Seven-year course of asymptomatic acromioclavicular osteoarthritis diagnosed by MRI

Asymptomatic acromioclavicular osteoarthritis (AC-OA) is a frequent finding in shoulder magnetic resonance imaging (MRI). Its natural course is unknown. Therefore, the question arises whether a resection should be performed simultaneously with shoulder surgery for another reason to prevent future pain and reoperation. The purpose of this study was to investigate the mid-term course of asymptomatic AC-OA.

Overall, 114 asymptomatic AC-OA diagnosed on MRI were followed for 7 years between 2011 and 2018. At baseline, MRI signal enhancement in the clavicle and acromion, OA grade, physical demand as well as the parameters (1) Constant Score Visual Analogue Scale, (2) pain on AC-joint compression, and (3) cross-body adduction test were measured. All patients were followed up after 7 years by interview, and in case of symptoms by clinical examination. The endpoint "deterioration" was reached if 2 of the 3 parameters turned worse.

Asymptomatic AC-OA remained asymptomatic in 83% of cases, 7% turned better, 10% turned worse. Physical demand and osteoarthritis grade increased the risk of deterioration, whereas MRI signal enhancement in the clavicle or acromion had no influence on outcome. During follow-up, the frequency of pain on AC-joint compression increased from 11% to 16% (P = .24), the frequency of a positive cross-body adduction test increased from 6% to 20% (P = .017), and the mean Constant Score Visual Analogue Scale increased from 10 to 13 points (P < .001) indicating less pain.

Asymptomatic AC-OA remained asymptomatic in 90% over 7 years. A simultaneous resection of an asymptomatic AC-OA during shoulder surgery for another reason is not indicated in every patient.