Efficacy of quantitative CT in assessment of fracture healing / 中华创伤杂志

ABSTRACT

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 At 2, 4, 8 and 12 weeks, Kirschner wire was withdrawn and plain X-ray and QCT scanning were performed on the bilateral tibia.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.