The clinical impact of laser-assisted synovectomy was investigated in a two-part study consisting of a morphological part with morphometric measurements and an in vivo part using an animal model. A continuous wave Nd:YAG laser (Z = 1064 nm; power density 18-106 W/mm2; exposure 0.5-5 s) and a XeC1 excimer laser (7, = 308 nm; pulsewidth 20 ns; repetition rate 10-70 Hz; energy density 2045 mJ/mm2; exposure 10-60 s) were employed in combination with a fused silica fiber with diameters of 600 ~tm and 800 gm, respectively. In vitro study.
Under light microscopy, synovium exposed to Nd:YAG laser energy presents a transitional band (with a mean diameter of 2 mm) with three zones: a carbonized area, a vesicular zone, and a coagulated part. In contrast, pulsed UV-laser irradiation leads only to a narrow transitional zone extending 10-70 gm. Scanning electron microscopy reveals a clear-cut surface following excimer synovectomy, whereas Nd:YAG laser irradiation forms an irregular surface with numerous bursts due to vaporizing activity. In vivo study. Partial synovectomy of the knee joint was performed in two groups of 14 New Zealand white rabbits with a 1064-nm Nd:YAG laser and a 308-nm XeC1 excimer laser. Another 14 animals synovectomized in a conventional technique served as a control. Morphological examination and histopathological scoring of the synovial membrane were performed 4 days to 6 months after the operation. The progress of synovial regeneration following excimer laser synovectomy did not differ from observations in the control group. However, Nd:YAG laser irradiation led to a significantly delayed formation of a "neosynovium". In addition, Nd:YAG laser application provided an efficient hemostasis. In conclusion, the Nd:YAG laser is a suitable instrument for synovectomy and is superior to conventional techniques, as it provides J. Raunest (N~) โข E. Derra Abteilung ftir Allgemein-und Unfallchirurgie,