- Author: Elizabeth Dulaney-Cripe, MD; Chief Editor: Erik D Schraga, MD more...
The Magnuson-Stack procedure is a historic nonanatomic procedure for shoulder instability. The procedure is predicated on tightening of the subscapularis by altering the insertion site from the lesser tuberosity to a groove created lateral to the bicipital groove. This produces a “sling effect” on the humeral head.
An image depicting the Magnuson-Stack procedure can be seen below.
The Magnuson-Stack procedure was first published by Paul B. Magnuson and James K. Stack in December 1943. The advantages of this procedure over other procedures for anterior instability of the shoulder include the ease of execution of the procedure and a lesser degree of shoulder functional limitation. The disadvantages of this procedure include the predictable loss of external rotation in addition to not addressing any capsular or labral pathology.[1, 4]
Due to the loss of external rotation, the applicability of the procedure is limited. Athletes and laborers requiring a normal range of motion in external rotation would be limited with this procedure. This also would limit use for throwers and overhead athletes.
This procedure was originally indicated for patients with unidirectional anterior instability of the shoulder.
Excluding voluntary, posterior, and multidirectional instability as diagnoses prior to this procedure is important. Any restriction in external rotation preoperatively would be exacerbated following this type of repair.
General anesthesia is used for this procedure.
The patient is positioned supine in a beach chair position. The room should be arranged as to allow the arm to be fully abducted and externally rotated throughout the procedure.
Adequate padding is imperative in prevention of intraoperative complications. Also, identification of the neurovascular structures in the approach to the subscapularis.
The technique has been taken directly from the original Magnuson-Stack paper. In general, the subscapularis is approached through a delto-pectoral 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.
See the list below:
Make an incision at the junction of the anterior and medial third of the deltoid, extending from the acromion down.
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.
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.
A sharp, thin-bladed chisel is driven parallel to the long axis of the bone. The chisel is moved 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).
Suture the tendon with doubled 00 chromic catgut suture; the sutures are repeated on both sides of the wedge.
Post-op and rehab
Immobilization is necessary immediately following the surgery and continued for 3-6 weeks.[3, 5] Rehabilitation follows immobilization, but external rotation is limited for 4-6 weeks following surgery.
Following surgical stabilization of the anterior shoulder, the main outcomes measured would be a recurrence of instability and the significance of the loss of external rotation. In an evaluation of 19 cases in 1960, Palumbo identified recurrence of dislocation in 10.5% of the patients. Karadimas and coworkers reported a 2% recurrence of instability, while Miller and coworkers reported a 17% recurrence of instability.
Regarding functional loss, Aamoth noted in 1977 that 92% of the athletes studied returned to their preoperative sport. They noted that 48% of the athletes had residual loss of external rotation at their side and 30% had a loss of external rotation with overhead motion. The average loss of external rotation within the athletes studied was 11 º.
Palumbo also saw a limitation of 15-50 º of external rotation in half of their patients and a limitation of 60-80 º in the other half of the patients. Karadimas and coworkers noted that 11 of their 135 patients were limited by 10-30 º in external rotation. It was noted by Regan et al that of the Magnuson-Stack, Bristow, and Putti-Platt, the Magnuson-Stack procedure limited external rotation the least.
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.
Ahmad et al mentioned that an anterior repair, such as the Magnuson-Stack procedure, would alter the loading of the glenohumeral joint. This alteration in loading increases the loading along the posterior aspect of the joint with 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.
Rokito AS, Namkoong S, Zukerman JD, Gallagher MA. Open Surgical Treatement of Anterior Glenohumeral Instabilty: an Historical Perspective and Review of the Literature Part II. The Americal Journal of Orthopedics. 1998/12. 784-790.
Magnuson PB, Stack JK. Recurrent dislocation of the shoulder. 1943. Clin Orthop Relat Res. 1991 Aug. 4-8; discussion 2-3. [Medline].
PALUMBO LT, SHARPE WS, NEJDL RJ. Recurrent dislocation of the shoulder repaired by the Magnuson-Stack operation; evaluation of results. Arch Surg. 1960 Nov. 81:834-7. [Medline].
Canale ST and Beaty JH. Shoulder. Canale&Beaty: Campbell’s Operative Orthopaedics. 11. Mosby; 2007. [Full Text].
Aamoth GM, O'Phelan EH. Recurrent anterior dislocation of the shoulder: a review of 40 athletes treated by subscapularis transfer (modified Magnuson-Stack procedure). Am J Sports Med. 1977 Sep-Oct. 5(5):188-90. [Medline].
Regan WD Jr, Webster-Bogaert S, Hawkins RJ, Fowler PJ. Comparative functional analysis of the Bristow, Magnuson-Stack, and Putti-Platt procedures for recurrent dislocation of the shoulder. Am J Sports Med. 1989 Jan-Feb. 17(1):42-8. [Medline].
Ahmad CS, Wang VM, Sugalski MT, Levine WN, Bigliani LU. Biomechanics of shoulder capsulorrhaphy procedures. J Shoulder Elbow Surg. 2005 Jan-Feb. 14(1 Suppl S):12S-18S. [Medline].