Scanning Force Microscopy of the Fine Structure of Cartilage Irradiated with a CO2 Laser.

Alterations of the cartilage matrix structure under non-destructive laser irradiation have been investigated by scanning force microscopy. Porcine nasal septum cartilage was irradiated with a CO2 laser with a power density of 50 W/cm(2) under two different time regimes: for 3 s and for 30 s. Short-time irradiation had little effect on the structure of the cartilage matrix. In comparison with non-irradiated cartilage, small channels of 100-400 nm in cross-section appeared. This observation gives evidence that the underlying mechanism of laser-induced stress relaxation of cartilage is based on short-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 sections 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.