Need for CT-based bone density modelling in finite element analysis of a shoulder arthroplasty revealed through a novel method for result analysis

Abstract

Treatment of common pathologies of the shoulder complex, such as rheumatoid arthritis and osteoporosis, is usually performed by total shoulder arthroplasty (TSA). Survival of the glenoid component is still a problem in TSA, whereas the humeral component is rarely subject to failure. To set up a finite element analysis (FEA) for simulation of a TSA in order to gain insight into the mechanical behaviour of a glenoid implant, the modelling procedure and the application of boundary conditions are of major importance because the computed result strongly depends upon the accuracy and sense of realism of the model. The goal of this study was to show the influence on glenoid stress distribution of a patient-specific bone density distribution compared with a homogenous bone density distribution for the purpose of generating a valid model in future FEA studies of the shoulder complex. Detailed information on the integration of bone density properties using existing numerical models as well as the applied boundary conditions is provided. A novel approach involving statistical analysis of values derived from an FEA is demonstrated using a cumulative distribution function. The results show well the mechanically superior behaviour of a realistic bone density distribution and therefore emphasise the necessity for patient-specific simulations in biomechanical and medical simulations.

Mechanical behavior of hybrid glenoid components compared to all-PE components: a finite element analysis

“…The bone density in each voxel was estimated by applying the method described by Pomwenger et al [11] (Additional file 1). Mean cortical () and mean trabecular () densities were first calculated, before the Young’s moduli () were assigned to the cortical and trabecular bone volumes according to the method proposed by Pomwenger et al [12] (Table 1). A Poisson ratio of 0.3 was assigned for both cortical and trabecular bone [13].…”

Quantifying the competing relationship between adduction range of motion and baseplate micromotion with lateralization of reverse total shoulder arthroplasty

“…Cancellous bone material properties were assigned on an element-by-element basis as calculated from corresponding CT data (Taddei et al, 2008 – http://bonemat.org); a linear relationship between Hounsfield Unit (HU) and density with a slope of 0.002 and an intercept of 0.001 was defined. Subsequently, previously established equations to convert Hounsfield Units (HU) to elastic modulus were employed (Pomwenger et al, 2014), resulting in cancellous bone element elastic moduli ranging from 0 (empty space) to 17,500 MPa.…”

Treating posteriorly eroded glenoids with augmented baseplate or bony increased-offset reverse shoulder arthroplasty: a finite element comparison

“…The HU intensity for each scan was internally calibrated using a linear regression technique of in-scan regions-of-interest (ROI) established by Michalski et al 29 . The calibrated HU values were then used to calculate the apparent bone density for each element using the equation of Pomwenger et al 32 .…”