#$%^&*AU2009230749B220120119.pdf#####Abstract A spinal fixation device combines an open-headed anchor member, such as a polyaxial bone screw or a hook, with a 5 rotatable closure that operably clamps a spinal fixation rod to the anchor member. The anchor member has spaced apart arms forming a rod receiving channel. The closure and inner surfaces of the arms and tabs have mating helical anti-splay guide and advancement flanges formed thereon which radially interlock and 10 mechanically cooperate to prevent splaying the arms and extensions as the closure is advanced into the rod receiving channel. The closure anti-splay flange may include a lip extending helically along the closure flange and the arm flange may include an axial groove extending therealong, the lipped 15 flange and groove flange being configured to enable radial engagement of portions of the lip and groove in response to the closure being advanced into the rod receiving channel. C:pofwt Docment4.doc
