Application Of The Limb X Imaging Measuring System In Leg Length Discrepancy After Total Hip Arthroplasty

Objective To introduce the application of the Limb X Imaging Measuring System in leg length discrepancy after total hip arthroplasty, and to study its validity, repeatability and accuracy in order to provide a accurate , practical and economical method and tool for the measurement of leg length after total hip arthroplasty.Methods Manufacture the leg length breadboard ,use standard metric scale to measure its length as the certified value, and use the Limb X Imaging Measuring System to measure its length as measured value. Compare the difference between the two groups of data, using t-text, to evaluate the accuracy of the measuring system. Analyse the variance of the measured values amoung different observers,and compare the differences amoung three groups, to judge the repeatability of this measuring system. Double leg length of 38 patients were measured , who undergone unilaterally total hip arthroplasty in our department for the first time, from January,2005 to January,2007. In order to evaluate the accuracy and practicality of the effection after total hip arthroplasty, the correlation between the measured values and Harris-Scores is analysed. This measured values were compared with the results measured by hand on the pelvis orthotropia X-ray film to find the difference in the outcome,and analyse the two groups of data using paired t-text.Results The measuring process of the Limb X Imaging Measuring System is simple and it reduce the manual measuring error. The measured value of length, compared with the standard value, has not significant difference(t=1.49, p>0.05). Its absolutly average deviation is 0.14±0.09cm , its average error rate is 0.15%.The comparesion of the measured values amoung different observers shows that there is a good repeatability to the values measured by different observers using the Limb X Imaging Measuring System(F= 1.11,p>0.05).The result of measurement about clinical cases is consistent with the extent of most patients' subjective satisfaction, which also has a good correlation with patient's Harris-Score , r_S closes to -1. There is a significant difference between the results of two legs' length measured by the Limb X Imaging Measuring System and by hand on the pelvis orthotropia X-ray film (t=4.81, p <0.001).Conclusion The Limb X Imaging Measuring System is a kind of digital limb length measuring tools,easy for using, decreasing manual error of measuremen.Recently,it is an idea tool that can be generally used to measure precise length of limb in all basement hospital. The difference of two leg's length precisely measured by this system after tatol hip arthroplasty, can accurately reflects curative effect affected by the leg length discrepancy and provides a precisely numerical direction for the further therapeutic measure.