The microstructural tensile properties and biochemical composition of the bovine distal femoral growth plate

Abstract

The tensile properties of distal femoral growth plates from 12-month-old cows were determined on uniformly prepared straight bone-growth plate-bone specimens (7 x 7 mm2 in cross-section) from predetermined anatomical sites on the physis. Each specimen was distracted to failure using a computer-controlled servo-hydraulic testing machine at a strain rate of 0.004 s-1. It was found that the exponential constitutive law, using finite deformation formulation for strain, provides an excellent description of the stress-strain behavior of all the specimens up to the point of failure. The ultimate stress and both tangent moduli (i.e., the toe region tangent modulus and the tangent modulus calculated at 75% of ultimate strain) varied with anatomical site. The anterior region was the strongest, followed by the posterior/lateral. The anterior and posterior/lateral regions were also the stiffest, whereas the posterior/medial and center regions were the weakest and most compliant. The bone-growth plate-bone specimen exhibited a low ultimate strain (13.8% +/- 6%) that did not vary significantly throughout the growth plate. This result suggests that disruption of the physis may occur in vivo even at the lower distractions currently recommended for the clinical chondrodiatasis procedure for leg lengthening. The biochemical composition of the growth plate in the anatomical regions correlated well with the tensile properties. There was a greater collagen content in the regions that were the stiffest and strongest. The gross morphology of the growth plate of the bovine distal femur is also described in this study. There is a regular pattern to the undulations of the physis at several dimensional levels. Histologic findings showed that orientation of the hypertrophic cell columns and transphyseal septa are aligned nearly parallel to the longitudinal axis of the diaphyseal shaft. This column orientation is not affected by the undulation of the primary contour of the physis, which at certain locations may be inclined as much as 60 degrees relative to the diaphyseal axis. The orientation of the hypertrophic cell columns appears to be one of the dominant microstructural features influencing the tensile behavior of the bone-growth plate-bone specimens.

Indian hedgehog Is an Essential Component of Mechanotransduction Complex to Stimulate Chondrocyte Proliferation

“…After overnight incubation at 37°C, the sponges were subjected to 5% elongation at 60 cycles/min, 15 min/h, by a computer-controlled Biostretch device (ICCT Technologies, Canada). This extent of matrix deformation may be comparable to that experienced in a growth plate in vivo (28). Biostretch exerts a uniaxial stretch with square wave patterns.…”

“…We tested this hypothesis in a new three-dimensional chondrocyte culture system that we established recently (27). In this system, primary chondrocytes from developing chick cartilage were cultured in a sponge of collagen networks to which cyclic mechanical stress was applied by a computer-controlled "Bio-stretcher" device (27), thereby mimicking the mechanical stimulation developing cartilage experiences in vivo (28). Our results show that mechanical stress induces the expression of Ihh, which in turn transduces the mechanical signals in a BMP-dependent manner to stimulate chondrocyte proliferation.…”

Regulation of immature cartilage growth by IGF-I, TGF-β1, BMP-7, and PDGF-AB: role of metabolic balance between fixed charge and collagen network

“…4c,d). Similarly, in comparison with articular cartilage, a higher tendency to grow is expected in cartilage of the growth plate where the proportion of GAG is higher and tensile strength and modulus are lower than those of articular cartilage (Cohen et al 1992;Nakano and Sim 1995). Indeed, a relatively high rate of axial growth is observed in the growth plate in vivo (up to ∼400 µm/day) (Wilsman et al 1996), as well as in vitro where larger increases in length were observed in cartilages containing one or more osteogenic zones as compared to that of entirely cartilaginous explants (Copray et al 1986).…”

DL‐penicillamine induced alteration of elastic fibers of periosteum‐perichondrium and associated growth inhibition: an experimental study

“…It is still completely unknown whether these pericliondrialperiosteal elastic fibres contribute to the mechanical competence of the collagen network in resisting to both physiological and pathological loading [2,5,50], and in regulating long bone growth [6,12,22,31,33]. Some recent observations of a dramatic reduction of perichondrial-periosteal elastic fibres in human and bovine Marfan syndromes led us to hypothesize that skeletal overgrowth, typical of this disorder, may be related to alterations of elastic fibres and of their microfibrillar component [19,20,27], the Marfan syndrome being a genetric disorder caused by mutations of the fibrillin-1 gene, a major constituent of elastin-associated microfibrils [ 131.…”

“…Extensive attention has been given to the latter, i.e., vascular supply, perichondrial-periosteal connective tissue and muscular activity [3,6,23,25,32,33,35,49,51,53]. It has been shown that experimental interference with the subchondral vascularisation has no effect on longitudinal skeletal growth; moreover, the legation of nutrient artery has only limited curbing effect on bones [31].…”