Kurtz Steven M, Rundell Steven A, Spece Hannah, Yarbrough Ronald V
Gyroid LLC, Haddonfield, NJ 08033, USA.
School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, PA 19104, USA.
Bioengineering (Basel). 2025 Feb 24;12(3):229. doi: 10.3390/bioengineering12030229.
A novel total joint replacement (TJR) that treats lumbar spine degeneration was previously assessed under Mode I and Mode IV conditions. In this study, we relied on these previous wear tests to establish a relationship between finite element model (FEM)-based bearing stresses and in vitro wear penetration maps. Our modeling effort addressed the following question of interest: Under reasonably worst-case misaligned conditions, do the lumbar total joint replacement (L-TJR) polyethylene stresses and strains remain below values associated with Mode IV impingement wear tests? The FEM was first formally verified and validated using the risk-informed credibility assessment framework established by ASME V&V 40 and FDA guidance. Then, based on criteria for unreasonable misuse outlined in the surgical technique guide, a parametric analysis of reasonably worst-case misalignment using the validated L-TJR FEM was performed. Reasonable misalignment was created by altering device positioning from the baseline condition in three scenarios: Axial Plane Convergence (20-40°), Axial Plane A-P Offset (0-4 mm), and Coronal Plane Tilt (±20°). We found that, for the scenarios considered, the contact pressures, von Mises stresses, and effective strains of the L-TJR-bearing surfaces remained consistent with Mode I (clean) conditions. Specifically, the mechanical response values fell below those determined under Mode IV (worst-case) boundary conditions, which provided the upper-bound benchmarks for the study (peak contact pressure 83.3 MPa, peak von Mises stress 32.2 MPa, and peak effective strain 42%). The L-TJR was judged to be insensitive to axial and coronal misalignment under the in vitro boundary conditions imposed by the study.
一种用于治疗腰椎退变的新型全关节置换术（TJR）此前已在I型和IV型条件下进行了评估。在本研究中，我们依据之前的磨损测试，建立了基于有限元模型（FEM）的轴承应力与体外磨损穿透图之间的关系。我们的建模工作解决了以下感兴趣的问题：在合理的最坏情况未对准条件下，腰椎全关节置换术（L-TJR）的聚乙烯应力和应变是否仍低于与IV型撞击磨损测试相关的值？首先，使用美国机械工程师协会（ASME）V&V 40和美国食品药品监督管理局（FDA）指南建立的风险知情可信度评估框架，对有限元模型进行了正式验证和确认。然后，根据手术技术指南中概述的不合理误用标准，使用经过验证的L-TJR有限元模型对合理的最坏情况未对准进行了参数分析。通过在三种情况下将设备定位从基线条件改变来创建合理的未对准：轴向平面会聚（20 - 40°）、轴向平面前后偏移（0 - 4 mm）和冠状面倾斜（±20°）。我们发现，对于所考虑的情况，L-TJR轴承表面的接触压力、冯·米塞斯应力和有效应变与I型（清洁）条件一致。具体而言，力学响应值低于在IV型（最坏情况）边界条件下确定的值，IV型边界条件为该研究提供了上限基准（峰值接触压力83.3 MPa、峰值冯·米塞斯应力32.2 MPa和峰值有效应变42%）。在本研究施加的体外边界条件下，L-TJR被判定对轴向和冠状未对准不敏感。
