Strain distribution in the proximal human femoral metaphysis

• Published in: Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine Journal of engineering in medicine, 2009-04, Vol.223 (3), p.273-288
• Main Authors: Cristofolini, L, Juszczyk, M, Taddei, F, Viceconti, M
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Anatomy; Anisotropy; Biomechanics; Biomedical materials; Bones; Compatibility; Compressive properties; Compressive Strength - physiology; Computer Simulation; Correlation; Cortical bone; Elastic Modulus - physiology; Female; Femur; Femur Head - physiology; Fractures; Gauges; Head; Hip; Hip joint; Humans; In vitro methods and tests; Male; Measuring instruments; Mechanical loading; Metaphysis; Middle Aged; Models, Biological; Prostheses; Simulation; Strain; Strain distribution; Strain gauges; Stress; Stress analysis; Stress concentration; Stress, Mechanical; Surgical implants; Variability; Weight-Bearing - physiology
• ISSN: 0954-4119; 2041-3033
• DOI: 10.1243/09544119JEIM497

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.