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An unexpected posterior shoulder dislocation1
The Journal of Emergency Medicine, Vol 21, No 4, pp 435– 436, 2001 Copyright © 2001 Elsevier Science Inc. Printed in the USA. All rights reserved 0736-4679/01 $–see front matter
PII S0736-4679(00)00409-7
Visual Diagnosis in Emergency Medicine
AN UNEXPECTED POSTERIOR SHOULDER DISLOCATION Nabil J. Bahu,
MD,
and Craig P. Adams,
MD
Department of Emergency Medicine, Sinai-Grace Hospital, Detroit Medical Center, Detroit, Michigan Reprint Address: Nabil J. Bahu, MD, Department of Emergency Medicine, Sinai-Grace Hospital, 6071 West Outer Drive, Detroit, MI 48235
A 24-year-old man with a history of recurrent left anterior shoulder dislocation presented to the Emergency Department (ED) complaining of left shoulder pain for 2 h. The patient had been passing a basketball with his left hand in a forward, pushing motion at the time of injury. He stated that his arm seemed to pop forward at
the shoulder joint in its usual fashion. The pain, at onset, was associated with numbness in the shoulder and upper arm that had subsequently resolved. On examination, the patient was holding the affected arm in adduction and a greater degree of internal rotation than provided by a sling applied at triage. There was an
Figure 1. Standard AP radiograph of the left shoulder showing the characteristic “light bulb” sign (arrows) of posterior shoulder dislocation, as the humeral head is profiled in internal rotation.
Visual Diagnosis in Emergency Medicine is coordinated by Stephen R. Hayden, MD, of the University of California San Diego Medical Center, San Diego, California
RECEIVED: 15 September 2000; FINAL ACCEPTED: 3 April 2001
SUBMISSION RECEIVED:
15 March 2001;
435
436
obvious deformity of the shoulder, as it appeared squared-off, losing its normal rounded contour. The expected anterior fullness of the dislocated humeral head was not noted on palpation. Passive abduction and external rotation were limited secondary to pain. After a thorough examination of the neurovascular status, including that of the frequently injured axillary nerve, multiple X-ray views of the left shoulder were obtained. A standard AP radiograph increased our suspicion that the patient’s clinical examination had actually pointed toward a posterior dislocation of the glenohumeral joint (Figure 1). Immediately obvious was the characteristic “light bulb” sign associated with these injuries, attributed to the humeral head being profiled in internal rotation. Another typical finding noted on this view was an increase in the distance between the anterior glenoid rim and the humeral head (rim sign). Anteroposterior radiographs of these injuries are commonly misread as appearing normal (1). To confirm the diagnosis, including the direction of dislocation, an axillary view (Figure 2) should be obtained (1,2). This projection is invaluable in outlining the relationship between the humeral head and the glenoid fossa. If the necessary positioning is met with difficulty secondary to pain, then a transscapular lateral view may be helpful. Recurrence after an initial anterior dislocation is often attributed to the classic Bankart lesion, a detachment of the inferior glenohumeral ligament from the anterior glenoid rim (2,3). Each subsequent injury may lead to greater instability of the anterior and, less frequently, the posterior capsuloligamentous structures (3,4). Spread of involvement to include the posterior stabilizers may have allowed for a posterior dislocation in this patient. An obvious candidate for surgery, the patient was referred to the orthopedic clinic after dislocation reduction in the ED.
N. J. Bahu and C. P. Adams
Figure 2. A post-reduction axillary view outlining the relationship between the humeral head and the glenoid fossa (arrow). This view is invaluable in determining the direction of shoulder dislocation. Note that the coracoid process (arrowhead) points anteriorly. (A, anterior; P, posterior.)
REFERENCES 1. Perron AD, Jones RL. Posterior shoulder dislocation: avoiding a missed diagnosis. Am J Emerg Med 2000;18:189 –91. 2. Wen DY. Current concepts in the treatment of anterior shoulder dislocations. Am J Emerg Med. 1999;17:401–7. 3. Warme WJ, Arciero RA, Taylor DC. Anterior shoulder instability in sport: current management recommendations. Sports Med 1999; 28:209 –20. 4. Hottya GA, Tirman PF, Bost FW, et al. Tear of the posterior shoulder stabilizers after posterior dislocation:. MR imaging and MR arthrographic findings with arthroscopic correlation. Am J Roentgenol 1998;171:763– 8.
PII S0736-4679(00)00409-7
Visual Diagnosis in Emergency Medicine
AN UNEXPECTED POSTERIOR SHOULDER DISLOCATION Nabil J. Bahu,
MD,
and Craig P. Adams,
MD
Department of Emergency Medicine, Sinai-Grace Hospital, Detroit Medical Center, Detroit, Michigan Reprint Address: Nabil J. Bahu, MD, Department of Emergency Medicine, Sinai-Grace Hospital, 6071 West Outer Drive, Detroit, MI 48235
A 24-year-old man with a history of recurrent left anterior shoulder dislocation presented to the Emergency Department (ED) complaining of left shoulder pain for 2 h. The patient had been passing a basketball with his left hand in a forward, pushing motion at the time of injury. He stated that his arm seemed to pop forward at
the shoulder joint in its usual fashion. The pain, at onset, was associated with numbness in the shoulder and upper arm that had subsequently resolved. On examination, the patient was holding the affected arm in adduction and a greater degree of internal rotation than provided by a sling applied at triage. There was an
Figure 1. Standard AP radiograph of the left shoulder showing the characteristic “light bulb” sign (arrows) of posterior shoulder dislocation, as the humeral head is profiled in internal rotation.
Visual Diagnosis in Emergency Medicine is coordinated by Stephen R. Hayden, MD, of the University of California San Diego Medical Center, San Diego, California
RECEIVED: 15 September 2000; FINAL ACCEPTED: 3 April 2001
SUBMISSION RECEIVED:
15 March 2001;
435
436
obvious deformity of the shoulder, as it appeared squared-off, losing its normal rounded contour. The expected anterior fullness of the dislocated humeral head was not noted on palpation. Passive abduction and external rotation were limited secondary to pain. After a thorough examination of the neurovascular status, including that of the frequently injured axillary nerve, multiple X-ray views of the left shoulder were obtained. A standard AP radiograph increased our suspicion that the patient’s clinical examination had actually pointed toward a posterior dislocation of the glenohumeral joint (Figure 1). Immediately obvious was the characteristic “light bulb” sign associated with these injuries, attributed to the humeral head being profiled in internal rotation. Another typical finding noted on this view was an increase in the distance between the anterior glenoid rim and the humeral head (rim sign). Anteroposterior radiographs of these injuries are commonly misread as appearing normal (1). To confirm the diagnosis, including the direction of dislocation, an axillary view (Figure 2) should be obtained (1,2). This projection is invaluable in outlining the relationship between the humeral head and the glenoid fossa. If the necessary positioning is met with difficulty secondary to pain, then a transscapular lateral view may be helpful. Recurrence after an initial anterior dislocation is often attributed to the classic Bankart lesion, a detachment of the inferior glenohumeral ligament from the anterior glenoid rim (2,3). Each subsequent injury may lead to greater instability of the anterior and, less frequently, the posterior capsuloligamentous structures (3,4). Spread of involvement to include the posterior stabilizers may have allowed for a posterior dislocation in this patient. An obvious candidate for surgery, the patient was referred to the orthopedic clinic after dislocation reduction in the ED.
N. J. Bahu and C. P. Adams
Figure 2. A post-reduction axillary view outlining the relationship between the humeral head and the glenoid fossa (arrow). This view is invaluable in determining the direction of shoulder dislocation. Note that the coracoid process (arrowhead) points anteriorly. (A, anterior; P, posterior.)
REFERENCES 1. Perron AD, Jones RL. Posterior shoulder dislocation: avoiding a missed diagnosis. Am J Emerg Med 2000;18:189 –91. 2. Wen DY. Current concepts in the treatment of anterior shoulder dislocations. Am J Emerg Med. 1999;17:401–7. 3. Warme WJ, Arciero RA, Taylor DC. Anterior shoulder instability in sport: current management recommendations. Sports Med 1999; 28:209 –20. 4. Hottya GA, Tirman PF, Bost FW, et al. Tear of the posterior shoulder stabilizers after posterior dislocation:. MR imaging and MR arthrographic findings with arthroscopic correlation. Am J Roentgenol 1998;171:763– 8.