Neurohistology of the subacromial space.
Subacromial decompression is one of the most commonly performed shoulder procedures. Debridement of the subacromial soft tissues is a critical part of the procedure. However, the extent of soft tissue debridement is not well defined. The purpose of this study was to identify neural elements within the soft tissues composing the subacromial space. Using special immunohistochemical stains and electron microscopy, neural elements were identified within the subacromial bursa, rotator cuff tendon, biceps tendon and tendon sheath, and transverse humeral ligament. There was a significantly richer supply of free nerve fibers in the bursa compared with the other tissues. The nociceptive information relayed by these fibers may be responsible for the pain associated with impingement syndrome.