Effect of the trabecular bone microstructure on its thermal conductivity: measurements and a computer modelling-based study

Abstract

Objective: Computer models have been proposed to evaluate heat transfer in bone tissues resulting from thermal ablation, mechanical drilling, or associated with bone cement in joint prosthesis. The lack of knowledge of the influence of microstructure and marrow on the effective thermal conductivity of trabecular bone makes these modeling less accurate. We conduct experiments and computer simulations in order to quantify it. Approach: Thermal conductivities of twenty bovine trabecular bone samples were measured in two states: non defatted and defatted. A two dimensional realistic computer model was built from microscope images of a typical sample. Main results. Temperature dependence similar to that reported for most tissues (+0.2 % ºC-1) was found. The effects of microstructure, marrow content, and the experimental conditions were explained by computer modeling considering only three media: matrix, marrow (pore), and gap (between probe and sample). The inclusion of the gap filled by PBS has implied an increase of the effective thermal conductivity and generates a systematic error that can be disaffected. Computer results have also shown that the presence of a gap around the energy applicator during hyperthermic procedures is negligible (<0.7ºC) when the gap has been full by PBS and practically does not modify the isotherms location. Significance. Experimental studies where thermal conductivity is measured by inserting a probe in the bone through a drill should take our findings into account. Homogeneous tissue models can be considered for simulations of trabecular bone heat conduction using the temperature depence coefficient found in this work.