Locking screw with synchronized thread

Abstract

A targeting system for a bone plate having a bore therethrough with a first thread adjacent an outer surface of the bone plate and a second thread adjacent a bone contacting surface. The first thread has a larger diameter than the second thread. A targeting device has a coupling portion, an outer sleeve with an axial through bore for guiding a boring tool and a bone screw into the bone plate bore. The coupling portion is connected to a first end of the outer sleeve, wherein the coupling portion comprises an exterior threaded portion threadably engageable with the first thread of the bone plate bore and has a through bore having an axis corresponding to the axis of the through bore of the outer sleeve. The outer sleeve and coupling portion comprises two collapsible slits extending parallel to the outer sleeve bore axis dividing the coupling portion in two parts.

1 . A targeting system for applying a boring tool and a screw to a bone plate, the system comprising:
 a bone plate having a bone contacting inner surface and an outer surface with a bore extending from the outer surface to the bone contacting surface, the bore having a first thread adjacent the outer surface and a second thread adjacent the bone contacting inner surface, the first thread having a larger diameter than the second thread;   a targeting device having an outer sleeve with a through bore extending along an axis for guiding a boring tool and a bone screw into the bone plate bore and a coupling portion, wherein the coupling portion is connected to a first end of the outer sleeve, wherein the coupling portion comprises an exterior threaded portion threadably engageable with the first thread of the bone plate bore and has a through bore having an axis corresponding to the axis of the through bore of the outer sleeve;   wherein the outer sleeve comprises two slits extending in the direction of the outer sleeve bore axis at the first end of the outer sleeve forming two arms,   wherein the coupling portion exterior threaded portion comprises two slits extending in the direction of coupling portion bore axis dividing the coupling portion in two parts, and   wherein the two slits of the outer sleeve continue into the respective slits of the two slits of the coupling portion, so that the parts of the coupling portion exterior threaded portion are collapsible in a direction perpendicular to the axial direction to allow the exterior threaded portion to disengage from the bone plate first thread.   
     
     
         2 . The targeting system of  claim 1 , further comprising;
 an inner sleeve having an outer contour and a through bore extending along an axis aligned with the outer sleeve through bore;   wherein the outer sleeve having an inner contour;   wherein the inner sleeve is releasably insertable within the through bore of the outer sleeve; and   wherein at least a part of the outer contour of the inner sleeve conforms to the inner contour of the outer sleeve for preventing the slitted coupling portion from collapsing.   
     
     
         3 . The targeting system of  claim 1 , wherein the through bore of the coupling portion is of a smaller diameter than the through bore of the outer sleeve, wherein a transition portion between the through bore of the coupling portion and the through bore of the outer sleeve is a smooth transition. 
     
     
         4 . The targeting system of  claim 3 , wherein the inner sleeve is movable along axial direction with respect to the outer sleeve, urging the arms to move outwardly when abutting to the transition portion. 
     
     
         5 . The targeting system of  claim 2 , wherein the inner sleeve and the outer sleeve each comprise corresponding defining means for defining an axial position with respect to each other. 
     
     
         6 . The targeting system as set forth in  claim 2  wherein the outer and inner sleeve through bore axes are coaxial. 
     
     
         7 . A targeting system for applying a bore tool or a screw to a bone plate, the targeting system comprising:
 a bone plate having a bone contacting inner surface and an outer surface with an at least partially threaded bore extending therethrough;   a targeting element having an outer sleeve having a through bore extending in an axial direction along a central axis; and   a coupling portion wherein the coupling portion is connected in the axial direction to a first end of the outer sleeve wherein the coupling portion comprises an exterior thread portion and a through bore having a corresponding axis to the through bore of the outer sleeve,   wherein the exterior thread portion being adapated to be screwed in into a corresponding thread of the bone plate,   wherein the outer sleeve comprises two slits extending in axial direction to the first end of the outer sleeve forming two arms,   wherein the coupling portion comprises two slits in axial direction dividing the coupling portion in two parts,   wherein the slits of the outer sleeve continue into the respective slits of the coupling portion so that the parts of the coupling portion are movable in a direction perpendicular to the axial direction.   
     
     
         8 . The targeting system of  claim 7 , wherein the targeting element further comprises an inner sleeve having an outer surface and a through bore extending in the axial direction;
 wherein the outer sleeve has an inner surface;   wherein the inner sleeve is releasably connectable within the through bore of the outer sleeve;   wherein at least a part of the outer surface of the inner sleeve conforms to the inner surface of the outer sleeve for preventing movement of the central axis of the slitted coupling portion towards the outer sleeve.   
     
     
         9 . The targeting system of  claim 8 , wherein the through bore of the coupling portion is of a smaller diameter than the through bore of the outer sleeve, wherein a transition between the through bore of the coupling portion and the through bore of the outer sleeve is a smooth transition. 
     
     
         10 . The targeting system of  claim 9 , wherein the inner sleeve is movable along the axial direction with respect to the outer sleeve, urging the arms to move outwardly when adjacent a transition point. 
     
     
         11 . The targeting system of  claim 10 , wherein the inner sleeve and the outer sleeve each comprise corresponding means for defining an axial position with respect to each other. 
     
     
         12 . A targeting system for inserting a bone screw in a bone plate comprising:
 a bone plate having a threaded through bore extending along an axis;   a bone screw having a threaded head and a threaded shaft, with the diameter of the threads in the bone screw head being larger than the diameter of the threads on the shaft;   a targeting device comprising a tubular body having a pair of axially extending slits at a first threaded end for engaging the threaded through bore;   wherein the bone plate comprises   an inner surface being adapted for facing a bone surface to which the bone plate is to be mounted;   an outer surface being adapted for facing away a bone surface to which the bone plate is to be mounted;   the through bore extending from the inner surface to the outer surface;   wherein the through bore comprises a guiding portion and a blocking portion;   wherein the guiding portion is provided with a guiding thread for guiding a threaded shaft of the bone screw, and the blocking portion is provided with a blocking thread for blocking the threaded head of the bone screw;   wherein the blocking portion of the through bore is wider than the guiding portion and the guiding portion is located closer to the bone plate inner surface than the blocking portion;   wherein the thread of the targeting device engages the blocking thread of the bone plate.   
     
     
         13 . The targeting system of  claim 12 , wherein a pitch (p) of the blocking thread and a pitch (p) of the guiding thread are equal and correspond to the corresponding threads of the bone screw. 
     
     
         14 . The targeting system of  claim 13 , wherein an axial gap portion is provided in the through bore between the guiding portion and the blocking portion of the bone plate, and the blocking portion extends radially towards the through bore axis in the gap portion. 
     
     
         15 . The targeting system as set forth in  claim 12 , wherein the blocking thread comprises a double lead thread. 
     
     
         16 . The targeting system of  claim 12 , wherein the bone plate through opening comprises a tapered portion; wherein the tapered portion is wider than the blocking portion; wherein the tapered portion is located closer to the outer surface than the blocking portion. 
     
     
         17 . The targeting system of  claim 16 , wherein the tapered portion comprises a spherically shaped tapering. 
     
     
         18 . The targeting system of  claim 12  further comprising an inner sleeve having an outer surface and a through bore extending in the axial direction;
 wherein the outer sleeve has an inner surface; 
 wherein the inner sleeve is releasably connectable within the through bore of the outer sleeve; 
 wherein at least a part of the outer surface of the inner sleeve conforms to the inner surface of the outer sleeve for preventing movement of the central axis of the slitted coupling portion towards the outer sleeve. 
 
     
     
         19 . A targeting device for applying a bore tool or a screw to a bone plate, the targeting device comprising:
 an outer sleeve having a through bore in axial direction; and   a coupling portion;   wherein the coupling portion is connected in axial direction to a first end of the outer sleeve;   wherein the coupling portion comprises an exterior thread portion and a through bore having a corresponding axis to the through bore of the outer sleeve,   wherein the exterior thread portion being adapted to be screwed in into a corresponding blocking thread of a bone plate,   wherein the outer sleeve comprises two slits extending in axial direction to the first end of the outer sleeve forming two arms,   wherein the coupling portion comprises two slits in axial direction dividing the coupling portion in two parts, and   wherein the slits of the outer sleeve continue into the respective slits of the coupling portion, so that the parts of the coupling portion are movable in a direction perpendicular to the axial direction.   
     
     
         20 . The targeting device of  claim 19 , further comprising;
 an inner sleeve having an outer contour and a through bore in axial direction;   wherein the outer sleeve having an inner contour;   wherein the inner sleeve is releasably connectable within the through bore of the outer sleeve; and   wherein at least a part of the outer contour of the inner sleeve fits the inner contour of the outer sleeve for keeping the slit coupling portion in shape.   
     
     
         21 . The targeting device of  claim 19 , wherein the through bore of the coupling portion is of a smaller diameter than the through bore of the outer sleeve, wherein a transition portion between the through bore of the coupling portion and the through bore of the outer sleeve is a smooth transition. 
     
     
         22 . The targeting device of  claim 21 , wherein the inner sleeve is movable along axial direction with respect to the outer sleeve, urging the arms to move outwardly when abutting to the transition portion. 
     
     
         23 . The targeting device of  claim 20 , wherein the inner sleeve and the outer sleeve each comprise corresponding defining means for defining an axial position with respect to each other.