计算机处理MR图像股骨头坏死体积测定与初步力学测验

Volumetric measurement of osteonecrosis of the femoral head using computerized MR and primary mechanical test

目的依据MR图像数据在计算机上测定股骨头坏死的部位和体积,探讨其准确性及临床意义,并获得初步有限元分析结果。方法29例(38髋)晚期股骨头坏死行全髋人工关节置换术的患者,术前获得髋关节MR图像冠状面T1WI的医学数字影像传输(DICOM)格式数据。利用Mimics等软件获得相应的股骨头三维重构模型,读取股骨头及其坏死病灶的体积。使用移水法测出大体股骨头及其坏死病灶的体积。模拟人体载荷计算机有限元分析。结果股骨头坏死病灶位于股骨头的前外上方,与大体股骨头坏死病灶位置相符。计算机上测得坏死病灶和整个股骨头的体积分别为(20.1±6.6)cm3、(49.0±4.6)cm3,与大体测量值(20.2±6.5)cm3、(49.3±4.5)cm3间差异无统计学意义(t=-0.965,P=0.341;t=-1.592,P=0.120)。有限元计算结果当坏死体积>30%时,可见片状塌陷区。结论股骨头坏死的计算机三维模型可以直观地理解病灶的形状和位置,准确地测出病灶体积。如股骨头坏死体积>30%,易发生股骨头塌陷。

Objective To explore the accuracy and the clinical value of necrotic lesion location and vohme measured using MRI （ T1-weighted） coronal data sets. Methods Twenty-nine patients （38 hips） with osteonecrosis of the femorul head at late stage were performed by total hip arthroplasty. All patients were subjected to MRI imaging before operation. MRI （T1-weighted） coronal data sets were transferred to a computer in DICOM format using import and export images software（Mimics）. A three-dimensionul model of osteonecrosis of the femorul head was reconstructed. The vohme of the femorul head and the volume of the necrotic lesion were calculated using soflwsre. The volume of the entire femorul head and the necrotic lesion were measured using fluid displacement. The risk of collapse of different osteonecrotic vohme of the femorul head was evaluated using three-dimensionul finite element snulysis. Results The necrotic lesion was at anterolsteral and superior portion of the femorul head in the reconstructed three-dimensionul model of osteonecrosis of the femorul head, according with the anstomicul location of the lesion. The volumes of the necrotic lesion and entire femoral head obtained by computer and anatomical measurememts were （20. 1 ± 6.6） cm^3 , （ 49.0 ±4.6 ） cm^3 , and （ 20. 2 ± 6.5 ） cm3 , （ 49.3 ± 4. 5 ） cm^3. There was no significant difference between these two methods（ t = - 0. 965, P = 0. 341 ; t = - 1. 592, P = 0. 120）. When the necrotic vohme was more than 30%, large area of collapse would occur. Condusion A three-dimensionul model of osteonecrosis of the femorul head can be reconstructed exactly using computer. This will be helpful for orthopeadic surgeon to understand the shape and location of necrotic lesion of the femorul head intuitively and stereospeeificlly. The vohme of osteonecrosis can be determined with accuracy by computer, which is to match with anatomic vohme of lesion, if the necrotic vohme of the femorul head was more than 30%, it is easy to lead to collapse.