title: The effects of immobilization on the ultrastructure and mechanical properties of the medial collateral ligament of rats.
abstract: Rat medial collateral ligaments from one group of animals were tensile tested following immobilization. Ligaments from a second group of animals were examined using transmission electron microscopy to determine collagen fibril cross-sectional area and density. Immobilized and contralateral control ligaments were compared to determine the effect of immobilization on these parameters. There was a significant decrease in the linear stress, maximum stress, and stiffness of immobilized ligaments. There was no significant difference in the strain values reported. There was a significant decrease in the proportion of smaller, cross-sectional area fibrils (0-10,000 nm2) following immobilization. There was also a significant increase in the proportion of larger (30,000-40,000 nm2 and 40,000-50,000 nm2) fibrils following immobilization. This finding was attributed to a decreased synthesis and decreased degradation of collagen during immobilization; post-immobilization, the density of collagen fibrils in the ligament decreased. There may be a relationship between ultrastructural and mechanical alterations following immobilization. Significant clinical implications are apparent in the altered mechanical properties following immobilization.
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D006614:Hindlimb; D007103:Immobilization; D007719:Knee Joint; D008023:Ligaments, Articular / Q000502:physiology / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D051381:Rats; D011919:Rats, Inbred Strains