Total shoulder arthroplasty

Preparation of the humerus

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  Place the patient in the beach chair position using a headrest to allow positioning of the patient at the top and edge of the table. Pad all bony prominences. The medial border of the scapula should be free and off the table, allowing full adduction to gain access to the intramedullary canal.

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  Secure the patient’s head to the headrest, holding the head in a position that avoids hyperextension or tilting of the neck, which can cause compression of the cervical roots.

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  Prepare the arm and drape it widely. We recommend using occlusive dressings to cover the entire surgical field because of the risk of contamination from the axilla.

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  Make an incision anteriorly, approximately one third of the way between the coracoid and the lateral aspect of the acromion ( Fig. 7.1 ). Carry dissection down to the deltoid and raise medial and lateral flaps to mobilize the deltoid.

  

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  Open the deltopectoral interval and allow the cephalic vein to fall medially.

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  Perform subdeltoid, subcoracoid, and subacromial releases to release the proximal humerus. In the subcoracoid space, locate the axillary nerve by passing the volar surface of the index finger down along the anterior surface of the subscapularis muscle ( Fig. 7.2 ). If scarring and adhesions make identification of the nerve difficult, pass an elevator along the anterior surface of the subscapularis muscle to create an interval between the muscle and the nerve. Always identify the axillary nerve and carefully retract and hold it out of the way, especially during the crucial steps of releasing the anteroinferior capsule.

  

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  Incise the subscapularis 1 cm medial to the lesser tuberosity. Place two retention sutures in the subscapularis to be used as traction sutures when freeing the rest of the tendon from the underlying capsule and scar tissue. At closure, use the heavy nonabsorbable sutures to repair the tendon.

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  Some authors prefer either a lesser tuberosity osteotomy or a release of the subscapularis directly off of bone. If external rotation is markedly limited, the subscapularis also can be reattached to the proximal humerus more medially to allow increased external rotation. Alternatively, the tendon can be lengthened with a coronal Z-plasty technique.

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  Incise the rotator interval, directing the cut medially toward the glenoid. Typically, a large amount of synovial fluid escapes as the joint is entered.

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  Release the anteroinferior capsule from the humerus and externally rotate the arm to bring the inferior aspect of the shoulder capsule into view. If osteophytes are present inferiorly on the humeral head, remove them to expose the capsule more fully. Take care to stay directly on bone so as not to injure the axillary nerve during the capsular release. The importance of the inferior capsule release cannot be overstated and must be thoroughly carried out to at least the 6 o’clock position to dislocate the humeral head and gain access to the glenoid.

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  Once the capsule is adequately released, place a large Darrach retractor in the joint and gently externally rotate, adduct, and extend the arm to deliver the humeral head up and out of the glenoid fossa ( Fig. 7.3 ). If the humeral head cannot be delivered in this fashion, the inferior capsule must be released further.

  

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  Prepare the humeral canal, using the humeral axis to reference the osteotomy. Initially, open the canal with a high-speed burr at the base of the rotator cuff footprint and ream it to a size where appropriate “chatter” is felt in the shaft. Do not use motorized equipment for reaming and be careful not to overream the canal, which could create a stress riser or cause a fracture.

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  We prefer to use a cutting guide that employs extramedullary referencing, using the axis of the forearm as the reference point. With the cutting guide pinned into position at 30 degrees of retroversion. Other surgeons may prefer a free-hand, anatomic neck-cutting technique. Regardless, care must be taken to avoid violating the rotator cuff.

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  Complete the osteotomy with an oscillating saw. If any inferior humeral head osteophyte remains, remove it with a rongeur.

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  After the head cut, broach the humeral canal to the same size as the reamed canal. It is imperative to confirm proper position of the broaches in 30 degrees of retroversion during this step to prevent component malposition.