Tensile strength of wire-reinforced bone cement and twisted stainless-steel wire

To assess the tensile strength of wire-reinforced bone cement as used for posterior spine fusion, standardized bone-cement specimens reinforced with stainless steel and Vitallium wires 0.5 and one millimeter in diameter were tested in tension. The results showed that tensile strength of bone cement was increased significantly by reinforcing it with metal wires, the increase in strength being proportional to the number of wires used. Even after failure of the cement, the reinforcing wires still carried an appreciable amount of load, thus avoiding the catastrophic failure of the cement alone. Specimens reinforced with Vitallium wires in general failed at higher loads than specimens reinforced with similar stainless-steel wires. Pull-out studies showed that a hook or a loop at the embedded end of straight wires significantly increased the load necessary to pull the wires out. The tensile strength of twisted stainless-steel wire composed of two 0.5-millimeter strands increased with the number of turns up to about eight turns per inch (2.54 centimeters) and then decreased.