Adjustable angle bone fixation assembly
A bone fixation screw is provided for coupling with a bone fusion plate to join bone fusions. The bone fixation screw comprises a head portion and a shank that is comprised of distal threads and extends to a tapered portion and a rounded distal end. The head portion includes proximal threads extending circumferentially around an inferior end of the head portion. The proximal threads are configured to advantageously cross-thread with aperture threads of the bone fusion plate when the bone fixation screw is obliquely angled relative to the bone fusion plate. Slots disposed around the head portion allow the proximal threads to disengage and reengage with the aperture threads as the bone fixation screw turns. A shaped opening in a superior end of the head portion engagedly receives a tool for driving the bone fixation screw into a bone hole.
1 . A method for a bone fixation screw to couple with a bone fusion plate, comprising:
providing a bone fusion plate and configuring a head portion for engaging a fixation aperture of the bone fusion plate wherein the bone fixation screw is configured to be coupled with the fixation aperture at an oblique angle with respect to the bone fusion plate;
the bone fusion plate having at least an aperture to receive a bone fixation screw wherein the bone fixation screw is configured to be coupled with the fixation aperture at an oblique angle with respect to the bone fusion plate;
providing the bone fixation screw comprising a head portion comprised of a superior end and an inferior end, the head portion having at least a proximal thread extending circumferentially around the head portion;
extending a shank distally from the head portion and providing a tapered portion of the shank extending to a distal end and having a plurality of flutes thereon
providing a tapered portion of the shank extending to a rounded distal end comprising the plurality of flutes that extend along the shank adjacent of the rounded distal end and into the distal threads wherein flute corresponding to and bordering a cutting edge wherein at least one the cutting edge borders each of the one or more flutes and is configured to clean an interior of the bone hole and increase a diameter of the bone hole to accept the distal threads of the bone fixation screw;
disposing distal threads on the shank for engaging with bone wherein a portion of the distal threads extends past a region formed by at least one of a multiplicity of uniformly disposed slots wherein a portion of the distal threads extends past a region formed by at least one of the multiplicity of uniformly disposed slots;
terminating a tapered portion of the shank at a rounded distal end; and
disposing a multiplicity of slots around a perimeter of the head portion.
2 . The method of claim 1 , wherein configuring the head portion includes configuring a shaped opening on a superior end of the head portion for engagedly receiving a tool suitable for driving the bone fixation screw into a bone hole.
3 . The method of claim 1 , wherein configuring the head portion includes configuring proximal threads on an inferior end of the head portion for threadably coupling with one or more aperture threads disposed within the fixation aperture.
4 . The method of claim 3 , wherein configuring the proximal threads includes configuring a thread pitch of the proximal threads to be substantially similar to a thread pitch of the one or more aperture threads.
5 . The method of claim 3 , wherein configuring the proximal threads includes configuring the head portion to couple with the fixation aperture at an oblique angle with respect to the bone fusion plate, such that a countersunk side of the head portion threads deeper into the fixation aperture than a protruding side of the head portion.
6 . The method of claim 5 , wherein configuring the proximal threads includes configuring adjacent proximal threads to share a portion of a first aperture thread at the countersunk side and share a portion of a second aperture thread at the protruding side.
7 . The method of claim 5 , wherein configuring the proximal threads includes configuring the proximal threads to cross-thread with the aperture threads when the bone fixation screw is obliquely angled relative to the bone fusion plate.
8 . The method of claim 1 , wherein disposing the multiplicity of slots includes configuring the multiplicity of slots to allow the proximal threads to disengage and reengage with the fixation aperture when the bone fixation screw is turned while obliquely angled relative to the bone fusion plate.
9 . The method of claim 8 , wherein disposing the multiplicity of slots includes disposing six cylindrically shaped cutout portions uniformly around the perimeter of the head portion.
10 . The method of claim 8 , wherein disposing the multiplicity of slots includes disposing a multiplicity of angled cutout portions around the perimeter of the head portion.
11 . The method of claim 8 , wherein disposing the multiplicity of slots includes disposing a multiplicity of square-shaped cutouts around the perimeter of the head portion.
12 . The method of claim 8 , wherein disposing the multiplicity of slots includes disposing differently shaped cutouts around the perimeter of the head portion.
13 . The method of claim 12 , wherein disposing differently shaped cutouts includes disposing a first portion of the multiplicity of slots comprising a first shape and disposing a second portion of the multiplicity of slots comprising a second shape that is different than the first shape.
14 . The method of claim 13 , wherein disposing the first portion and disposing the second portion comprises disposing the first portion and the second portion in an alternating arrangement around the head portion.
15 . The method of claim 1 , wherein configuring the head portion includes configuring a shaped opening having a size and a shape that cooperates with an arrangement of the multiplicity of slots.
16 . The method of claim 15 , wherein configuring the shaped opening includes orienting peripheral regions of the shaped opening between adjacent slots comprising the multiplicity of slots.
17 . The method of claim 15 , wherein configuring the shaped opening includes configuring a hexalobe shape that is substantially concentric with the head portion and the shank.
18 . The method of claim 1 , wherein configuring the head portion includes configuring proximal threads having a thread pitch that is substantially the same as a thread pitch of one or more aperture threads disposed within the fixation aperture of the bone fusion plate.
19 . The method of claim 18 , wherein configuring the proximal threads includes configuring the proximal threads to have substantially one-half of a mating thread size of one or more aperture threads.
20 . The method of claim 19 , wherein configuring the proximal threads includes selecting the thread pitch to facilitate engaging the bone fixation screw within the fixation aperture at an oblique angle with respect to the bone fusion plate.