A three-dimensional finite element model from computed tomography data: A semi-automated method

Abstract

Three-dimensional finite element analysis is one of the best ways to assess stress and strain distributions in complex bone structures. However, accuracy in the results may be achieved only when accurate input information is given. A semi-automated method to generate a finite element (FE) model using data retrieved from computed tomography (CT) was developed. Due to its complex and irregular shape, the glenoid part of a left embalmed scapula bone was chosen as working material. CT data were retrieved using a standard clinical CT scanner (Siemens Somatom Plus 2, Siemens AG, Germany). This was done to produce a method that could later be utilized to generate a patient-specific FE model. Different methods of converting Hounsfield unit (HU) values to apparent densities and subsequently to Young's moduli were tested. All the models obtained were loaded using three-dimensional loading conditions taken from literature, corresponding to an arm abduction of 90 degrees. Additional models with different amounts of elements were generated to verify convergence. Direct comparison between the models showed that the best method to convert HU values directly to apparent densities was to use different equations for cancellous and cortical bone. In this study, a reliable method of determining both geometrical data and bone properties from patient CT scans for the semi-automated generation of an FE model is presented.

Subject-specific finite element models of long bones: An in vitro evaluation of the overall accuracy

“…The different behaviour we found for the twomaterial homogeneous and density-based inhomogeneous models confirms the results obtained by other authors (Cattaneo et al, 2001;Dalstra et al, 1995). In addition to their findings, where only superficial stresses were compared, we assert that the stress distributions inside the bone are significantly different as well.…”

“…However, it should be verified that the adoption of a two-material model does not compromise the accuracy of a simulation to a non-acceptable level. Other authors have addressed this question, but either lacked the experimental validation (Cattaneo et al, 2001) or limited their comparison to the maximum stress predicted on the surface of the bone without investigating the differences in the stress field distribution in the whole bone (Dalstra et al, 1995). In both cases, the authors came to the conclusion that adopting a two-material model does change the stress field distribution, however the point is to quantitatively evaluate how much it lowers the accuracy of the predicted results.…”

A new approach for assigning bone material properties from CT images into finite element models

“…Assigning material properties into a FE model usually needs an in-house program code, e.g., BONEMAT (Zannoni et al, 1998), AMAB (Kluess et al, 2009), and others (Cattaneo et al, 2001), to connect the CT dataset and FE dataset. The assignment program determines all CT image pixels that fall inside an element volume and assigns to the element the average value of these pixels Zannoni et al, 1998).…”

Effects of osteoarthritis on load transfer after cemented total shoulder arthroplasty

“…The number of elements was determined by a mesh convergence study that calculated the strain energy density within a region of interest in the glenoid (variance between consecutive models was <2%) as described in the literature. 3,14 Convergence of displacements in x, y, and z directions was also confirmed. The same baseline mesh was able to simulate changes in peg length.…”