Histomorphological findings on proprioception in the shoulder

Purpose of this study was the evaluation of distribution and morphology of mechanoreceptors in the glenohumeral joint capsule and rotator cuff in comparison to the coracoacromial ligament by means of specific immunfluorescence microscopy. The complemente joint capsules, rotator cuffs and coracoacromial ligaments of three fresh cadaver shoulder were harvested. Serial cryostate sections were taken and alternately incubated with antiserum against neurofilament, lamin or myelin of peripheral nerves. The antibody-reaction was visualized with fluorescin Ig-G. The nerve endings were photographed and computer-aided 3-dimensional reconstructions were performed. Three types of corpuscular and free nerve endings of different morphology were found in different distributions: whereas the Ruffini corpuscles were much more frequent in the coracoacromial ligament and rotator cuff, Pacini endings were predominantly found in the joint capsule. Generally corpuscular nerve endings were more frequent in the coracoacromial ligament and the rotator cuff than in the antero-inferior capsule and the number of corpuscles increased from medial to lateral within the anterior and inferior parts of the capsule. The dense ligamentous tissue was almost aneural whereas the periarticular fatty or loose connective tissue contained nerve fibres and nerve endings. In view of the results of other experimental and clinical studies the high frequency of Ruffini and Pacini endings in the rotator cuff and coracoacromial ligament suggest, that both are involved in the neurosensory control of glenohumeral stability and subacromial impingement. In contrast our findings in the joint capsule do not clearly proove, that those joint receptors predominantly maintain joint stability.