Bagheri Zahra S, Tavakkoli Avval Pouria, Bougherara Habiba, Aziz Mina S R, Schemitsch Emil H, Zdero Radovan
J Biomech Eng. 2014 Sep;136(9):091002. doi: 10.1115/1.4027669.
Femur fracture at the tip of a total hip replacement (THR), commonly known as Vancouver B1 fracture, is mainly treated using rigid metallic bone plates which may result in "stress shielding" leading to bone resorption and implant loosening. To minimize stress shielding, a new carbon fiber (CF)/Flax/Epoxy composite plate has been developed and biomechanically compared to a standard clinical metal plate. For fatigue tests, experiments were done using six artificial femurs cyclically loaded through the femoral head in axial compression for four stages: Stage 1 (intact), stage 2 (after THR insertion), stage 3 (after plate fixation of a simulated Vancouver B1 femoral midshaft fracture gap), and stage 4 (after fracture gap healing). For fracture fixation, one group was fitted with the new CF/Flax/Epoxy plate (n = 3), whereas another group was repaired with a standard clinical metal plate (Zimmer, Warsaw, IN) (n = 3). In addition to axial stiffness measurements, infrared thermography technique was used to capture the femur and plate surface stresses during the testing. Moreover, finite element analysis (FEA) was performed to evaluate the composite plate's axial stiffness and surface stress field. Experimental results showed that the CF/Flax/Epoxy plated femur had comparable axial stiffness (fractured = 645 ± 67 N/mm; healed = 1731 ± 109 N/mm) to the metal-plated femur (fractured = 658 ± 69 N/mm; healed = 1751 ± 39 N/mm) (p = 1.00). However, the bone beneath the CF/Flax/Epoxy plate was the only area that had a significantly higher average surface stress (fractured = 2.10 ± 0.66 MPa; healed = 1.89 ± 0.39 MPa) compared to bone beneath the metal plate (fractured = 1.18 ± 0.93 MPa; healed = 0.71 ± 0.24 MPa) (p < 0.05). FEA bone surface stresses yielded peak of 13 MPa at distal epiphysis (stage 1), 16 MPa at distal epiphysis (stage 2), 85 MPa for composite and 129 MPa for metal-plated femurs at the vicinity of nearest screw just proximal to fracture (stage 3), 21 MPa for composite and 24 MPa for metal-plated femurs at the vicinity of screw farthest away distally from fracture (stage 4). These results confirm that the new CF/Flax/Epoxy material could be a potential candidate for bone fracture plate applications as it can simultaneously provide similar mechanical stiffness and lower stress shielding (i.e., higher bone stress) compared to a standard clinical metal bone plate.
全髋关节置换（THR）末端的股骨骨折，通常称为温哥华B1型骨折，主要使用刚性金属骨板进行治疗，这可能会导致“应力遮挡”，进而导致骨吸收和植入物松动。为了尽量减少应力遮挡，已开发出一种新型碳纤维（CF）/亚麻/环氧树脂复合板，并与标准临床金属板进行了生物力学比较。对于疲劳测试，使用六根人工股骨进行实验，通过股骨头在轴向压缩下循环加载四个阶段：第1阶段（完整）、第2阶段（THR植入后）、第3阶段（模拟温哥华B1型股骨干中段骨折间隙的钢板固定后）和第4阶段（骨折间隙愈合后）。对于骨折固定，一组安装新型CF/亚麻/环氧树脂板（n = 3），而另一组用标准临床金属板（Zimmer，华沙，印第安纳州）修复（n = 3）。除了轴向刚度测量外，还使用红外热成像技术在测试过程中捕捉股骨和钢板表面应力。此外，进行了有限元分析（FEA）以评估复合板的轴向刚度和表面应力场。实验结果表明，CF/亚麻/环氧树脂板固定的股骨与金属板固定的股骨具有相当的轴向刚度（骨折时 = 645±67 N/mm；愈合时 = 1731±109 N/mm）（金属板固定的股骨骨折时 = 658±69 N/mm；愈合时 = 1751±39 N/mm）（p = 1.00）。然而，与金属板下方的骨相比，CF/亚麻/环氧树脂板下方的骨是唯一平均表面应力显著更高的区域（骨折时 = 2.10±0.66 MPa；愈合时 = 1.89±0.39 MPa）（金属板下方的骨骨折时 = 1.18±0.93 MPa；愈合时 = 0.71±0.24 MPa）（p < 0.05）。有限元分析得出的骨表面应力在远端骨骺处（第1阶段）峰值为13 MPa，在远端骨骺处（第2阶段）为16 MPa，在骨折近端最近螺钉附近，复合板固定的股骨为85 MPa，金属板固定的股骨为129 MPa（第3阶段），在骨折远端最远螺钉附近，复合板固定的股骨为21 MPa，金属板固定的股骨为24 MPa（第4阶段）。这些结果证实，新型CF/亚麻/环氧树脂材料可能是骨折钢板应用的潜在候选材料，因为与标准临床金属骨板相比，它可以同时提供相似的机械刚度和更低的应力遮挡（即更高的骨应力）。
