| Background:Steroids are a leading cause of femoral head osteonecrosis.Currently there are no medications available to prevent steroid-associated osteonecrosis.Some studies have reported that low-intensity pulsed ultrasound(LIPUS)can enhance bone repair in a rabbit model of steroid-associated osteonecrosis.We determined whether the addition of microbubbles enhances the effect of LIPUS on bone repair in a steroid-associated osteonecrosis model.Methods:Bilateral femoral head necrosis was induced by lipopolysaccharide and methylprednisolone.Eight rabbits from control group received low-intensity pulsed ultrasound therapy(200mW/cm2)for 20 minutes daily.Eight rabbits from microbubble-mediated ultrasound(MUS)group received an intra-capsular injection of microbubbles before LIPUS treatment.Eight rabbits from control group did not receive therapy.All rabbits were euthanized 6 weeks after therapy.Micro-CT,biomechanical testing,histologic evaluation,immunohistochemistry,quantitative real-time PCR,and Western blot were used for examination.Results:Six weeks after treatment,a lower bone mineral density,Tb.N,maximal loading strength,and mineral apposition rate were observed in the control group,demonstrating that a steroid-associated osteonecrosis model had been successfully established.MUS significantly increased the bone mineral density of the proxinal femur,Tb.N,Con.D,and maximal loading strength in the MUS group compared to that in the control and US groups.A higher mineral apposition rate was observed in the MUS group compared to both the control and US groups.Messenger RNA and protein expression of BMP-2,messenger RNA and protein expression of VEGF were higher in the MUS group.The number of blood vessels in the MUS group was greater than the number in the control and US groups.Conclusions:The results of this study indicate that MUS enhance LIPUS on promoting osteogenesis and neovascularization,thus promoting bone repair in this steroid-associated osteonecrosis model. |
PDF Full Text Request