Matrix Assessment of the Articular Cartilage Surface After Chondroplasty With the Holmium:YAG Laser

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Abstract
The goal of this study was to evaluate, histologically and biochemically, repair of the articular cartilage in a rabbit joint after the use of the holmium:yttrium-alumi num-garnet laser in a cartilage chondroplasty model. In 30 New Zealand White rabbits, chondroplasty was per formed with the laser at an intensity of 0.8 J at a rate of 10 Hz. The animals were sacrificed 12 weeks after surgery. Histologically, the safranin O staining index of proteoglycan correlated well with the biochemical re sults, illustrating a decrease of proteoglycan in the repaired articular cartilage after laser articular cartilage chondroplasty. The damaged articular cartilage sur face after the laser application was extensive. The damaged area observed was gradually distributed along the radius from the central point of the laser beam application. Biochemically, the amount of glycos aminoglycan in the repaired tissue (8 ± 2 mg of hex osamine per gram of dry cartilage) was statistically less when compared with that in the sham-treated tissue (40 ± 5 mg). The amount of sulfate incorporated into proteoglycans was 8 to 10 times less in the chondro plasty model compared with the control, suggesting that cell viability was greatly reduced in the treated tissues or expression of proteoglycans was greatly reduced. In the subchondral area, histologic evaluation showed the lack of osteocytes in lacunae of the bone tissue after use of laser energy. The architecture of the subchondral bone in the chondroplasty area was dam aged, with damage also seen in the membranes of the blood vessels.