[Relationship between the gray level of X-ray photograph and the cortical thickness].

OBJECTIVE: In order to get three dimensional measurements simply an plain X-ray photographs. METHODS: The multi-layers of bone pieces were made by use of bone saw, and piled up to spiral ladder, which was used as a calibrating module for to living bone in clinics. The relationship between the cortical thickness and gray level of the X-ray photographs was obtained. RESULTS: The correlation can be described with a cubic regression curve, and it can be simplified to a linear regression equation when cortical thickness is small than 3.8 mm. CONCLUSION: It can be realized to get three dimensional measures of the bone on plain X-ray photographs, by use of the bony spiral ladder described here.

[Revealing mechanical property of intact rabbit tibia in three-point bending test].

OBJECTIVE: To explore the mechanical property of intact long bone through three-point bending test of rabbit tibia according to mechanics of materials. METHODS: Ten pairs of normal rabbits tibia were treated on three-point bending test with 80 mm supporting distance in order to corroborate the virtual loading test on bone model. RESULTS: Bending stiffness and strength of 10 pairs of normal rabbit tibia were obtained. The maximum flexibility of the right and the left tibia was (2.737 +/- 0.262) mm and (2.739 +/- 0.233) mm respectively. The maximum load, which indicated the bending strength, of the right and the left tibia was (17.803 +/- 2.675) kg and (18.366 +/- 2.653) kg respectively. The area under the load-flexibility curve before fail of the right and the left tibia was (23.829 +/- 4.413) kg/mm and (24.725 +/- 4.101) kg x mm respectively. The slope of the load-flexibility curve which indicate the stiffness of the right and the left tibia was (7.545 +/- 1.310) kg/mm and (7.631 +/- 1.174) kg x mm respectively. CONCLUSION: The discrepancy between different animal body is larger than conventionally required. It's suggested for performing three-point bending test of long bone of the body both sides in pair.