兔股骨节段缺损模型研究磷酸钙骨水泥骨愈合性能

Bone Healing Capacity of Calcium Phosphate Cement Cyfinder in a Rabbit Femur Segmental Defect Model

目的：利用大白兔股骨节段性缺损模型研究磷酸钙骨水泥（CPC）柱骨愈合能力，比较肌肉和骨膜分别包绕对CPC柱成骨和吸收的影响。方法：CPC柱固化后行扫描电镜观察微结构，X线衍射分析固相成分。60只新西兰大白兔随机分成4组，股骨中段截骨15mm，8孔钢板置于股骨外侧，上下分别以3枚皮质骨螺钉固定，制备骨缺损模型。A组切除骨膜、B组保留骨膜、c组肌肉包绕CPC、D组骨膜包绕CPC。分别于第4、8、12周处死，取标本行X线检查、生物力学及HE染色组织学分析。结果：水泥表面分布不规则颗粒状晶体，微孔分布均匀，直径10μm左右。固相分析主要为羟基磷灰石衍射峰。X线片示A组4周少量斜形骨痂相向性生长；8周3只骨连接；12周4只骨连接。B组4周较多骨痂生长；8周4只骨连接；12周均骨连接。C组4周CPC和股骨界面清晰；8周界面模糊，部分骨痂从CPC旁侧生长；12周4只在CPC旁侧形成连续性骨痂，1只被新生骨痂包裹。D组4周CPC和股骨界面模糊；8周有较多骨痂从CPC旁侧生长；12周CPC被新生骨痂包裹。CPC柱均保持植入轮廓，无破碎或溶解。股骨抗弯曲强度测试术后8、12周的抗弯曲强度明显增高，A、B2组和C、D2组组间差异有统计学意义（P〈0．01）。组织学观察A、B组术后4周骨缺损为纤维组织填充，第8、12周骨愈合标本的骨小梁排列规则。C组4周股骨两端与CPC界限清楚，肌肉包绕，8周CPC表面有新骨形成。第12周新骨和CPC接触较紧密，少量骨组织长入CPC；D组4周两端股骨与CPC界面可辨，骨膜包绕，中间区未见新骨，第8周新骨形成增多，CPC内有少量新骨长入，第12周新骨和CPC界面模糊，新骨长入增多。结论：植入兔股骨节段缺损的CPC柱骨愈合反应好，吸收有限。CPC填充股骨的机械强度比正常骨愈合后股骨的强度弱。

Objective： To investigate the bone healing capacity of calcium phosphate cement （CPC） cylinder in a rabbit femur seg mental defect model by comparing the influence of muscle or periosteum as wrapping material. Methods ： Pre - hardened CPC eylinde was prepared. Three specimens were analyzed by scanning electron microscopy and X - ray diffraction to characterize its microstructur and chemical composition. Sixty adult rabbits were randomly assigned to four groups,then received a defect size of 15 mm osteotomy withil the femurs. The 8 - hole plate was fixed with three screws in the proximal and distal part of the defect, respectively. In group A, the fern oral defects were left alone; in group B, the defects with retained periosteum; in group C, the defects were grafted with CPC cylinde wrapped by muscle ; and in group D, the defects were grafted with CPC cylinder wrapped by periosteum. Five rabbits from each grou] were sacrificed at 4, 8 and 12 weeks postoperatively. The samples were evaluated with radiological, biomechanical and histological meth ods. Results： Irregular particles were seen on the surface of specimens, the pore size was approximately 10 p,m. The peak locations f~ the hydroxyapatite were seen in the X - ray diffraction patterns of the specimens. Group A showed a few radiographic evidence of new bon formation within the boundary of the defect at 4 weeks. Three bone defects bridged at 8 weeks and 4 bone defects bridged at 12 weeks Group B showed radiographic evidence of new bone formation at 4 weeks. Four bone defects bridged at 8 weeks and 5 bone defects bridge. at 12 weeks. Group C showed discernable interface between the CPC cylinder and both femoral cut ends at 4 weeks, which became invisi ble at 8 weeks. Defects bridged by continuous callus beside the CPC cylinder in 4 rabbits and completely surrounded in 1 rabbit at 1~ weeks. Group D showed better quality of new bone formation, the CPC cylinders were surrounded by new bone at 12 weeks. However, aJ CPCs retained their cylindrical shapes. A significant difference in flexural strength between Group A and B, Group C and D at 8 and 1＇, weeks were detected, respectively （ p 〈 0.01 ）. Histological analyses showed that the defect site was filled with organized fibrous tissue a 4 weeks, and bridging of the defect occurred by regular bone formation at 8 and 12 weeks in Group A and B. Direct contact between CP（ and the proximal and distal femoral bone was limited in Group C and D at 4 weeks. New bone formation was observed at the surface c CPC, with limited bone ingrowth at 8 and 12 weeks in Group C. In contrast to Group C, more new bone formation and bone ingrowth wer observed in Group D at 8 and 12 weeks, respectively. Conclusion： The pre -hardened CPC cylinder showed good bone healing respons and limited absorption after implantation in rabbit femurs. The mechanical strength of the reconstruction femur was less than that of normal bone bridged femur.