Malalignment is a common complication in the treatment of distal fractures of the tibia. Numerous efforts have been made to reduce the malalignment ratio. However, the reported cases with this disorder are still high. This study aimed at investigating an adaptive design of an intramedullary nail with a novel interlocking mechanism (AINIM), as an alternative for the customary nailing, in reducing malalignment ratio. A verified finite element model was employed to compare the performance of AINIM with the customary nail. The finite element model of the tibia follows the exact shape of the medullary canal, and nonhomogeneous material properties were assigned to the bone from bone ash density. It was assumed that the nails were implanted and interlocked in the tibia according to surgical protocols, and physiological-like loading was applied to finite element models. The results of this study showed that AINIM reduces the mean shear interfragmentary strains by about 30%, and the axial interfragmentary strain by 55%, also it increases the uniformity in the interfragmentary movements, compared to the customary nail. It was also found that AINIM caused a reduction of the stress on the nail by 60%, and an increase of 25% on the bone, compared to the customary nail. Moreover, average compressive principal strains in the tibia fixed by AINIM increased by 40% from 485 to 678 με, compared to the tibia fixed by the customary nailing method. The results of this work also showed that AINIM causes an increase in the contact area with the intramedullary canal, particularly at the fracture site, and it also escalates the magnitude of contact pressure. Results of this work indicate that, from the biomechanical standpoint, the adaptive nail, i.e. AINIM, with an innovative interlocking mechanism, compared to the customary nailing, can lessen intra- and post-operative malalignment occurrence, and it also mitigates the side effects of stress shielding, and thus better conserves neighboring bone density in a long period.

中文翻译：

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具有新型联锁机构的自适应髓内钉的设计与数值研究

畸形是胫骨远端骨折的常见并发症。已经进行了许多努力来减小未对准比率。但是，报告的这种疾病病例仍然很高。这项研究旨在研究一种具有新型互锁机制（AINIM）的髓内钉的自适应设计，以替代传统的钉扎方法，以减少错位比。使用经过验证的有限元模型来比较AINIM和常规指甲的性能。胫骨的有限元模型遵循了髓管的确切形状，并且根据骨灰密度将非均质的材料属性分配给了骨骼。假设根据手术方案将钉子植入并锁在胫骨中，并将类似生理的载荷应用于有限元模型。这项研究的结果表明，与常规指甲相比，AINIM可以将平均剪切片段间应变降低约30％，将轴向片段间应变降低55％，并且还可以增加片段间运动的均匀性。还发现，与常规指甲相比，AINIM可使指甲上的应力减少60％，并使骨骼上的应力增加25％。此外，AINIM固定胫骨的平均压缩主应变从485增加到678，增加了40％。还发现，与常规指甲相比，AINIM可使指甲上的应力减少60％，并使骨骼上的应力增加25％。此外，AINIM固定胫骨的平均压缩主应变从485增加到678，增加了40％。还发现，与常规指甲相比，AINIM可使指甲上的应力减少60％，并使骨骼上的应力增加25％。此外，AINIM固定胫骨的平均压缩主应变从485增加到678，增加了40％。与通过常规钉扎方法固定的胫骨相比，με。这项工作的结果还表明，AINIM引起与髓内管的接触面积增加，特别是在骨折部位，并且还增加了接触压力的大小。这项工作的结果表明，从生物力学的角度来看，与常规的钉子相比，具有创新的互锁机制的自适应钉子即AINIM可以减少术中和术后错位的发生，并且还减轻了钉子的副作用。应力屏蔽，因此可以更好地长期保存邻近的骨密度。