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Shoulder Instability: Incorrect, Delayed, and Missed Diagnoses

When a shoulder dislocates more than once, the joint becomes unstable. Usually shoulder dislocation is in the forward or anterior direction. In a small number of patients the dislocation is backward or posterior. In this article, recurrent posterior shoulder dislocation and instability are reviewed.

Trauma, especially during high-risk sports activities is the most common cause of posterior shoulder instability. Pain or tenderness along the joint line may be the only symptom. Strength and motion are usually normal.

The doctor must perform specific tests for shoulder posterior instability to make the diagnosis. Often the diagnosis is incorrect, delayed, or missed altogether. The authors describe (including patient photos) four tests that can be done. These include the posterior stress test, the jerk test, the load and shift test, and the modified load and shift test.

X-rays are also used to make sure the joint is in place. The doctor uses X-rays to look for fractures, changes in anatomy, and any problems with the rim around the socket. CT scans and MRIs are needed to see any small changes in the shape of the shoulder socket. The same imaging studies help find changes in the normally round head of the humerus (upper arm bone). These imaging tests are critical when surgery is needed to treat the problem.

Physical therapy (PT) to strengthen the muscles that stabilize the joint is the first step in treating this problem. About 80 per cent of the patients with recurrent posterior instability have a good result with PT. Details of arthroscopic surgery for the remaining 20 per cent are described. Patient position, surgical technique, and postoperative rehab are presented.

Stiffness, tightness, and recurrence of dislocation are the major problems after surgery. Fracture and nerve injury occur but less often. The authors conclude by saying that with careful planning and understanding of the problem, treatment of recurrent posterior shoulder stability can be successful.

References: Peter J. Millett, MD, MSc, et al. Recurrent Posterior Shoulder Instability. In Journal of the American Academy of Orthopaedic Surgeons. August 2006. Vol. 14. No. 8. Pp. 464-476.

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