Tests for Acromioclavicular Joint Pain

Authors: Murrell et al.

References: ICSS, Washington, 2004

Abstract
Introduction: This study aimed to describe a compression test for AC Joint pain and to compare this test with other clinical and imaging tests in order to improve the diagnosis of AC joint pain.  Methods: Of 1037 patients examined, 113 were eligible for inclusion in this study and 38 agreed to participate. The main inclusion criterion was that patients mapped their pain on a pictorial diagram of the upper torso within the area bounded by the mid-clavicle and deltoid insertion. The patients were examined with 20 clinical tests, X-ray, MRI, bone scan, and an AC Joint infiltration test which served as the gold standard if 50% relief was reported with 10 minutes of Lignocaine injection. For the Paxinos test, the examiner’s hand was placed superior to the ipsilateral mid-clavicle. Pressure was applied by thumb in an anterosuperior direction and inferiorly with the index-middle finger to the mid shaft of the clavicle. The test response was positive if pain was felt or increased in the region of the AC joint and negative if there was no change in pain level.  Results: AC tenderness, MRI, and the Paxinos test had high sensitivities but low specificities. O’Brien’s test and X-rays had low sensitivities but high specificities. Bone scan had high sensitivity (82%) and good specificity (70%). Using stepwise regression, the only independent variables retained in the regression model were bone scan and the Paxinos test. The ability to predict AC joint pain was greatly enhanced when the results of the Paxinos test and the bone scan were combined. In our study, almost 61% of the patients were positive for both tests. All of these patients were in the group which responded positively to the Lignocaine injection. No patients in the group which responded positively to the injection were negative in both tests.  Conclusion: Shoulder pain mapping is useful for screening patients with possible AC joint pain. Direct compression of the AC joint (the Paxinos test) is an effective clinical diagnostic tool and bone scan is the best imaging modality for AC joint pain. When both tests are positive in a patient with shoulder pain, the diagnosis of AC joint pain is virtually certain.