Scanning force microscopy of the fine structure of cartilage irradiated with a CO2 laser

Alterations of the cartilage matrix structure under non-destructive laser i rradiation have been investigated by scanning force microscopy. Porcine nas al septum cartilage was irradiated with a CO, laser with a power density of 50 W/cm(2) under two different time regimes: for 3 s and for 30 s. Short-t ime irradiation had little effect on the structure of the cartilage matrix. In comparison with non-irradiated cartilage, small channels of 10-400nm in cross-section appeared. This observation gives evidence that the underlyin g mechanism of laser-induced stress relaxation of cartilage is based on sho rt-time depolymerisation and subsequent re-formation of proteoglycan units. The 30 s laser treatment results in melting and denaturation of the matrix . For the first time, small crystals, 100-800 nm, were found on cut section s of the laser treated cartilage. The crystals mainly consist of resolvable sodium carbonate. Thus, they cannot be responsible for the formation of a stable cartilage configuration after laser treatment.