Blunt Tip Bone Screw

Abstract

In one embodiment, a bone screw includes a shaft having a proximal shaft end and a distal shaft end spaced from the proximal shaft end in a distal direction along a central axis. The shaft is helically threaded between the proximal and distal shaft ends. A tip extends from the distal shaft end in the distal direction, and defines a plurality of lands with cutting flutes disposed between adjacent lands. Each land has a bore-cutting edge that extends from an inner cutting edge end to an outer cutting edge end. The inner cutting edge end is disposed at a center of the distal end of the tip, and the outer cutting edge end is spaced from the center of the distal end of the tip. The bore-cutting edges may blunt the feel of the tip so as to reduce the likelihood of soft-tissue damage.

What is claimed is: 
     
         1 . A bone screw comprising:
 a shaft having a proximal shaft end and a distal shaft end spaced from the proximal shaft end in a distal direction along a central axis, wherein the shaft is helically threaded between the proximal and distal shaft ends; and   a tip that extends from the distal shaft end in the distal direction to a tip end, the tip defining one or more lands and at least one cutting flute disposed adjacent the one or more lands, each of the lands having a bore-cutting edge configured to cut a bore into bone, each bore-cutting edge extends from an inner cutting-edge end to an outer cutting-edge end, wherein:
 the inner cutting-edge end is disposed at a center of the tip end; 
 the outer cutting-edge end is spaced from the center of the tip end; and 
 the bore-cutting edge defines a cutting angle with respect to a plane that is perpendicular to the central axis, the cutting angle in the range of approximately zero degrees to approximately 45 degrees. 
   
     
     
         2 . The bone screw of  claim 1 , wherein:
 the shaft is helically threaded in a first direction of rotation as viewed along the distal direction;   each land is defined by a leading side and a trailing side with respect to the first direction of rotation; and   each bore-cutting edge is defined at the leading side of a corresponding land.   
     
     
         3 . The bone screw of  claim 1 , wherein the tip defines a plurality of lands, each land having a bore-cutting edge. 
     
     
         4 . The bone screw of  claim 1 , wherein the center is a point. 
     
     
         5 . The bone screw of  claim 1 , wherein the cutting angle in the range of approximately  15  degrees to approximately 30 degrees. 
     
     
         6 . The bone screw of  claim 1 , wherein:
 the shaft is helically threaded in a first direction of rotation as viewed along the distal direction;   each land is defined by a leading side and a trailing side with respect to the first direction of rotation; and   each leading side includes a thread-cutting surface configured to cut threading into the bone.   
     
     
         7 . The bone screw of  claim 1 , wherein an outer curved surface of the tip is tapered from the distal shaft end toward the tip end. 
     
     
         8 . The bone screw of  claim 1 , wherein the tip end is solid about the central axis. 
     
     
         9 . The bone screw of  claim 1 , wherein the tip end is cannulated so as to define a hole about the central axis of the tip end. 
     
     
         10 . A bone screw comprising:
 a shaft having a proximal shaft end and a distal shaft end spaced from the proximal shaft end in a distal direction along a central axis, wherein the shaft is helically threaded between the proximal and distal shaft ends; and   a tip that extends from the distal shaft end in the distal direction to a tip end, the tip defining one or more lands and at least one cutting flute disposed adjacent the one or more lands, each of the lands having a bore-cutting edge configured to cut a bore into bone, each bore-cutting edge extends from an inner cutting-edge end to an outer cutting-edge end, wherein:
 the tip end is solid about the central axis; 
 the inner cutting-edge end is disposed at a center of the tip end; and 
 the outer cutting-edge end is spaced from the center of the tip end. 
   
     
     
         11 . The bone screw of  claim 10 , wherein each bore-cutting edge extends radially from the center of the tip end. 
     
     
         12 . The bone screw of  claim 10 , wherein:
 the shaft is helically threaded in a first direction of rotation as viewed along the distal direction;   each land is defined by a leading side and a trailing side with respect to the first direction of rotation; and   each bore-cutting edge is defined at the leading side of a corresponding land.   
     
     
         13 . The bone screw of  claim 10 , wherein the tip defines a plurality of lands, each land having a bore-cutting edge. 
     
     
         14 . The bone screw of  claim 13 , wherein the center is a point. 
     
     
         15 . The bone screw of  claim 10 , wherein the bore-cutting edge defines an angle with respect to a plane that is perpendicular to the central axis, the angle in the range of 15 to 30 degrees 
     
     
         16 . The bone screw of  claim 10 , wherein:
 the shaft is helically threaded in a first direction of rotation as viewed along the distal direction;   each land is defined by a leading side and a trailing side with respect to the first direction of rotation; and   each leading side includes a thread-cutting surface configured to cut threading into the bone.   
     
     
         17 . The bone screw of  claim 10 , wherein an outer curved surface of the tip is tapered from the distal shaft end toward the tip end. 
     
     
         18 . A method of fixing a bone screw having a shaft and a tip to a bone, the method comprising:
 (a) abutting a tip of the bone screw against a bone, wherein the tip extends from the shaft in a distal direction to a tip end of the tip, the tip defining a plurality of lands, each of the lands having a bore-cutting edge, each bore-cutting edge extending in a radial direction from an inner cutting-edge end disposed at a center of the tip end to an outer cutting-edge end spaced from the center of the tip end;   (b) rotating the bone screw in a first direction of rotation as viewed along the distal direction such that the plurality of cutting edges cut into the bone to form a bore in the bone, the bore having an inner curved surface;   (c) guiding chips cut from the bone away from the tip end in a proximal direction, opposite the distal direction, through cutting flutes formed in the tip between adjacent lands; and   (d) continuing to rotate the bone screw in the first direction such that a helical threading disposed on the shaft purchases the inner curved surface of the bore, wherein the helical threading is disposed on the shaft in the first direction of rotation between a proximal shaft end of the shaft and a distal shaft end of the shaft that is spaced from the proximal shaft end in the distal direction.   
     
     
         19 . The method of  claim 18 , wherein the bore-cutting edge defines a cutting angle with respect to a plane that is perpendicular to the central axis, the angle in the range of approximately zero degrees to approximately 45 degrees. 
     
     
         20 . The method of  claim 18 , wherein the tip end is solid about the central axis.