RESUMO
Objective To evaluate the application value of ultrasound in vascularization of different artificial bones . Methods A total of 15 New Zealand rabbits were utilized for model establishment of classic segmental bone defect in bilateral radius . Recombinant human bonemorphogenic protein-2 ( rhBMP-2 ) coralline hydroxyapatite(CHA) and CHA were implanted into left and right limbs . Each CHA was divided into 4 equal parts which were examined with conventional ultrasonography and contrast-enhanced ultrasonography( CEUS ) on 3 d ,7 d ,11 d ,15 d ,30 d and 45 d respectively . CEUS quantitative was performed by time-intensity curve(TIC) ,which parameters including the basic intensity(BI) ,peak intensity (PI) ,increased signal intensity ( ΔSI) and time to peak ( TTP) . Then the results were analyzed and compared to pathology . Results Within the same duration ,the vascularization degree in rhBMP-2 group was stronger than that in the ordinary group with advanced vascularization time . Positive correlation was detected between ΔSI and time of both groups ( r =0 .938 ,0 .890 ;P =0 .000) ,and negative correlation was found between BI/PI or TTP and time ( BI/PI: r = -0 .798 ,-0 .899 ; P = 0 .000 ;TTP= r -0 .874 ,-0 .868 ;P = 0 .000 ) . No statistical significance was observed among four observation points of both CHA ,which indicated no obvious difference in vascularization degree of each observation point . Conclusions The structure of bone graft can be clearly displayed by conventional ultrasound ,and CEUS is able to show the early blood perfusion in two CHA grafts and to accurately evaluate the difference of CHA microvascular growth before and after rhBMP-2 application . The combination of these two techniques is a promising approach of evaluating bone graft vascularization in clinical practice .
RESUMO
Objective To investigate the osteogenic ability of dextran sulfate/recombinant human bone morphogenetic protein-2/chitosan (DS/rhBMP2/CS) nano microspheres combined with coralline hydroxyapatite (CHA) in repair of segmental bone defects.Methods DS/rhBMP2/CS microspheres prepared by ionic crosslinking method were adsorbed into CHA by lyophilization.Seventy-two New Zealand rabbits were randomly divided into 3 equal groups after they had been made into models of bone defect at the right radius.The defects in the 3 groups were implanted respectively with CHA,rhBMP2/CHA and DS/rhBMP2/ CS/CHA.Another 18 animals served as a blank control group.Blood and bone samples were obtained at 4,8 and 12 weeks after implantation.The serum BGP was detected,and the bone grafts were scanned by micro-CT for calculation of volume ratio of the new bone.Hematoxylin and eosin (HE) staining was performed after bone decalcification.Results All the 72 animals recovered well without any infection or graft exposure.Gross observation at postoperative 12 weeks showed that the DS/rhBMP2/CS/CHA group was the best in the quality,quantity and strength of the new bone,as well as in the healing of bone defects.The serum levels of bone gamma-carboxyglutamic-acid-containing protein at all time points in the DS/rhBMP2/CS/CHA group were significantly higher than those in the CHA and rhBMP2/CHA groups (P ＜ 0.05).Micro-CT scanning demonstrated obvious progress in bone formation,cortical bone and marrow cavity at all time points in the DS/rhBMP2/CS/CHA group which showed significantly faster bone reconstruction synchronized with material degradation and significantly higher volume ratio of the new bone than the other 2 groups (P ＜ 0.05).Histological examinations showed better morphology of mature cortical bone and new marrow cavity at all time points in the DS/rhBMP2/CS/CHA group than in the other 2 groups.Conclusion Since DS/rhBMP2/CS/CHA possesses a better mechanism of sustained-releasing rhBMP2 to induce bone formation because of its reticular and hole-hole-connected structure,it may perform better in repairing segmental bone defects than simple CHA or rhBMP2/CHA.
