Spinal stabilization using bone anchor and anchor seat with tangential locking feature

A stabilization system for implantation in a patient, comprising:

• a bone anchor including a head having a contour;
• and
• a tulip including:
• (i) a base having an outer surface and an inner surface defining a volume for receiving the head, the contour of the head being of substantially complementary shape such that the tulip may articulate about the head, (ii) a first opening operable to permit a neck extending from the head to articulate there-within and exit the base through the first opening, and (iii) a second opening extending through the base transversely with respect to the first opening, and defining a profile that permits insertion of the head into the volume of the base at substantially one orientation of the head with respect to the profile, and does not permit insertion or removal of the head with respect to the volume of the base in substantially any other orientation of the head with respect to the profile.

A bone anchor, comprising:

• a head;
• a neck depending from the head;
• and
• a shaft extending away from the neck and being operable for connection to a bone of a patient,
• wherein the neck includes at least one bend such that the head is transversely oriented with respect to the shaft.

A tool, comprising:

• a first shaft having a proximal end and a distal end, the first shaft including a rod engagement element at the distal end that is operable to releasably and rotationally engage a stabilization rod used to interconnect a plurality of bone anchors coupled to one or more bones of a patient;
• a second shaft having a proximal end and a distal end, the proximal end of the second shaft being pivotally coupled to the first shaft at a position intermediate between the proximal and distal ends thereof, the distal end of the second shaft including a hitch element operable to permit connection of the tool a given one of the bone anchors, wherein:
• a force applied to the proximal end of the first shaft produces a torque at the proximal end of the second shaft, with the rod engagement element being at a fulcrum position, that transfers the torque into a translational force at the hitch element;
• and
• a bone to which the given bone anchor is connected is moved in response to the translational force.

A method of forming a stabilization system, comprising:

• providing a bone screw having a contoured head and a keyed surface;
• providing a tulip having:
• (i) an outer surface, an (ii) an inner surface defining a volume for receiving the head of the bone screw, and (iii) an opening extending through the base into the volume and defining a profile that permits insertion of the head into the volume of the base at substantially one orientation of the head with respect to the profile, and does not permit insertion or removal of the head with respect to the volume of the base in substantially any other orientation of the head with respect to the profile;
• and
• sliding the head through the opening into the volume in a first orientation.