Variable angle cannulated bone screw and methods for use thereof

Abstract

A bone screw and a method for using same, the bone screw comprising an elongated shaft including a proximal end, a distal end, a leading portion, and intermediate portion and a trailing portion, the elongated shaft defining a longitudinal axis; a cannula bored completely through said elongated shaft extending from said distal end to said proximal end, the cannula aligned with said longitudinal axis; the leading portion having at least one thread; the intermediate portion being unthreaded; and the trailing portion comprising a threaded tapered head adapted engage a threaded hole at a selectable angle.

We claim: 
     
         1 . A bone screw comprising:
 An elongated shaft including a proximal end, a distal end, a leading portion, and a trailing portion;   a cannula bored completely through said elongated shaft extending from said distal end to said proximal end, the cannula aligned with said shaft;   the leading portion having at least one thread; and   the trailing portion comprising an externally threaded head adapted to engage a threaded hole.   
     
     
         2 . The bone screw of  claim 1  wherein said externally threaded head is tapered. 
     
     
         3 . The bone screw of  claim 1  wherein said cannula is adapted to receive a K-wire therethrough. 
     
     
         4 . The bone screw of  claim 1  wherein said externally threaded head is adapted to engage said threaded hole at a range of angles selectable at the time of engagement. 
     
     
         5 . A method for attaching a bone plate having a threaded hole and a hole axis to a bone, using a bone screw having a cannulated shaft and an externally threaded head, the method comprising the steps of:
 inserting a K-wire through the threaded hole and into the bone along an insertion axis not collinear with said hole axis;   drilling a cavity in the bone in alignment with the inserted K-wire by using a cannulated drill over the K-wire;   inserting the bone screw over the k-Wire and through the threaded hole by engaging the cannulated shaft of the bone screw with the K-wire;   advancing the bone screw over the K-wire until the leading end of the screw enters the drilled bone cavity;   driving the bone screw into the bone until the externally threaded head of the screw bone engages the threaded hole of the bone plate;   driving the threaded head of the bone screw into the threaded hole of the bone plate until it lockingly cross-threads; and   removing the k-Wire.   
     
     
         6 . The method of  claim 5  wherein said insertion axis is selected at the time of insertion of the K-wire.