Srinivas C. Tadepalli

IA-FEMesh: An open-source, interactive, multiblock approach to anatomic finite element model development

Finite element (FE) analysis is a valuable tool in musculoskeletal research. The demands associated with mesh development, however, often prove daunting. In an effort to facilitate anatomic FE model development we have developed an open-source software toolkit (IA-FEMesh). IA-FEMesh employs a multiblock meshing scheme aimed at hexahedral mesh generation. An emphasis has been placed on making the tools interactive, in an effort to create a user friendly environment. The goal is to provide an efficient and reliable method for model development, visualization, and mesh quality evaluation. While these tools have been developed, initially, in the context of skeletal structures they can be applied to countless applications.

An interactive multiblock approach to meshing the spine

Finite element (FE) analysis is a useful tool to study spine biomechanics as a complement to laboratory-driven experimental studies. Although individualized models have the potential to yield clinically relevant results, the demands associated with modeling the geometric complexity of the spine often limit its utility. Existing spine FE models share similar characteristics and are often based on similar assumptions, but vary in geometric fidelity due to the mesh generation techniques that were used. Using existing multiblock techniques, we propose mesh generation methods that ease the effort and reduce the time required to create subject-specific allhexahedral finite element models of the spine. We have demonstrated the meshing techniques by creating a C4-C5 functional spinal unit and validated it by comparing the resultant motions and vertebral strains with data reported in the literature.

Feature-based multiblock finite element mesh generation

Hexahedral finite element mesh development for anatomic structures and biomedical implants can be cumbersome. Moreover, using traditional meshing techniques, detailed features may be inadequately captured. In this paper, we describe methodologies to handle multi-feature datasets (i.e., feature edges and surfaces). Coupling multi-feature information with multiblock meshing techniques has enabled anatomic structures, as well as orthopaedic implants, to be readily meshed. Moreover, the projection process, node and element set creation are automated, thus reducing the user interaction during model development. To improve the mesh quality, Laplacian- and optimization-based mesh improvement algorithms have been adapted to the multi-feature datasets.

Toward the Development of Virtual Surgical Tools to Aid Orthopaedic FE Analyses

Computational models of joint anatomy and function provide a means for biomechanists, physicians, and physical therapists to understand the effects of repetitive motion, acute injury, and degenerative diseases. Finite element models, for example, may be used to predict the outcome of a surgical intervention or to improve the design of prosthetic implants. Countless models have been developed over the years to address a myriad of orthopaedic procedures. Unfortunately, few studies have incorporated patient-specific models. Historically, baseline anatomic models have been used due to the demands associated with model development. Moreover, surgical simulations impose additional modeling challenges. Current meshing practices do not readily accommodate the inclusion of implants. Our goal is to develop a suite of tools (virtual instruments and guides) which enable surgical procedures to be readily simulated and to facilitate the development of all-hexahedral finite element mesh definitions.

A Framework for Finite Element Mesh Quality Improvement and Visualization in Orthopaedic Biomechanics

The finite element method (FEM) is an invaluable tool in the numerical simulation of biological processes. FEM entails discretization of the structure of interest into elements. This discretization process is termed finite element meshing. The validity of the solution obtained is highly dependent on the quality of the mesh used. Mesh quality can decrease with increased complexity of the structure of interest, as is often evident when meshing biologic structures. This necessitated the development/implementation of generalized mesh quality improvement algorithms.© 2009 ASME

Cervical Laminoplasty Construct Stability: A Finite Element Study

Cervical laminoplasty is one of many modern techniques utilized in the management of cervical myelopathy. In the United States cervical spondylotic myelopathy (CSM) has been classically treated with multilevel decompression and fusion. Furthermore, multi-level anterior cervical decompression and fusion (ACDF), via disectomies or corpectomies, and multi-level cervical laminectomy and fusion have been well described [1]. In the last decade cervical laminoplasty has grown in popularity as a non-fusion alternative that allows multi-level cervical decompression.Copyright

Semi-Automated Patient Specific Hexahedral Mesh Generation of Articular Cartilage

Articular cartilage is a critical component in the movement of one bone against another. It possesses unique chemical properties allowing it to serve as a bearing surface, capable of transferring loads from one bone to another while simultaneously allowing the load bearing surfaces to articulate with low friction. Patient-specific finite element (FE) models incorporating articular cartilage provide insight into articular joint mechanics [1, 2]. To date, the methods/tools available to create accurate FE mesh definitions of the articular cartilage are limited. Semi-automated morphing methods have been developed, but many intermediate steps have to be performed to get the final cartilage mesh definition [3]. Commercially available software [4] is capable of generating tetrahedral/shell/pyramid element based meshes of the cartilage from the underlying bony surface, but hexahedral meshes are preferred over tetrahedral meshes [5]. IA-FEMesh currently provides the ability to project a pre-defined set of elements a uniform distance [6]. This technique has been adopted in several models [1, 2]. Cartilage does not necessarily exist as such; rather the thickness of the cartilage is non-uniform and varies over the surface. Consequently an accurate representation of the articular cartilage is crucial for an accurate contact FE analysis. The goal of this study was to develop an algorithm that will aid in the generation of anatomically accurate cartilage FE mesh definitions in a reliable manner based on patient-specific image data.Copyright

Toward Patient-Specific Cervical Spine Functional Spinal Unit FE Modeling and Validation

Preventive measures and treatment modalities for correcting spinal disorders benefit significantly from advancements aimed at understanding the biomechanics of the human spine in the normal as well as altered states [1]. Finite element (FE) modeling is a useful tool to understand the behavior of the cervical spine under such conditions. In order for an FE model to yield clinically relevant results, the geometry must be as realistic as possible [2], in addition to incorporating accurate material properties and boundary conditions. The spine’s anatomy is very complex, rendering it difficult to acquire accurate geometrical representations for FE analysis. Many meshes in the literature are based on simplified or idealized geometries, or are assumed to be symmetric about the sagittal plane [3]. Traditional meshing techniques are time consuming and tedious, and lack remeshing capabilities [2]. The ability to create hexahedral cervical spine FE models on a patient-specific basis is a desirable task because it can account for variations in anatomy, as well as provide insight for surgical planning/treatment. Our mesh development methods improve on existing multi-block meshing methods to make this possible. We have created a C45 functional spinal unit (FSU) using these techniques, and to date have validated it by comparison to data presented in the literature.Copyright