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Locked Posterior Subluxation of the Shoulder: Diagnosis and Treatment
Locked Posterior Subluxation of the Shoulder Diagnosis and Treatment
HARRISON L. McLAUGHLIN, M.D., F.A.C.S.
LOCKED posterior subluxation of the shoulder is so uncommon that it almost invariably serves as a diagnostic trap for the unwary clinician. Thirteen such lesions have been encountered in our practice. They had remained unrecognized for an average period of eight months before the correct diagnosis was made. The clinical diagnosis is clear-cut and unmistakable, but only when posterior subluxation is suspected. The history should make the diagnosis suspect. Fifty per cent of these lesions were produced by a convulsive episode, the other 50 per cent by trauma to the flexed and adducted arm. A stiff and painful shoulder following either of these incidents is likely to be a locked posterior subluxation of the humeral head. To the casual observer the lesion simulates the much more common condition usually termed "frozen shoulder" or "periarthritis." Differentiation depends upon three constant abnormal findings. 1. A fixed internal rotation deformity so that the arm cannot be rotated outward, even to the neutral position. 2. An unduly prominent coracoid when compared with the other side. 3. Palpable and often visible backward displacement of the humeral head under the scapular spine. The roentgen diagnosis is equally apparent, but again, only when the lesion is suspected. 1. Ordinary anteroposterior films reveal a small incongruity of fit between the humeral and glenoid articulating surfaces. 2. Continuity of a line drawn along the inferior border of the humeral head and neck to the lateral and inferior border of the scapula is interrupted. 3. Tangential films of the scapula reveal the posterior displacement of the humeral head. 4. An axillary view reveals not only the true diagnosis, but also the tenon-and-mortise engagement of the posterior rim of the glenoid with a defect in the anterior aspect of the humeral head.
1621
1622
HARRISON
L.
MCLAUGHLIN
All of these clinical and roentgen abnormalities are usually present, but may be so small in degree as to escape the notice of one who fails to rule out locked posterior subluxation of the humerus in the differential diagnosis of a stiff and painful shoulder. Treatment depends upon the duration of the mechanism which locks the humeral head in its displaced position. The anterior humeral head defect is, in fact, an impression fracture caused by the impaction of the hard posterior rim of the glenoid into the soft bone of the humeral head. This defect increases in size and depth by erosion with the passage of time. In the early stages following injury, therefore, the subluxation can be reduced easily by traction and gentle rotation of the humerus. Immobilization in mild external rotation for several weeks is adequate after-care. In a lesion of some duration the glenoid rim becomes so deeply and securely engaged in the humeral head defect that manipulative reduction is rarely possible. Operative replacement and stabilization of the humeral head is necessary. The procedure utilized in the 13 lesions we have encountered has been described. 1 The shoulder joint was exposed from in front through a deltoid-splitting approach and the subscapularis insertion separated from the lesser tuberosity. Medial retraction of the subscapularis opened the shoulder joint and exposed the locked displacement of the humeral head. It is often necessary to lever the humerus into place. Once reduced, it is obvious that the humeral defect promotes immediate redislocation when the arm is rotated internally, and that obliteration of this defect is necessary for maintenance of normal position. This has been accomplished by reinsertion of the large subscapularis tendon into the depths of the defect. Following operation the limb is dressed in a sling and bound to the thorax for several weeks. Gradually progressive gravity-free motions are commenced as soon as the incision heals. After four to six weeks, progressive motion and use are encouraged. In the 13 patients with locked posterior subluxation treated in this manner the average duration of the lesion was eight months. All were completely disabled and unable to work. All returned to their former jobs. None has experienced redislocation. The results have been very satisfactory. REFERENCE 1. Hill, N. A. and McLaughlin, H. L.: Locked posterior dislocation simulating a "frozen
shoulder." J. Trauma 3: 225-34 (May) 1963. 630 West 168th Street New York 32, N.Y.
HARRISON L. McLAUGHLIN, M.D., F.A.C.S.
LOCKED posterior subluxation of the shoulder is so uncommon that it almost invariably serves as a diagnostic trap for the unwary clinician. Thirteen such lesions have been encountered in our practice. They had remained unrecognized for an average period of eight months before the correct diagnosis was made. The clinical diagnosis is clear-cut and unmistakable, but only when posterior subluxation is suspected. The history should make the diagnosis suspect. Fifty per cent of these lesions were produced by a convulsive episode, the other 50 per cent by trauma to the flexed and adducted arm. A stiff and painful shoulder following either of these incidents is likely to be a locked posterior subluxation of the humeral head. To the casual observer the lesion simulates the much more common condition usually termed "frozen shoulder" or "periarthritis." Differentiation depends upon three constant abnormal findings. 1. A fixed internal rotation deformity so that the arm cannot be rotated outward, even to the neutral position. 2. An unduly prominent coracoid when compared with the other side. 3. Palpable and often visible backward displacement of the humeral head under the scapular spine. The roentgen diagnosis is equally apparent, but again, only when the lesion is suspected. 1. Ordinary anteroposterior films reveal a small incongruity of fit between the humeral and glenoid articulating surfaces. 2. Continuity of a line drawn along the inferior border of the humeral head and neck to the lateral and inferior border of the scapula is interrupted. 3. Tangential films of the scapula reveal the posterior displacement of the humeral head. 4. An axillary view reveals not only the true diagnosis, but also the tenon-and-mortise engagement of the posterior rim of the glenoid with a defect in the anterior aspect of the humeral head.
1621
1622
HARRISON
L.
MCLAUGHLIN
All of these clinical and roentgen abnormalities are usually present, but may be so small in degree as to escape the notice of one who fails to rule out locked posterior subluxation of the humerus in the differential diagnosis of a stiff and painful shoulder. Treatment depends upon the duration of the mechanism which locks the humeral head in its displaced position. The anterior humeral head defect is, in fact, an impression fracture caused by the impaction of the hard posterior rim of the glenoid into the soft bone of the humeral head. This defect increases in size and depth by erosion with the passage of time. In the early stages following injury, therefore, the subluxation can be reduced easily by traction and gentle rotation of the humerus. Immobilization in mild external rotation for several weeks is adequate after-care. In a lesion of some duration the glenoid rim becomes so deeply and securely engaged in the humeral head defect that manipulative reduction is rarely possible. Operative replacement and stabilization of the humeral head is necessary. The procedure utilized in the 13 lesions we have encountered has been described. 1 The shoulder joint was exposed from in front through a deltoid-splitting approach and the subscapularis insertion separated from the lesser tuberosity. Medial retraction of the subscapularis opened the shoulder joint and exposed the locked displacement of the humeral head. It is often necessary to lever the humerus into place. Once reduced, it is obvious that the humeral defect promotes immediate redislocation when the arm is rotated internally, and that obliteration of this defect is necessary for maintenance of normal position. This has been accomplished by reinsertion of the large subscapularis tendon into the depths of the defect. Following operation the limb is dressed in a sling and bound to the thorax for several weeks. Gradually progressive gravity-free motions are commenced as soon as the incision heals. After four to six weeks, progressive motion and use are encouraged. In the 13 patients with locked posterior subluxation treated in this manner the average duration of the lesion was eight months. All were completely disabled and unable to work. All returned to their former jobs. None has experienced redislocation. The results have been very satisfactory. REFERENCE 1. Hill, N. A. and McLaughlin, H. L.: Locked posterior dislocation simulating a "frozen
shoulder." J. Trauma 3: 225-34 (May) 1963. 630 West 168th Street New York 32, N.Y.