聚己内酯半月板支架应力-应变特性的有限元分析

目的：分析聚己内酯（PCL）半月板支架在膝关节中的应力-应变特性，评估其作为植入材料的可行性。方法：通过磁共振成像（MRI）扫描志愿者膝关节获取平面图像数据，建立包括股骨、胫骨、腓骨、股骨髁及胫骨平台关节软骨、内和外侧半月板及韧带在内的完整膝关节三维有限元模型，通过计算胫骨平台的接触面积与既往文献对比验证模型的有效性；分别建立内侧半月板切除术后的膝关节三维有限元模型及PCL半月板支架替代后的膝关节模型；对比分析在1400N股骨轴向垂直压力下3种膝关节模型的半月板位移和接触压力变化以及股骨髁关节软骨和胫骨平台关节软骨的压缩应力变化。结果：在1400N股骨轴向压缩载荷下健康膝关节模型内、外侧半月板位移分别为0.83和1.76mm，PCL模型内、外侧半月板位移分别为1.15和2.20mm。在同等载荷下，健康膝关节在胫骨平台关节软骨内、外侧最大压缩应力分别为2.5和1.7MPa，在内、外侧股骨髁关节软骨最大压缩应力分别为2.7和2.1MPa。在内侧半月板完整切除模型，内、外侧胫骨平台关节软骨最大压缩应力较健康模型分别增加260.0%和311.7%；内、外侧股骨髁关节软骨最大压缩应力较健康模型分别增长214.8%和271.4%。而在将内侧半月板替换为PCL支架的模型中，内、外胫骨平台关节软骨最大压缩应力较健康模型分别增加8.0%和5.9%；内、外侧股骨髁关节软骨最大压缩应力较健康模型分别增加11.1%和4.8%。结论：PCL支架在膝关节三维有限元模型中具有较好的生物力学特性，能够降低半月板切除后股骨髁及胫骨平台关节软骨的应力，达到保护关节软骨的目的。

Finite element analysis of stress-strain characteristics of polycaprolactone meniscus scaffold

Objective: To analyze the stress-strain characteristics of the polycaprolactone (PCL) meniscus scaffold in the knee joint,and to evaluate its feasibility as an implant material.Methods: The magnetic resonance imaging (MRI) scan of volunteer knee joints was used to obtain the planar image data.A three-dimensional finite element model including the femur, tibia, fibula, femoral condyle and tibial plateau articular cartilage, medial and lateral menisci, and ligaments was established.The validity of the model was verified by calculating the contact area of the tibial plateau and comparing with the previous literatures.On this basis, the three-dimensional finite element model of the knee joint after medial meniscectomy was established by deleting the medial meniscus unit and node of the normal knee joint.The knee joint model was established after replacement of the PCL meniscus.The changes of meniscal displacement and contact pressure in three types of knee joint models under 1 400 N femoral axial vertical pressure and the changes of compressive stresses on the femoral articular cartilage and tibial plateau articular cartilage were compared.Results: The displacements of the medial and lateral menisci of the healthy knee joint under the axial compression load of 1 400 N femur were 0.83 and 1.76 mm,respectively. The displacements of the medial and lateral meniscus of the PCL model were 1.15 and 2.20 mm,respectively. Under the same load, the maximum compressive stresses of the healthy knee joint on the medial and lateral cartilage of the tibial plateau were 2.5 and 1.7 MPa,respectively; the maximum compressive stresses on the medial and lateral femoral articular cartilage were 2.7 and 2.1 MPa, respectively. In the medial meniscus complete resection model, the maximum compressive stresses on the medial and lateral cartilage of the tibial plateau articular cartilage were 9.0 and 7.0 MPa, respectively, which were normal increase of 260.0% and 311.7%, respectively, compared with the healthy model; and the maximum compressive stresses on the medial and lateral femoral condylar cartilage were 8.5 and 7.8 MPa, respectively, which were 214.8% and 271.4% higher than the normal models, respectively. When the medial meniscus was replaced with the PCL scaffold, the maximum compressive stresses on the medial and lateral cartilage of the tibial plateau articular cartilage were 2.7 and 1.8 MPa, respectively, which were 8.0% and 5.9% higher than those of the healthy knee joint model, respectively. The maximum compressive stresses on the medial and lateral femoral condyle cartilage were 3.0 and 2.2 Mpa, respectively, which were 11.1% and 4.8% higher than the normal model.Conclusion: The three-dimensional finite element model of knee joint of PCL material has good biomechanical ability, which can reduce the stress of articular cartilage of femoral condyle and tibial plateau after meniscectomy and achieve the purpose of protecting the articular cartilage.