Stabilizing bone using spinal fixation devices and systems

A bone fixation assembly comprising:

• a coupling element having:
• an upper surface with a first diameter defining a first bore extending along a first axis;
• a lower surface with a second diameter defining a second bore extending along a second axis;
• and
• an internal surface area defining a seating portion adjacent to the lower surface;
• and
• a bone anchor having an insertion end opposite of a head, the head being curved for receipt within the seating portion,
• wherein the second diameter is greater than the first diameter, and
• wherein the first and second axes intersect such that the first and second bores are in communication with one another.

A coupling element comprising:

• an upper portion defining an upper bore extending along a first axis from an upper end;
• a lower portion defining a lower bore extending along a second axis transverse to the first axis, the lower bore having an internal cavity and a seating portion spaced apart along the second axis;
• and
• a channel bifurcating the upper bore and at least a portion of the lower bore along a third axis transverse to the first and second axes,
• wherein the first and second axes intersect at a point within the internal cavity.

A bone fixation system comprising:

• a spinal rod;
• a plurality of bone anchors having a head opposite of an insertion end implantable in a bone;
• and
• a plurality of rod coupling elements, each having:
• an upper surface with a first diameter defining a first bore extending along a first axis;
• a lower surface with a second diameter defining a second bore extending along a second axis;
• an internal cavity extending between the upper and lower surfaces and defining a seating portion having a sidewall adapted to receive the head of the bone anchor;
• and
• a channel bifurcating the upper surface and a portion of the internal cavity along a third axis transverse with the first and second axis,
• wherein each rod coupling element is adapted to be affixed to bone when the head of each bone anchor is received within the seating portion and the insertion end of each bone anchor is implanted in bone, and
• wherein the polyaxial motion between the plurality of rod coupling elements and plurality of bone anchors permits the spinal rod to be received within the channel of each affixed rod coupling element without bending.