The supraspinatus fascia: a consistently two-layered structure with nociceptive innervation and differential functional anatomy

PURPOSE: Pain in the scapular region is a common musculoskeletal complaint, yet its anatomical basis often remains unclear. This study investigates the supraspinatus fascia as a potential contributor to shoulder pain, with particular emphasis on its surgical relevance. METHOD: A total of 24 body donors were examined using dissection and histological analysis to characterize the fascia's morphology, topography, and neurovascular features. RESULTS: The supraspinatus fascia consistently demonstrated a distinct two-layered architecture. Both layers showed considerable interindividual variability, ranging from thin and translucent to dense and collagen rich. There is an interposed fat layer between the superficial and deep fascial layer suggesting a potential sliding interface. The fascia forms a tubular sheath around the supraspinatus muscle, attaching to the margins of the supraspinatus fossa as well as the superior transverse scapular ligament, clavicle, and coracoid process. The deep layer is continuous with the subacromial bursa and the posterior origin of the supraspinatus muscle. In contrast, the superficial layer integrates into surrounding fascial systems, including connections to the fasciae of the levator scapulae and rhomboid minor muscles. Histological analysis identified neurovascular bundles within and traversing both fascial layers. A subset of nerve fibres showed substance P immunoreactivity, supporting a nociceptive role of the supraspinatus fascia. CONCLUSION: The supraspinatus fascia is a complex structure rather than a passive wrapping. Its distinct two-layered architecture and substance P-positive innervation provide an anatomical basis for idiopathic scapular pain. Clinically, the deep layer's continuity with the subacromial bursa suggests that inadequate fascial release during subacromial decompression may lead to persistent symptoms. Finally, the superficial layer's connection to the "levator-rhomboid-minor-fascia" establishes a myofascial bridge for force transmission, suggesting that "shoulder pain" could be a manifestation of cervicoscapular fascial tension.