Bilateral ultrasound findings in patients with unilateral subacromial pain syndrome

Background: Subacromial pain syndrome is a common musculoskeletal shoulder problem. The accuracy of clinical tests is low and techniques such as ultrasound and magnetic resonance imaging have been added to set up a diagnosis. Previous researchers have usually only examined the symptomatic shoulder. However, there might be similar findings in the asymptomatic shoulder. Objective:The aim of the present study was to investigate the prevalence of structural abnormalities of both shoulders in patients with clinically diagnosed unilateral subacromial pain syndrome using diagnostic ultrasound. Methods: Bilateral ultrasound examinations were performed in 115 consecutive patients, 54 men and 61 women. The patients were recruited from primary care centers in the area of Stockholm, Sweden. Results: Abnormal ultrasound findings were found in both shoulders and increased with age (p = .0004). Bursitis was the most common ultrasound finding and significantly more prevalent in the symptomatic shoulder compared to the asymptomatic shoulder (90%:74%; p = .0021), though 73% of the bursitis were bilateral. Supraspinatus is the most vulnerable tendon of the rotator cuff in both shoulders. In terms of partial-thickness tears and tendinosis, the tendon was affected more commonly in the symptomatic shoulder compared to the asymptomatic shoulder (30%:14%: 14%; p = .0026) and (24%:10%; p = .0054), respectively, but for calcification no significant difference between the shoulders was found (18%:12%; 0.1988). Conclusion: Ultrasound detected shoulder abnormalities were present in both symptomatic and asymptomatic shoulders. Bursitis and partial-thickness tears were more common in the affected shoulder when compared to the unaffected shoulder. Ultrasound as well as clinical examination findings and patient´s history should be taken into consideration when diagnosing patients with subacromial pain syndrome.