Strain distribution in the proximal human femoral metaphysis

Abstract

There is significant interest in the stress-strain state in the proximal femoral metaphysis, because of its relevance for hip fractures and prosthetic replacements. The scope of this work was to provide a better understanding of the strain distribution, and of its correlation with the different directions of loading, and with bone quality. A total of 12 pairs of human femurs were instrumented with strain gauges. Six loading configurations were designed to cover the range of directions spanned by the hip joint force. Inter-specimen variability was reduced if paired specimens were considered. The principal strain magnitude varied greatly between loading configurations. This suggests that different loading configurations need to be simulated in vitro. The strain magnitude varied between locations but, on average, was compatible with the strain values measured in vivo. The strain magnitudes and the direction of principal tensile strain in the head and neck were compatible with the spontaneous fractures of the proximal femur reported in some subjects. The principal tensile strain was significantly larger where the cortical bone was thinner; the compressive strain was larger where the cortical bone was thicker. The direction of the principal strain varied significantly between measurement locations but varied little between loading configurations. This suggests that the anatomy and the distribution of anisotropic material properties enable the proximal femur to respond adequately to the changing direction of daily loading.

The influence of resection height on proximal femoral strain patterns after Metha short stem hip arthroplasty: an experimental study on composite femora

“…However, it has been reported [4] that studies, in which the testing set-up did not feature muscles [4,5], can reliably analyse the strain patterns of the proximal femur.…”

“…Level C was chosen to be around the distal tip of the Metha stem, while level B was directly in between levels A and C. The strain gauges at level D had a considerable distance from the distal tip of the implant so that they would not be affected by it. Thus, the read-outs of these gauges showed whether identical loading conditions were applied to intact and implanted femur [5].…”

Accuracy of finite element predictions in sideways load configurations for the proximal human femur

“…Sixteen triaxial strain gauges (C2A-06-031WW-350, Vishay Micro-Measurement, USA) were bonded around each femur (anterior, posterior, medial and lateral side) at four levels (head, neck, lesser trochanter and diaphysis) (Cristofolini et al, 2009). With respect to the reference study, an additional strain gauge was placed on the lateral neck aspect.…”

Extracting accurate strain measurements in bone mechanics: A critical review of current methods

“…The strain distribution in the proximal human femoral metaphysis was measured in different configurations resembling single leg stance, using non-destructive tests [36]. A force corresponding to 0.75 BW was applied, and bone was assumed to behave linearly until 2.5 BW.…”

“…Finally, SGs themselves have non-negligible stiffness, which leads to the so-called "reinforcement effect" [37]. The entity of the reinforcement can be calculated theoretically under certain conditions [55], [56], and has been estimated to be up to 15% on thin cortical sections of a femur using a validated FE procedure [36].…”