Analysis of mechanoreceptors and free nerve endings in the lateral collateral ligament of the elbow using immunofluorescence and confocal microscopy.

Abstract

The lateral collateral ligament (LCL) of the elbow is an essential static stabilizer against varus and posterolateral rotatory forces. It is hypothesized that injury to the LCL might impair elbow proprioception, although direct evidence for this impairment remains limited and warrants further investigation. This study aimed to describe the morphology and distribution of mechanoreceptors and free nerve endings within the LCL. Twenty ligaments were obtained from 10 fresh cadavers, in compliance with local legislation. Each ligament was measured, weighed, and sectioned. Histological integrity was confirmed using hematoxylin-eosin staining on 10 μm sections, while 50 μm sections underwent immunofluorescence with protein gene product 9.5 as the primary antibody and Alexa Fluor 488 as the secondary antibody, followed by analysis with a confocal laser scanning microscope (Zeiss LMS 710). The LCL was identified in 100% of dissections, with an average length of 36.2 ± 3.4 mm, width of 9.5 ± 2.24 mm, and weight of 0.8 ± 0.13 g. Hematoxylin-eosin staining revealed dense, organized collagen fibers and vascular tissue. Type I (Ruffini-like) and type IV (free nerve endings) mechanoreceptors were identified, along with unclassified nerve endings. These findings suggest a potential additional role for the LCL in proprioception, highlighting the possible importance of neural structures preservation. However, further clinical studies are necessary to determine the actual functional impact beyond mechanical stabilization.