Study Of Osseointegration And Anti-infection Capacities Of Hydrofluoric Acid Treated Si₃N₄ And Mg Alloy Implant Materials

Objective:The major aim of the present study is to test potential osseointegrative and anti-infective capabilities of several attractive orthopaedic implants of silicon nitride?Si₃N₄?,silicon nitride modified by hydrofluoric?Modified Si₃N₄?,pure titanium?Ti?and magnesium alloy?Mg alloy?simultaneously using an Sprague-Dawley rats?SD-rats?tibial osteomyelitis model.Methods:The first part:Topography of orthopaedic materials were characterized by scanning electron microscopy?SEM?,atomic force microscopy?AFM?and biodegradable experiment.In vitro biocompatibility was evaluated by mouse osteoblast?MC3T3-E1?proliferation assays for1 day and 3 days.Antibacterial property in vitro was showed using Staphylococcus aureus to perform.The second part:Eight rats were divided into two groups:osteomyelitis and blank group.An Sprague-Dawley rats?SD-rats?tibial osteomyelitis model was established and confirmed by general condition?weight,temperature,red blood cell,white blood cell?,bone morphology at preoperative,1,3,7,14 days postoperative.On 14^th days postoperative rats were sacrificed,X-ray,tibial tissue microbiological and histological examination.The third part:24 rats were divided into six groups:Ti,Mg alloy,Modified Si₃N₄,Si₃N₄,Blank and Sham groups.The osseointegration and anti-infection capacities of Si₃N_4,Modified Si₃N₄,Ti and Mg alloy were analyzed simultaneously using the SD-rats tibial osteomyelitis model.4 weeks after operation,Mircro-CT was performed to evaluate the new bone volume peri-implant and the osseointegration property of these implants.Results:The first part:The number of bacteria of anti-infection experiment in vitro of Modified Si₃N₄ was significantly less than Si₃N₄,Ti and Mg alloy.In addition,the number of bacteria in Mg alloy was more than Modified Si₃N₄ though,but less significantly than Si₃N₄ and Ti.There was a notably difference in the surface topological structure between Modified Si₃N₄ and Si₃N₄.The pH values of the PBS solution with immersed Mg alloy sample was obviously higher than those of the Ti,Modified Si₃N₄ and Si₃N₄ samples at all of the time points.The second part:External views of osteomyelitis group present evidence of cortical destruction and cortical thickening.X-ray showed more extensive metaphyseal osteolysis in osteomyelitis group.Histological analysis?modified gram staining?of osteomyelitis group present evidence of acute pyogenic infection.An abundant viable bacteria was found in the proximal medullary.In contrast,no bacteria was found in blank group.The general condition of mean WBC value was much higher than preoperative level in osteomyelitis group compared to blank group.The third part:On 14^th days after implantation,the mean weight of blank,sham and modified Si₃N₄ groups had an evident increase,but there was a mild decrease in Si₃N₄,Ti and Mg alloy groups.The mean temperature of Si₃N₄ and Ti groups were abidingly higher than preoperative baseline.RBC loss were found in all groups compared to preoperative level.Ti and Si₃N₄ had a wild WBC raise,and there was a slightly increase in Mg alloy group.No WBC raise was found in modified Si₃N₄,blank and sham groups.Mg alloy and modified Si₃N₄ had less bacterial colony density compared to that in Ti and Si₃N₄ groups.No bacteria were found in blank and sham groups.Fot the histological analysis,Ti implant and Si₃N₄ implant present evidence of acute pyogenic infection in the shape of an abundant viable bacteria.In contrast,less viable bacteria were found in Mg alloy and Modified Si3N4-rod implant groups.The mean new bone volume within the interest cylindrical in Mg alloy,modified Si3N4 and Si3N4 were significantly higher than Ti implant.Conclusions:Modified Si₃N₄ and Mg alloy demonstrate an excellent anti-infection capability associated with osseointegration effect compared to pure Ti and Si₃N₄.Based on this osteomyelitis infection model,the anti-infection and osseointegration properties of orthopaedic materials can be assessed simultaneously.