OPTICAL-PROPERTIES OF HUMAN ARTICULAR TISSUE AS IMPLICATION FOR A SELECTIVE LASER APPLICATION IN ARTHROSCOPIC SURGERY

Background and Objective: Optical density of normal and pathological h yaline cartilage, meniscus, and synovium is determined using native an d laser-irradiated tissue samples in order to examine potentials for a selective laser ablation. Study Design/Materials and Methods: One hun dred forty-four autopsy specimens were irradiated in a direct contact mode using a XeCl excimer laser (lambda = 308 nm; 20 ns; 40 Hz; 40 +/- 2.1 J/mm(2); 800 mu m fused silica fiber) and a continuous-wave Nd:YA G laser (lambda = 1,064 nm; 1 s; 124 +/- 5.4 W/mm(2); 600 mu m fused s ilica fiber). Transmission spectra were obtained by microspectrophotom etry in a spectral range from 250 to 770 nm. Results: In the ultraviol et spectrum analyzed, optical density (OD) is calculated to 0.81 +/- 0 .05 for native hyaline cartilage, to 1.0 +/- 0.07 for meniscal tissue, and to 0.68 +/- 0.04 for synovium. With increasing wavelength the OD steadily decreases reaching mean values of 0.06 +/- 0.01, 0.13 +/- 0.0 3, and 0.15 +/- 0.04 at 750 nm. Compared to normal tissue degeneration of cartilage and meniscus lead to a significant increase in OD with a maximum relative OD of 4.39 and 1.26, respectively (P < .001 and P < .01). In synovitis the OD increases with a maximum ratio of 1.45:1 (P < .01). Following Nd:YAG; laser exposition the OD of the coagulated zo ne exceeded the value of native tissue by a factor of 9.71 for cartila ge, 4.71 for meniscus, and 3.04 for synovium (P < .001). Excimer irrad iation leads to a 3.38-fold increase in OD for cartilage, 2.23-fold fo r meniscal tissue, and 1.6-fold for synovium (P < .01). Conclusion: Th e results presented indicate that a preferential ablation of pathologi cal tissue structures in articular surgery is possible by selecting la ser systems with an appropriate spectral emission range. However, ther mal laser tissue interaction may lead to severe alterations in optical properties reducing potentials of a preferential or selective laser a pplication. (C) 1995 Wiley-Liss, Inc.