Topographical mapping of subacromial pain syndrome

Background and aims: Topographical pressure pain thresholds (PPTs) maps can be used to assess spatial sensitivity in musculoskeletal conditions, including subacromial pain syndrome (SAPS). No studies have investigated how the distribution of topographical mapping of patients with SAPS is associated with findings on ultrasound. This study aimed to investigate the association between spatial sensitivity and findings on ultrasound in patients with unilateral SAPS.

Methods: Patients were recruited from either an orthopaedic department, rheumatological practice or social media. Patients were included if they experienced persistent pain at the proximal lateral aspect of the upper arm for ≥3 months, at least three positive findings on a 7-item test cluster, minimal to no limitation of passive shoulder range of movement, and evidence of structural abnormalities on ultrasound. PPTs were assessed bilaterally at the Biceps, Acromion, Spina Scapula, C7, Supraspinatus, Coracoid Processus, Infraspinatus, Deltoideus, Extensor Carpi Radialis Brevis, and Quadriceps. Tendon thickness was measured at the Biceps tendon, Supraspinatus tendon (5mm and 10mm), Infraspinatus, Subscapularis, and Subacromial Bursa on ultrasound. Doppler was graded through Newman’s grading scale.

Results: 37 participants completed two sessions with eight weeks between. The average highest pain reported was 7± 1.3 at baseline and 6.2 ± 2.2 after eight weeks. All participants reported structural abnormalities on ultrasound, mostly seen in the Supraspinatus tendon.

Conclusions: This study will provide a visual “heat map” of how spatial sensitivity is distributed in SAPS. Furthermore, it will investigate if quantitative measures of pain are associated with structural abnormalities, which can provide useful clinical information.