The First Clinical Medical College, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, China.
Department of Orthopedic, Zhongxiang People's Hospital, Jingmen, Hubei, China.
BMC Musculoskelet Disord. 2021 Dec 2;22(1):1010. doi: 10.1186/s12891-021-04878-2.
There are concerns regarding initial stability and cutout effect in proximal femoral nail antirotation (PFNA) treating intertrochanteric fractures. No study have used finite element analysis (FEA) to investigate the biomechanics. This study aimed to compare the cutout effect, stress and displacement between stable (AO31-A1.3) and unstable (AO31-A2.2) intertrochanteric fractures treated by cement augmented PFNA.
Four femoral finite element models (FEMs) were constructed and tested under the maximum loading during walking. Non-augmented and augmented PFNA in two different intertrochanteric fractures were respectively simulated, assuming Tip Apex Distance (TAD) < 25 mm within each FEM. The cutout effect, stress and displacement between femur and PFNA were compared in each condition.
Cutout effect was observed in both non-augmented femoral head and was more apparently in unstable intertrochanteric fracture model. After reinforced by bone cement, no cutout effect occurred in two models. Stress concentration were observed on medial part of intertrochanteric region and the proximal part of helical blade before augmented while were observed on femoral shaft and the conjunction between blade and nail after augmented in both FEMs. Displacement mainly appeared on femoral head and the helical blade tip before augmented while distributed moderately on intertrochanteric region and the upper part of nail after augmented in both FEMs. The maximum stress and displacement value of femur decreased both in stable and unstable model after augmented but was more significantly in the unstable one. The maximum stress and displacement value of PFNA increased both in stable and unstable model after augmented but was more significantly in the unstable one.
Our FEA study indicated that the cement augmentation of the PFNA biomechanically enhances the cutout resistance in intertrochanteric fracture, this procedure is especially efficient for the unstable intertrochanteric fracture.
股骨近端防旋髓内钉（PFNA）治疗股骨转子间骨折存在初始稳定性和切出效应的担忧。目前尚无研究采用有限元分析（FEA）来研究生物力学。本研究旨在比较稳定（AO31-A1.3）和不稳定（AO31-A2.2）转子间骨折经骨水泥增强 PFNA 治疗后的切出效应、应力和位移。
构建并测试了 4 个股骨有限元模型（FEM），在步行时最大载荷下进行测试。分别模拟了非增强和增强的 PFNA 在两种不同的转子间骨折中，假设每个 FEM 中 Tip Apex Distance（TAD）<25mm。在每种情况下比较了股骨和 PFNA 之间的切出效应、应力和位移。
在非增强的股骨头中均观察到切出效应，在不稳定的转子间骨折模型中更为明显。增强后，两种模型均未发生切出效应。增强前，在转子间区域的内侧部分和螺旋刀片的近端部分观察到应力集中，增强后则在两个模型中均在股骨和刀片与钉之间的连接处观察到。在增强之前，位移主要出现在股骨头和螺旋刀片的尖端，而在增强之后，位移则均匀分布在转子间区域和钉的上部。在增强后，无论是稳定型还是不稳定型模型，股骨的最大应力和位移值均降低，但不稳定型更为显著。在增强后，无论是稳定型还是不稳定型模型，PFNA 的最大应力和位移值均增加，但不稳定型更为显著。
我们的 FEA 研究表明，PFNA 的骨水泥增强在生物力学上增强了转子间骨折的切出阻力，对于不稳定的转子间骨折，这种方法尤其有效。
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