Factors Influencing the Choice of a Modified Magnuson Procedure for Recurrent Anterior Dislocation of the Shoulder With a Note on Technique
ANTHONY F. DEPALMA, M.D., F.A.C.S.
No JOINT in the human skeleton has been subjected to more varied operative procedures for the correction of one defect, that being recurrent dislocation, than the shoulder joint. For its correction, no component, be it bony, capsular, muscular, ligamentous or tendinous in or about the shoulder, has been immune to surgical insult. In reviewing the literature, one becomes bewildered by the many techniques described and the many added modifications of these techniques. This maze of confusion can only he the result of lack of comprehension of the basic pathology responsible for the lesion. Nevertheless, in spite of this maze of confusion, some steps in the right direction have evolved. These steps are the ones which attempt to make a direct attack on what is believed to be the essential pathologic lesions responsible for the dislocation. Also, recognition of certain principles based on anatomic observations are being adhered to, which, if instituted, result in a cure of the disorder or, at least, a reduction in the incidence of recurrence. With regard to the so-called "essential" lesions, many of us cannot help but come to the conclusion that too much emphasis has been placed on anyone single pathologic state as being the responsible culprit. To be more specific, it is true that many recurrent dislocating shoulders exhibit a pulling away or fraying of the anterior labrum or a tear of the fibrous capsule of the joint from the neck of the scapula. Also, a posterior defect of the humeral head is found in a high percentage of cases; and it is true that many patients believe that there has been some increase in the overall capacity of the shoulder joint, which has often been described as a pouch that readily accommodates the humeral head on dislocation. But to designate anyone of these singly or in combination as the respon-
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ANTHONY
F.
DEPALMA
sible factor would be an error. The record is clear on this point. Many cases of recurrent dislocation occur when there is no defect in the labrum, or, if a defect is found, the lesion is only of minor intensity. Dislocations occur in the absence of a defect in the humeral head, and we must remember that under normal conditions the joint capsule is capable of accommodating a surface area twice the size of the humeral head. The reported work of Adams and of Palmer lends support to these observations. In addition, it must be mentioned that, in describing pathologic lesions on the anterior aspect of the shoulder joint, one must not overlook the fact that many of them may be the result of normal wear and tear and of aging and are frequently encountered in shoulders in which dislocations never occur. Certain conclusions have been drawn from the numerous investigations conducted on the shoulder joint. Essentially these are: 1. Any operative procedure that will buttress the anterior aspect of the shoulder will result in a cure. This buttress effect may be produced by a bony block, by shortening of the subscapularis tendon or by imbrication of the anterior structures of the shoulder joint. 2. Any operative procedure that will control the external rotatory motion of the arm will result in a cure. In considering the varied clinical pictures of recurrent dislocation of the shoulder, one must face up to the facts that are before us. Excluding recurrent dislocations which are based entirely on some anatomic defect of the glenoid fossa or of the humeral head and those that are noted in individuals with a generalized laxity of all the collagen tissue of the skeletal system permitting marked hypermobility of all joints, recurrent dislocation in the greater majority of cases occurs in young, strong, muscular individuals. It is true that the initial dislocation, in many instances, is in the form of violent trauma producing abduction, external rotation and some extension of the joint. However, it is also true that in the same individuals the initial dislocation may follow only a minor strain or injury of the shoulder girdle. All gradations of violence may be accompanied by subsequent dislocations. These gradations may vary from a simple abduction-external rotation maneuver to forceful displacement of the arm when in the critical position. In the face of this evidence, to me at least it appears that following an initial injury, regardless of the severity of the violence, some other factor is necessary to trigger the subsequent episode. The trigger mechanism, in my estimation, is some neuromuscular imbalance of the shoulder girdle. It is also my belief that all the pathologic states described on the anterior aspect of the glenoid cavity and the capsule and on the posterior aspect of the humeral head are secondary in nature and that these pathologic states, at first, favor more rapid fire of the trigger mechanism. Later, as they increase in intensity, they may even replace this trigger mechanism.
Factors Influencing Choice of a Modified Magnuson Procedure
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Fig. 1. Magnuson operation (modified) for recurrent dislocation. The end of the subscapularis tendon is transferred to a bony trough below the greater tuberosity and parallel to the posterior lip of the bicipital groove. (From DePalma, Surgery of the Shoulder. Philadelphia, J. B. Lippincott Co., 1950.)
Based on this philosophy, over the course of many years, I have chosen to perform the most simple operation that would fulfill the criteria for a cure of this lesion, namely, to create an anterior buttress on the anterior aspect of the shoulder and to control external rotation. The operation of my choice has been Magnuson's operation slightly modified (Fig. 1). Essentially this operation comprises the transplantation of the subscapularis tendon from the lesser tuberosity to a position lateral to the outer lip of the bicipital groove and at a slightly lower level from its normal line of attachment. The interior aspect of the joint is not tampered with. In some cases I have in the past utilized a staple to fix the tendon in the desired position. This technique now has been discarded because, in reviewing these patients, many of the staples broke or became fragmented. Nevertheless, this did not interfere with the overall result. In order to prevent such a complication, the tendon is now sutured in a slot made lateral to the bicipital groove. These patients have a short convalescence and have an excellent range of motion. They do have some limitation of external rotation but a very high percentage, as will be shown later in this symposium. are cured. 248 South 21st Street Philadelphia 3, Pennsylvania