obvious cosmetic deformity in the anterior arm as the muscle retracts distally.
Tests used to diagnose superior labral lesions will be discussed in a separate section.
IMAGING AND DIAGNOSTIC STUDIES
Anteroposterior (AP), outlet, and axillary view radiographs should be obtained to rule out any fractures or associated injuries.
In chronic cases of subscapularis tears, anterior subluxation of the humeral head may be noted on the axillary view.18
MRI is the modality of choice for diagnosing subscapularis tears (FIG 1).
MR arthrography improves the study accuracy to detect partial-thickness tears.
Fatty degeneration of the subscapularis correlates with poor tendon quality.20
Although not sensitive, these signs are highly specific for subscapularis tears15 :
Leakage of contrast material onto the lesser tuberosity
Fatty degeneration of the subscapularis muscle
Abnormalities in the course of the long biceps tendon
Biceps dislocation deep to the subscapularis tendon is pathognomonic for a subscapularis tear.
Ultrasound is a noninvasive method for assessing the subscapularis and can be performed in the office. It is less expensive than MRI, but results are operator-dependent.
DIFFERENTIAL DIAGNOSIS
Impingement syndrome
Subscapularis tendinitis
Bicipital tendinitis
Posterosuperior rotator cuff tear (supraspinatus, infraspinatus, teres minor)
Biceps pathology
Coracoid impingement
Labral tear
Glenoid fracture
Glenohumeral instability
Glenohumeral arthritis
Pectoralis major injury
Contusion
Cervical radiculopathy
NONOPERATIVE MANAGEMENT
For subscapularis tears, nonoperative management is reserved for some chronic and atraumatic, degenerative, and asymptomatic tears.
Treatment includes activity modification, anti-inflammatory medications, and physical therapy.
Corticosteroid injections may be performed in the bicipital groove or subcoracoid bursa to treat biceps tendinitis and coracoid impingement.
It is likely that some degenerative subscapularis tendon tears are successfully treated nonsurgically without ever being diagnosed.
In most cases, an acute symptomatic subscapularis tear should be managed operatively and whenever possible within the first 6 to 8 weeks, when retraction and scarring are minimal, to reduce the risks of dissection in the axillary recess.
In young, active patients, attempts are made to repair acute biceps ruptures.
In older, less active patients and in cases of chronic biceps ruptures more than 8 weeks old, biceps repair is discouraged.
SURGICAL MANAGEMENT
Preoperative Planning
Physical therapy or a home exercise program emphasizing range of motion may be used to prevent stiffness and improve range of motion before surgery.
All imaging studies are reviewed.
An examination under anesthesia is performed before beginning surgery to evaluate for instability, increased external rotation, or decreased range of motion.
Positioning
The patient is placed in a low beach chair position with the arm draped free.
A McConnell arm holder (McConnell Orthopedic Manufacturing Co., Greenville, TX) is useful for maintaining arm positions throughout the case (FIG 2).
FIG 1 • Axial T2-weighted MR images of right shoulders with an intact subscapularis tendon (A; arrow) and a complete rupture of the subscapularis tendon.
Approach
Both the deltopectoral and anterolateral deltoid-splitting approaches have been described.20
The anterolateral deltoid-splitting approach is useful for partial tears of the upper subscapularis and tears associated with supraspinatus tears. It is not recommended for large, retracted full-thickness subscapularis tears.
The deltopectoral approach provides greater visualization and access to the inferior portion of the subscapularis. It also allows for concomitant biceps tenodesis and coracoplasty.
FIG 2 • Positioning for a subscapularis repair. The patient is placed in a beach chair position with the arm stabilized in a McConnell holder.
TECHNIQUES
INCISION AND DISSECTION
The deltopectoral approach is started just proximal to the coracoid process and extended distally 8 to 10 cm.
Adducting the arm identifies the major axillary crease.
The cephalic vein and deltoid muscle are carefully retracted laterally and the pectoralis muscle is retracted medially to facilitate exposure (TECH FIG 1A).
Once the deltopectoral interval is developed, the clavipectoral fascia is identified.
The clavipectoral fascia is divided at the lateral aspect of the conjoined tendon.
Avoid excessive retraction on the conjoined tendon to avoid injuring the musculocutaneous nerve.
The tendon of the subscapularis is often retracted inferiorly and medially and requires mobilization.
A layer of scar tissue may be seen overlying the lesser tuberosity, which can mimic the subscapularis tendon.
If the subscapularis tendon cannot be brought back to the lesser tuberosity easily, then the subscapularis requires systematic release from the glenohumeral ligaments.
Begin by releasing the superior aspect of the tendon from the coracohumeral ligament. The rotator interval is opened from the glenoid to the bicipital groove to facilitate the release.
Next release the inferior portion of the tendon from the capsular attachments. Care must be taken to identify and protect the axillary nerve and vascular supply inferiorly.
Finally, release the remaining capsular attachments on the undersurface of the subscapularis (TECH FIG 1B).
TECH FIG 1 • A. Deltopectoral interval in a right shoulder. The deltoid muscle (D) and cephalic vein are retracted laterally and the pectoralis muscle (P) is retracted medially. B. The subscapularis is released from the capsule to facilitate mobilization of the tendon. Note the proximity of the axillary nerve inferiorly.
BICEPS TENODESIS
If a biceps tenotomy is performed, it is important to warn the patient of the resultant cosmetic deformity when the biceps retracts distally.
Indications for biceps tenodesis include the following.
Tears involving more than 50% of the biceps tendon
Medial subluxation of the biceps tendon
Open the bicipital groove from the medial side to expose the biceps tendon.
The biceps tendon is released from the superior glenoid with curved scissors.
The tendon is retracted distally from the bicipital groove.
To ensure proper tensioning of the biceps tendon, the proximal portion of the tendon is resected to leave about 20 to 25 mm of tendon proximal to the musculotendinous junction.
Running locking Krakow or whipstitches are placed up and down the proximal 15 mm of the biceps tendon.
Abrade the bicipital groove to develop a bleeding surface.
A burr hole the size of the biceps tendon is made in the bicipital groove about 15 mm from the articular surface. Two smaller 3.2-mm holes are made 15 mm distal to the burr hole in a triangular configuration.
The tendon end is passed into the proximal hole by pulling the sutures out the distal holes. The sutures are then passed through and tied over the overlying biceps tendon (TECH FIG 2A,B).
Another fixation option is to use a biotenodesis screw for the biceps tendon.
The tendon is prepared as above.
An 8-mm reamer is used to make a 25-mm-deep bone tunnel about 15 mm from the articular surface.
An 8 × 23-mm Arthrex Bio-Tenodesis screw is used for fixation.
One end of the suture is passed through the biotenodesis screw while the other suture passes outside of the screw. This ensures that the tendon will be pulled into the hole as the screw is advanced.
When the screw is flush with the bone tunnel, the sutures are tied over the screw (TECH FIG 2C). This provides both an interference fit and suture anchor stability.
TECH FIG 2 • A,B. The tunnel technique uses bone tunnels to fix the biceps tendon upon itself. C. A biceps tenodesis with interference screw fixation.
CORACOPLASTY
The conjoined tendons are identified.
Care is taken not to retract vigorously on the conjoined tendons to avoid injury to the musculocutaneous nerve.
The coracoacromial ligament is released from the coracoid.
The posterior aspect of the coracoid is exposed by removing the overlying soft tissue. The posterolateral portion is then resected in line with the subscapularis muscle with an osteotome (TECH FIG 3). Alternatively, a burr may be used to accomplish the same resection. Protect the neurovascular structures by placing a retractor on the posterior aspect of the coracoid.
A rasp is then used to smooth out the bony surface.
The goal is a 7to 10-mm clearance between the coracoid and subscapularis.
Confirmation of adequate decompression can be determined by manipulating the arm into the impingement position and confirming that there is adequate clearance for the subscapularis.
TECH FIG 3 • The posterolateral portion of the coracoid is resected, leaving the conjoined tendon attached. The goal is a 7to 10-mm clearance space for the subscapularis.
SUBSCAPULARIS REPAIR
The residual soft tissue is cleaned from the lesser tuberosity. A burr is then used to expose bleeding bone for the tendon to heal to.
To recreate the anatomic footprint of the subscapularis insertion, four suture anchors are used for the repair.
Two anchors are placed at 1-cm intervals along the medial aspect of the lesser tuberosity and two are placed at the lateral aspect of the lesser tuberosity (TECH FIG 4A).
The sutures from the medial anchors are passed in a mattress fashion near the musculotendinous junction of the subscapularis (TECH FIG 4B).
The sutures from the lateral anchor are passed through the lateral edge of the tendon in a simple fashion and tied down to the lesser tuberosity.
After repair of the subscapularis tendon, the shoulder is taken through a gentle range of motion to determine the safe arcs for postoperative rehabilitation.
The lateral aspect of the rotator interval is closed while maintaining about 30 degrees of external rotation of the arm to prevent overtightening of the subscapularis repair.
TECH FIG 4 • A. Four suture anchors are placed for the repair of the completely torn subscapularis tendon. Two anchors are placed medially and two laterally. B. The sutures from the two medial anchors have been passed in a mattress fashion through the subscapularis tendon (S). C. The diagram shows the suture configuration for the subscapularis repair with mattress sutures at the musculotendinous junction and simple sutures at the lateral tendon insertion. D. Once the subscapularis tendon has been repaired, it is important to close the rotator interval. Wide straight arrows indicate the tied mattress sutures; narrow straight arrows point to the tied simple sutures; and the curved arrow indicates the rotator interval.
POSTOPERATIVE CARE
The most important postoperative management for subscapularis tears is limitation of external rotation for 6 weeks to avoid stressing the repair.
Complete tears are not allowed to externally rotate past 0 degrees.
Partial tears are allowed to externally rotate 20 to 30 degrees.
At 6 weeks the patient may begin active and active-assisted external rotation exercises, as well as overhead stretching.
At 12 weeks strengthening exercises are initiated for partial tears. At 16 weeks strengthening exercises are initiated for complete tears.
OUTCOMES
Isolated subscapularis tears have favorable surgical outcomes.
At 2 years of follow-up, good or excellent results were reported in 13 of 14 isolated subscapularis tears.4
Another study demonstrated good or excellent results in 13 of 16 patients with acute traumatic subscapularis tears at 43 months of follow-up. The Constant scores were 82% of age-matched controls.8
Poor prognostic factors include chronic tears (symptoms for more than 6 months), fatty degeneration of the subscapularis muscle, and anterosuperior tears (combination of subscapularis and supraspinatus tears).19
Comparative outcomes between open and arthroscopic techniques remain to be determined.
COMPLICATIONS
Repair failure
Infection
Loss of motion
Axillary nerve injury
Vascular injury
REFERENCES
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