[Bone atrophy in rheumatoid arthritis--a morphological and histometrical study of proximal tibial condyles].

A qualitative and quantitative histological study of the proximal tibial condyles was performed to elucidate the features of the bone atrophy in rheumatoid arthritis. Undecalcified, methyl-methacrylate embedded sections were prepared from 21 cases of rheumatoid arthritis, 3 cases of osteoarthritis and 3 cases of non-arthritic subjects. The rheumatoid bone marrow was classified into three layers according to its morphological features. The first layer was pannus, the second was fibrofatty bone marrow and the third was fatty bone marrow. This third layer was used for this study. The characteristic finding in the rheumatoid bone marrow was their inflammatory changes observed in arterioles and venulocapillary beds. The trabecular bones were sparse and thin, and resorption surfaces associated with osteoclasts were increased, whereas osteoblastic activity on osteoid surfaces seemed to be inhibited. These findings may have consequently resulted from the inflammatory changes of vessels around the trabeculae. Inflammatory exudates from venulocapillary beds may stimulate the production of osteoclasts, while stenotic vascular change caused by arteriolitis may reduce the intramedullary blood flow, so that inhibition of osteoblastic activity and retardation of mineralizing process at osteoid surfaces may occur in rheumatoid bone.