Panagiotopoulou Vasiliki C, Ovesy Marzieh, Gueorguiev Boyko, Richards R Geoff, Zysset Philippe, Varga Peter
AO Research Institute Davos, Switzerland; School of Chemical and Process Engineering, University of Leeds, UK.
ARTORG Center for Biomedical Engineering Research, University of Bern, Switzerland.
J Mech Behav Biomed Mater. 2021 Apr;116:104344. doi: 10.1016/j.jmbbm.2021.104344. Epub 2021 Jan 22.
Surgical treatment of proximal humerus fractures remains challenging, with a reported failure rate ranging from 15% to 35%. The dominant failure mode is secondary, i.e. post-operative screw perforation through the glenohumeral joint. A better understanding and the ability to predict this complication could lead to improved fracture fixation and decreased failure rate. The aims of this study were (1) to develop an experimental model for single screw perforation in the human humeral head and (2) to evaluate the ability of densitometric measures and micro finite element (microFE) analyses to predict the experimental failure event. Screw perforation was investigated experimentally in twenty cuboidal specimens cut from four pairs of fresh-frozen human cadaveric proximal humeral heads. A centrally inserted 3.5 mm screw was pushed quasi-statically at a constant displacement rate until perforation of the articular cartilage in each specimen. Force and displacement were recorded and evaluated at both initial screw loosening and perforation events. Bone volume was calculated around and in front of the screw and tip-to-joint distance was measured on the combined pre- and post-instrumentation micro computed tomography (microCT) scans. Implicit linear and explicit non-linear microFE models were created based on the microCT scans. The strength of these densitometric, geometrical and microFE methods to predict the experimental results was evaluated via correlation analysis. The bone volume measures were optimized in a parametric analysis to maximize correlation coefficients. The strongest and quantitatively correct predictions of perforation force (R = 0.93) and displacement (R = 0.77) were achieved using the explicit, non-linear microFE models. Linear microFE simulations provided the strongest predictions of loosening force (R = 0.90). Correlation strengths reached by optimized bone volume measures for predicting experimental force and by tip-to-joint distance for predicting displacement were only slightly inferior compared to the results of microFE models. The strong correlations achieved with densitometric and geometric measures indicate that monotonic perforation of single screws through the articular surface of the humeral head can be well predicted with these easily accessible measures. However, non-linear microFE models delivered even stronger correlations and quantitatively correct predictions of perforation force and displacement. This indicates that if computational resources are available, non-linear simulations may have a high potential to investigate more complex fixations and loading scenarios.
肱骨近端骨折的手术治疗仍然具有挑战性，报道的失败率在15%至35%之间。主要的失败模式是继发性的，即术后螺钉穿破盂肱关节。更好地理解并能够预测这种并发症可能会改善骨折固定并降低失败率。本研究的目的是：（1）建立人肱骨头单枚螺钉穿破的实验模型；（2）评估骨密度测量和微观有限元（microFE）分析预测实验失败事件的能力。在从四对新鲜冷冻的人尸体近端肱骨头切下的二十个长方体标本上进行螺钉穿破的实验研究。一枚中心插入的3.5毫米螺钉以恒定的位移速率准静态推压，直至每个标本的关节软骨被穿破。在初始螺钉松动和穿破事件时记录并评估力和位移。在螺钉周围和前方计算骨体积，并在术前和术后联合的微观计算机断层扫描（microCT）上测量尖端到关节的距离。基于microCT扫描创建隐式线性和显式非线性微观有限元模型。通过相关性分析评估这些骨密度、几何和微观有限元方法预测实验结果的能力。在参数分析中优化骨体积测量以最大化相关系数。使用显式非线性微观有限元模型对穿破力（R = 0.93）和位移（R = 0.77）实现了最强且定量正确的预测。线性微观有限元模拟对松动力给出了最强的预测（R = 0.90）。与微观有限元模型的结果相比，优化的骨体积测量预测实验力以及尖端到关节距离预测位移所达到的相关强度仅略逊一筹。骨密度和几何测量所实现的强相关性表明，通过这些易于获取的测量可以很好地预测单枚螺钉单调穿破肱骨头关节表面的情况。然而，非线性微观有限元模型给出了更强的相关性以及对穿破力和位移的定量正确预测。这表明如果有计算资源，非线性模拟在研究更复杂的固定和加载情况方面可能具有很大潜力。
