Magnuson-Stack Procedure Technique

Updated: Aug 30, 2017
  • Author: Elizabeth Dulaney-Cripe, MD; Chief Editor: Erik D Schraga, MD  more...
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Technique

Approach Considerations

The following description of the Magnuson-Stack procedure is directly based on the original paper by Magnuson and Stack. [1]  In general, the subscapularis is approached through a deltopectoral interval. The insertion of the subscapularis is identified and detached with a bone block. This is then attached to a groove lateral to the bicipital groove at the greater tuberosity of the humerus.

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Magnuson-Stack Procedure

Make an incision at the junction of the anterior and medial third of the deltoid, extending from the acromion down. Expose the anterior surface of the capsule (see the image below).

Anterior shoulder. Anterior shoulder.

Externally rotate the arm and identify the subscapularis muscle. Pull the subscapularis tendon tight, and incise the subscapularis muscle from the musculotendinous junction to its attachment along the anterior lip of the bicipital groove. Insert a chisel along the distal side of the attachment medial to the lip of the bicipital groove (see the image below).

Use of a chisel to detach the subscapularis. Use of a chisel to detach the subscapularis.

Lift the tendinous attachment with a wedge of bone, and reflect it medially to expose the head of the humerus and the anterior edge of the humerus (see the image below).

Elevation of the subscapularis with a bone block. Elevation of the subscapularis with a bone block.

Inspect the head of the glenoid and the head of the humerus (see the image below).

Inspection of the anterior shoulder and glenoid. Inspection of the anterior shoulder and glenoid.

Internally rotate the arm and stretch the subscapularis tendon across the bicipital groove to the greater tuberosity. Manipulate the arm. The ideal placement allows 50% external rotation.

Drive a sharp, thin-bladed chisel parallel to the long axis of the bone. Move the chisel back and forth laterally to spread the cancellous bone and leave a wedge-shaped gutter, into which the bone attached to the subscapularis tendon is forced (see the image below).

Creation of a wedge on the lateral side of the bic Creation of a wedge on the lateral side of the bicipital groove.

Suture the tendon with doubled 00 chromic catgut suture; repeat the sutures on both sides of the wedge. Tack down the lower border of the subscapularis muscle with interrupted sutures far enough under the head of the humerus to allow the muscle and capsular tendon to have a firm grip around the head (see the image below).

Sutured subscapularis with bone block to the creat Sutured subscapularis with bone block to the created wedge lateral to the bicipital groove.
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Postoperative Care

Immobilization is necessary immediately following the surgery and is continued for 3-6 weeks. [4, 6] Rehabilitation follows immobilization, but external rotation is limited for 4-6 weeks following surgery. [4]

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Complications

Complications that are possible with this procedure include loss of functional abilities due to a significant loss of external rotation, recurrence of instability, and neurovascular injury. A recurrence of instability is seen in patients who regain normal external rotation. [5]

Ahmad et al mentioned that an anterior repair, such as the Magnuson-Stack procedure, would alter the loading of the glenohumeral joint. [8] This alteration in loading increases the loading along the posterior aspect of the joint, with the potential to create an abnormal posteroinferior humeral head subluxation. This would result in increased wear along the posterior aspect of the glenoid, likely leading to secondary osteoarthritis.

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