Pectoralis Major Rupture - Shoulder & Elbow

SUMMARY
- A rare acute injury caused by avulsion of the pectoralis major tendon and usually seen in weightlifters.
- Diagnosis is generally made clinically and is confirmed with MRI studies.
- Treatment is usually surgical repair when presenting acutely.

Epidemiology
- Incidence
  - rare injury (< 1 per 100,000 per year) that is increasing in incidence
    
    75% of all reported cases have occurred since 1990
- Demographics
  - almost exclusively seen in males (20-40 years of age)
  - often occurs in weightlifters
    
    commonly during bench-pressing
- Location
  - most commonly occurs as a tendinous avulsion
  - sternocostal head of the pectoralis major tendon is the most common site of rupture
- Risk factors
  - anabolic steroid use

Etiology
- Pathophysiology
  - mechanism
    
    excessive tension on a maximally eccentrically contracted muscle
    
    occurs during the downward portion of a bench press, with the arm in the final 30 degrees of humeral extension while pushing against heavy resistance
    
    tendon fails in a predictable sequence
    
    inferior fibers of sternocostal head fail first
    
    then superior fibers of the sternocostal head
    
    finally the clavicular head

Anatomy
- Pectoralis major
  - innervation
    
    lateral pectoral nerve (C5-C7)
    
    supplies lower muscle belly
    
    medial pectoral nerve (C8-T1)
    
    lateral pectoral nerve supplies upper portion
  - origin (two heads)
    
    clavicular head
    
    from medial clavicle and proximal sternum
    
    sternocostal head
    
    from distal sternum, costal cartilage ribs 1-6, external oblique aponeurosis
    
    sternocostal portion is larger (>80% of muscle volume)
  - insertion
    
    humeral shaft just lateral to the bicipital groove
  - action
    
    shoulder adduction and internal rotation, to a lesser extent forward flexion (chiefly the clavicular head)
  - other
    
    one of four muscles connecting the upper limb to the thoracic wall
    
    other muscles include
    
    pectoralis minor
    
    subclavius
    
    serratus anterior
- Biomechanics
  - inferior fibers of sternal head at maximal stretch during final 30 degrees of humeral extension
    
    position at which pectoralis major is most vulnerable to rupture (as with bench pressing)

Classification

Modified Tietjen (Anatomic) Classification
Type	Description
I	Muscle contusion or sprain
II	Partial tear
III	Complete tear (further subclassified by location)
Location
III-A	Muscle origin
III-B	Muscle belly
III-C	Musculotendinous junction
III-D	Intra-tendinous rupture
III-E	Tendon avulsion off humerus (no bone)
III-F	Bony tendon avulsion off humerus

Presentation
- History
  - patient may report a sudden pop or tearing sensation with resisted adduction and internal rotation
- Symptoms
  - pain and weakness of shoulder
- Physical exam
  - inspection & palpation
    
    swelling and ecchymosis of anterolateral chest wall and/or proximal medial brachium
    
    if localized to the anterior brachium, then humeral attachment rupture is more likely than a musculotendinous junction rupture
    
    "dropped nipple" sign
    
    ipsilateral nipple will appear lower than the unaffected side due to medial retraction of muscle belly
    
    palpable defect and loss of anterior axillary contour
    
    accentuated by resisted adduction
  - motion & strength
    
    weakness most pronounced in adduction and internal rotation
    
    to a lesser extent forward flexion

Imaging
- Radiographs
  - indications
    
    limited utility
  - recommended views
    
    standard shoulder trauma series (true AP, scapular Y, and axillary lateral)
  - findings
    
    most often normal
    
    may show loss of pectoralis major shadow or bony avulsion
- MRI
  - indications
    
    investigation of choice
    
    can differentiate between complete and partial tears
  - views
    
    requires dedicated sequence (standard shoulder MRI will not capture adequately)
    
    T2 sequence better for acute injuries
    
    T1 for evaluating chronic injuries
  - findings
    
    useful in identifying the location and extent of the rupture (partial versus complete)
    
    may show avulsion of the pectoralis major tendon from the humerus
    
    integrity of clavicular head may mask partial rupture of sternocostal head

DIAGNOSIS
- Complete tears
  - diagnosis can be made by history and physical exam and confirmed by MRI
- Partial tears
  - generally require MRI to differentiate from complete tears

Treatment
- Nonoperative
  - initial sling immobilization, rest, ice, NSAIDs, physical therapy
    
    indications
    
    low-demand, sedentary, and elderly patients
    
    muscle belly tears, low-grade partial ruptures
    
    outcomes
    
    inferior to operative management for young, active individuals
    
    cosmetic disfigurement, significant deficit in strength (most pronounced with isokinetic adduction) and peak torque, delayed recovery, poor patient satisfaction, lower return to competitive sports
- Operative
  - open primary repair
    
    indications
    
    gold standard for acute tears in high level athletes, and most young, active patients
    
    tendon avulsion, myotendinous junction tears
    
    outcomes
    
    reliable strength recovery, return to sport, and patient satisfaction
    
    may show improvement regardless of location of tear
    
    excellent success with all methods
    
    some evidence suggests that cortical button fixation and transosseous suture repair with cortical trough are superior to suture anchor repair
  - reconstruction
    
    indications
    
    chronic tears that cannot be adequately mobilized for primary repair
    
    primary repair may still be possible years after the injury
    
    persistent strength deficit in chronic tears
    
    outcomes
    
    reliable strength recovery and patient satisfaction, albeit generally inferior to primary repair
    
    still significantly better than nonoperative management in young, active patients

Techniques
- Initial sling immobilization, rest, ice, NSAIDs, physical therapy
  - technique
    
    sling in adduction and internal rotation, begin passive range of motion immediately as tolerated
    
    active assisted and active motion over the first 6 weeks
    
    transition to strengthening and unrestricted activity at 2-3 months
- Open primary repair
  - approach
    
    standard deltopectoral approach
  - repair technique
    
    all repair techniques have been shown to have comparably excellent success
    
    transosseous suture repair with cortical trough
    
    cortical button fixation
    
    suture anchor repair
    
    both PEAK screw and all suture available
    
    some evidence suggests that cortical button fixation and are superior to
    
    direct repair may be indicated for tears at the muscle belly or myotendinous junction
- Reconstruction
  - approach
    
    standard deltopectoral approach
  - mobilization
    
    need to release adhesions superficial and deep to pectoralis major
    
    careful to avoid injury to the medial and lateral pectoral nerves during deep release
    
    supplemental fascial release may be necessary to mobilize the muscle belly in chronic situations
  - graft options
    
    Achilles allograft (most common)
    
    advantages
    
    avoids donor site morbidity, excellent load characteristics, favorable dimensions, and good surgical outcomes reported
    
    Gracillis weave (allograft versus autograft)

Complications
- Re-rupture (5-7%)
  - failure most often occurs at suture-tendon interface
- Persistent pain
  - incidence
    
    most common complication
- Residual weakness
- Cosmetic deformity