Function of the glenohumeral ligaments in active stabilisation of the shoulder joint

The joint capsules and the glenohumeral ligaments of 12 human shoulder specimens were histologically investigated by light microscopy. Serial sections of 15 microns thickness were cut. The tissue was stained following the haematoxylin-eosin and van Giesson techniques. For specific identification of neural elements we made use of a special silver impregnation technique, described by Novotny, for staining axons in peripheral nerves. Axons of different diameters ranging from 0.2 microns to 70 microns were discovered within the ligaments. Close to the humeral site we found small nerves forming neurovascular bundles. Within their connective tissue sheaths, the axons exhibited a serpentine configuration, which may give extra length and may allow stretching of the nerve during motion. Most of the axons discovered were located in the subsynovial layer of the ligaments. In general the diameter of these subsynovial axons did not exceed 10 microns. In addition to these axonal structures, we detected nerve endings which can be classified according to Freeman and Wyke as type II mechanoreceptors (Pacinian corpuscles). These mechanoreceptors had a diameter of approximately 150 microns. They were also positioned directly beneath the synovial membrane and close to the humeral site of insertion of the ligaments.

The described neural structures in the glenohumeral ligaments are of particular clinical importance in the light of the high incidence of recurrent shoulder dislocation and concomitant Bankart lesions. The mechanoreceptors located in the glenohumeral ligaments may control the stabilising shoulder musculature. On this premise, rupture or detachment of these ligaments will lead to a loss of a feedback mechanism.