北京生物醫(yī)學(xué)工程

基于顯微磁共振成像和有限元分析的股骨近端微觀力學(xué)行為研究

Study on micromechanical behavior of the proximal femur based on micro-magnetic resonance imaging and finite element analysis

作者：張凌云王玲劉有軍劉艷東梁偉張薇程曉光楊海勝

單位：北京工業(yè)大學(xué)生命科學(xué)與生物工程學(xué)院生物醫(yī)學(xué)工程系（北京100124）北京積水潭醫(yī)院放射科（北京100035）

關(guān)鍵詞：顯微磁共振成像；有限元分析；骨質(zhì)疏松；股骨；骨折風(fēng)險評價

分類號：R318.01

出版年·卷·期（頁碼）：2020·39·2（111-116）

摘要：

目的本研究利用高分辨率顯微磁共振成像（micro-magnetic resonance imaging, μMRI）在呈現(xiàn)骨微結(jié)構(gòu)方面的優(yōu)勢和對人體無輻射的優(yōu)點，結(jié)合有限元分析（finite element analysis, FEA），無創(chuàng)探究人體在自然站立狀態(tài)下股骨近端微觀力學(xué)行為，明確股骨易骨折危險區(qū)域，為μMRI-FEA未來臨床應(yīng)用提供理論基礎(chǔ)。方法采集5例年齡55~63歲女性志愿者（58.4歲±3.4歲）的股骨近端μMRI圖像。將圖像中骨骼和軟組織分割，三維重建得到包含股骨近端皮質(zhì)骨和松質(zhì)骨微結(jié)構(gòu)的大尺度三維有限元模型（約一千萬六面體單元），賦予非均勻材料屬性。模擬人體自然站立時股骨的受力，將其遠(yuǎn)端固定，在股骨頭部位施加壓縮載荷，進(jìn)行線彈性有限元分析，得到股骨近端的應(yīng)力和應(yīng)變分布，并選取股骨頸和大轉(zhuǎn)子部位10 mm3松質(zhì)骨感興趣區(qū)域進(jìn)行比較。結(jié)果人體自然站立姿態(tài)下，股骨頸上、下側(cè)皮質(zhì)骨分別出現(xiàn)拉、壓應(yīng)力集中現(xiàn)象。股骨頸松質(zhì)骨感興趣區(qū)域在上下（superior-inferior, SI）、內(nèi)外（medial-lateral, ML）和前后（anterior-posterior, AP）三個方向上的正應(yīng)力（σSI、σML、σAP）分別為大轉(zhuǎn)子部位的13.4、2.2和1.9倍；正應(yīng)變（εSI、εML、εAP）分別為大轉(zhuǎn)子部位的7.4、5.0和4.0倍。結(jié)論自然站立時股骨頸皮質(zhì)骨和松質(zhì)骨所受應(yīng)力和應(yīng)變較大，提示股骨頸是易發(fā)生骨折的高危區(qū)域，與臨床觀察一致。本研究為μMRI-FEA未來應(yīng)用于臨床無創(chuàng)評估股骨骨折風(fēng)險進(jìn)而鑒別骨折高風(fēng)險人群提供了一定的前期理論支撐。

Objective Taking the advantages of high-resolution micro magnetic resonance imaging (μMRI) on visualizing bone microstructure and having little radiation to patients, the current study used μMRI in combination with finite element analysis (FEA) to non-invasively explore the micromechanical behavior of the human femur under standing posture in order to identify regions at high risks of femoral fractures and eventually to provide a theoretical basis for future clinical applications of μMRI-FEA. Methods μMRI images of the proximal femurs were obtained from 5 female volunteers aged 55-63 years (mean 58.4±3.4 years old). The proximal femurs were segmented out from surrounding muscles and other soft tissues in the images. Large-scale three-dimensional finite element models (about 10 million hexahedral elements), including cortical and cancellous bone microstructures, were built and assigned with inhomogeneous material properties. To simulate the loading condition of the femur for the standing posture, the distal femur was fixed and a compressive load was applied to the femoral head. Linear elastic FEA was performed to obtain the distributions of stress and strain in the proximal femur. Regions of interest of 10 mm3 cancellous bone in the femoral neck and greater trochanter were selected for comparative analysis. Results Under the standing posture, tensile and compressive stress concentrations were observed in superior and inferior cortical bone of the femoral neck, respectively. For the cancellous regions of interest, the normal stresses along the superior-inferior (SI), medial-lateral (ML), and anterior-posterior (AP) directions (σSI, σML and σAP) in the femoral neck were 13.4, 2.2 and 1.9 times greater than those in the greater trochanter; the normal strains (εSI, εML, and εAP) in the femoral neck were 7.4 times, 5.0 times, and 4.0 times greater than those of the greater trochanter region. Conclusions Under the standing posture, the cortical and cancellous bone in the femoral neck was subjected to high stress and strain, indicating that the femoral neck is a region at high risk of fractures. This result is consistent with clinical observations. This study provides some preliminary theoretical basis for the future application of μMRI-FEA in clinical non-invasive assessment of fracture risk and identification of high-risk population.

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