Stress trabecular bone

Picherit et al., 2000 1 yr old OVX rats oral administration, 90 d genistein or daidzein at 10 mg/kg body weight Overall daidzein > genistein in this study. Total femoral BMD losses and vertebral trabecular bone were protected by estradiol and daidzein, but genistein was not efficient. Bone strength (femoral failure stress) protected by estradiol, daidzein and genistein... 

Under normal circumstances, the skeleton undergoes a dynamic process of bone remodeling. Bone tissue responds to stress and injury through continuous replacement and repair. This process is completed by the basic multicellular unit, which includes both osteoblasts and osteoclasts. Osteoclasts are involved with resorption or breakdown of bone and continuously create microscopic cavities in bone tissue. Osteoblasts are involved in bone formation and continuously mineralize new bone in the cavities created by osteoclasts. Until peak bone mass is achieved between the ages of 25 and 35, bone formation exceeds bone resorption for an overall increase in bone mass. Trabecular bone is more susceptible to bone remodeling in part owing to its larger surface area. 

Fyhrie, D.P.and Carter, D. R. (1986) A unifying principle relating stress to trabecular bone morphology. Journal of Orthopedic Research 4 304-317... 

M. Kawagai et al Multi-scale stress analysis of trabecular bone considering trabeculae morphology and biological apatite crystallite orientation. J. Soc. Matls. Sci. Japan 55,... 

As the major stress hormone, cortisol has many functions. For example, in trabecular bone, cortisol inhibits synthesis of new bone by osteoblasts and decreases absorption of Ca + in the G1 tract, leading to osteopenia. However, the two principal influences of cortisol are on metabolism and the immune system. 

FIGURE 8.11 Dependence of ultiinaie stress on age for trabecular bone from the human vertebra and femur. For both anatomic sites, strength decreases approximately 10 percent per decade. (Data from Rrfs. 15 and 149.)... 

TABLE 8.5 Power-Law Regressions Between Ultimate Stress Apparent Density p (in g/cm ) for Compressive Loading of Human Trabecular Bone Specimens from a Range of Anatomic Sites... 

Criteria such as the Tsai-Wu criterion have only a limited ability to describe multiaxial failure of trabecular bone for arbitrary stress states. Coupling between normal strengths in different directions (longitudinal versus transverse, for example) appears to be minimal. 

When trabecular bone is loaded in compression beyond its elastic range, unloaded, and reloaded, it displays loss of stiffness and development of permanent strains (Fig. 8.14). In particular, it reload with an initial modulus close to its intact Young s modulus but then quickly loses stiffness. The residual modulus is statistically similar to the perfect-damage modulus (a secant modulus from the origin to the point of unloading). In general, the reloading stress-strain curve... 

Deligianni, D.D., Maris, A. and Missirlis, Y.F. (1994) Stress relaxation behaviour of trabecular bone specimens. J. Biomech., 27, 1469-1476. 

Early loosening can result from excessive loading of the cement-bone interface with possible trabecular fractures combined with undesired features in the preparation and insertion of the cement. Micromotion leads to a thickened fibrous capsule. During the early postoperative course, the randomly oriented trabecular bone may act as a sufficient energy absorbing medium between the cement and cortical bone unless unduly stressed. With time, the trabeculae respond to stress by reorientation and hypertrophy of the trabeculae. Frequently, the diameters of the trabeculae adjacent to the interface were two to six times that of more distant trabeculae. The cement particulate at the interface ranged from 300 to 600 microns in thickness. ... 

Figure 7.1. Early diagrams showing the relationship between stresses created by forces on bones and the internal architecture of the skeleton (a) Culmann s calculation of the stress trajectories in a crane, (b) Wolff s drawing of the trabecular orientation in the upper part of the femur, and (c) a photograph of the cross-section of the upper part of the femur.

The skeletal age, which is not necessarily identical with the calendar age of the individual, has an important impact on the fluorine uptake, because osteoporosis is a process that fundamentally influences the bone structure. The disease pattern becomes visible in material loss within both the trabecular and the compact bone structure. Furthermore, the mineral density even in a healthy individual is not uniform in compact bone, but is a function of bone stress at this skeletal position and is increased at the point where muscles and tendons are fixed. 

On the other hand, Fukada et al.[5] found piezoelectricity properties in bone which was stressed. There are several reports [11,20,21] which are based on evidence that bone demonstrates a piezoelectric effect. This is used to explain the concept of stress- or strain-induced bone remodelling which is often refered to as Wolfs law[3]. Thus, bone converts mechanical stress to an electrical potential that influences the activity of osteoclasts and osteoblasts[l]. It is also known that the interior structure of bone(trabecular architecture) is arranged in compressive and tensile systems corresponding to the principal stress directions[4]. The role of the voltage signals induced in bamboo and palm we found may also be similar to the piezoelectric effect in bone. 

There are two basic structural types of bone cancellous (trabecular, spongy) and cortical (dense) bones. Cancellous bone matter is less dense than that of cortical bone and is found across the ends of the long bones. Owing to its lower density, cancellous bone has also a much lower modulus of elasticity but higher strain-to-failure rate compared to cortical bone (Table 3.1). Bone has higher moduli of elasticity than soft connective tissues, such as tendons and ligaments. The difference in stiffness (elastic modulus) between the various types of connective tissues ensures a smooth gradient in mechanical stress across a bone, between bones and between muscles and bones (Hench, 2014). 

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