Experimental Study Of Treatment Of Rabbits’ Tibial Osteomyelitis With Lysostaphin-loaded Hydroxyapatite/Chitosan Composite

Objective:To find an optimal animal model for the research of chronic osteomyelitis, and then discuss the effectiveness and toxicity of Lysostaphin and hydroxyapatit/chitosan composite material in treatment of osteomyelitis of the tibia in rabbits.Methods:1.Establish a tibial osteomyelitis model in rabbits and make a lysostaphin loaded atrigel by use of Hydroxyapatite/chitosan composite materials and lysostaphin.2.Evaluate the effectiveness and toxicity of the lysozgme in the treatment of rabbit tibial osteomyelitis by Controlled trials in animals.esults1.One rabbit dead in the group1and three in the group2. In group1, the swelling tissue were confined to the knee joint semisphere or semi elliptic shped; In group2, the swelling soft sissue of the knee involve the thigh and the calf. When the swelling was squeezed, yellow or yellowish-white pus drainaged from the sinus. Excide the skin in the swelling and expose the tibia, we can see the sinus and the hole drilled previously on the tibia communicate with each other, then necrotic tissue and yellow/white pus were found in the partially seclerotic and occlusive medullary cavity. On the x-ray,varying degrees of decreased bone mineral density, trabecula reduced in the number, thin and gap widened, thinned cotical bone can be seen, we can also see heterogeneous dense sequestrum. The connective tissue, bone, and marrow were diffuse infiltrated by neutrophils on the pathological section. In the marrow cavity, we saw massive necrosis of the myeloid cells, interstitial hemorrhage, patial abscessation accompanied organization. Staphylococcus aureus were found in the germiculture, gram stain test and coagulase test. Both the infect rate of the marrow in the two inplantation method are100%.2.We saw the specimen generally normal in appearance12weeks afer surgery in both group A and B, and we found no significant destruction of bone and no pus in the medullary cavity. The materials was closecontact with the bone in group A, but in the remaining three groups, the specimen thickened, obviously destruct, and irregular hyperplasia and sclerosis were seen on the margin of the defect. The materials and the bone were not close contact with each other in group C and we saw purulent discharge between them. We also conduct a statistical analysis with the modified norden score for osteomyelitis in each group12weeks after surgery, and the results suggest that there were statistical significance when group A and B compared with group C and D respectively. When group A compared with group B, there was no statistical significance, no statistical significance between group C and D too. We conducted a statistical analysis with the logarithmic of the bacteria count4and8weeks after sugery, the bacteria count in group A and B are less than the bacteria count in group C and D, and the difference was statistical significance.The bacteria count in group A is not less than the bacteria count in group B, and the difference was not statistical significance, similar result was obtained when group C compared whit group D. Serum biochemical test shows that aspartate aminotransferase(AST),alanine amiotransferase(ALT), usea nitrogen(BUN) and creatinine(Cr) in the experimental group are similar with the control group’s in each phase, and the difference was statistical insignificant. When pairwise comparison conducted between each group, there were no significant difference too. Liver and kidney showed no abnormal changes histologically in the experimental group.Conclusions1.We can induce an osteomyelitis model by inject3×108CFU/ml staphylococcus aureus bacteria into the proximal tibia medullary through a small aperture(d=l mm), and this method was well standardized and can be used in the follow-up study of osteomyelitis.2. Lysostaphin loaded atrigel by use of Hydroxyapatite/chitosan composite materials has a certain ability to resist infection, and compared with vancomycin loaded by use of bone cement, the ability to resist infection is weaker but the ability to ossify is stronger. It has no obvious toxic and side-effect in the short term in rabbits. After a thorough debridement, it can fill in the bone defect by first intention, so it is an ideal bone filling material in the treatment of chronic osteomyelitis.