骨科金属置入物并发感染的动物模型构建方法及效果评价

目的]构建一种基于钛合金置人物的兔胫骨金黄色葡萄球菌感染模型,并探讨不同菌液浓度在模型制备中的作用.方法]48只新西兰大白兔随机分成5组,4个实验组每组10只,对照组8只.在胫骨结节内侧钻孔后,向各实验组动物胫骨髓腔内注入浓度分别为1.0 ×105、1.0×106、1.0×107、1.0×108 CFU/ml的ATCC25923金黄色葡萄球菌悬液.然后在髓腔内置入长4.0 cm,直径0.25 cm钛合金棒.对照组注入等量生理盐水后置入相同规格的钛合金棒.术后4周通过肢体外观、体温测量、影像检查、微生物学检测和组织学分析,评价感染模型建立情况,筛选最佳细菌浓度.结果]术后动物患肢早期局部软组织肿胀,出现跛行,体温呈现2周内明显升高、之后逐渐下降的趋势.术后4周实验组动物放射学显示不同程度骨膜反应,皮质溶解,死骨形成及软组织肿胀等表现.细菌培养结果显示注入的细菌浓度越高,感染越严重,其中C、D组感染率均为100％,高于A、B组；D组死亡率最高.4周组织切片出现骨髓纤维化、坏死骨片等感染表现.结论]适当浓度的金黄色葡萄球菌菌液髓腔注射联合钛合金棒置入可以构建稳定的兔长骨感染模型,此为骨科金属置人物并发感染的防治研究奠定了基础.

Establishment and evaluation of a metallic implant-related infection model in orthopedics

Objective]To develop a titanium implant-related infection model(IRIM) in rabbit tibia with staphylococcus aureus,and analyze the relationship between the concentration of inoculums and the development of infection in the model.Method]Forty-eight New Zealand rabbits were randomly divided into 5 groups.There were 10 rabbits in the experimental group A,B,C and D,while 8 rabbits in the control group.In the experimental groups,the serial dilutions of the bacteria of S.aureus ATCC25923 105 to 108 colony-forming units(CFU)/ml] suspended in saline were inoculated into the medullary cavity of the animals,after drilled a hole in the medial surface of the tibial tuberosity,then a titanium cylinder(4.0 cm length and 0.25 cm diameter) was put into the medullary cavity.While in the control group,the same volume of saline was inoculated and then the same size of titanium cylinder was implanted.The efficiency of the experimental IRIM in rabbit was evaluated by clinical,radiologic,microbiologic and histological parameters at the 4th week after the operation,and then an optimal concentration of the bacteria inoculated was chosen.Result]Clinical progression was observed by the postoperative swelling of the local soft tissue,a postoperative limp that subsided in all rabbits,and a significant increase in body temperature within the early two weeks and then had a decrease.There were varying degrees of periosteal reaction,osteolysis,sequestrum formation and soft tissue swelling in the experimental groups at the 4th week after the operations on radiology.Bacteriological culturing showed that the severity of infection was aggravated in the experimental groups,with the increase of the concentration of inoculums.The infection rate of group C and D was 100%,which was higher than in the groups A and B.While there was the highest mortality in the group D.Intramedullary fibrosis and sequestrum formation indicated infection on histology at the 4th week after the operations.Conclusion]A stable infection model in the long-bone of rabbit can be induced by using inoculation of a proper concentration of S.aureus suspension in saline and titanium cylinder implanted into the medullary cavity.This novel,reproducible experimental model will facilitate the study of new prophylaxis and therapeutic modalities of metallic implant-related infection in orthopedics.