Comparative Performance Of Three Bone Grafe Substitutes As Carrier Material For Vancomycin In The Treatment Of Chronic Osteomyelitis: Studies In Vitro And In Vivo

Objective:To compare the efficacy of infection controlling and osseous healing of three bone graft substitutes(BGS) loading vancomycin and explore the characteristics of the three available BGS through in vitro and in vive.Methods:The experiment was divided into three parts.1.The establishment of chronic osteomyelitis modelFifty-four healthy adult New Zealand white rabbits were selected in the experiment,local inoculation was done by injecting 10~6cfu Staphylococcus aureus suspension through a hole drilled in the double tobial metaphysis to establishing the chronic osteomyelitis model.To evalue the chronic osteomyelitis model with X-ray after 4 weeks,and 2 rabbits were sacrificed randomly for pathological and bacteriological examination.2.The study of three vancomycin -loaded BGS in vitroThree BGS,the calcium sulfate(CS),calcium phosphate cement(CPC) and partially decalcified bone(PDCB) were respectively loaded appropriate vancomycin,placed in the simulated body fluid(SBF),measured and recorded the weight loss every week within 6 weeks.On the other hand,the amount of the vancomycin releasing in the SBF were measured and the release rate of the vancomycin of the three BGS were calculated every 24h within 30days.3.The animal control experiments in treating the chronic osteomyelitis with three vancomycin-loaded BGS materialsAfter debridement,48 rabbit were randomly divided into four groups:A group, single subcutaneouly injection of vancomycin as the control group.B group,the treatment group with vancomycin-loaded CS.C group,the treatment group with vancomycin-loaded CPC.D groups,the treatment group with vancomycin-loaded PDCB.To observe and record the changes in weight,the count of WBC and ESR, then take X-ray film at postoperative 1,2,3 month respectively.At the time point of postoperative 1,2,3 month,4 animals were killed in each groups,separated the post-tibial in two longitudinal part then took bacteriological culture and pathological examination,then put the results into statistical analysis,separately.Results:1.Four rabbits died after the operation and 50 rubbits were confirmed of tobial osteomyelitis by X-ray.One died of anesthesia,three died from sepsis,two were killed for bacteriological and pathological examination to confirm the medullary cavity infection.2.The CS pellets were almost 100%weight loss within 6w in vitro,while the CPC 42%weight loss,PDCB 60%weight loss.The cumulative release rate of the antibiotics was more than 90%in the vancomycin-loaded PDCB within the first three days,then the drug concentration was maintained a very low level(less than 2ug/ml),the cumulative release rate of the antibiotics was about 60%in the vancomycin-loaded CS within the first three days,but in the 30-day observation period,the concentration of vancomycin was maintained more than 2ug/ml,the release rate of antibiotics was 85.18%at the end of observation period;the cumulative release rate of the antibiotics was less than 20%in the vancomycin-loaded CPC within the first three days,while in the 30-day observation period,the concentration of vancomycin was maintained at a relatively high level(＞2ug/ml),the release rate of antibiotics was 45.82%at the end of observation period.3.There was no difference in the change of body weight,WBC count and ESR between all the 4 groups:almost all the animals displayed a tendency to slight weight loss after operation,recovering to normal after 7 to 14 days,then gradually increased wihin 3 months.The pattern of changes in body weight after operation were also reflected in the WBC count,which increased after operation,decreased at the 4th day and then returned to normal at the 14th day.The ESR showed a similar pattern,increased rapidly at day 2,decreased at the 4th day,then returned to normal within the the 14th day to the 21 th day.There was no different of the score of the X-ray and pathological examination between the B and C group at month 1,2,3 after operation.The scores of the X-ray and pathological examination in D group was higher than the scores in B and C group,while was obviously less than the score in A group.There was no significant difference of the bacteriological culture rate between the B and C group,it also saw in the A and D group,the bacteriological culture rate in A and D group was higher than which in the B and C group.The positive rate of bacterial culture of the A,B,C,D group was 50%,12.5%,12.5%and 37.5%.Conclusions:The change of body weight,WBC count and ESR may reflect the acute phase changes(such as trauma,anesthesia,surgery so on) to a certain extent,but it seemed difficult to reflect the results of the treatment of chronic osteomyelitis.The vancomycin-loaded CS and CPC were able to release the antibiotics in a high level more than 30 days in vitro,and the treatment for the chronic osteomyelitis was satisfatory in vivo.The cumulative release rate of the antibiotics was more than 90%in the vancomycin-loaded PDCB within the first three days,then the drug concentration was maintained a very low level in vitro.The treatment for the chronic osteomyelitis was a higher rate of infection,which might be due to excessive release of vancomycin,it was difficult to maintain an effective vancomycin concentration in longer period of time at the affective site in vivo.However,in regard to defect healing of the affected site,the rapid CS scaffold resorption(4w) and the CPC provoked a serious inflammatory response,which might impair bone healing in vivo to some extent.At the same time,since the PDCB had basic structure of bone,it was able to provide bone conduction and bone-induced effects,so it could stimulate new bone formation in the defect site if the infection was controlled.