US Patent 8128671 Variable flank bone screw

A bone screw comprising a threaded shank having a longitudinal axis and including a first helical threading extending along a first length of the threaded shank portion and a second helical threading extending from a location proximately adjacent the first helical threading and along a second length of the threaded shank portion. The first helical threading defines a first volume between adjacent thread turns along the first length, and the second helical threading defines a second volume between adjacent thread turns along the second length, with the first volume being different from the second volume.