Reformation of the Synovial Membrane Following Capsulectomy (According to Mori) Performed in the Knee Joint of Rabbits

Abstract

The author studied macroscopically and histologically the process of reformation of the synovial membrane of the knee joints of rabbits in which synovectomy and capsulectomy were performed using as nearly as possible the same as Mori's technique.
Specimen taken at various intervals following surgery was embedded in paraffin and sectioned and stained in a manner similar to that of Key (1925) and Wollcott) 1927).
The technical difference of Mori's Synovectomy from that of Swett or Jones is th at in the former both joint capsule and synovial membrane is removed, whereas in the latter the synovial layer only is removed. In the author's experiments, therefore, contrary to the technique of Swett, the surgical intervention to the knee is more extensive through the capsular layer from the extra- or intra-muscular to sub-periosteal connective tissues.
Our findings in this experiment fall into two groups: one is the reconfirmation of fac ts already established by the old pioneers which includes the following;
1. The reformation of the synovial membrane con be bu ilt in roughly 3 weeks.
2. The reparative process in the capsulectomized and synovectomized knee joint is essentially different from that of the surgical defect in skin or mucous membrane where the wound closure has to be accomplished by the extension of the e pithelial cells surrounding the original defect. In the synovectomized defect, h e lining cells are newly formed by the secondary differentiation of the proliferating co n nective tissue cells which are derived from the bottom of the defect.
The second group is of new findings from this experiment which include the following;
1. The connective tissue participating in the reconstruction of the synovial lining is often derived form the peri-orintra-muscular tissue or sub-periosteal connective tissue located more deeply than the connective tissue in the outer layer ( Stratum fibrosum) of the joint capsule previously pointed out by Key as the single so u r se for synovial reformation.
2. The newly formed membrane is more fibrous in nature than the normal one. We suggest a new concept, however, that the change in the synovial membrane into a more fibrous and less vascular tissue can be regarded as evidence of convertion from an active to inactive (or from sensitive to resistant) tissue. The new synovial membrane therefore would be far less responsive to allergic inflammation. This agrees with our clinical experience that the long term follow up of synovectomized patients rarely if ever show subsequent involvement of the regenerated synovium in new inflammatory process.