| Objective:1.to explore the way to improve the accuracy of prediction of the length of tibial intramedullary nail in the preoperative plan;2.To investigate and comparative the accuracy of preoperative digital radiological measurement corrected by different ways and anthropometric measurements for determining tibial nail lengths.Methods:1.As part of phase I of our study, postoperative radiographs of 52 patients who underwent intramedullary nailing of their tibial shaft fractures using PACS(picture archiving communication systems) were retrieved in a retrospective study from 2011.11 to2015.4 in Shanxidayi Hospital department of orthopedics. A doctor achieve the length of nail on DR image by averaging the testing values of repeated measurement three times.The results of the three measurements are tested the reliability of digital measurement by the introclass correlation coefficient test(ICC). The average of repeated measurements and the length of nail used in surgery analyzed by Pearson correlation analysis rank correlation coefficient to test the validity of digital measurement, preliminarily the reliability and validity of digital measurement were evaluated, and the average magnification rate(M1) of the tibial AP is obtained.2.Different length of the tibial nail are measured from different heights which distance from radiography bed 0mm, 25 mm, 50 mm, 75 mm and 100 mm away, computing the rates of DR radiography magnification. According to experienmental data collected, the linearregression equation between DR magnification rate(M) and the object distance photography bed height(H) is estimated, at the same time, tibial shaft distance from the height of the radiograghy bed is based on the affected side calf circumference. So we can individualiy estimate DR magnification every patients, provide every patient individual calibration value, for correction mode II.In phase III, a prospective study on 20 patients who undergo tibial nailing surgical treatment from 2015.4 to 2016.3 in Shanxidayi Hospital department of orthopedics, a doctor digital measures the patients' DR radiography using SIEMENS syngo.via, and the measured values are used to predict the length of tibial nail(L1 and L2) with correction mode I and II, respectively, at the same time, another doctor predicts the length of the nail(L3) with anatomical measurements. We can collect three sets of data, and compare the accuracy of the prediction of the length of tibial nail using these three methods.Retrospectively collected from 2011.11 to 2015.4 postoperative tibial AP.Results:The reliability between repeated measurement is 0.996~0.999 and 95% credibility intervals were centered. The measurement of nail length on tibial AP shows a high-positive correlation with the actual size during operation(r=0.908, P<0.05). And the average magnification of tibial AP is 19.6±2.7%, higher than 15% which is the general X-ray magnification(P<0.05). To explored the change of DR magnification with different height distance with radiograghy bed obtains the linear regression equation of DR magnification(M) and the height of the object distance photographic bed(H):Y=0.121X+14.207(P<0.05, r2=0.986). Prospectively collected 20 cases of tibial fracture in the treatment of intramedullary nail, preoperatively the digital measurement value of tibial AP corrected by average nail predictive length(L1) is(316.87±24.74)mm,the digital measurement value corrected by individualized nail predictive length(L2) is(315.19 ±24.42)mm, the length of anatomical measurement prediction(L3) is(325.85 ±2.639)mm. L1, L2, L3 are analyzed with the actual length of intramedullary nail(L) bypaired t-test respectively, there are no significant differences(P>0.05), the differences between the three groups of data(L1, L2, L3) respectively and the length of intramedullary nail length(L), are compared with Friedman M test, and there are differences in three ways in the predictive accuracy of intramedullary nail(P<0.05), and utilizing q-test for pairwise comparison judgment, among them,digital measurement corrected by the average magnification or corrected by individual corrected have a higher accuracy compaired with anatomical measurement for predicting the length of tibial intramedullary nail preoperative(P<0.05), While for the two correction methods of digital measures, it can not be considered different in the predictive accuracy of the intramedullary nail length(P>0.05).Conclusion:1.The digital measurement of lower limb DR image in distance between two points has a high level of reliability and validity;2.The magnification of DR is positively correlated with the height of the radiography bed, and the individual magnification can be obtained through reasonable correction;3.Through reasonable correction, the accuracy of radiograghy digital measurement is higher than the anatomical measurement preoperatively. |
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