THE EFFECT OF NONABLATIVE LASER ENERGY ON JOINT CAPSULAR PROPERTIES -AN IN-VITRO HISTOLOGIC AND BIOCHEMICAL-STUDY USING A RABBIT MODEL

The purpose of this study was to evaluate the effect of laser energy a t nonablative levels on joint capsular histologic and biochemical prop erties in an in vitro rabbit model. The medial and lateral portions of the femoropatellar joint capsule from both stifles of 12 mature New Z ealand White rabbits were used. Specimens were divided into three trea tment groups (5 watts, 10 watts, and 15 watts) and one control group u sing a randomized block design. Specimens were placed in a 37 degrees bath of lactated Ringer's solution and laser energy was applied using a holmium:yttrium-aluminum-garnet laser in four transverse passes acro ss the tissue at a velocity of 2 mm/sec with the handpiece set 1.5 mm from the synovial surface. Histologic analysis revealed thermal altera tion of collagen (fusion) and fibroblasts (pyknosis) at all energy den sities, with higher laser energy causing significantly greater morphol ogic changes over a larger area (P < 0.05). Application of laser energ y did not significantly alter the biochemical parameters evaluated, in cluding type I collagen content and nonreducible crosslinks (P > 0.05) . This study demonstrated that nonablative laser energy caused signifi cant thermal damage to the joint capsular tissue in an energy-dependen t fashion, but type I collagen content and nonreducible crosslinks wer e not significantly altered.