In vitro comparative testing of fracture fixation implants is limited by the highly variable material properties of cadaveric bone. Bone surrogate specimens are often employed to avoid this confounding variable. Although validated surrogate models of normal bone (NB) exist, no validated bone model simulating weak, osteoporotic bone (OPB) is available. This study presents an osteoporotic long-bo...

Studies of torsional properties of natural silk fibers seem to open a new window in understanding the correlation between their extraordinary mechanical properties and their microscopic structure. In this paper, the torsional relaxation profiles of single-stranded Bombyx mori silk was obtained from our experiment, and a prominent under-damping mode was identified. It was concluded that the sing...

This study compares the functional capabilities of different metacarpal fixation constructs under physiological loadings in an attempt to identify the optimal construct rather than the strongest one. One hundred and twenty-six preserved human metacarpals were mechanically tested after oblique osteotomies and internal fixation. Maximum load to failure, average structural rigidity, and energ...

Picosecond time-dependent fluorescence depolarization techniques have been used to monitor the reorientation of ethidium bromide intercalated in DNA and RNA. The fluorescence polarization anisotropy reveals a nonexponential, exp(-at 1/2), torsional relaxation of the DNA double helix and provides an accurate value for its torsional rigidity, C = 1.3 +/- 0.2 X 10(-19) erg cm. Furthermore, from ac...

PURPOSE To compare tibial fracture healing in rats with or without soft-tissue attachment. METHODS The left tibias of 30 Wistar rats were osteotomised and equally randomised into 3 groups. In the avascular segmental fracture group, an 8-mm bone segment were first removed and then immediately put back. In the vascular segmental fracture group, the 8-mm bone segment was not displaced, with peri...

We consider shape functionals obtained as minima on Sobolev spaces of classical integrals having smooth and convex densities, under mixed Dirichlet-Neumann boundary conditions. We propose a new approach for the computation of the second order shape derivative of such functionals, yielding a general existence and representation theorem. In particular, we consider the p-torsional rigidity functio...