Microscopic Multi-Directional Permeability Coefficient of Human Lumbar Vertebral Cancellous Bone Tissue

摘要

The mechanical performance of cancellous bone is characterized using experimental measure of parameters (elastic moduli, permeability, etc.) which apply poroelasticity theory. Poroelastic investigations of bone are being extended to investigations of micro-mechanisms of remodeling processes and transport of metabolic product in bone. To understand physiological and pathological behavior of human skeletal system, the accurate measurement of biomechanical properties for bone is the one of important works. Particularly, the microscopic measurement is very important since the biomechanical behavior at the small scale of bone could be closely related to the remodeling of bone. But microscopic measurement of permeability coefficient which is one of important parameter of poroelasticity theory was never measured. In this study, a small scale permeability testing machine was developed to measure accurate coefficient of microscopic specimen permeability. Total of twenty one cylindrical cancellous specimens with a diameter of 500 μm from seven fresh male and female lumbar vertebrae (14, 39, 59, 61, 69, 75, and 77 years) were fabricated using a micro-milling machine having a resolution of 10 μm. To determine the directional permeability, bone coordinate was set to be x_1 (longitudinal axis) and others were set as x_2 (postero-anterior axis) and x_3 (latero-medial axis). The measured mean permeability (+ SD) values of each direction from x_1 to x_3 were 5.56×l0~(-9)(S.D. ±7.10×10~(-10)), 6.66×10~(-9)(S.D. ±6.56×10~(-10)), and 7.04×10~(-9)(S.D. ±8.47×10~(-10)) m~2/Pa/sec, respectively. Mean value in the x_1 direction of specimens were the smallest (p<0.01) in comparison to x_2 and x_3 directions.