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.