Polyaxial screw

A spinal stabilization system comprising:

• a fastener member including a head portion and a shaft portion, wherein the shaft portion extends along a longitudinal axis from the head portion, wherein at least a portion of the shaft portion is tapered, wherein at least a portion of the head portion comprises a rounded surface and a recess formed through a top of the head portion;
• a coupling element for receiving the fastener member such that the fastener member is capable of polyaxial movement relative to the coupling element, the coupling element comprising a lower portion and an upper portion, wherein the upper portion of the coupling element includes a first extension and a second extension opposing the first extension, wherein a channel is formed between a first inner surface of the first extension and a second inner surface of the second extension for passing a rod member therethrough, wherein the first extension includes a first end and a second end and a first exterior sidewall formed between the first end and the second end, wherein the second extension includes a third end and a fourth end and a second exterior sidewall formed between the third end and the fourth end, wherein the first exterior sidewall has a first axis that extends substantially in a direction from a top of the coupling element to a bottom of the coupling element, wherein an engagement channel is formed along a second axis substantially transverse to the first axis in the first exterior sidewall, wherein the engagement channel comprises a recessed channel having an upper boundary and a lower boundary, wherein a distance between the upper boundary and the lower boundary changes along a length of the channel such that (1) at a first point along the second axis that is closer to the first end than a second point along the second axis, the distance between the upper boundary and lower boundary is greater at the first point than the second point and (2) at a third point along the second axis that is farther from the first end than the second point along the second axis, the distance between the upper boundary and the lower boundary is greater than at the second point;
• a rod member received in the channel between the first and second extensions, wherein the rod member includes a proximal end and a distal end and a body between the proximal end and the distal end that is capable of being received in the channel;
• and
• a locking cap attachable to the coupling element, wherein the locking cap is rotatable relative to the coupling element, the locking cap comprising an upper surface and a lower surface that faces the rod member.

A spinal stabilization system comprising:

• a fastener member including a head and a shaft, wherein the shaft extends along a longitudinal axis from the head, wherein at least a portion of the shaft is tapered, wherein at least a portion of the head comprises a rounded surface and a recess formed through a top of the head;
• a coupling element for receiving the fastener member such that the fastener member is capable of polyaxial movement relative to the coupling element, the coupling element comprising a lower portion and an upper portion, the lower portion including a clamp element, wherein the clamp element has an inner surface that clamps around an outer surface of the head, wherein the upper portion of the coupling element includes a first extension and a second extension opposing the first extension, wherein a channel is formed between a first inner surface of the first extension and a second inner surface of the second extension for passing a rod member therethrough, wherein the first and second extensions each include an exterior sidewall, wherein the exterior sidewall has a first axis that extends substantially in a direction from a top of the coupling element to a bottom of the coupling element, wherein an engagement channel is formed along a second axis substantially transverse to the first axis, wherein the engagement channel comprises a channel having an upper boundary and a lower boundary that is recessed within the exterior sidewall, wherein the upper boundary of the engagement channel comprises an arcuate portion that partially encloses a recessed area, wherein each of the first and second extensions further includes a hole formed along a third axis substantially transverse to the first axis, wherein the hole is a blind hole such that the hole is formed through the exterior sidewall of each of the first and second extensions but does not extend into the inner surfaces of the first and second extensions, a rod member passed through the channel between the first and second extensions, wherein the rod member includes a first end and a second end and a cylindrical body between the first end and the second end that is capable of being received in the channel;
• and
• a locking cap attachable to the coupling element, wherein the locking cap is rotatable relative to the coupling element, the locking cap comprising an upper surface and a lower surface that faces the rod member, wherein rotation of the locking cap relative to the coupling element changes the locking cap from a first position to a second position.