Experimental Study Of Clindamycin-loaded Calcium Phosphate Cement For The Prophylaxis Of Implant-related Infection

ObjectiveTo determine the feasibility of calcium phosphate cement (CPC) as a carrier material for clindamycin and the effect of the different material implants on the biofilm formation of Staphylococcus epidermidis. Investigate the possibility of clindamycin-loaded calcium phosphate cement (CLCPC) to prevent the implant-related infection and effects of the clindamycin releasing from CLCPC on its bone regeneration in vivo.MethodsThe study of calcium phosphate cement (CPC) as a carrier material for clindamycin: The setting time of 0%, 2% and 5%CLCPC were measured according to ASTM C266-89 method. Clindamycin content eluting from the samples of 2% and 5% CLCPC in PBS were analyzed by HPLC at different times. The 2%, 5% CLCPC and 2% PMMA samples were used for bacteriostasis test by plate diffusion method and the diameters of samples bacteriostasis ring and bacteriostasis duration were observed. Setting product and crystal size of 0%, 2% and 5%CLCPC were observed and analyzed by XRD and SEM.The effect of the different material implants on the biofilm formation in vitro: Staphylococcus epidermidis and the ability of biofilm formation identificated. The different material implants were cultured with lml×0.5 MCc Staphylococcus epidermidis suspension. Biofilm on the different samples surface was observed with SEM. Biofilm on the different sample surfaces was dissolved with 0.5% trypsin and the trypsin was removed by centrifusion.The sediment of bacteria was diluted with PBS. 10ul of each diluted bacterial suspension was inoculated and CFU were counted.Experimental study of CLCPC for the prophylaxis of implant-related infection: 15 New Zealand rabbits were randomly devided into control group, injection group and CLCPC group.The model of right total knee implant-related infection in rabbits were developed with 1m1×0.5 Mc Staphylococcus epidermidis. Thelatter two group rabbits were treated with injected clindamycin and CLCPC respectively. Postoperative wounds were observed every day to determined whether there is a sinus or abscess or not. Body temperature and body weight were measured and WBC tests were run. Biofilm on UHMWPE washer surface was observed with SEM and LCSM.Observation of the bone regeneration of CLCPC in vivo: The rabbits used in this experiment were the same ones as in the third part. Specimens of distal femur were retrieved at postoperative 34 days and radiograph taken at 3, 33 days was observed for new bone formation of CLCPC. The degradation and the osteogenic response of CLCPC were evaluated in nondecalcified section. The integration of CLCPC into bone was studied under SEM.ResultsThe study of calcium phosphate cement (CPC) as a carrier material for clindamycin: The setting time shorten when CPC loaded clindamycin. Clindamycin was burst-release from CLCPC within the intial 6h period and the release rate slow down gradually within 4 days. The release prolonged to the 42th day of observation. The ring of 2% CLCPC bacteriostasis was smaller than that of 5%CLCPC and the ring of 2%PMMA bacteriostasis was smaller than that of 2%CLCPC. The bacteriostasis of 2%, 5%CLCPC and 2%PMMA lasted to the 42th day of test. Clindamycin don t have an influence on setting product and crystal size of CLCPC by XRD and SEM.The effect of the different material implants on the biofilm formation in vitro: The strain obtained was be Staphylococcus epidermidis and could produce biofilm. The UHMWPE implant surfaces were found more biofilms by SEM. Staphylococcus epidermidis are single on the PMMA and CPC surfaces and are agglomerate on the titanium alloy surface. Bacteria count showed the adhesive bacteria on the PMMA surface were significantly more than that on the CPC surface. The most bacteria on the PMMA surface were discovered and the least bacteria on the titanium alloy surface.Experimental study of CLCPC for the prophylaxis of implant-related infection: There were 3 rabbits with sinus and 1 rabbit with absecess in the control group. There were 2 rabbits with sinus in the injection group and the CLCPC group respectively. Much secretion was found in the sinus of the control andinjection group and little secretion in the sinus of the CLCPC group. The mean postoperative body temperature of the rabbits in the CLCPC group was between those of the control group and the injection group. The mean body weight of the rabbits in the CLCPC group slowly increased postoperatively. The increasing extent of WBC of the rabbits in the CLCPC group was lower than that in the control and injection group. Biofilms on all UHMWPE washer surfaces were discovered with SEM and LCSM.Observation of the bone regeneration of CLCPC in vivo: The new bone formation of CLCPC could be seen on the distal femur retrieved at postoperative 34 days and on the rabbit knee radiograph. The degradation and the osteogenic process of CLCPC were found in nondecalcified section. The integration of CLCPC into bone was observed under SEM.ConclusionCPC could be a carrier material for clindamycin. There are significant differences among the different material surfaces for the adherecnce and biofilm formation of Staphylococcus epidermidis and Staphylococcus epidermidis produce more biofilms on the UHMWPE surface. CLCPC and system administration couldnt prevent implant-related infection. CLCPC can relieve clinical symptoms. CLCPC couldn't prevent biofilm formation on the surface of UHMWPE washer. The clindamycin eluting from CLCPC don t have side effect on the new bone fromation of CPC in vivo.