Geometric, elastic, and structural properties of maturing rat femora

Keller, T. S.<sup>1</sup>; Spengler, D. M.<sup>1</sup>; Carter, D. R.<sup>1</sup>

Affiliations

¹Orthopaedic Biomechanics Lab, Veterans Administration Medical Center, and Department of Orthopaedics and Rehabilitation, Vanderbilt Medical Center North, Nashville, Tennessee and Department of Mechanical Engineering, Stanford University, Stanford, and Rehabilitation Research and Development Center, Veterans Administration Medical Center, Palo Alto, California

Abstract and keywords

Geometric, elastic, and structural properties of growing rat femora were determined from bending and torsion tests followed by bone sectioning and measurement of areal properties. Rosette strain gages bonded to the bone surface measured the strain during testing. A computer generated elliptical cross‐sectional representation of the cross section geometry was used for calculation of material and structural properties. All structural and material properties increased with increasing age, exhibiting age‐related changes that were best represented by an allometric or “heterauxic” growth pattern (y = ax^b) up to maturity. The femoral axial, flexural, and torsional rigidity increased 5.7, 10.1, and 14.8 fold, respectively, during maturation from 21 to 119 days of age. The increase in whole bone rigidity during maturation was caused primarily by changes in geometry. The bone tissue tensile longitudinal elastic modulus and shear modulus approximately doubled, and the shear strength increased approximately fourfold over this same period. Following maturity, a much slower increase in bending and torsional properties was noted. The results suggest that bone structural properties are regulated by changes in both geometric and material properties.

Keywords: Bone; Heterauxic; Growth; Material properties; Geometry

Links

DOI: 10.1002/jor.1100040107

PubMed: 3950809

WoS: A1986A508600007

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