Abstract:Objective To discuss the reasonable position of screws in intramedullary fixation for intertrochanteric fractures.We used quantitative computed tomography(QCT)method to detect the bone mineral density(BMD)of the cadaveric femoral head and made the quantitative analysis.Methods The 16 femoral heads of 12 corpses were minute dissected and dislocated from the hip joint.All the femoral heads accepted the QCT scan.The geometry center of the femoral head as the origin point.The X axis was defined as the long axis along the femoral neck and going through the origin point,and the Y axis was defined as perpendicular to the X axis and going through the origin point either in coronary plane,while the Z axis pass the same origin point of the femoral head and perpendicular to both the X axis and Y axis in oblique sagittal plane.These three axes perpendicular to each other through the origin point,constructed the three-dimensional structure in space.The scan thickness was 3mm along every axis,and the distribution curve of bone mineral density within the femoral bone was described after statistical analysis.Results The BMD of these femoral heads in the X,Y,Z axis showed the unimodal curve of continuous change,the sample density distribution was consistent(P>0.05).The relative peak value of BMD areas appeared in proximal of femoral head original point within about 0.9~1.5 cm along the X axis,bone mineral density peak area along the Y axis and Z axis of 0.9 cm and 0.6 cm on both sides of original point(P<0.05).The high bone density area of the three axes forms a space structure indicating the optimal position area for the lag screws of the femoral head.Conclusion According to the determination of quantitative CT,the BMD curve change of the femoral heads appears along the direction of the vector law,and high relative BMD value exist in this space area,indicated that we should put the lag screws in this space area with relative high BMD value using intramedullary fixation system in the treatment of senile intertrochanteric fractures,in order to obtain good clinical results.
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