Collagen fiber sliding during ligament growth and contracture.

It is hypothesized that the sliding of collagen fibers past one another plays an important role in changes of ligament length during growth or contracture. To explore this possibility, we used the fluorescent dye dichlorotriazinyl fluorescein to stain collagen fibers perpendicular to their orientation in a rat medial collateral ligament model. Growth, contracture, and control models (with rats weighing 50-75 g in the first and 500-600 g in the latter two groups) were studied. In the contracture model, the medial collateral ligament was transected distally. Marking sutures were used to verify the presence of growth or contracture in each medial collateral ligament. Fluorescence photomicrography after 2 weeks demonstrated stained collagen fibers protruding from either side of the original mark as one would expect, in either growth or contracture, if the fibers slid past one another and away from their initial location during changes in length. By measuring the initial and final widths of the growth and contracture model marks and correlating them to controls that had minimal growth (rats grow throughout their life) and were free of contracture, we have provided evidence that collagen sliding plays a significant role in changes in ligament length.