The Challenge of Diagnosing Patients Presenting With Signs and Symptoms of Subacromial Pain Syndrome: A Descriptive Study of 741 Patients Seen in a Secondary Care Setting

Background: Subacromial pain syndrome has no universally accepted definition. Patients with shoulder pain are often diagnosed with subacromial pain syndrome without consideration of conflicting or concomitant diagnoses. Purpose: To investigate the prevalence of conflicting and concomitant diagnoses in patients with signs and symptoms of subacromial pain syndrome. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Using standardized diagnostic criteria, a prospective cohort of patients with signs and symptoms of subacromial pain syndrome was divided into 2 mutually exclusive groups: (1) patients with conflicting diagnoses—e.g., frozen shoulder or glenohumeral osteoarthritis (OA); (2) patients with subacromial pain syndrome. Patients with subacromial pain syndrome were further divided into 2 groups: (1) isolated subacromial pain syndrome; (2) subacromial pain syndrome with concomitant diagnoses—e.g., acromioclavicular OA, full-thickness rotator cuff tears, shoulder instability, long head biceps tendon pathology, labral lesions, and calcified tendinopathy. Standardized physical examination tests, radiographs, ultrasound, and magnetic resonance imaging scans were utilized. Tests were performed by experienced orthopaedic specialists in accordance with predefined standardized protocols. Results: We systematically screened 3321 patients, of whom 576 had signs and symptoms of subacromial pain syndrome (mean age, 56 years; 57% women). Of these, 168 (29%) patients had conflicting diagnoses, with frozen shoulder accounting for the majority of these diagnoses. The remaining 408 patients were diagnosed with subacromial pain syndrome. Of these, 172 (42%) had at least 1 concomitant diagnosis, and 55 (13%) had multiple concomitant diagnoses. In total, 22 different combinations of concomitant diagnoses were observed across the 172 patients. Acromioclavicular OA and full-thickness rotator cuff tears, particularly of the supraspinatus, were the most common concomitant diagnoses. Biceps tendon pathology, calcified tendinopathy, minor shoulder instability, and superior labrum anterior to posterior (SLAP) lesions were less common. Conclusion: Patients presenting with signs and symptoms of subacromial pain syndrome have a high prevalence of conflicting and concomitant diagnoses. This heterogeneity is a clinical challenge that necessitates a systematic and transparent diagnostic approach in patients presenting with signs and symptoms of subacromial pain syndrome. ClinicalTrials.gov: NCT05549674.