Directional control for a multi-axial screw assembly

Abstract

A multi-axial screw assembly comprises a receiver, a base member, and a crown. The receiver comprises a channel for receiving a rod and an aperture extending from a bottom portion of the receiver. The base member comprises an aperture extending through the base member and an opening on a bottom portion of the base member. The base member is configured to couple to the receiver such that the aperture of the receiver is generally aligned with the aperture of the base member. The base member is rotatable relative to the receiver. The crown is received in the receiver and configured to mate to the base member. The crown has a mating feature configured to couple to the base member such that the crown rotates the base member when the crown is rotated.

1 - 14 . (canceled) 
     
     
         15 . A multi-axial screw assembly, comprising:
 a receiver extending along a longitudinal axis between opposite top and bottom surfaces and comprising a throughhole extending parallel to the longitudinal axis between a proximal portion and a distal portion, an upper limit of the distal portion being defined by a first flange that extends transverse to the longitudinal axis;   a base member comprising an aperture extending through opposite upper and lower surfaces of the base member, the base member comprising a cutout that extends from the lower surface into a sidewall of the base member, the base member comprising second and third flanges that each extend transverse to the longitudinal axis, the base member being positioned within the distal portion such that the upper surface engages the first flange and the second flange engages the bottom surface;   a crown comprising a passageway extending through opposite proximal and distal surfaces of the crown, the crown being positioned within the proximal portion such that the distal surface engages the third flange; and   a bone screw having a head that is positioned within the aperture and the passageway.   
     
     
         16 . A multi-axial screw assembly as recited in  claim 15 , wherein the crown is rotatable relative to the receiver when the crown is positioned within the proximal portion such that the distal surface engages the third flange. 
     
     
         17 . A multi-axial screw assembly as recited in  claim 15 , wherein:
 the crown is rotatable relative to the receiver when the crown is positioned within the proximal portion such that the distal surface engages the third flange; and   the crown is fixed to the base member such that the cutout is positionable relative to the receiver.   
     
     
         18 . A multi-axial screw assembly as recited in  claim 15 , wherein the crown comprises a plurality of surface projections extending from an outer surface of the crown, the projections being disposed in indentations extending into an upper surface of the base member to fix the crown relative to the base member. 
     
     
         19 . A multi-axial screw assembly as recited in  claim 18 , wherein:
 the projections are uniformly spaced apart and disposed circumferentially about the outer surface of the crown; and   the indentations are uniformly spaced apart and disposed circumferentially about the upper surface of the base member.   
     
     
         20 . A multi-axial screw assembly as recited in  claim 15 , wherein the bone screw is movable relative to the base member between a first orientation in which a shaft of the bone screw that is coupled to the head is parallel to the longitudinal axis and is spaced apart from the cutout and a second orientation in which the shaft is transverse to the longitudinal axis and at least a portion of the shaft is disposed in the cutout. 
     
     
         21 . A multi-axial screw assembly as recited in  claim 15 , wherein the base member is rotatable relative to the receiver when the base member is positioned within the distal portion such that the upper surface engages the first flange and the second flange engages the bottom surface. 
     
     
         22 . A multi-axial screw assembly, comprising:
 a receiver extending along a longitudinal axis between opposite top and bottom surfaces and comprising a throughhole extending parallel to the longitudinal axis between a proximal portion and a distal portion, the receiver comprising a first groove that is in communication with the distal portion;   a base member rotatably positioned within the distal portion and comprising an aperture extending through opposite upper and lower surfaces of the base member, the base member comprising a cutout that extends from the lower surface into a sidewall of the base member, the base member comprising a second groove that extends into the sidewall;   a ring member positioned within the grooves to connect the base member with the receiver such that the base member is rotatable relative to the receiver;   a crown positioned within the proximal portion and comprising a passageway extending through opposite proximal and distal surfaces of the crown; and   a bone screw comprising a shaft and a head that extends from the shaft, the head being positioned within the aperture and the passageway.   
     
     
         23 . A multi-axial screw assembly as recited in  claim 22 , wherein the crown comprises a plurality of surface projections extending from an outer surface of the crown, the projections being disposed in indentations extending into an upper surface of the base member to fix the crown relative to the base member. 
     
     
         24 . A multi-axial screw assembly as recited in  claim 23 , wherein:
 the projections are uniformly spaced apart and disposed circumferentially about the outer surface of the crown; and   the indentations are uniformly spaced apart and disposed circumferentially about the upper surface of the base member.   
     
     
         25 . A multi-axial screw assembly as recited in  claim 22 , wherein the shaft comprises a proximal portion that is threaded and a distal portion that is unthreaded. 
     
     
         26 . A multi-axial screw assembly as recited in  claim 22 , wherein the receiver comprises a channel extending transverse to the longitudinal axis for receiving a rod. 
     
     
         27 . A multi-axial screw assembly as recited in  claim 22 , wherein the cutout is convexly curved. 
     
     
         28 . A multi-axial screw assembly as recited in  claim 22 , wherein the head directly engages a concave bottom surface of the crown. 
     
     
         29 . A multi-axial screw assembly, comprising:
 a receiver extending along a longitudinal axis between opposite top and bottom surfaces and comprising a throughhole extending parallel to the longitudinal axis between a proximal portion and a distal portion;   a base member rotatably positioned within the distal portion and comprising an aperture extending through opposite upper and lower surfaces of the base member, the base member comprising a single cutout that extends from the lower surface into a sidewall of the base member;   a crown positioned within the proximal portion and comprising a passageway extending through opposite proximal and distal surfaces of the crown; and   a bone screw comprising a shaft and a head that extends from the shaft, the head being positioned within the aperture and the passageway, at least a portion of the shaft being threaded, the shaft is movable between a first orientation in which the shaft extends parallel to the longitudinal axis and is spaced apart from the cutout and a second orientation in which the shaft extends transverse to the longitudinal axis and at least a portion of the shaft is disposed in the cutout.   
     
     
         30 . A multi-axial screw assembly as recited in  claim 29 , wherein the lower surface extends continuously in one plane that is transverse to the longitudinal axis from a first end of the single cutout to an opposite second end of the single cutout. 
     
     
         31 . A multi-axial screw assembly as recited in  claim 29 , wherein at least a portion of the shaft is unthreaded. 
     
     
         32 . A multi-axial screw assembly as recited in  claim 29 , wherein the cutout has a concave down configuration with a continuous radius of curvature. 
     
     
         33 . A multi-axial screw assembly as recited in  claim 29 , wherein the bone screw is movable relative to the base member between a first orientation in which the shaft is parallel to the longitudinal axis and is spaced apart from the cutout and a second orientation in which the shaft is transverse to the longitudinal axis and at least a portion of the shaft is disposed in the cutout. 
     
     
         34 . A multi-axial screw assembly as recited in  claim 29 , wherein:
 the receiver comprises a channel extending transverse to the longitudinal axis for receiving a rod;   the assembly further comprises the rod positioned within the channel; and   the rod engages an uppermost planar surface of the crown when the rod is positioned within the channel.