| 摘要 |
A spinal fixation device combines an open-headed anchor member, such as a polyaxial bone screw or a hook, with a 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 arms have arm extensions or tabs connected to main portions of the arms by weakened regions to enable the extensions to be broken-off or separated after the rod is clamped. 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 mechanically cooperate to prevent splaying the arms and extensions as the closure is advanced into the rod receiving channel. The increased length of the arms with the extensions enables the rod to be captured at a greater distance from the seat of the channel and allows the rod to be urged toward the seat by helical advancement of the closure into the channel, starting between the extensions. Separation of the break-off extensions results in an implant with a desirable low profile. |
