Construction and evaluation of a model of chronic osteomyelitis in sheep tibia

BACKGROUND: The plateau environment affects the immune function and metabolic status of patients with osteomyelitis, leading to acceleration or complication of the disease process. The construction of effective and stable animal models of chronic osteomyelitis is essential for experimental studies of chronic osteomyelitis. OBJECTIVE: To establish a sheep model of chronic osteomyelitis in plateau regions for toxicity assessment and therapeutic research. METHODS: Fifteen healthy sheep were selected in this study. Sodium morrhuate and Staphylococcus aureus suspension were injected into the medullary cavity of the middle segment of the tibia to establish the chronic osteomyelitis model. General observation, body mass and temperature monitoring, blood infection index detection, radiological scoring, and microbial culture were performed for evaluation and analysis. RESULTS AND CONCLUSION: (1) Local tissue swelling and lameness of the affected leg were observed in all sheep in the early stage after modeling, accompanied by varying degrees of anorexia. A slight decrease in body mass was observed in sheep 1 week after modeling, while no significant changes in body temperature were observed. (2) The erythrocyte sedimentation rate significantly accelerated 4 days after modeling (P < 0.05) and gradually returned to normal levels after 1 month. The white blood cell count showed a significant increase within 4 days after modeling and returned to normal after 1 week. The level of C-reactive protein increased significantly after modeling (P < 0.05) and remained significantly higher than normal until the end of the experiment (P < 0.05). (3) Fifteen sheep exhibited typical radiological manifestations of osteomyelitis, including unclear boundaries, irregular osteolytic lesions, and low-density bright absorption areas with interspersed necrotic bone fragments of increased and uneven density. Different degrees of periosteal reaction were observed in the cortex near the lesion. (4) Thirteen sheep were cultured for a single strain of Staphylococcus aureus, while two sheep were cultured for Staphylococcus aureus and Escherichia coli. These findings indicate that a reliable chronic osteomyelitis animal model of sheep tibia can be successfully established in plateau regions by injecting an appropriate amount of Staphylococcus aureus suspension into the medullary cavity of sheep, combined with local implantation of foreign cotton thread and sodium morrhuate.