[Morphologic, biomechanical and experimental in vivo studies of laser-assisted meniscus resection].

Arthroscopic meniscectomy is associated with an irregularly shaped resection rim leading to further degeneration and a considerable rate of iatrogenic lesions to the adjacent cartilage. In a controlled experimental trial the clinical value of laser-assisted meniscectomy was assessed with special reference to whether laser application can overcome these common shortcomings of conventional surgery. An XeCl excimer laser (lambda = 308 nm, pulsewidth: 20 ns, repetition rate: 10-70 Hz, radiant exposure: 10-50 mJ/mm2) and a continuous wave Nd:YAG laser (lambda = 1064 nm, energy density: 21-93 W/mm2) were used with 600 microns and 800 microns quartz fibers, respectively. The study comprised an analysis of morphological and biomechanical characteristics of the meniscus exposed to laser treatment and an evaluation of reparative and degenerative changes following laser meniscectomy in an animal model. Light microscopy and scanning electron microscopy showed that excimer laser irradiation leads to well delineated resection borders with a transitional zone measuring 20 microns. Specimens exposed to Nd:YAG laser irradiation present extensive vaporization zones with the surface covered by an amorphous structure. Menisci irradiated by excimer or Nd:YAG laser energy show increased stiffness; the maximum value of radial strain at flexion is reduced, with a mean value of 1.5 +/- 0.3% following Nd:YAG laser irradiation and a mean value of 2.4 +/- 0.3% following excimer laser irradiation, compared with 3.0 +/- 0.5% in nonirradiated menisci. In vivo experiments show that laser energy prevents fibrillation of the menisceal structure, which was common in the control group; menisceal regeneration was not observed in any of the experimental groups. The extent of cellular infiltration in the synovial membrane is significantly increased following laser meniscectomy, indicating reactive synovitis (P < 0.05). Radiographs show enhanced progression of degenerative changes following laser surgery compared with conventional menisectomy; measurements of the subchondral bone density in the tibial plateau reveal significantly increased density following Nd:YAG (P < 0.01) and excimer laser irradiation (P < 0.05), confirming these observations. The proteoglycan content in the femoral cartilage corresponding to the zone of meniscus resection is significantly lower in the laser group than in the group subjected to conventional meniscectomy (P < 0.01). These results have various implications for clinical practice.(ABSTRACT TRUNCATED AT 400 WORDS)