Systematic Displacement Bone Screw

Abstract

The present invention is a systematic displacement bone screw having minor and major thread diameters that are constant instead of tapered. The crests at the tip of the screw are narrower than the crests near the screw head resulting in a smaller distance between the thread flanks, which displaces and/or compresses more bone matter. Because the major diameter remains constant, the diameter of the hole made by inserting the screw is consistent over the length of the screw allowing the screw to be adjusted without loosening. The systematic displacement screw with varying crest thicknesses also avoids the need to use a larger diameter screw in place of a removed screw during a repair procedure. Rather than increasing the size of the hole, the systematic displacement screw can be used for the both the original screw and the replacement screw.

What is claimed is: 
     
         1 . A systematic displacement bone screw for maximizing bone displacement through a bone aperture which remains constant in size, comprising:
 a root;   a plurality of bone compressing flanks extending outward of said root, each flank having a crest width measured substantially parallel to a longitudinal axis of the root;   each flank separated from an adjacent flank by a flank spacing;   a screw tip;   a screw head;   a major diameter that is substantially constant along the length of the screw;   a minor diameter that is substantially constant along the length of the screw;   wherein the crest width of each flank progressively increases from said screw tip to said screw head such that a flank with the smallest crest width is adjacent to said screw tip and a flank with the largest crest width is adjacent to said screw head; and   wherein the flank spacing between adjacent flanks progressively decreases from said screw tip to said screw head.   
     
     
         2 . The systematic displacement bone screw of  claim 1  wherein a crest of one or more of said flanks is flattened. 
     
     
         3 . The systematic displacement bone screw of  claim 1  wherein a crest of one or more of said flanks is rounded. 
     
     
         4 . The systematic displacement bone screw of  claim 1  wherein at least one crest of said flanks is rounded and at least one crest of said flanks is flattened. 
     
     
         5 . The systematic displacement bone screw of  claim 1  wherein said crests have one or more variations in crest width. 
     
     
         6 . The systematic displacement bone screw of  claim 1  wherein said tip has at least one lateral cut which forms a tooth. 
     
     
         7 . A method of making a systematic displacement bone screw comprising:
 securing at least one blank screw having a desired head, tip and a diameter which corresponds to a desired major diameter, said desired major diameter bearing a directly proportional relationship to a n aperture to be made in a bone during a surgical procedure;   determining one or more crest widths and flank spacing which regulate the amount of bone displacement without the affecting the size of the bone aperture;   determining a desired minor diameter that is directly proportionate to the major diameter;   designating one or more threaded regions, each of said one or more threaded regions having a uniform major diameter, minor diameter and crest width; and   cutting a first helical path creating a thread having crests of a first crest width.   
     
     
         8 . The method of making a systematic displacement bone screw of  claim 7  which further includes cutting one or more subsequent helical paths creating crests having a width narrower that than of said first crest width. 
     
     
         9 . The method of making a systematic displacement bone screw of  claim 7  which further includes blending the transition area between the crests of first crest width and said narrower crests. 
     
     
         10 . A method of orthopedic revision surgery to replace a first bone screw with a replacement bone screw without increasing a bone aperture comprising:
 removing said first bone screw from the bone; and   replacing said first bone screw with said replacement bone screw;   wherein said replacement bone screw has a constant major diameter proportional to the bone aperture, a constant minor diameter proportional to the major diameter, and one or more crest widths and flank spacing which regulate the amount of bone displacement without affecting the size of the bone aperture.   
     
     
         11 . The method of orthopedic revision surgery of  claim 10 , further including the step of identifying the size of the bone aperture created during a first orthopedic surgery and selecting said replacement bone screw with a major diameter proportional to said bone aperture. 
     
     
         12 . The method of orthopedic revision surgery of  claim 10 , further including the step of selecting the replacement bone screw from a kit containing a plurality of replacement bone screws, each of the plurality of replacement bone screws of the kit having differing major diameters.