Thermally induced shrinkage of joint capsule.

Thermal shrinkage of collagen currently is being used in orthopaedic surgery to treat ligamentous laxity. Understanding the kinetics of collagen shrinkage is key to revealing the events that take place during application of thermal energy. To elucidate the thermokinetic properties of collagen, punch biopsies of bovine joint capsule were immersed in a heated saline bath at temperatures between 20 degrees and 90 degrees C for periods up to 60 minutes. The resulting tissue thermal shrinkage was measured by the change in the cross-sectional area of the specimens. Only a small amount of shrinkage occurred at temperatures below 63 degrees C, and increasing amounts and rates of shrinkage were seen at temperatures between 63 degrees and 72 degrees C. The denaturation kinetics of bovine knee collagen, which could be described by a first order reaction rate, had an activation energy of 2.3 x 10(5) kJ/mol.