Effect of increasing temperature on the properties of four bone cements.

This investigation uses a laboratory model to evaluate the effects of a heated femoral stem on the biomechanical properties of four common acrylic bone cements. American Society for Testing Materials dog bone shaped acrylic cement specimens made at four test temperatures, 0 degree C, 23 degrees C, 37 degrees C and 50 degrees C, were tested for modulus, ultimate tensile strength, fracture toughness, and percent porosity. Fatigue strength was tested in Simplex P at 23 degrees C and 37 degrees C. The data allow direct comparison among four cement brands at each of the four temperature conditions. No adverse changes of the mechanical properties were found for any cement at any temperature. Modulus, fracture toughness, and fatigue strength were unaffected by increased temperature. Ultimate tensile strength increased in Simplex P and Zimmer Osteobond but was unaffected for Zimmer Regular and Palacos R cements. Percent porosity was related to temperature changes inversely in all brands studied, except for Palacos R which consistently had low porosity, unaffected by temperature variation. Fatigue strength of Simplex P was unaffected by heating to 37 degrees C. Based on this laboratory model, heating of the femoral stem could save time without sacrificing mechanical properties of acrylic bone cement.