[Immunohistochemical study on the effect of high tibial osteotomy on the distribution pattern of neuropeptides in the synovium of the osteoarthritic knee].

Synovial tissue was obtained from 18 knees with medial compartmental osteoarthritis (OA) and from 20 knees on which a high tibial osteotomy had been performed. Neuropeptides were stained with a specific avidin-biotin-peroxidase method. Comparisons were made of the incidence of staining as well as the location of staining within the synovia (medial, lateral, and suprapatellar regions). The results showed that the synovium had an extensive neural network of both the somatic and autonomic nervous systems. In the medial synovium of the preoperative knees, the neuropeptides were found in abundance. An especially strong response for substance P (SP) and calcitonin gene-related peptide (CGRP) was observed at the free nerve endings. However, the postoperative incidence of SP-positive free nerve endings was reduced to 54% of the preoperative amount and the inflammation subsided in the medial region. These findings suggested that free nerve endings containing SP might be mainly involved in the inflammation and pain of OA.