INDUCTION OF ARTHROSIS BY LASER-SURGERY

In a controlled experimental trial the induction of gonarthrosis follo wing laser-assisted meniscectomy was assessed. A XeCl excimer laser (l ambda = 308 nm, pulsewidth 20 ns, repetition rate 10-70 Hz, radiant ex posure 10-40 mJ/mm(2)) and a continuous wave Nd:YAG laser (lambda = 10 64 nm, energy density 21-93 W/mm(2)) were employed in connection with 600-mu m and 800-mu m quartz fibers, respectively. In an animal model, effects on the remaining meniscus and the corresponding cartilage sur faces were studied in vivo within an observation period of 6 months. F or evaluation of the pathogenesis in laserinduced arthrosis, morpholog ical and biomechanical studies were performed on native human menisci. Compared to conventional meniscectomy, laser energy effectively preve nts further fibrillation of the meniscal structure. A remodelling of t he meniscus did not occur in any experimental group. The degree of rea ctive synovitis, assessed by macroscopic and histologic scoring, was s ignificantly greater following Nd:YAG laser surgery than after excimer laser resection and conventional surgery (P < 0.05). On X-ray, more p rogression of degenerative changes was observed following laser proced ures than after conventional meniscectomy. The proteoglycan content in the femoral cartilage corresponding to the zone of meniscus resection was significantly lower in the laser group than after conventional me niscectomy (P < 0.01), which substantiates macroscopic and radiographi c findings indicating degenerative derangement of the hyaline cartilag e. On light microscopy and scanning electron microscopy of meniscus sp ecimens, excimer laser irradiation led to well-delineated resection bo rders with a mean transitional zone of 20 mu m, whereas menisci expose d to Nd:YAG laser irradiation presented extensive vaporization zones w ith the surface covered by an amorphous structure. Menisci irradiated by excimer or Nd:YAG laser energy showed significantly increased rigid ity (P < 0.05 and P < 0.01); the maximum value of radial strain at fle xion was lower following Nd:YAG laser irradiation (mean 1.5 +/- 0.3%) and following excimer laser irradiation (mean 2.4 +/- 0.3%) than in no n-irradiated menisci (mean 3.0 +/- 0.5%). These observations lead to t he conclusion that laser-assisted meniscectomy promotes the early mani festation of gonarthrosis by virtue of a reduced femorotibial contact area and alterations in the biomechanical properties of the meniscus.