Hip osteoarthritis - histopathological aspects.

Osteoarthritis is a complex, degenerative disease that can affect all the anatomical structures of the synovial joints. Most frequently, the joints of the hand, hip, and knee are affected, especially in the elderly patients. In our study, we evaluated 27 femoral heads, examining the histopathological changes that occurred in the articular cartilage, subchondral bone, and perisynovial soft tissues. At the level of the articular cartilage, there were observed a reduction in thickness, deformation of the articular surface, degradation of the cartilaginous matrix, the occurrence of fissures or fractures in the cartilaginous piece, a reduction in the number of chondrocytes, and changes in their morphology. In the subchondral bone, a rarefaction of the bone trabeculae and a reduction in their thickness were observed, along with an increase in the size of the alveolar cavities. These changes were accompanied by the formation of cystic cavities, non-homogeneous hypertrophy of the subchondral bone plate as a response to the reduction in thickness and change of the articular cartilage structure, or the reduction in the thickness of the subchondral bone plate. The trabecular bone exhibited an atrophic endosteum, absence of bone remodeling processes, cracks or even fractures in the trabecular bone. Likewise, we observed rare ectopic osteogenesis processes, either endochondral or desmal ones, forming osteophytes. The synovium and perisynovial connective tissue contained immune cells, vascular endothelial cells, fibroblasts, adipocytes, and other mesenchymal-derived stromal cells. The immunohistochemical study highlighted the presence of T-lymphocytes, B-lymphocytes, and macrophages, cells capable of synthesizing and releasing matrix metalloproteinases that are involved in the degradation of the articular cartilage. Exploration of cell proliferative capacity using the proliferating cell nuclear antigen (PCNA) showed that, in the articular cartilage, there are few cells (chondrocytes) capable of proliferation, while in the synovium there are numerous young fibroblasts capable of mitotic division.