Evaluation of Changes in Trabecular Bone Architecture and Mechanical Properties of Minipig Vertebrae by Three-Dimensional Magnetic Resonance Microimaging and Finite Element Modeling

Abstract

The study objective was to analyze the three-dimensional (3D) trabecular architecture and mechanical properties in vertebral specimens of young and mature Sinclair minipigs to assess the relative contribution of architecture to bone strength. We used 3D magnetic resonance microimaging (MRI) and direct image analysis to evaluate a set of standard structural measurements and new architectural descriptors of trabecular bone in biopsy specimens from L2, L3, and L4 vertebrae (n ‫؍‬ 16 in each group) from young (mean age, 1. .05). Overall, ConnD, star volume, % plate, and % bone LD provided a coherent picture of the architectural changes between the two age groups. Apparent modulus and maximum stress were determined experimentally on biopsy specimens from L2 vertebrae (n ‫؍‬ 16). When apparent modulus was predicted using 3D MRI data sets as input for finite element modeling (FEM), the results were similar to the experimentally determined apparent modulus (p ‫؍‬ 0.12). Both methods were then used to compare the young and the mature animals; the experimental and predicted apparent modulus were significantly higher for the mature group (p ‫؍‬ 0.003 and 0.012, respectively). The experimental maximum stress in the vertebra of the mature animals was twice as high as that for the young animals (p ‫؍‬ 0.006). Bone quantity (BV/TV or bone mineral content [BMC]) alone could explain approximately 74 -85% of the total variability in stress and modulus.

The three-dimensional microstructure of the trabecular bone in the mandible

“…In the studies of the vertebrae of young Sinclair minipigs [4] and the effects of mechanical stimulation in the hind limbs of adult sheep [34], the trabecular bone volume fraction, the trabecular bone thickness, the plate-like structure and the trabecular bone strength were reported to increase according to load or mechanical stimulation.…”

“…Because of this, it has not been considered to be an important factor during dental treatment and has only been analyzed subjectively, if at all. Generally, the analysis of bone microstructure, as well as of bone volume, plays a major role in predicting the biomechanical properties and risk of bone fracture [4,18,20,32].…”

Biomechanics of the Bat Limb Skeleton: Scaling, Material Properties and Mechanics

“…Microscopy is often poorly suited to this task; although histological preparation followed by microscopic examination facilitates measurement at the appropriate scale, relatively small distortions can have a large impact on estimates of the second moment of area, I , which includes a term that raises distance of each areal increment to the fourth power. We suggest that micro-CT scanning, an increasingly accessible technique, is well suited to the precise and nondestructive measurement of cross-sectional geometry of small skeletal specimens [Feldkamp et al, 1989;Ruegsegger et al, 1996;Barbier et al, 1999;Borah et al, 2000;Laib et al, 2000;Mulder et al, 2004].…”

Review of Nonprimate, Large Animal Models for Osteoporosis Research

“…In quadrupeds, the longitudinal orientation of the spine is supported by large musculature along the animal's back, which can generate four to eight times as much load on the spine as from gravity in the cranial-caudal axis (CH Turner, personal communication, 2006). (38) Human vertebral bodies are larger in diameter than those of dogs, pigs, goats, and sheep, and comparatively enlarged cranial endplates and intervertebral disks increase the surface area (39) to facilitate the redistribution of dynamic loads. Vertebral bodies of mature canine, ovine, and porcine species have more height in proportional terms than they do in humans, (37) and the forces generated by the supporting muscle bulk expose animals to higher axial compression stresses leading to vertebral volumetric BMDs that greatly exceed those of humans.…”