Assessing the use of finite element analysis for mechanical performance evaluation of intervertebral body fusion devices

Abstract

Background: Intervertebral body fusion devices (IBFDs) are a widely used type of spinal implant placed between two vertebral bodies to stabilize the spine for fusion in the treatment of spinal pathologies. Assessing mechanical performance of these devices is critical during the design, verification, and regulatory evaluation phases of development. While traditionally evaluated with physical bench testing, empirical assessments are at times supplemented with computational models and simulations such as finite element analysis (FEA). However, unlike many mechanical bench tests, FEA lacks standardized practices and consistency of implementation. Objectives: The objectives of this study were twofold. First, to identify IBFD 510(k) submissions containing FEA and conduct a comprehensive review of the elements provided in the FEA reports. Second, to engage with spinal device manufacturers through an anonymous survey and assess their practices for implementing FEA. Methods: First, a retrospective analysis of 510(k) submissions for IBFDs cleared by the FDA between 2013 and 2017 was performed. The contents of FEA test reports were quantified according to FDA guidance. Second, a survey inquiring about the use of FEA was distributed to industry and academic stakeholders. The survey asked up to 20 questions relating to modeler experience and modeling practices. Results: Significant gaps were present in model test reports that deemed the data unreliable and, therefore, unusable for regulatory decision-making in a high percentage of submissions. Nonetheless, the industry survey revealed most stakeholders employ FEA during device evaluation and are interested in more prescriptive guidelines for executing IBFD models. Conclusions: This study showed that while inconsistencies and gaps in FEA execution do exist within the spinal device community, the stakeholders are eager to work together in developing standardized approaches for executing computational models to support mechanical performance assessment of spinal devices in regulatory submissions.

Reproducibility in modeling and simulation of the knee: Academic, industry, and regulatory perspectives

“…With another orthopedic implant (intervertebral body fusion devices), the FDA observed that basic information needed to assess a computational model (code verification, mesh convergence, validation, and so on) was often not included in regulatory submissions. 50 Knee device submissions likely follow a similar trend. Therefore, the computational modeling community should focus on reproducibility and more trustworthy simulations.…”

“…Material models and contact interactions associated with the knee (bone, cartilage, ligaments, tendons, muscles, and so on) all present challenges when evaluating model credibility and associated device performance. With another orthopedic implant (intervertebral body fusion devices), the FDA observed that basic information needed to assess a computational model (code verification, mesh convergence, validation, and so on) was often not included in regulatory submissions 50 . Knee device submissions likely follow a similar trend.…”

Understanding the etiopathogenesis of lumbar intervertebral disc herniation: From clinical evidence to basic scientific research

“…209,210 Model translatability concerns refer to the challenges in translating model predictions to general experimental or clinical observations, which mainly arise from the wide range of assumptions used for model development, the large variations in constitutive descriptions used to simulate tissue behavior, and the lack of a standardized process for model validation. 181,211,212 181,213 In recent years, issues centered around model translatability has become a growing concern, as a greater number of implant companies use data from finite element models for regulatory clearance purposes. 211 4 | DISCUSSION: FUTURE DIRECTIONS Decades of herniation-oriented research resulted in many important and insightful studies that identified risk factors for herniation, characterized the structure-composition-function relationship in healthy, degenerated, and herniated disc tissues, and examined mechanisms of disc failure.…”

“…181,211,212 181,213 In recent years, issues centered around model translatability has become a growing concern, as a greater number of implant companies use data from finite element models for regulatory clearance purposes. 211 4 | DISCUSSION: FUTURE DIRECTIONS Decades of herniation-oriented research resulted in many important and insightful studies that identified risk factors for herniation, characterized the structure-composition-function relationship in healthy, degenerated, and herniated disc tissues, and examined mechanisms of disc failure. This substantial body of work improved our understanding of herniation etiopathogenesis.…”

Method of manufactured solutions code verification of elastostatic solid mechanics problems in a commercial finite element solver

“…As described in ASME V&V40-2018 [1], model predictions relied on for decision making should be accompanied by verification and validation (V&V) evidence demonstrating simulation credibility commensurate with the risk associated with the intended model use. However, rigorous code verification evidence for medical device simulations is often omitted (e.g., see Figure 1 in [2]), in part due to the lack of detailed examples to facilitate these studies. Herein, we aim to provide such an example for superelastic nitinol.…”