The physics of heat generation during reaming of the medullary cavity.

Clinical experience of special cases of reaming of a small diameter medullary cavity has shown a remarkable temperature increase with associated thermal damage to the surrounding tissue. By applying known solutions of the heat conductivity equation to simplified models of a reamer to bone tube system, the effects of the most important parameters on heat generation and temperature distribution are explained. The results allow a quantitative assessment of reaming techniques for small cavities which gives rise to the following recommendations: reamers used consecutively should not increase more than 0.5 mm in diameter; blunt instruments must be replaced or sharpened; prepare very narrow medullary cavities with the small diameter hand reamer; if the reamer ceases to advance do not increase the axial force but withdraw it and check the reamer and the temperature. Cooling, cleaning and replacement of the reamer should be considered, if appropriate.