Mischler Dominic, Schader Jana Felicitas, Dauwe Jan, Tenisch Lara, Gueorguiev Boyko, Windolf Markus, Varga Peter
AO Research Institute Davos, Davos, Switzerland.
Department of Trauma Surgery, UZ Leuven, Leuven, Belgium.
Front Bioeng Biotechnol. 2022 Jun 23;10:919721. doi: 10.3389/fbioe.2022.919721. eCollection 2022.
Joint-preserving surgical treatment of complex unstable proximal humerus fractures remains challenging, with high failure rates even following state-of-the-art locked plating. Enhancement of implants could help improve outcomes. By overcoming limitations of conventional biomechanical testing, finite element (FE) analysis enables design optimization but requires stringent validation. This study aimed to computationally enhance the design of an existing locking plate to provide superior fixation stability and evaluate the benefit experimentally in a matched-pair fashion. Further aims were the evaluation of instrumentation accuracy and its potential influence on the specimen-specific predictive ability of FE. Screw trajectories of an existing commercial plate were adjusted to reduce the predicted cyclic cut-out failure risk and define the enhanced (EH) implant design based on results of a previous parametric FE study using 19 left proximal humerus models (Set A). Superiority of EH versus the original (OG) design was tested using nine pairs of human proximal humeri ( = 18, Set B). Specimen-specific CT-based virtual preoperative planning defined osteotomies replicating a complex 3-part fracture and fixation with a locking plate using six screws. Bone specimens were prepared, osteotomized and instrumented according to the preoperative plan a standardized procedure utilizing 3D-printed guides. Cut-out failure of OG and EH implant designs was compared in paired groups with both FE analysis and cyclic biomechanical testing. The computationally enhanced implant configuration achieved significantly more cycles to cut-out failure compared to the standard OG design ( < 0.01), confirming the significantly lower peri-implant bone strain predicted by FE for the EH versus OG groups ( < 0.001). The magnitude of instrumentation inaccuracies was small but had a significant effect on the predicted failure risk ( < 0.01). The sample-specific FE predictions strongly correlated with the experimental results (R = 0.70) when incorporating instrumentation inaccuracies. These findings demonstrate the power and validity of FE simulations in improving implant designs towards superior fixation stability of proximal humerus fractures. Computational optimization could be performed involving further implant features and help decrease failure rates. The results underline the importance of accurate surgical execution of implant fixations and the need for high consistency in validation studies.
对于复杂不稳定的肱骨近端骨折，保留关节的手术治疗仍然具有挑战性，即使采用最先进的锁定钢板，失败率也很高。增强植入物可能有助于改善治疗效果。通过克服传统生物力学测试的局限性，有限元（FE）分析能够实现设计优化，但需要严格的验证。本研究旨在通过计算增强现有锁定钢板的设计，以提供更好的固定稳定性，并以配对方式进行实验评估其益处。进一步的目标是评估器械置入的准确性及其对FE针对特定标本的预测能力的潜在影响。根据先前使用19个左侧肱骨近端模型（A组）进行的参数化FE研究结果，调整现有商用钢板的螺钉轨迹，以降低预测的循环切出失败风险，并确定增强型（EH）植入物设计。使用九对人类肱骨近端（n = 18，B组）测试EH设计相对于原始（OG）设计的优越性。基于特定标本的CT虚拟术前规划确定了模拟复杂三部分骨折的截骨术，并使用六枚螺钉用锁定钢板进行固定。根据术前计划制备骨标本、进行截骨并置入器械——这是一种利用3D打印导向器的标准化程序。通过FE分析和循环生物力学测试，在配对组中比较OG和EH植入物设计的切出失败情况。与标准OG设计相比，计算增强后的植入物配置实现切出失败的循环次数显著更多（p < 0.01），证实FE预测EH组相对于OG组的植入物周围骨应变显著更低（p < 0.001）。器械置入不准确的程度较小，但对预测的失败风险有显著影响（p < 0.01）。当纳入器械置入不准确因素时，特定样本的FE预测与实验结果高度相关（R = 0.70）。这些发现证明了FE模拟在改进植入物设计以实现肱骨近端骨折更好的固定稳定性方面的能力和有效性。可以对进一步的植入物特征进行计算优化，并有助于降低失败率。结果强调了准确进行植入物固定手术的重要性以及验证研究中保持高度一致性的必要性。
