Effects of bone density alterations on strain patterns in the pelvis: Application of a finite element model

Abstract

Insufficiency fractures occur when physiological loads are applied to bone deficient in mechanical resistance. A better understanding of pelvic mechanics and the effect of bone density alterations could lead to improved diagnosis and treatment of insufficiency fractures. This study aimed to develop and validate a subject-specific three-dimensional (3D) finite element (FE) model of a pelvis, to analyse pelvic strains as a function of interior and cortical surface bone density, and to compare high strain regions with common insufficiency fracture sites. The FE model yielded strong agreement between experimental and model strains. By means of the response surface method, changes to cortical surface bone density using the FE model were found to have a 60 per cent greater influence compared with changes in interior bone density. A small interaction was also found to exist between surface and interior bone densities (< 3 per cent), and a non-linear effect of surface bone density on strain was observed. Areas with greater increases in average principal strains with reductions in density in the FE model corresponded to areas prone to insufficiency fracture. Owing to the influence of cortical surface bone density on strain, it may be considered a strong global (non-linear) indicator for insufficiency fracture risk.

Finite element analysis of a hemi-pelvis: the effect of inclusion of cartilage layer on acetabular stresses and strain

“…This relationship predicted accurate distribution of Young's modulus within the cancellous bone in earlier studies Anderson et al 2005;Leung et al 2009;Zhang et al 2010). The range of Young's modulus for cancellous bone varied between 2.1 and 3846.54 MPa, similar to other studies (Anderson et al 2005;Zhang et al 2010).…”

“…The FE modelling approach of the pelvic bone was based on CT-scan data and image segmentation of cortical and cancellous bone boundaries, similar to previous studies Thompson et al 2002;Anderson et al 2005;Leung et al 2009;Zhang et al 2010). The CT-scan images of the pelvic bone of a 62-year-old female patient were stored in 500 X 410 pixels, having a pixel size of 0.781 mm and a slice thickness of 2.5 mm (equal to the distance between consecutive slices).…”

“…Second-order asymmetric surface-to-surface contact elements with Coulomb friction were simulated at the femoral head-cartilage interface for the models having cartilage layer (models 1 and 2) and at the spherical headacetabular interface (model 3), having a coefficient of friction 0.01 (Leung et al 2009). Since the cartilage layer is fixed to the bone surface, a bonded interface was assumed between the cartilage and the acetabular cavity ( Figure 1 (a)).…”

“…Email: sangupta@mech.iitkgp.emet.in stresses and strain (Anderson et al 2005;Cilingira et al 2007;Shim et al 2008;Leung et al 2009). Results of their studies, however, were not focused on acetabular stresses and strain.…”

Implementation of a standardized protocol to manage elderly patients with low energy pelvic fractures: can service improvement be expected?

“…Fractures of the pubis, which are visible on the X-ray, are nearly always associated with injuries of the posterior pelvic elements [21]. As most forces are transmitted through the posterior pelvic ring and the posterior joints [22], posterior fractures are viewed as more crucial than anterior fractures, and some clinicians and researchers plead for standardizing the use of CT scans in the diagnosis of elderly people presenting with low energy pelvic injury [17]. As shown also to our cohort, balancing decision making on plain imaging would mislead the mobilization guidance in 24.4%.…”