Pop-on-cap assemblies having opposing splay-resisting features and generally demi-teardrop opposing rotation-preventing/rotation-resisting features for spinal surgery

A system for use in spinal surgery, comprising:

• a pop-on cap for installing to a rod-receiver, the cap having a generally cylindrical body, a set of opposing splay-resisting flanges extending radially from the body, and a set of opposing rotation-preventing/rotation-resisting wings extending radially from the body, each cap wing having a lateral rotation-preventing surface and a lateral rotation-resisting surface;
• the receiver extending between opposite proximal and distal ends, the receiver comprising a having opposing arms spaced equally from a longitudinal axis of the receiver, each arm extending to a respective proximal end from a common distal base and having an inner proximal protrusion at or adjacent the proximal end, the proximal end forming a wing-receiving cavity having a lateral rotation-preventing side and a lateral rotation-resisting side, each receiver proximal protrusion having (i) a proximal-facing sloped receiver pop-on surface extending distally and radially inward toward the longitudinal axis, and (ii) a distal-facing sloped receiver splay-resist surface extending distally and radially inward toward the longitudinal axis, the distal end comprising an end surface and an opening extending through the end surface, the opening extending 360 degrees about the opening;
• wherein:
• each cap flange has a proximal-facing cap splay-resist surface, sloped proximally and radially outward, and a distal-facing cap pop-on surface;
• each cap rotation-preventing surface contacts a corresponding one of the rotation-preventing side and each rotation-resisting surface contacts a corresponding one of the rotation-resisting sides when the cap is popped onto the receiver;
• the cap rotation-preventing surfaces are configured such that when the cap is installed onto the receiver, the rotation-preventing surfaces contacting the rotation-preventing sides prevents cap rotation in a first direction;
• the cap rotation-resisting surfaces are configured such that when the cap is installed onto the receiver, the rotation-resisting surfaces contacting the rotation-resisting sides resists cap rotation in a second direction, opposite the first direction, but allows cap rotation in the second direction in response to a threshold torque being applied in the second direction to the cap;
• and
• the cap rotation-resisting surfaces force the arms to splay when the cap is rotated by at least the threshold torque in the second direction in use of the system.

A system for use in spinal surgery, comprising:

• a receiver for receiving a pop-on cap, the receiver extending between opposite proximal and distal ends, the receiver comprising a having opposing arms spaced equally from a longitudinal axis of the receiver, each arm extending to a respective proximal end from a common distal base and having an inner proximal protrusion at or adjacent the proximal end, the proximal end forming a wing-receiving cavity having a lateral rotation-preventing side and a lateral rotation-resisting side, the distal end comprising an end surface and an opening extending through the end surface, the opening extending 360 degrees about the opening;
• the cap having a generally cylindrical body, a set of opposing splay-resisting flanges extending radially from the body, and a set of opposing rotation-preventing/rotation-resisting wings extending radially from the body, each cap wing having a lateral rotation-preventing surface and a lateral rotation-resisting surface, and each cap flange has a proximal-facing cap splay-resist surface, sloped proximally and radially outward, and a distal-facing cap pop-on surface;
• wherein:
• each receiver proximal protrusion has (i) a proximal-facing sloped receiver pop-on surface extending distally and radially inward toward the longitudinal axis, and (ii) a distal-facing sloped receiver splay-resist surface extending distally and radially inward toward the longitudinal axis;
• each receiver rotation-preventing side is positioned and oriented to contact a corresponding one of the rotation-preventing surfaces, and each receiver rotation-resisting side is positioned and oriented to contact a corresponding one of the rotation-resisting surfaces, when the receiver receivers the cap;
• the receiver rotation-preventing surfaces are configured such that when the cap is installed onto the receiver, the rotation-preventing surfaces contacting the rotation-preventing sides prevent cap rotation in a first direction;
• the receiver rotation-resisting surfaces are configured such that when the cap is installed onto the receiver, the rotation-resisting surfaces contacting the rotation-resisting sides resists cap rotation in a second direction, opposite the first direction, but allows cap rotation in the second direction in response to a threshold torque being applied to the cap in the second direction;
• and
• the receiver rotation-resisting sides, and so the receiver arms, splay in response to force from the rotation-resisting surfaces when the cap is rotated by at least the threshold torque in the second direction in use of the system.