Establishment Of Tibia Chronic Osteomyelitis Model Of SD Rat And Effect Assessment

Objective:To establish a stable and reproducible tibia chronic osteomyelitis model of SD rat with a relative simple method.Method:30 SD rat were randomized divided into experimental group(n=20)and control group(n=10).After anesthesia by intraperitoneal injection of 3%sodium pentobarbital solution,the right hind leg were accepted pre-operative skin preparation,sterilization by iodine,then covered with aseptic towel.After finished these preoperative preparation steps,a 0.5 cm longitudinal incision was cut at proximal metaphysis of right tibia,expose the bony cortex,drilling a hole electric drill and kirschner wire at the site of 0.5cm inner/under side of tibial tubercle.After well preparation of bony hole,we injected 0.1ml 5%sodium morrhuate and inoculated 0.1 ml 2 × 108/ml CFU suspension liquid of standard staphylococcus aureus(strain:ATCC25934)in the medullary cavity of right tibia of experimental group.As a control study,the medullary cavity of right tibia of control group were injected in 0.1ml 5%sodium morrhuate and inoculated 0.1ml isotonic saline solution.We observe the weight of rat,gross infection situation of local site,and the X ray performance of right tibia at 1 week and 3 week post-operation.All the X ray performance were independently evaluated score by radiologist according to the Norden score.We select 5 rat at random respectively from two groups at 1 week post-operation to sacrifice it with excessive amounts of anesthetics,then we harvest the right tibia sample for histopathological H&E staining analysis and harvest the soft tissue around the local site for microbiology bacteria culture.At the time of 3 week post-operation,we sacrifice all the rest animals at both groups to harvest the right tibia sample for histopathological H&E staining analysis and harvest the soft tissue around the local site for microbiology bacteria culture.All the statistic analysis were conducted by IBM SPSS 19 version software.The comparison of rat weight between experimental group and control group at 1 week and 3 week post-operation were made by Repeated measure analysis of variance.The comparison of X ray performance Norden score of right tibia between experimental group and control group at 1 week and 3 week post-operation were conducted by the method of Mann-Whitney U nonparametric test of two independent sample tests.The comparison of X ray performance Norden score of right tibia between 1 week and 3 week of two groups were made by the method of nonparametric test Wilcomxon matching operator rank test.Result:1 week post-operation:the rat weight of the experimental group was significantly lighter than the control group.All the animal in experimental group showed obvious infection in surgery site,the incision were not union.The incision were basically union in animal of control group.The X ray performance of experimental group showed high light shadow in the medullary,light periosteal reaction,without obvious bone defect and sequestrum,Norden score were 1.15 ± 0.587.But the X ray performance of control group were similar to the normal side,Norden score were 0.30 ±0.483.The Norden score in experimental group were significantly higher than control group.The result of histopathological H&E staining analysis of tibia bone sample of experimental group showed that we can see a large number of inflammatory cells and periosteal proliferation.There was a few inflammatory cell in the result of H&E staining in tibia bone sample of control group.The bacterial culture of soft tissue all showed positive in experimental group and negative in control group.3 week post-operation:there was no significant difference between the rat weight of the experimental group control group.The the infection situation of animal in experimental group turned to chronic,besides 4 rats occurring sinus tract at infection site,other rat' s were union with deep pigmentation.The incision were union in animal of control group.The X ray performance of experimental group showed severe periosteal reaction,new bone formation,bone destruction and sequestrum,Norden score were 2.67 ± 0.617.But the X ray performance of control group were similar to the normal side,Norden score were 0.The Norden score in experimental group were significantly higher than control group.And the Norden score in 3 week were significantly higher than Norden score in 1 week in both two groups.The result of histopathological H&E staining analysis of tibia bone sample of experimental group showed that we can see a large number of inflammatory cells,severe bone cell destruction,and periosteal proliferation.There showed normal bone structure in the result of H&E staining in tibia bone sample of control group.The bacterial culture of soft tissue all showed positive in experimental group and negative in control group.Conclusion:This method of making tibia chronic osteomyelitis rat model is stable and feasible.After injecting 0.1ml 5%sodium morrhuate and inoculating 0.1ml 2× 108/ml CFU suspension of staphylococcus aureus in the medullary cavity of right tibia of rat,we can successfully make a tibia chronic osteomyelitis rat model at 3 week post-operation.