Patent ID: 8303634

Claim:
A bone screw ( 1 ) comprising (a) a threaded proximal portion ( 2 ) having a proximal core ( 11 ) with a constant diameter and a proximal thread ( 12 ) with a constant diameter and a proximal pitch; (b) a threaded median portion ( 3 ) having a conical median core ( 15 ) with a diameter that becomes increasingly larger from a distal end of the threaded median portion ( 3 ) to a proximal end of the threaded median portion ( 3 ) and a median thread ( 16 ) with a constant diameter which is smaller than the diameter of the proximal thread ( 12 ) and a median pitch that becomes increasingly smaller from the distal end of the threaded median portion ( 3 ) towards the proximal end of the threaded median portion ( 3 ), the median pitch at the proximal end of the threaded median portion ( 3 ) being larger than the proximal pitch; and (c) a threaded distal portion ( 4 ) having a distal core with a constant diameter ( 17 ) and a distal thread ( 18 ) with a constant diameter that is smaller than the diameter of the median thread ( 16 ) and a pitch that is larger than the pitch of the median thread ( 16 ) at the distal end of the threaded median portion ( 3 ).