计算机髋关节置换导航中股骨柄假体前倾角度设定方法的可行性

Feasibility to set a femoral shaft anteversion angle in the surgical navigation system of total hip arthroplasty

将CT扫描股骨资料进行计算机三维影像重建,在虚拟空间中,通过髓腔及股骨上髁确立髁平面、股骨近段冠状面,并进行虚拟股骨柄假体颈干面与它们的夹角间关系的推理计算。同时,对应股骨柄假体前倾角度的改变,对假体于髁平面上的投影像进行颈干角测定,以此模拟术中C臂机二维X射线投射所获取之髋关节正位像及像中假体颈干角。近段股骨髓腔冠状面替代髁平面对股骨柄前倾角度进行表示,并未导致明显的偏差。角度读数间作配对t检验,差异未见显著性意义(P>0.05)。柄假体前倾角与其在髁平面上投影像的颈干角度间具曲线回归关系。为满足计算机导航操作中解剖取点图像注册,而选取股骨髓腔中心弧线的近段部分(近似直线),与股骨髁上间线的平行线相交共面重构近段冠状面,可作为基准而评价股骨柄前倾角度,以替代髁平面。人工髋关节置换过程中C臂机的应用,由髋部正位X射线影像中柄颈干角推断柄假体前倾状态的方法,也可作为手术导航的补充。

CT scan data of the femur was used to reconstruct 3D image. The condylar plane and femoral proximal coronal plane were established in the simulated space with the marks of medullary cavity and epicondyles. The correlation between the anteversion angle, Le. angle between neck-shaft plane and femoral condylar plane, and the modified one, Le. angle between neck-shaft plane and femoral proximal coronal plane, were calculated. In addition, the change of neck-shaft plane projection on the condylar plane was compared with the change of anteversion angle of the shaft to simulate the neck-shaft angle on the anterior C-armed X-ray images of the hip. Medullary cavity sagittal plane of proximal femur, rather than condylar plane, was used to represent femoral shaft anteversion angle. Paired t-test showed no significance difference （P 〉 0.05）. Linear regression was found between the change of neck-shaft angle of shaft-projection on the condylar plane and the change of anteversion angle of shaft. Femoral proximal condylar plane could be used to substitute condyle plane and be regarded as the reference to evaluate the anteversion of shaft. C-arm machine could be used as the supplement of surgical navigation technique. Neck-shaft angle of shaft-projection on the condylar plane shown in C-arm machine （anterior-posterior image of hip）, could be used to evaluate the anteversion of shaft.