Achieving satisfactory fracture fixation in osteoporotic patients with unstable proximal humerus fractures remains a major clinical challenge. Varus collapse is one of the more prominent complications that may lead to screw cutout. This aim of this study was to compare the fixation provided by conventional locking plates with novel design concepts that are only feasible through additive manufacturing (AM) techniques. In addition to reversed engineered implants, two novel implant designs with integrated struts were included in the study to provide medial support to humeral head. The medial strut was either solid or included a porous lattice structure intended to promote bone ingrowth. Biomechanical tests were performed using low density synthetic bones with simulated 3-part comminuted fractures. Nondestructive torsion and compression were performed, followed by increasing cyclic loading. The relative displacements between the bone fragments were determined using a 3D motion capture system. The AM manufactured implants with medial strut showed significant reduction of varus displacement during the increasing cyclic loading when compared to conventional designs. AM reversed-engineered locking plates showed similar mechanical behavior to conventional plates with identical geometry. This study demonstrates the feasibility and potential of employing alternative design via AM for fixation of unstable comminuted proximal humerus fractures to reduce fragment displacement.

中文翻译：

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增材制造的肱骨近端骨折固定板的生物力学测试

在不稳定的肱骨近端骨折的骨质疏松患者中实现令人满意的骨折固定仍然是一项重大的临床挑战。内翻塌陷是可能导致螺钉切开的最突出的并发症之一。这项研究的目的是将常规锁定板提供的固定与只有通过增材制造（AM）技术才可行的新颖设计概念进行比较。除了反向工程植入物外，该研究还包括两种带有集成支杆的新型植入物设计，以为肱骨头提供内侧支撑。内侧支柱是实心的或包括旨在促进骨骼向内生长的多孔网格结构。使用具有模拟的三部分粉碎性骨折的低密度合成骨进行生物力学测试。进行无损扭转和压缩，其次是增加循环载荷。使用3D运动捕捉系统确定骨骼碎片之间的相对位移。与常规设计相比，AM制造的具有内侧支撑的植入物在循环载荷增加期间内翻位移明显减少。AM逆向工程锁板显示出与具有相同几何形状的传​​统锁板相似的机械性能。这项研究证明了采用替代设计的可行性和潜力 AM逆向工程锁板显示出与具有相同几何形状的传​​统锁板相似的机械性能。这项研究证明了采用替代设计的可行性和潜力 AM逆向工程锁板显示出与具有相同几何形状的传​​统锁板相似的机械性能。这项研究证明了采用替代设计的可行性和潜力 通过AM固定不稳定的肱骨近端粉碎性骨折，以减少碎片移位。