Neurohistological examination of the inferior glenohumeral ligament of the shoulder.

The neural histology of the anterior band of the inferior glenohumeral ligament (IGHL) was studied in 11 fresh shoulder specimen using a special silver impregnation technique. Between the collagen fibers small myelinated and unmyelinated dendrites could be detected. The appearance of neurovascular structures in the adjacent synovial layer clearly exceeded the typical supply to soft tissues. Analysing about 11,000 sections Ruffini mechanoreceptors that are known to be slow adapting were found on the humeral insertion of the band. The sections containing these neural end organs were identified by means of transillumination and reflection-contrast microscopy and reconstructed using three-dimensional image processing. The presence of neural structures including Ruffini corpuscles in these most important passive stabilizers of the shoulder joint shows that these ligaments function also as an active safety device. There slow adaption is a prerequisite for muscular reflexes counteracting the tensile stresses to which the passive stabilizing structures of the shoulder are exposed. A disruption of the continuity of these structures by mechanical forces or surgery can reduce the biofeedback and proprioceptive quality and thus lead to a decrease of shoulder function and/or stability. These observations should be taken into account when planning surgical interventions involving the IGHL. Procedures like capsule shifts or plications may affect mechanoreceptor orientation and concentrations, thereby affecting the interaction between these structures and the synergistic muscles. When possible, these intervention should avoid receptor-dense regions while attempting to restore normal anatomical orientation and tissue tension.