New Cause of Shoulder Pain in Overhead Throwing Athletes

Overhead athletes are at risk for shoulder injury from repetitive motions with the arm in an overhead position. This can include baseball or softball pitchers, swimmers, or cheerleaders. Other athletes who repeatedly use an overhead motion of the arm are also at increased risk.

When the pain occurs along the back of the shoulder (posterior), it can be caused by injury to the rotator cuff, the labrum, or nerve entrapment. In this report, two orthopedic surgeons from Stanford University present four cases of quadrilateral space syndrome (QSS). QSS is another possible (but rare) cause of posterior shoulder pain.

A quadrilateral is any four-sided shape. In the case of the quadrilateral space of the shoulder, the top and bottom edges are formed by the teres minor (top) and teres major muscles (bottom). The long head of the triceps muscles is located along the medial (inside edge). The neck of the humerus (upper arm bone) is along the lateral (outer border) of the quadrilateral.

In QSS, the axillary nerve is being compressed or pinched as the nerve leaves this space. Pain occurs directly over the quadrilateral space. Symptoms are aggravated by overhead arm motion. There is tenderness when the area is pressed or palpated.

In this study, all four patients tried at least six months of conservative care without success. Electromyography (EMG), computed tomography (CT) scans, and magnetic resonance imaging (MRIs) were done to help make the diagnosis. Eventually a positive axillary nerve block identified the specific problem area.

Surgery to take the pressure off the nerve was done. The authors describe this decompression procedure in detail. During the operation, fibrous adhesions were cut away from the full length of the nerve. In one case, a dilated vein was also noted.

After the operation, gentle motion was started to prevent scar tissue from forming again. Active and passive motion was also used to keep the nerve and vein moving freely. The patients had to avoid overusing the arm for the first four weeks of therapy. By the end of six weeks, the therapist had prescribed a sport-specific therapy program.

Results were measured using pain and other symptoms. Range of motion, strength, and ability to return to overhead sports activities were also measured and compared before and after surgery. Twelve weeks later, all four patients were back to their pre-surgical level of sports activity. Everyone was pain free with full shoulder motion.

The authors point out that QSS can be very difficult to diagnose. This is true even with one (or more) arthroscopic exam(s). They offer a review of their own clinical decision pathway for this problem.

First, they take a history and perform a physical exam. Physical therapy is the first type of nonoperative care provided. If there's no improvement with conservative care, then further testing includes an MRI and then a lidocaine block test. If the lidocaine block test is positive, then a CT angiogram is done to show the quadrilateral space and look for nerve compression.

A positive lidocaine block test is the most useful diagnostic tool. They also advise ordering a CT angiography with the arm in two positions: neutral (next to the body) and in the overhead position.

Reference: 

Timothy R. McAdams, MD, and Michael F. Dillingham, MD. Surgical Decompression of the Quadrilateral Space in Overhead Athletes. In The American Journal of Sports Medicine. March 2008. Vol. 36. No. 3. Pp. 528-532.

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