6th ESACP Congress, Heidelberg, April 7-11, 1999

A151
PRESENTATION OF AN NEW EX VIVO MODEL USING CONFOCAL MICROSCOPY TO ASSESS LASER INDUCED CARTILAGE INJURIES
Weiler Ch 1 3 4, Frenz M 2, Schaffner T 1, Mainil-Varlet P 1

1) Inst.Pathology, University Bern, 2) Inst.Applied Physics, University Bern, 3) Hôpital Cantonal de Fribourg, Orthopedic Dept, Switzerland, 4) Inst.Pathology, LMU-University Munich, Germany

INTRODUCTION: Although there is an increasing popularity of lasers in orthopaedic surgery there is a growing concern about negative side effects of this therapy e.g. prolonged restitution time, radiation damage to adjacent cartilage or depth effects like bone necroses. Despite case reports and experimental investigations in the last few years little is known about the extent of acute cartilage damage induced by different lasers types and energies. Histological examination offers only limited insights in cell viability and metabolism. Ho:YAG and Er:YAG lasers emitting at 2.12 and 2.94 µm, respectively, are ideally suited for tissue treatment because these wavelengths are strongly absorbed in water (claim to lower the risk of iatrogenic cartilage damage). The purpose of the present study is to evaluate the effect of laser type and energy on chondrocyte vitality in an ex vivo model. Free running Er:YAG (E=100/150 mJ) and Ho:YAG (E=500/800 mJ) lasers were used at a fixed pulse length of 400 µs. RESULTS AND CONCLUSIONS: Although the energy is lower, cartilage ablation was 3 times higher with Er:YAG laser than with Ho:Lasers. Thermal damage - as assessed with the life and death cell viability test - was much higher with Ho:YAG than with Er:YAG lasers. The extent of thermal injury was as deep as 1800 µm with Ho:YAG and 70 µm with Er:YAG. Confocal microscopy is a powerful tool for assessing changes in tissue structure after laser treatment. In addition this technique allows us to quantify these alterations in a temporal and spatial resolution without using animal experiments.