Matrix assessment of the articular cartilage surface after chondroplasty with the holmium:yttrium-aluminum-garnet laser. A long-term study.

A long-term in vivo study was performed to assess biochemical changes after laser repair of articular cartilage. Forty New Zealand White rabbits were sacrificed 26 weeks after undergoing an articular cartilage chondroplasty with use of a holmium:yttrium-aluminum-garnet laser at 0.8 joules per pulse and a rate of 10 Hz. Glycosaminoglycan content in the repaired tissue decreased significantly with both perpendicular (19.59+/-5.6 microg hexosamin/mg of dry tissue) and tangential delivery (14.78+/-4.5 microg/mg) compared with the sham-treated tissue (39.6+/-5.0 microg/mg). Cellular viability was also significantly decreased. Sulfate incorporation was decreased to 203+/-142 cpm/mg of dry cartilage in the tangential mode and 461+/-209 cpm/mg in the tangential mode, compared with the sham at 1845 cpm/mg. Uptake of [3H]thymidine decreased to 463+/-473 cpm/mg of dry tissue and 455+/-170 cpm/mg in the tangential and perpendicular modes, respectively, compared with 2465 cpm/mg in the sham tissue. There were no significant differences between the tangential and perpendicular delivery modes in any assessments performed. The shortterm chondrocyte destruction previously noted in a 12-week study after laser treatment was not reversed during a longer-term 26-week study, and cellular viability was not recovered, suggesting that the loss of chondrocyte function may be permanent.