NTX在兔实验性骨不连早期诊断中的作用

Serum N- terminal Telopeptide of Type I Collagen Concentration for Early Diagnosis of Fracture Nonunion in Rabbits

目的建立骨不连的动物模型,发现实验性骨不连的生化指标变化规律。方法选取纯种新西兰大白兔分为两组,实验组在前臂桡骨中段截除1.5 cm（包括骨膜）,骨断端用骨蜡封闭髓腔,对照组只是在前臂桡骨中段造成骨折,两组分别于术前、术后2周、3周、4周、5周、6周、7周、8周、10周、12周进行X线检查及抽取血样。骨形成特异标志物选择：骨特异性碱性磷酸酶（bone-specific alkaline phosphatase,BSAP）。骨吸收特异标志物包括Ⅰ型胶原氨基端末肽（N-terminal telopeptide of type I collagen,NTX）,人抗酒石酸酸性磷酸酶5b（tartrate-resistant acid phosphatase5b,TRACP 5b）。检测方法采用生物素双抗体夹心酶联免疫吸附法（enzyme-linked immunosorbent assay,ELISA）。结果实验组第2周3例有少许骨痂形成,但5周后骨痂情况稳定,术后8周仍无一例愈合。骨折组术后2周开始骨折线模糊,术后6~8周骨痂大量生长。两组间的BSAP、NTX有统计学意义（NTX F值187.512,P〈0.001。BSAP F值16.051,P=0.001）,BSAP术前、术后两组内各数值无统计学意义,TRACP 5b术前术后、组间、组内各数值无统计学意义。实验组NTX在术后5周开始出现明显下降,术后5周与术前术后各个时间均有统计学意义,术后7周、8周、10周、12周均与术后3周、4周、5周有统计学意义,术后6周以后NTX水平基本稳定。结论新西兰大白兔骨不连缺损的模型可以选择为前臂桡骨中段,截除1.5 cm（包括骨膜）,骨断端用骨蜡封闭髓腔。多个血清生化指标的检测有益于骨折愈合过程的临床评估。术后5周,NTX的显著下降,是否可以早期诊断兔实验性骨不连。

Objective Purpose The aim of this study was to establish an experimental animal model of fracture nonunion, and investigate the changes in serum biomarker concentrations in fracture nonunion. Methods Twenty purebred New Zealand rabbits were divided into two groups. In the bone defect group, a 15 - mm length of bone （including the periosteum ）was re- moved from the mid - radius, and the medullary cavities were closed with bone wax. In the bone fracture group, the mid - radius was fractured. X- rays were taken and blood samples were collected preoperatively and at 2,3,4,5,6,7,8,10, and 12 weeks after surgery. The serum concentrations of bone - specific alkaline phospbatase （BSAP） as markers of bone formation, and of N - terminal telopeptide of type I collagen （ NTX）, and tartrate - resistant acid phosphatase 5b （ TRACP 5b） as markers of bone resorption, were measured using biotin double - antibody sandwich enzyme - linked immunosorbent assay. Results In the bone defect group, bone callus was observed on X - ray at 2 weeks in three rabbits and the bone calluses stabilized at 5 weeks, but none of the bones had healed at 8 weeks. In the bone fracture group, the fracture line was blurry at 2 weeks and bone callu- ses formed at 6 -8 weeks. In the bone defect group, the serum BSAP and TRACP 5b concentrations increased after surgery, peaked at 4 weeks, began to decrease at 5 weeks, and stabilized after 6 weeks. The serum NTX concentration fluctuated during the first 4 weeks, was significantly lower at 5 weeks than at all other time points, and stabilized after 6 weeks. Conclusion These results show that a bone nonunion model can be established in New Zealand rabbits by reseeting a 15 -mm length of bone from the mid - radius with bone wax blocking. Measurement of the serum BSAP, NTX, and TRACP 5b concentrations may be useful for the early detection of bone nonunion. The serum NTX concentration changed significantly in rabbits with bone nonunion. Further studies are needed to determine the feasibility of using the serum NTX concentration for the early diagnosis of bone nonunion.