基于静态磁共振图像构建髌股关节准动态三维运动模型

Three-dimensional reconstruction of subject-specific dynamic patella of femoral joint using static magnetic resonance based methodology

目的创建基于多屈膝角度静态膝关节磁共振图像,构建完整屈伸膝过程的髌股关节准动态三维模型的方法。方法选择1名健康成年男性,年龄30岁,体重65 kg,身高172 cm,对其右膝关节分别在0°、30°、60°、90°、120°5个屈膝角度进行MRI扫描,并将扫描结果以Dicom格式导入Mimics软件中,提取髌骨、股骨轮廓,重建五个屈膝角度的静态髌股关节三维模型,再将上述五个静态模型导入逆向工程软件Rapidform中进行同一坐标系的配准,利用三次样条插值算法,将离散静态髌股关节模型配准为动态三维运动模型。据此动态三维模型计算髌骨运动轨迹并与既往文献结果对比以验证模型的准确性。结果基于静态核磁共振图像可以快速构建准确而无辐射的髌股关节准动态三维运动模型,以此动态模型计算出的髌骨运动轨迹和髌股关节旋转轴与既往文献结果相一致。结论本方法成功构建了包含屈膝0°到120°间的完整髌股关节运动过程,在屈膝过程中,随着屈膝角度的增加,髌骨相对于股骨滑车不断俯屈,同时轻度的外倾和外旋。

Objective To reconstruct the dynamic 3D motion model of patellofemoral joint based on multi- angle static magnetic resonance imaging. Methods A healthy adultmale was enrolled, whose right knee was scanned with a MR machine at 0°, 30°, 60°,90°, and 120° of knee flexion, then the MR images were imported into the Mimics in Dicom format, the shape of patella and femoral were extracted to calculate the static 3D model of patellofemoral joint at the five flexion angles. Then import the models into Rapidform at the same coordinate system to match the dynamic model using spline interpolation algorithm, and the patella tracking was calculated and compared with the experiments in literatures. Results Using static MR scanning technology could reconstruct the quasi dynamic 3D motion model of patellofemoral joint accurately and without radiation in a short time. The patellar tracking was within the range of experimental measurements which was calculated based on the dynamic model. Conclusion The dynamic 3D model of patellofemoral joint is successfully reconstructed which includes the full process of knee bending from full extension to the maximum flexion; during the flexion of knee, the patella keeps rotating and mildly flexing and tilting at the same time.