EXCIMER LASER ABLATION OF FIBROCARTILAGE - AN INVITRO AND INVIVO STUDY

To date, lasers have found only limited applications in orthopedics. We employed a 308 nm XeCl excimer laser for ablation of fibrocartilage, in order to investigate the feasibility of excimer laser assisted meniscectomy. Experiments were conducted both in vitro and in vivo. For the in vitro study, human menisc, obtained during surgery and autopsy, were irradiated via a 600-mu-m core fiber at radiant exposures ranging between 20 mj/mm2 and 80 mj/mm2, at 20 Hz. Ablation rate measurements and histological analysis of the samples were performed. The ablation rates were found to range from 3-mu-m/pulse to 100-mu-m/pulse depending on the radiant exposure and/or the applied pressure on the fiber delivery system. Thermographic analysis was also performed during pulsed excimer as well as CW Nd:Yag and CW CO2 laser irradiation. Temperatures were lower for excimer laser (T(max) < 65-degrees) than CW ND:Yag (T(max) < 210-degrees) or CW CO2 (T(max) < 202-degrees) laser. For the in vitro study, medial meniscectomy was performed in 15 rabbits with the excimer laser and a CW Nd:Yag laser in the right and left knee respectively. Excimer laser irradiation was performed at 70 mj/mm2. Nd:Yag irradiation was performed via a 600-mu-m core fiber at power outputs between 20 to 40 W for 10 and 20 seconds duration. The healing response to injury was investigated by histological analysis of the menisci after 1 day, 1, 2, 4, and 8 weeks following the laser procedure. Excimer laser treated menisci showed less inflammatory reaction and noticeable repair with minimal inflammatory response. Carbonization, induced in the Nd:Yag treated menisci remained up to 8 weeks and only minimal healing was observed. The results suggest that, with the development of an appropriate delivery system, excimer laser ablation may be useful in arthroscopic meniscectomy.