股骨远端前缘骨缺损对股骨假体稳定性影响的有限元分析

Finite Element Analysis of the Effect of Anterior Bone Defects at the Distal End of the Femur on the Stability of Femoral Prostheses

摘要: 背景：骨缺损是膝关节翻修术中最困难的挑战之一，对骨缺损进行正确的评估和分型至关重要。Anderson骨科研究所分型系统(AORI)是广为接受的骨缺损分型系统，在临床上最为常用，但该分型系统没有提及股骨远端前缘缺损类型。本研究旨在通过有限元分析来模拟股骨远端前缘骨缺损对翻修假体应力分布的影响。此外，本研究还探讨了针对这类缺损的合理治疗方案。方法：使用健康志愿者的计算机断层扫描图像构建股骨远端的三维有限元模型。首先，在该模型的前缘上，人为构建两种不同大小的骨缺损模型。然后模拟三种膝关节翻修方案：未填充、骨水泥填充、以及用患者个性化钛合金骨小梁(TTM)填充，并根据缺损大小、缺损填充方式以及假体的类型，通过不同的组合方式模拟了7种翻修膝关节有限元模型。研究设定在膝关节屈曲不同角度(15˚、45˚和60˚)，并在统一载荷和边界条件下进行了有限元研究。选取两个感兴趣区域(ROI)，ROI1是骨水泥套层区域，ROI2是用TTM或骨水泥填充的缺损区域，分析这些感兴趣区域的最大接触压力和载荷分布。结果：骨水泥套层区和填充的缺损区域的应力分布受膝关节屈曲角度和骨缺损大小的影响。大缺损模型上的接触压力与小缺损模型相比显著增加，最大可达737.3 MPa。在大缺损模型中，用钛合金骨小梁(TTM)填充骨缺损可将骨水泥套层上的最大应力显著降低至91.30 MPa。此外，翻修模型中带有延长柄假体的膝关节表现出优越的生物力学性能。结论：股骨前缘骨缺损影响股骨远端的生物力学性能。特别是大的骨缺损可能导致骨–假体界面上的应力更加集中，这可能会影响假体的稳定性。患者的个性化TTM可以为治疗骨缺损提供一种新颖、合理的方法。尽管现有临床观察与生物力学模拟结果提示该股骨远端前缘骨缺损具备独特力学表现，其生物力学特征提升其可能是一种值得进一步临床研究的特殊缺损类型，但针对该类缺损的规范化治疗方案目前尚无统一共识。因此，有必要进行进一步的研究，包括生物力学实验和临床试验，以应对骨缺损的挑战。

Abstract: Background: Bone defects are one of the most difficult challenges in knee revision surgery, and their accurate assessment and classification are crucial. The Anderson Orthopaedic Research Institute (AORI) classification system is a widely accepted and clinically prevalent system for classifying bone defects; however, it does not address defects involving the anterior aspect of the distal femur. This study aims to simulate the effects of distal femoral anterolateral bone defects on stress distribution in revision prostheses using finite element analysis. Additionally, this study explores reasonable treatment strategies for this type of defect. Methods: A three-dimensional finite element model of the distal femur was constructed using computed tomography (CT) images from healthy volunteers. First, two bone defect models of different sizes were artificially created on the anterolateral aspect of the model. Then, three knee revision scenarios were simulated: unfilled, cement-filled, and filled with patient-specific titanium trabecular metal (TTM). Seven finite element models of revision knee joints were simulated through various combinations based on defect size, filling method, and prosthesis type. The study was conducted at different knee flexion angles (15˚, 45˚, and 60˚) under uniform loading and boundary conditions. Two regions of interest (ROIs) were selected: ROI1 was the cement sleeve region, and ROI2 was the defect region filled with TTM or bone cement. The maximum contact pressure and load distribution in these regions of interest were analyzed. Results: The stress distribution in the cement sleeve region and the filled defect region was influenced by the knee flexion angle and the size of the bone defect. Contact pressure on the large defect model increased significantly compared to the small defect model, reaching a maximum of 737.3 MPa. In the large defect model, filling the bone defect with titanium trabecular mesh (TTM) significantly reduced the maximum stress on the cemented liner to 91.30 MPa. Furthermore, the knee joint with an extended-stem prosthesis in the revision model exhibited superior biomechanical performance. Conclusion: Anterior femoral bone defects affect the biomechanical performance of the distal femur. In particular, large bone defects may lead to increased stress concentration at the bone-prosthesis interface, which could compromise prosthesis stability. Patient-specific TTMs offer a novel and rational approach to treating bone defects. Although existing clinical observations and biomechanical simulation results indicate that bone defects at the anterior aspect of the distal femur exhibit unique mechanical behavior—and their biomechanical characteristics suggest that this may be a specific type of defect warranting further clinical research—there is currently no consensus on a standardized treatment protocol for such defects. Therefore, further research, including biomechanical experiments and clinical trials, is necessary to address the challenges posed by bone defects.