定量CT探讨老年转子间骨折髓内固定时头钉的合理位置

Exploration of Reasonable Position of Screws using Intramedullary Fixation for Geratic Intertrochanteric Fracture with Quantitative CT

目的通过定量计算机断层扫描(QCT)方法对老年尸体股骨头内的骨密度分布进行矢量性定量分析,探讨老年转子间骨折使用髓内固定系统时头钉的合理位置,为临床治疗此类疾病提供理论依据。方法以8具16侧高龄尸体髋部为研究对象,行髋关节离断,行QCT扫描。以股骨头几何中心点为原点,沿股骨颈长轴并经原点为X轴,经股骨头原点且在冠状位上垂直于X轴的为Y轴,经股骨头原点且垂直于冠状面的为Z轴,三轴互相垂直通过原点,构建三维立体空间结构。分别依X、Y、Z轴方向进行QCT扫描,扫描厚度为3 mm,依扫描骨密度值,经统计学分析后描绘股骨头内部骨密度的分布曲线。结果离体高龄尸体股骨头内骨密度在X、Y、Z轴矢量方向上均呈单峰样连续曲线变化,样本骨密度分布表现一致,差异无统计学意义(P>0.05)。沿X轴骨密度峰值区域出现在股骨头中心点近端约0.9~1.5cm范围内;沿Y轴骨密度峰值区域出现在以Y轴为轴心线两侧0.9cm区域内;沿Z轴骨密度峰值区域出现在以Z轴为轴心线两侧0.6cm区域内(P<0.05)。三个轴线的高骨密度区域围成的三维空间区域,提示为股骨头内头钉最佳放置区域。结论经定量CT测定,股骨头内骨密度呈现沿矢量方向规律曲线变化,并存在相对骨密度高值区域,提示临床在使用髓内固定系统治疗老年转子间骨折时应将头钉置于合理的骨密度较高区域,以获得良好的内固定效果。

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 3 mm 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.