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Testing the Tests for Shoulder Pain Caused by the AC Joint

The results of this study will help doctors diagnose shoulder problems. Many patients with shoulder pain really have a problem with the acromioclavicular (AC) joint. The AC joint is where the outer edge of the collarbone (the clavicle) meets the acromion. The acromion is a bony projection off the shoulder blade. It forms a roof or shelf over the shoulder joint.

Researchers at the Sports Medicine and Shoulder Service in Sydney, Australia, carried out 20 tests on patients with shoulder pain. Muscles were examined, and X-rays and other imaging studies were done. Range of motion was measured, and some special tests just for AC problems were done.

Then each patient had a steroid injection with a numbing agent into the AC joint. Patients who got more than 50 percent relief from pain had a true AC joint problem. The researchers compared the results of the tests with the results from the successful injections.

They found that two tests were very accurate when used together. The Paxinos test and a positive bone scan gave the best information. The Paxinos test is done by applying front-to-back pressure through the AC joint. If these tests are both positive, then there's a 99 percent chance the patient has an AC joint problem.

A pain diagram is also a good screening tool for AC joint pain. The most common pattern with AC joint pain starts in the middle of the clavicle and goes out over the shoulder to the middle of the upper arm. The authors suggest more testing is needed if one test is positive and one is negative.

References: Judie Walton, BSc, PhD, et al. Diagnostic Values of Tests for Acromioclavicular Joint Pain. In The Journal of Bone and Joint Surgery. April 2004. Vol. 86-A. No. 4. Pp. 807-812.

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