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Transection of the Subscapularis



- Evaluation of Muscle:
    - about 5% of shoulders that have had an anterior dislocation will sustain a irrepairable injury to the subscapularis, which will contribute to 
           further instability;
           - in this case, a pectoralis transfer would be indicated;



- Preparation:
    - identify the anterior humeral circumflex vessels (three sisters) at the inferior aspect of tendinous portion subscapularis;
          - note that the axillary nerve passes just inferior to the three sisters
          - the nerve goes on to courses toward quadrangular space;
          - a spade retractor can be placed just above the three sisters to protect the axillary nerve;
          - alternatively a Joker can be inserted deep to the joint capsule at a point just lateral to the superior border of the subscapularis;
                 - the Joker will then pass out of the joint capsule at the inferior border of the subscaularis tendon - just above the 3 sisters;
                 - again the point of this is to protect the axillary nerve;
    - before an incision is made in the subscapularis, the arm should be externally rotated to avoid damage to axillary nerve and circumflex 
           vessels;
    - prior to incision into the subscapularis tendon, appropriate retractors need to be in place, which allows indentification of the insertion of the
           subscapularis, and its superior and inferior borders;
    - note: in a minority of patients with anterior instability, the subscapularis will be avulsed from the lesser tuberosity or may have a tear in the
           the distal half of subscapularis tendon;

           



- Subscapularis Transection:

           

    - the subscapularis insertion is comprised of a tendinous portion occupying the proximal 2/3 and a muscular portion occupying the 
           inferior 1/3;
    - generally only the tendinous portion requires transection, whereas the muscular portion is preserved inorder to protect the AHCA and 
           underlying axillary nerve;
    - the vertical incision thru the tendinous portion of the subscapulais tendon is usually made 1-2 cm medial to its insertion on the lesser 
          tuberosity to facilitate subscapularis closure at the end of the case;
           - a more medially placed verticle incision will make it easier to separate the subscapularis from the underlying capsule;
           - it is usually necessary to retract the coracohumeral ligament superiorly inorder to complete the transection of the subscapularis 
                  tendon;
           - the lateral portion of the subscapularis tendon is elevated off the underlying capsule to facilitate closure at the end of the case;



- Subscapularis Elevation:
    - medially, the subscapularis tendon is reflected off the capsule using cautery;
    - insert two or three tagging sutures just medial to the line of transection, which will facilitate retraction;

             

    - the underlying joint capsule can be perserved by leaving some fibers of the subscap attached to the capsule, as the subscapularis is 
           dissected medially;
    - the tendon is elevated off the joint capsule w/ use of a periosteal elevator or scissors, and with constant tension on the sutures;
    - as the dissection procedes medially the subscapularis will be less adherent to the underlying capsule and should be gently separated 
           past the glenoid;
             
    - the remaining intact muscular portion of the subscapularis should be gently separately from the underlying capsule with care not to injure 
           the axillary nerve;
    - once the subscapularis is transected, it can be retracted medially, but take care not to place excessively traction on the axillary nerve