Spinal fixation system

A spinal fixation system, comprising:

• a pedicle screw having a longitudinal axis and a non-threaded portion;
• a fixation element configured to connect the pedicle screw to at least one additional pedicle screw;
• and
• a coupling mechanism comprising:
• a collet having a surface in contact with an outer surface of the non-threaded portion of the pedicle screw, wherein the collet is adapted to secure the coupling mechanism to the pedicle screw, the collet having an aperture sized to fit over the pedicle screw;
• a split ring having a surface in contact with a surface of the fixation element, wherein the split ring is configured to secure the coupling mechanism to the fixation element;
• and
• a fastening mechanism, the fastening mechanism located along the longitudinal axis of the pedicle screw, wherein rotation of the fastening mechanism about the longitudinal axis causes the surface of the collet to engage the outer surface of the non-threaded portion of the pedicle screw and also the surface of the split ring to engage the surface of the fixation element
• wherein the collet comprises external threads configured to engage corresponding internal threads in the split ring.

A spinal fixation system, comprising:

• a pedicle screw having a longitudinal axis and a non-threaded portion;
• a fixation element configured to connect the pedicle screw to at least one additional pedicle screw;
• and
• a coupling mechanism comprising:
• a collet adapted to secure the coupling mechanism to the pedicle screw, the collet located along the longitudinal axis of the pedicle screw and having compressible arms, the compressible arms having inner surfaces in contact with an outer surface of the non-threaded portion of the pedicle screw;
• a split ring to secure the coupling mechanism to the fixation element, the split ring having a surface in contact with a surface of the fixation element;
• wherein the collet comprises external threads configured to engage corresponding internal threads in the split ring;
• wherein rotation of the collet causes both the inner surfaces of the compressible arms to engage the outer surface of the non-threaded portion of the pedicle screw and also the surface of split ring to engage the surface of the fixation element.