THE THERMAL-PROPERTIES OF BOVINE JOINT CAPSULE - THE BASIC SCIENCE OFLASER-INDUCED AND RADIOFREQUENCY-INDUCED CAPSULAR SHRINKAGE

Orthopaedic surgeons have recently adapted the holmium:yttrium-aluminu m-garnet (YAG) laser for the shrinkage of capsular tissues for treatme nt of glenohumeral instability. The molecular mechanism of capsular sh rinkage has not been documented to date. This study examined the effec ts of heating on bovine calf knee capsule and subsequent shrinkage of the capsule. Capsule specimens were placed in a saline bath at tempera tures ranging from 55 degrees to 75 degrees C for 1, 3, 5, and 10 minu tes. Shrinkage was quantified by digital imaging, and the tissue was e xamined by light and polarized light microscopy. Tissue contraction wa s not measurable al or below 57.5 degrees C. At 60 degrees C, tissue s hrinkage occurred with corresponding basophilic staining and loss of b irefringence in collagen fibers. For specimens heated at 60 degrees C and 62 degrees C, shrinkage directly correlated with duration of therm al exposure. Maximal shrinkage of approximately 50% in length occurred at and above 65 degrees C with thermal exposures of 1 minute or great er. This study demonstrates that thermal shrinkage of bovine knee caps ule correlates with denaturation of collagen fibers and depends on bot h time and temperature. Capsular shrinkage treatments may be performed with any energy source that is capable of well-controlled heating of capsular tissue and does not depend on the special properties of laser light.