Abstract: Knowledge of bone mechanical properties is important
for bone substitutes design and fabrication, and more efficient
prostheses development. The aim of this study is to characterize the
viscoelastic behavior of bone specimens, through stress relaxation
and fatigue tests performed to trabecular bone samples from bovine
femoral heads. Relaxation tests consisted on preloading the samples
at five different magnitudes and evaluate them for 1020 seconds,
adjusting the results to a KWW mathematical model. Fatigue tests
consisted of 700 load cycles and analyze their status at the end of the
tests. As a conclusion we have that between relaxation stress and
each preload there is linear relation and for samples with initial
Young´s modulus greater than 1.5 GPa showed no effects due fatigue
test loading cycles.
Abstract: Bone properties and response behavior after static or
dynamic activation (loading) are still interesting topics in many fields
of the science especially in the biomechanical problems such as bone
loss of astronauts in space, osteoporosis, bone remodeling after
fracture or remodeling after surgery (endoprosthesis and implants)
and in osteointegration. This contribution deals with the relation
between physiological, demineralized and deproteinized state of the
turkey long bone – tibia. Three methods for comparison were used: 1)
densitometry, 2) three point bending and 3) frequency analysis. The
main goal of this work was to describe the decrease of the protein
(collagen) or mineral of the bone with relation to the fracture in three
point bending. The comparison is linked to the problem of different
bone mechanical behavior in physiological and osteoporotic state.
Abstract: To achieve accurate and precise results of finite
element analysis (FEA) of bones, it is important to represent the
load/boundary conditions as identical as possible to the human body
such as the bone properties, the type and force of the muscles, the
contact force of the joints, and the location of the muscle attachment.
In this study, the difference in the Von-Mises stress and the total
deformation was compared by classifying them into Case 1, which
shows the actual anatomical form of the muscle attached to the femur
when the same muscle force was applied, and Case 2, which gives a
simplified representation of the attached location. An inverse
dynamical musculoskeletal model was simulated using data from an
actual walking experiment to complement the accuracy of the
muscular force, the input value of FEA. The FEA method using the
results of the muscular force that were calculated through the
simulation showed that the maximum Von-Mises stress and the
maximum total deformation in Case 2 were underestimated by 8.42%
and 6.29%, respectively, compared to Case 1. The torsion energy and
bending moment at each location of the femur occurred via the stress
ingredient. Due to the geometrical/morphological feature of the femur
of having a long bone shape when the stress distribution is wide, as
shown in Case 1, a greater Von-Mises stress and total deformation are
expected from the sum of the stress ingredients. More accurate results
can be achieved only when the muscular strength and the attachment
location in the FEA of the bones and the attachment form are the same
as those in the actual anatomical condition under the various moving
conditions of the human body.
Abstract: Postmenopausal osteoporosis is a disorder
characterized by the progressive bone loss induced by estrogen
deficiency in postmenopausal women. This imbalance affects
calcium–phosphate metabolism and results in secondary
hyperparathyroidism. Purariae Radix (PR), the root of P. lobata
(Wild.) Ohwi, is one of the earliest medicinal herbs employed in
ancient China. PR contains a high quantity of isoflavones and their
glycosides, which are regarded as phytoestrogen. Few investigations
of PR are related to its osteoprotective effects. The present study is
designed to administer PR water extract to ovariectomized (OVX)
female rats, for the investigation of its possibly protective actions on
bone and to delineate the potential mechanisms involved. Our results
demonstrated that long-term treatment of PR could not significantly
improve bone properties, whereas it greatly ameliorated the condition
of secondary hyperparathyroidism induced by ovariectomy in those
animals. PR might be useful as alternative regimen for protecting
against postmenopausal bone loss.