The knowledge that pain and effusion in joint disease originate from the synovial membrane has led to the use of methods aimed at eliminating this synovium in various types of arthritis. Chemical synovectomy can delay or render unnecessary the need for surgery. Osmic acid (Os 04) for this purpose was first used in 1951 by von Reis and Swensson. Since then, many studies were under-taken to evaluated the effects of osmic acid on the synovial membrane. But the synovial change and synovial regeneration has not been clearly clarified.
It is the goal of this study to observe the sequential process of degeneration-regeneration of synovial membrane and to evaluate the pattern of deposition of the osmic acid on it.
The author injected 1.Oml of 1 % osmic acid to 50 rabbit´s knee separately. Then the synovial changes were observed grossly, light microscopically and transmission electron microscopically. The following results were obtained.
1. Grossly, the colour of the synovium turned dark brown one day after injection, and the degree of the discoloration became lighter with time. The synovium became thicker. There was edema around the joint through the whole period.
2. Microscopically, most synovium were necrotic at the early phase, but a few remaining svnoval cells were observed electron microscopically. With time, the fibrosis was more progressed and the inflammatory reaction was slightly decreased.
3. At the second week, there were layers which were composed of the synovial like cells. The regeneration process was almost completed at the sixteenth weeks.
4. Osmic acid was deposited in the synovial tissue from the one day after injection. It was slightly diminished in the amount of osmic acid with time, but some osmic acid still observed at the end-of the experiment, 16 weeks.
It has been postulated, based on the results of this experiment, chemical synovectomy using osmic acid can be used for temporary synovectomy effect lasting several months, but the residual hyper-trophy of synovial and periarticular tissue could be a problem on joint mobility.
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