Annals of Biomedical Engineering

, Volume 37, Issue 9, pp 1910–1920

Assessing the Susceptibility to Local Buckling at the Femoral Neck Cortex to Age-Related Bone Loss

  • Taeyong Lee
  • Jae Bong Choi
  • Benjamin W. Schafer
  • W. Paul Segars
  • Felix Eckstein
  • Volker Kuhn
  • Thomas J. Beck
Article

DOI: 10.1007/s10439-009-9751-9

Cite this article as:
Lee, T., Choi, J.B., Schafer, B.W. et al. Ann Biomed Eng (2009) 37: 1910. doi:10.1007/s10439-009-9751-9

Abstract

Although it is known that long cortical bone structurally alter their area moment of inertia with age related bone loss maintaining their bending strength, the incidence of fragility fractures associated with cortical thinning still prevails. We hypothesize that cortical thinning with aging increases the local buckling susceptibility under abnormal or eccentric loads, and initiates fracture. The paper presents a series of 3D geometrical model derived from CT scans of a human femoral neck used to simulate age-related bone loss. The purpose of the model is to predict the susceptibility of local buckling at the femoral neck in falls by elderly folks. Geometric three-dimensional models of femoral neck cortices were developed from 7 human cadaver femurs (4 female, 3 male, 52–68 years). Three age related femoral neck models were simulated by either reducing (young age-related model) or increasing (old age-related model) the outer cortical surfaces in the radial-direction, by 1-mm. The control model was the middle-age related model. The inner cortex diameter was also adjusted to equilibrate the compressive stresses, based on the load-profile of a single-legged stance. Based on the old age related model, two additional “fragile” models were simulated by reducing the compressive load profile by 10 and 20% changing the inner cortex diameter, respectively. Using these models for each specimen, the consequence of a fall on the greater trochanter was evaluated. The Finite Strip Method (FSM) was used to investigate the association between local buckling at the femoral neck and the load to failure. Under constant loading, buckling progressively reduced the load to failure with aging, as seen in 2/7 of the middle age (by 9–15%) and 5/7 of the old age (by 7–32%) related models. In the fragile models, a 51% reduction in the load to failure was noted. Structural adaptation to age-related bone loss might preserves the bending strength under physiologic loads, but cortical thinning effects the buckling ratio reaching a critical threshold that would make the bone susceptible to local buckling at the femoral neck increasing the risk of fracture in a fall.

Keywords

Age related bone adaptationFemoral neck agingHomeostatic adaptationLocal buckling

Copyright information

© Biomedical Engineering Society 2009

Authors and Affiliations

  • Taeyong Lee
    • 1
  • Jae Bong Choi
    • 2
  • Benjamin W. Schafer
    • 3
  • W. Paul Segars
    • 4
  • Felix Eckstein
    • 5
  • Volker Kuhn
    • 6
  • Thomas J. Beck
    • 3
  1. 1.Division of Bioengineering, Faculty of EngineeringNational University of SingaporeSingaporeSingapore
  2. 2.Department of Mechanical Systems EngineeringHansung UniversitySeoulKorea
  3. 3.Department of Civil Engineering, Whiting School of EngineeringThe Johns Hopkins UniversityBaltimoreUSA
  4. 4.Department of Radiology and Radiological Science, School of MedicineThe Johns Hopkins UniversityBaltimoreUSA
  5. 5.Institute of Anatomy and Musculoskeletal ResearchParacelsus Private Medical University SalzburgSalzburgAustria
  6. 6.Department of Trauma Surgery and Sports MedicineMedical University InnsbruckInnsbruckAustria