Magnetic resonance imaging scans are not a reliable tool for predicting symptomatic acromioclavicular arthritis.

Background: We investigated whether magnetic resonance imaging (MRI) scans can accurately diagnose arthritis of the acromioclavicular joint (ACJ) because it has recently been suggested that bone marrow oedema on MRI scans is a predictive sign of symptomatic ACJ arthritis.

Methods: The MRI scans of 43 patients (50 shoulders) who underwent ACJ excision for clinically symptomatic ACJ arthritis were compared to a control group of 43 age- and sex-matched patients (48 shoulders) who underwent an MRI scan for investigation of shoulder pain but did not have clinical symptoms or signs of ACJ arthritis. The scans were evaluated by an experienced musculoskeletal radiologist, who was blinded to the examination findings.

Results: Bone marrow oedema was present in only 15 (30%) shoulders in the ACJ excision group, although this was higher than the six shoulders in the asymptomatic group ( p  = 0.03). Forty-one (82%) shoulders in the symptomatic group had grade III/IV ACJ arthritis compared to 31 (65%) in the asymptomatic group ( p  = 0.05). However, 44 out of 48 (92%) shoulders in the asymptomatic group had signs of osteoarthritis on MRI scans.

Conclusions: In contrast to recent reports, the present study shows that MRI is not helpful in making the diagnosis of ACJ arthritis. A focused history and clinical examination should remain the mainstay for surgical decision making.

Level of evidence: Level 3.