Structural changes in the distal articular end of the femur in experimental modeling of osteomyelitis

Features of structural changes in the joint components (synovial membrane, articular cartilage, subchondral bone) under the conditions of adjacent limb segment osteomyelitis are poorly understood and require thorough histological studies. Purpose Сomparative assessment of the structural reorganization of the main components of the distal articular end of the femur in experimental modeling of osteomyelitis. Material and methods Objects: distal metaphyses of the femur of intact rats (n = 5) and experimental ones (n = 16) in the conditions of modeled osteomyelitis of the femur. The culture of S. aureus was injected into the medullary canal in the experimental animals (n = 8) while saline was injected in the control group (n = 8). The animals were taken out of the experiment on the 21st day. Methods: histological, morphometric, and statistical methods were used. Results In the control group, the articular cartilage, subchondral bone plate, and subchondral zone retained their normal structure. Synovitis was not revealed. The values of the morphometric parameters were comparable with the intact norm. In the experimental group, bone microsequesters, osteoclastic resorption of the subchondral bone plate, inflammatory infiltration with the content of plasma cells and neutrophils were detected in the subchondral zone. Histological changes in the articular cartilage according to the classification of the International Society OARSI (2006) corresponded to grades 1 to 3 and were accompanied by synovitis. There was a significant (р < 0.05) decrease in the thickness of non-calcified cartilage, a significant twofold decrease in the thickness of the subchondral bone plate, while the values of the thickness of the calcified cartilage exceeded those in the control group and the intact norm. Conclusion Under the conditions of an experimental model of chronic osteomyelitis of the femur, the revealed structural changes in the subchondral zone contribute to the progression of the destruction of the subchondral bone plate, articular cartilage and synovitis. This model of chronic osteomyelitis can be used to experimentally study various therapeutic strategies aimed at modifying subchondral bone remodeling and relieving synovitis.