Significance of the mineral content of bone relative to its strength characteristics under hypodynamic conditions

Autor: I. E. Didenko, S. M. Remizov, A. N. Polyakov, A. I. Volozhin, G. P. Stupakov
Rok vydání: 1982
Předmět:
Zdroj: Mechanics of Composite Materials. 18:223-228
ISSN: 1573-8922
0191-5665
Popis: The experiments were carried out on eight dogs ranging in age from 1.5 to 4 years. Under thiopental anesthesia and aseptic conditions, the right leg of the animals was amputated at its lower third. The muscles were tied with catgut and silk sutures were placed in the skin. In all cases, the wound healed by primary intention. At 90 and 345 days after the operation, an equal number of dogs were sacrificed by means of ether and chloroform vapor. The femor were stripped and stored in 1% neutral formalin at 5~ The right, nonsupporting leg was the experimental sample and the left leg was the control. The thickness of the cortical layer in the middle part of the diaphysis, its width, and the cross-sectional diameter of the bone marrow canal were determined to +0.05 mm by means of radiographs of the bones taken in two projections using an MBS-2 microscope equipped with an ocular micrometer. The porosity of the spongy bone of the distal epiphysis and of the compact bone of the diaphysis was evaluated quantitatively relative to the density (g/cm 3 ), mineral content per unit of volume, and mineral saturation (g/cm 3 ) in dry defatted bone fragments. The degree of mineralization of the organic component was found using the ratio of the mineral mass to the mass of the fragment studied (ash, %) and microscopic x-ray diffraction analysis [3]. (~aant~tative elemental analysis was carried out for the mineral components: calcium was analyzed on an atomic absorptiometer, phosphorus was analyzed on a spectrophotometer using sodium molybdate, and potassium and sodium were analyzed by flame photometiy. For strength testing, the bone samples were sectioned using a saw from the distal epiphysis of the femur as 10 X 10 X 10-mm cubes and from the middle part of the diaphysis as 10-ram-long rods. The sectioning of the bone tissue of the epiphyses was carried out taking account of the orientation of the major trabeculae found using a radiogram of the bone samples. The strength tests were ,carried out on an Instron unit. Microhardness of the spongy and compact matter was found on polished cross-sectional sections poured into Protakrit plastic. Each sample was subjected to 20 stampings with a pyramidal diamond indentor at 100 gf load on a PMT-3 instrument. The results were treated by variational statistics and nonparametric methods. Elimination of the weight-bearing function led to resorption of the compact matter of the femur in the diaphysis starting from the bone marrow canal, resulting in a decrease in the thickness of the co_rtical layer. After 90 days, this layer in the weight-bearing limb was 3.86 + 0.12 mm overall from both sides while it was only 3.61 + 0.22 mm in the non-weight-bearing limb. Upon extending the experiment to 345 days, the thinning effect was more pronounced and these layers were 4.13 + 0.13 mm and 2.78 __+ 0.20 mm, respectively (p < 0.05). The decrease in the t~c~uess of the cortical layer was accompanied by an increase in the porosity of the bone matter in the 90-day experimental period as indicated by the change in the density and mineral saturation indices (Table 1).
Databáze: OpenAIRE
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