Duke Orthopaedics
Wheeless' Textbook of Orthopaedics

Subscapularis Muscle

- See: Rotator cuff:

- Anatomy:
    - origin: entire anterior surface of the subscapularis fossa;
    - insertion: lesser tuberosity of humerus and capsule of shoulder joint;
    - action:
              - main action: glenohumeral head depressor;
              - in certain positions allows extension, adduction and medial rotation of humerus at shoulder;
              - stabilization of the glenohumeral joint;
    - reversed origin insertion action:
              - when humerus is stabilized, abducts inferior border of the scapula;
              - synergists: teres major, pectoralis major, latissimus dorsi;
    - nerve supply:
              - upper & lower subscapular, C5, C6;
              - subscapular nerve arises from posterior division of upper trunk, rather than from posterior cord and herefore contains fibers only from C4-C6;
              - in some pts (30%) subscapular nerve does arise from posterior cord
    - exam:
             - belly press:
                     - rotation without the elbow dropping posterior to the midsagittal plane of the trunk indicates impaired subscapularis function;
                     - evaluates the upper subscapularis; 
                     - if test is positive, then elbow will drop backwards;
             - lift off:
                     - rotation with hand off the lumbar spine without extending the elbow;
                     - evaluates the lower subscapularis;
             - references:
                     - The Influence of Arm and Shoulder Position on the Bear-Hug, Belly-Press, and Lift-Off Tests. An Electromyographic Study
                     - The bear-hug test: a new and sensitive test for diagnosing a subscapularis tear

- Considerations for Subscapularis Repair:
biceps tendon management
      - references:
            - Repair of tears of the subscapularis. (see surgical technique article)
            - Stabilization of the long head of the biceps tendon in the context of early repair of traumatic subscapularis tendon tears.
            - Pectoralis Major Tendon Transfers Above or Underneath the Conjoint Tendon in Subscapularis-Deficient Shoulders
            - Repair of Tears of the Subscapularis. 
            - Traumatic anterosuperior rotator cuff tears: the outcome of open surgical repair.
            - Subscapularis tendon tear: an anatomic and clinical investigation.
            - The frequency of subscapularis tears in arthroscopic rotator cuff repairs: A retrospective study comparing MRI and arthroscopic findings.
            - Subscapularis tendon tears: identifying mid to distal footprint disruptions

- Pectoralis Major Transfer:
      - subcoracoid pectoralis major tendon transfer:
              - may improve function and diminish pain;
              - subcoracoid position of the transfer allows redirection of the pectoralis major in a direction recreating the vector of the subscapularis tendon;
              - references:
                    - Transfer of pectoralis major for the treatment of irreparable tears of subscapularis: does it work?
                    - Outcome of pectoralis major transfer for the treatment of irreparable subscapularis tears.
                    - Pectoralis major transfer in the treatment of chronic subscapularis insufficiency
                    - Pectoralis major tendon transfers above or underneath the conjoint tendon in subscapularis-deficient shoulders. An in vitro biomechanical analysis.
                    - Transfer of segmentally split pectoralis major for the treatment of irreparable rupture of the subscapularis tendon
                    - Anatomic evaluation of the subcoracoid pectoralis major transfer in human cadavers.

- Discussion:
Surgical Dissection for Anterior Shoulder Reconstruction;
    - w/ anterior dislocations the subscapularis is displaced forward, which creates traction injury to the axillary nerve;
            - nerve is tethered above by brachial plexus & below where it wraps around behind neck of humerus;
    - during anterior shoulder reconstruction, the axillary nerve may be identified by passing a digit along anterior surface of subscapularis until the nerve is
            encountered at lower margin of subscapularis as the nerve passes inferior to articular capsule on its way to quadrangular space;
    - before an incision is made in subscapularis, the arm should be externally rotated to avoid damage to axillary nerve & circumflex vessels

Repair of recurrent anterior dislocation of the shoulder using transfer of the subscapularis tendon.

Release of the subscapularis for internal rotation contracture and pain after anterior repair for recurrent anterior dislocation of the shoulder.

Operative treatment of irreparable rupture of the subscapularis

The Subscapularis Footprint: An Anatomic Description of Its Insertion Site.

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Wednesday, May 9, 2012 10:35 am

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