Experimental Study Of Magnesium Phosphate Bone Cement In Vertebroplasty

Objective:The aging population has contributed to an increased incidence of osteoporosis,indirectly raising the risk of osteoporotic vertebral compression fractures(OVCF)in patients with osteoporosis.Lower back pain is the main clinical symptom of OVCF,characterized by severe pain,limited spinal mobility,and a significant decline in the patients’ quality of life.Severe cases can progress to spinal kyphosis.Conservative treatment can effectively alleviate OVCF,but prolonged bed rest increases the risk of complications.Minimally invasive surgical treatments for OVCF commonly include percutaneous vertebroplasty(PVP)and balloon kyphoplasty(PKP),both of which yield significant results.Currently,the commonly used bone cement in clinical practice includes three types: polymethylmethacrylate(PMMA),calcium phosphate cement(CPC),and calcium sulfate cement(CSC).However,these options are gradually unable to meet the clinical requirements.Therefore,it is necessary to search for a bone repair material with excellent mechanical properties,injectability,biocompatibility,and biodegradability.In this study,an injectable self-setting magnesium phosphate cement was prepared through chemical reactions.Its physicochemical properties(setting time,compressive strength,and injectability),in vitro performance(biocompatibility,osteogenic and angiogenic potential),and in vivo biological properties(degradation rate and repair effect on SD rat femoral condyle defects)were evaluated to assess its potential as a novel bone filling material for vertebral augmentation procedures.Methods:1.Preparation of magnesium phosphate cement(MPC)solid powder and curing liquid: Magnesium oxide was treated in a high-temperature calcination furnace,and a certain particle size of magnesium oxide and potassium dihydrogen phosphate powder was obtained through planetary ball milling.The two components were mixed in a certain proportion as the solid phase of the cement and deionized water was used as the liquid phase.2.Preparation of magnesium phosphate cement: The magnesium oxide and potassium dihydrogen phosphate powder obtained from high-temperature calcination and planetary ball milling were mixed in a certain proportion.Then,the powder and liquid were mixed in a certain liquid-to-solid ratio,thoroughly stirred,and the cement slurry was transferred into a special PTFE mold.The magnesium phosphate cement(MPC)was prepared through an acid-base reaction.3.Physicochemical property testing of magnesium phosphate cement: The setting time,compressive strength,injectability,chemical composition,surface morphology,and element distribution of the prepared magnesium phosphate cement were tested.The setting time was measured using a Vicat apparatus,the compressive strength was measured using a universal testing machine,and the injectability was tested by weighing.The chemical composition of the magnesium phosphate cement was determined using an X-ray powder diffractometer(XRD),while the surface morphology and element distribution were examined using scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDS).4.In vitro biological performance testing of magnesium phosphate cement: The influence of different concentrations of magnesium phosphate cement extract(100%,50%,25%,and 12.5%)on the proliferation of MC3T3-E1 cells was evaluated using the CCK-8 assay.The effect of magnesium phosphate cement extract on the viability of MC3T3-E1 cells was observed using a live/dead staining assay.The effect of magnesium phosphate cement extract on the cytoskeleton of MC3T3-E1 cells was observed using phalloidin staining.The in vitro osteogenic performance of magnesium phosphate cement was evaluated using alkaline phosphatase staining,and the angiogenic ability was assessed using a tube formation assay.5.In vivo biological performance testing of magnesium phosphate cement: A bone defect with a diameter of2.5 mm and a depth of 2.5 mm was created in the femoral condyle of SD rats.The experimental groups included a blank group,calcium phosphate cement(CPC)group,calcium sulfate cement(CSC)group,and magnesium phosphate cement group,with 6SD rats in each group.Specimens were collected after 4 and 8 weeks,and gross images were captured.Subsequently,micro-computed tomography(Micro-CT)and histological staining(HE staining,Masson’s trichrome staining)were performed to analyze the bone regeneration in the defect area.Results: A injectable self-setting magnesium phosphate cement(MPC)was successfully prepared.The compressive strength test results showed that the compressive strength of MPC was(36.25±0.72)MPa,which was 2.29 times that of CPC(15.81±2.05)MPa and 2.44 times that of CSC(14.83±0.99)MPa.The injectability test results showed that the injectability of MPC was 98.87%±0.29%,which was comparable to that of CPC and superior to that of CSC.The setting time test results showed that the setting time of MPC was(15.16±0.32)min,which was similar to that of CSC but longer than that of CPC.XRD analysis revealed that the main hydration product of MPC was Mg KPO4·6H2O,while the main hydration products of CPC were Ca3(PO4)2 and Ca5(PO4)3(OH),and the main hydration product of CSC was semihydrated calcium sulfate.SEM results showed that the hydration product of MPC appeared as layered sheets with a compact arrangement,while CPC exhibited petalshaped crystals on the surface,and CSC mainly had a rod-like morphology.EDS spectra results showed that elements such as O,Mg,Ca,and P were evenly distributed in the cross-sections of MPC,CPC,and CSC.CCK-8 assay results showed that MPC extract at various concentrations did not exhibit significant toxicity to MC3T3-E1 cells,and the 25% MPC extract showed the most significant proliferative effect.The viability of MC3T3-E1 cells was not significantly affected by 100% CPC extract and 100% CSC extract.Live/dead staining and phalloidin staining results showed that MPC had good biocompatibility,and scratch assay results demonstrated that MPC had the strongest ability to promote the migration of MC3T3-E1 cells,with a migration rate 1.44 times that of CPC and 1.23 times that of CSC.Alkaline phosphatase staining results showed that MPC had the strongest osteogenic performance,and tube formation assay results demonstrated that MPC had the strongest angiogenic ability among the three materials,followed by CSC.Gross images and micro-CT scan results showed that MPC,CSC,and CPC did not cause significant infection,and they exhibited distinct degradation rates.Histological analysis results showed that after implantation of the scaffolds in the femoral condyles of rats,no significant inflammatory response or necrosis was observed in the surrounding bone tissue.Conclusion: In this study,by employing high-temperature calcination of magnesium oxide,planetary ball milling of magnesium oxide and potassium dihydrogen phosphate,a injectable self-setting magnesium phosphate cement(MPC)with excellent physicochemical properties,biocompatibility,osteogenic and angiogenic capabilities was successfully prepared.The results of physicochemical property tests showed that MPC had higher compressive strength than the clinically used calcium phosphate cement(CPC)and calcium sulfate cement(CSC),shorter setting time than CPC,and better injectability than CSC.The results of in vitro biological performance demonstrated that the prepared MPC exhibited good biocompatibility,promoted the migration of MC3T3-E1 cells,and possessed stronger osteogenic and angiogenic abilities compared to CPC and CSC,thus playing a more powerful role in the bone repair process.The results of in vivo biological performance experiments indicated that MPC exhibited more suitable degradability during the bone repair process compared to CPC and CSC,with degradation rate and bone regeneration speed being better matched,thereby better repairing the femoral condyle bone defects in SD rats.This study suggests that MPC has the potential to replace the currently used CPC and CSC in clinical applications and is a promising artificial bone material with excellent prospects.