Análise dos mecanorreceptores e terminações nervosas livres da banda anterior do ligamento glenoumeral inferior com imunofluorescência e microscopia confocal

Abstract

The anterior band of the inferior glenohumeral ligament (IGHL) has an important role in the mechanical stability of the shoulder and is considered the main static stabilizer of the shoulder when the arm is in abduction and external rotation. Six anterior bands of IGHL were carefully dissected from the bone attachments to describe the morphology of the mechanoreceptors and free nerve endings and to elucidate the interaction between the proprioceptive system and shoulder mechanics. For immunostaining, a protein gene product 9.5 marker was used as the primary antibody and Alexa Fluor 488 was used as the secondary antibody, followed by image examination using confocal laser scanning microscopy. All the ligament samples contained Meissner corpuscles with a diameter between 30 and 65 μm and length between 80 and 400 μm. This is the first report of these corpuscles in IGHL. Furthermore, these ligaments contained Pacinian corpuscles, with a diameter between 40 and 80 μm and length between 100 and 180 μm, free nerve endings with fiber thickness between 3 and 7 μm and length between 300 and 700 μm, and unclassified nerve endings with irregular, spindle, and rectangular shapes. The mechanoreceptors were approximately 1.2% of the area of the ligament. There was a predominance of Meissner- and Pacini-type rapidly adapting mechanoreceptors. The density of mechanoreceptors was approximately 1.1026%, and the density when the analysis was with a depth between 400 and 500 μm was 1.6102% and greater depth between 1500 and 1850 μm, was 0.6018%. These findings help to elucidate the physiology of shoulder stability, where mechanoreceptors are stimulated by pressure and vibration mechanisms and can explain the neuronal pathophysiology of shoulder instability as a deficient activation of the afferent pathway. However, this hypothesis requires to be confirmed in experimental models.