定量CT评价骨折愈合的有效性

目的 探讨定量CT(quantitative computed tomography,QCT)评价骨折愈合的有效性和准确性.方法 将24只健康新西兰兔随机数字表法分为A组(骨折愈合组,右胫骨中段横形骨折,用克氏针内固定)和B组(不愈合组,右胫骨中段横断骨折,制作5 mm骨缺损后以骨蜡封填断端和髓腔),分别于第2,4,8,12周各处理3只兔:先摄两侧胫骨X线片,拔出克氏针及定量CT检测,之后处死动物,将骨折段切取行组织学分析.以X线片和组织学表现为骨折愈合及不愈合的金标准,以受试者工作特征曲线(ROC)分析定量CT检测参数的评价效能,并以健侧胫骨相应节段为对照,观察定量CT参数结果的变化趋势.结果 A组X线片和组织学证实骨折在第2,4周骨折线清晰,为纤维骨痂填充,8～12周骨折线模糊至消失,骨皮质恢复完整连续性.B组X线片和组织学在第2、4周骨折线清晰,骨化不活跃,8～12周骨折线仍存在,骨细胞和骨小梁稀少.将定量CT检测结果进行ROC分析显示,材料学参数骨痂骨密度(BMD)、骨痂骨矿含量(BMC)的曲线下面积(准确度)为0.781和0.750,结构学参数横截面积(CSA)和截面惯性矩(CSMI)的曲线下面积(准确度)为0.781和0.469(P<0.05),材料学参数和结构学参数乘积引伸所得的横截面积力学强度指数(BSICSA)、截面惯性矩力学强度指数(BSICSMI)的曲线下面积(准确度)分别为0.913和0.813(P<0.05),BMD、CSA、BSICSA三者曲线下面积(准确度)分别为0.905,0.921,0.905(P<0.05).结论 定量技术测量骨折局部形态具有区分和反映骨折愈合与骨折不愈合模型及过程的潜能,所筛选出具有准确度的参数有BMD、CSA和BSICSA,这些参数具有准确、特异的优越性.

Efficacy of quantitative CT in assessment of fracture healing

Objective To investigate the efficacy and accuracy of quantitative computed tomography (QCT) in assessment of fracture healing. Methods Twenty-four healthy New Zealand rabbits were enrolled in the study and randomly divided into two groups, ie, Croup A (union model group, transverse fracture open created on mid-shaft of tibia and inter-fixed by kirschner wire) and Group B (non-union model group, transverse fracture with 5 mm defect on mid-shaft of tibia open created, then sealed with bone wax on fracture gap and medulla cavity, inter-fixed by kirschner wire). At 2, 4, 8 and 12 weeks, Kirschner wire was withdrawn and plain X-ray and QCT scanning were performed on the bilateral tibia. Then, rabbits were scarified and its bilateral tibia were desected and histologically examined. The result of X-ray and histological analysis was used as the "golden standard" for evaluation of fracture healing. Receiver operating characteristic curve (ROC) was used to analyze the evaluation performance of QCT. The corresponding segments of the contralateral healthy tibia were used as control to investigate the change of QCT parameters. Results In Group A, X-ray and histological analysis verified clear fracture line filled with irregular callus at 2 and 4 weeks but proved vague or vanishing fracture line and continuous and intact cortex of irregular callus at 8 and 16 weeks. In Group B, X-ray and histology analysis found clear fracture line with inactive ossification at 2 and 4 weeks but vague fracture line with scarce osteocyte and bone trabecula at 8 and 16 weeks. ROC analysis of QCT results showed the following results; (1) the areas under curve (accuracy) of material parameters including bone mineral density (BMD) and bone mineral content (BMC) were 0.781 and 0.750 respectively; (2) structure parameter-cross-sectional area (CSA) and the area under curve of cross-sectional moment of inertia (CSMI) were 0.781 and 0.469 respectively (P <0.05); (3) the areas under curve of the extending parameters bone strength indices (BSICSA) and CSMI bone strength indices ( BSICSMI) were 0. 913 and 0. 813 respectively (P < 0.05); (4) the area under curve (accuracy) of BSICSA, CSA and BMD were 0.905, 0.921 and 0.905 respectively (P<0.05). Conclusions QCT has potential in distinguishing fracture union and nonunion models in measurement of local fracture pattern. The screening parameters with more accuracy are BSICSA, CSA, BMD, which have advantages of accuracy and specialty in assessing fracture healing.