Mechanoreceptors distribution in the human medial collateral ligament of the elbow.

BACKGROUND: The human elbow maintains its stability mainly through its bony structure. Stability is enhanced by ligamentous structures. To allow the ligamento-muscular reflex, which protects against strain and stress, mechanoreceptors are embedded in the ligament. This report describes the existence and the distribution of the elbow medial collateral ligaments (MCLs) mechanoreceptors. HYPOTHESIS: The bony attachment site has the highest density of mechanoreceptors, and the anterior part has the highest density of mechanoreceptors. MATERIALS AND METHODS: Eight MCLs of elbow from fresh frozen cadavers were used. The MCLs were harvested deep to the periosteum from the medial epicondyle to the ulna. The fan-shaped ligaments were divided into six regions of interest (ROI) and stained with modified gold chloride stain. Specimens were evaluated under a light microscope. Golgi, Ruffini, and Pacinian corpuscles were found in every specimen. The number and the distribution of each mechanoreceptor in each ROI were recorded. The density of each mechanoreceptor was calculated in regards to its volume. RESULTS: Golgi, Ruffini, and Pacinian corpuscles were seen in the ligament with small nerve fibers. Ruffini corpuscles had the highest median density of all three corpuscles. The median corpuscle density was higher in the anterior than in the posterior part and higher in the bony attachment than in the mid-substance site except for Golgi corpuscle. CONCLUSION: The three typical types of mechanoreceptors were identified in human MCL with the anterior part and bony attachment as the dominant distribution site. LEVEL OF EVIDENCE: Basic Science Study.