EFFECT OF KTP LASER ABLATION OF ENDOCHONDRAL BONE ON BONE HEALING

The advantages of using a laser to cut a hole in the ossicular chain i nclude increased precision, decreased likelihood of disarticulation, a nd elimination of noise-induced threshold shift associated with conven tional drills. This study was designed to determine optimal energy set tings and cooling technique to minimize tissue injury. Laser ablated h oles were cut in rabbit femurs with different endostat fibers at power settings of 1.6 to 5.0 watts. Comparable burr holes were cut by a hig h-speed drill and the animals were sacrificed at different time interv als. Specimens were evaluated microscopically for tissue injury by the amount of cell necrosis of the surrounding osteocytes, bone marrow ch anges, and denaturation of bone matrix. Changes in healing were assess ed by the production and ossification of the granulation tissue. Laser ablated holes created with 1.6 to 2.0 watts at 2 to 7 days demonstrat ed thermal damage comparable to conventionally drilled holes. At 14 to 28 days these holes demonstrated advanced healing and integrated lame llar bone. In contrast, higher power (>3.5 watts) at 2 to 7 days demon strated significantly more osteocyte loss, marked bone marrow fibrosis , and bone matrix denaturation. At 14 to 28 days these holes showed ev idence of delayed healing and osseous plugs not integrated with the su rrounding bone.