doi: 10.1111/j.1460-2695.2010.01535.x The effect of adding 10% of barium sulphate radiopacifier on the mechanical behaviour of acrylic bone cement M. BALEANI and M. VICECONTI Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Bologna, Italy Received in final form 30 September 2010 ABSTRACT Barium sulphate (BaSO 4 ) is commonly used in bone cement as a radiopacifier. The addition of the BaSO 4 to the polymeric matrix may cause a decrease in the mechanical properties of the cement. In this work, the effect of adding 10%w/w BaSO 4 to a plain polymethylmethacrylate based bone cement was evaluated in terms of endurance limit, fatigue crack propagation and fracture toughness. A lower endurance limit (−13%), as well as a lower fracture toughness (−13%), was found for the radiopaque bone cement in comparison with the plain formulation. Conversely, a substantial decrease (66%) in the crack growth rate was found due to the radiopacifier addition. These are all effects that reflect the weakening of the polymeric matrix, caused by the addition of the radiopacifier. Keywords acrylic bone cement; biomaterials; fatigue limit; fatigue crack propagation; fracture toughness; fracture morphology. NOMENCLATURE a = crack length a i = crack length at i th increment a m = average value of crack length B = specimen thickness C = Paris’ law coefficient da/dN = crack growth rate K = stress intensity factor range K IC = fracture toughness N = number of loading cycles n = Paris’ law exponent P = load range R 2 = coefficients of determination Ra = arithmetic mean roughness value RSm = mean spacing of profile irregularities Rt = total roughness value W = specimen width INTRODUCTION Cementing with polymethylmethacrylate is a method ex- tensively used to fix joint prostheses. 1 Radiopacifiers are added to the polymethylmethacrylate to allow the visu- alization of the cement by X-ray imaging, as required by surgeons. The radiopacifier attenuates the X-rays because it has higher atomic number and density than the poly- meric bone cement. Although alternative radiopacifiers Correspondence: Massimiliano Baleani. E-mail: baleani@tecno.ior.it have been proposed, 2–5 currently the most commonly used radiopacifier in commercial bone cement formula- tions is barium sulphate (BaSO 4 ), which is replaced with zirconium oxide (ZrO 2 ) in some cement brands. 6 Several studies have investigated the effect of BaSO 4 on the mechanical properties of polymethylmethacrylate. It has been demonstrated that a large amount of BaSO 4 (30–40%) has a detrimental effect on both static and fa- tigue strength of the bone cement. 7 Such formulations are used for spine reconstructive surgery, while bone ce- ment used to fix joint prostheses contains BaSO 4 in a 374 c  2010 Blackwell Publishing Ltd. Fatigue Fract Engng Mater Struct 34, 374–382 Fatigue & Fracture of Engineering Materials & Structures