Patent Application
20080051793
For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to certain embodiments thereof and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the claims is thereby intended, such alterations, further modifications and further applications of the principles of the disclosure as described herein being contemplated as would normally occur to one skilled in the art to which the disclosure relates.
Referring to the figures, and particularly to
Tool 10 may include a longitudinal axis 15, drill tap portion 20, stop portion 30, shaft portion 40 and handle attachment portion 50. Tool 10 may also include markings such as size etchings 41 along shaft portion 40 indicating the particular size of tool 10. Similarly, tool 10 may include color coded markings 42, such as a colored epoxy fill, located in the recesses found near the center of shaft portion 40 that could also indicate the particular size of tool 10. Tool 10 may be formed of any biocompatible material capable of drilling and tapping bone. One type of material that may be acceptable is medical grade stainless steel.
As shown in
Hole cutting edge 100 and drill tip 101 are generally configured to bore a hole in bone when tool 10 is rotated about longitudinal axis 15. Hole cutting edge 100, in combination with spiral flute 120 and hole reaming edge 102, may be configured similarly to a conventional drill bit for bone tissue, as is illustrated in one embodiment in
Drill tap portion 20, in this embodiment, includes a spiral flute 120. Tap portion 24 may be considered to be a male thread flight or thread part that has a plurality of cutting edges 112 separated and defined by spiral flute 120 such that the threaded part of drill tap portion 20 that includes thread profile 110 is made discontinuous by spiral flute 120. The cutting edges 112 of this embodiment generally form a female thread in bone. In one embodiment, drill tap portion 20 may have two spiral flutes 120 that are diametrically opposed or equally spaced around drill tap portion 20. Fewer, or more, than two flutes may be formed in drill tap portion 20 of tool 10 in specific embodiments. In addition, the flutes may be straight, instead of helically formed about drill tap portion 20 of tool 10. Spiral flute 120 may extend along the length of drill tap portion 20 to remove bone debris or other tissue or matter removed by cutting edges 106 and 112.
As already noted, lead-in cutting edge 106 and thread cutting edge 112 may be configured to tap a female threaded hole in bone when tool 10 is rotated about longitudinal axis 15. In the illustrated embodiment, edge 106 is formed at the junction of tap lead-in thread 104 and spiral flute 120. Similarly, thread cutting edge 112 is formed at the junctions of thread profile 114 and spiral flute 120. Tap lead-in thread 104 may have a thread profile that gradually introduces increasingly larger lead-in cutting edges 106 (e.g. having increasing crest width or crest diameter) and may reach a constant crest-diameter full thread profile 110. In this way, lead-in thread 104 and lead-in cutting edge 106 form a tapered transition portion in this embodiment between full thread profile 110 and drill portion 22, with lead-in thread 104 and lead-in cutting edge 106 having threads with comparatively reduced cross sections. In the embodiment illustrated in
Tap portion 24′ may include tap lead-in thread 104, lead-in cutting edge 106, complete thread profile 110, thread cutting edge 112, major tap diameter Ø, spiral flute 120 and flute end 122, as previously disclosed. Lead-in thread 104 and lead-in cutting edge 106 may form a transition portion between the full thread profile 110 and drill portion 22′.
Stop portion 30 may include raised stop portion 114 located at a desired position along shaft portion 40 to limit the depth of any female threaded hole made by tool 10 to maximum depth L. Raised stop portion 114 may have an outer diameter that is substantially greater than the major tap diameter Ø. In one embodiment, the outer diameter of raised stop portion 114 may be 5 mm while the major tap diameter Ø is 4 mm. Alternatively, or in addition, flute end 122 of spiral flute 120 could limit the depth of any female threaded hole made by tool 10 to a predetermined maximum depth L. In various embodiments of tool 10, either raised stop portion 114 or flute end 122 may inhibit further drilling or tapping of a bone after the maximum depth L has been reached. Individual embodiments of tool 10 may be configured to specifically correspond to match the threaded length of individual screws such that individual embodiments of tool 10 may be specifically configured to drill and tap a female threaded hole to mate with a specific screw thread and screw length. Mating with a specific screw thread and screw length may entail drilling and tapping a hole that permits the complete insertion of the specific screw without any additional removal of bone from the hole. Alternatively, mating with a specific screw may entail drilling and tapping a hole that may require some additional thread tapping, possibly by the specific screw itself, possibly near the tip of the screw, to permit the complete insertion of the specific screw in the threaded hole in bone.
Configuring individual embodiments of tool 10 to specifically correspond to match the threaded length of individual screws may provide one or more of a variety benefits to the surgeon using tool 10. For example, having an individual tool 10 that specifically corresponds to an individual screw may provide holes with a more uniform depth than may be achievable by a similar tool that does not have a maximum depth L, or that can be used with a number of differently-configure screws. Furthermore, specifically tailoring tool 10 to an individual screw removes as a potential source of error in the surgeon's judgment in either setting an adjustable depth stop or a surgeon's judgment in determining a drilled and/or tapped hole is deep enough.
For example, in one embodiment of tool 10, maximum depth L could be equal to about 12.4 mm which may correspond to an individual screw having a length of 11 mm. In another embodiment, maximum depth L could be equal to 14.4 mm which may correspond to an individual screw having a length of 13 mm. Similarly, in yet another embodiment, maximum depth L could be equal to 16.4 mm which may correspond to an individual screw having a length of 15 mm. In yet another embodiment, maximum depth L could be equal to 18.4 mm which may correspond to an individual bone screw having a length of 17 mm. In this regard, the length of an individual bone screw is measured as the distance between the tip of the screw and the head of the screw.
In addition, specifically tailoring tool 10 to an individual screw allows the use of similar identification indicia on both tool 10 and the individual screw to further reduce any potential human error that could be encountered in the operating room wherein the incorrect tool could be selected for a particular screw. For example, it may be advantageous to mark the shaft portion 40 of tool 10 with a color coded size indicator. It may then be possible to mark some portion of the particular screw with a similar color coded size indicator that matches the size indicator utilized to mark tool 10. Color coding particular screws may also reduce misidentification of screws in the operating room.
Handle attachment portion 50 is attached to a drill or other appropriate turning tool, in certain embodiments, which can rotate tool 10 about longitudinal axis 15. Such an instrument may be a of a variety of types, including hand operated drills or a power drills, and may include features such as a slip clutch that inhibits application of excessive torque to tool 10 when tool 10 is forming a threaded hole in bone. Tool 10 is advanced while forming the threaded hole in bone at a rate generally related to the revolution speed of the tool and the pitch P of tap section 24 of tool 10. A hand operated drill may allow precise control of the revolution speed of the tool 10 to inhibit rapid advancement of the tool into bone.
In use, once tool 10 is connected to an appropriate drill, tool 10 may be rotated and pressed into bone so that drill portion 22 or trocar tip portion 22′ forms an opening in the bone. Tap portion 24 or tap portion 24′ may operatively follow into the opening formed by drill portion 22 or trocar tip portion 22′. Tap portion 24 or 24′ forms a thread in a wall of the opening as tool 10 is rotated and driven further into the bone. Thus, tool 10 performs both the functions of drilling a hole and tapping it in a single operation, and substantially simultaneously. Tool 10 may be advanced until stop portion 30 encounters bone tissue, or the edge of the hole drilled and tapped in it. At this point it may become increasingly difficult or impossible to rotate tool 10 about longitudinal axis 15, as stop portion 30 frictionally engages or binds against bone tissue. Tool 10 may be backed out of the threaded opening by reversing the direction of rotation used to form the threaded hole.
When initially positioning the location of a threaded hole in bone, trocar tip portion 22′ may advantageously allow the initial insertion of tool 10 into bone to occur exclusively with a driving or piercing force (using little or no rotation of tool 10). This may permit more accurate location of the threaded hole than may be possible utilizing drill portion 22. Furthermore, it may be possible to form an opening in the bone using trocar tip portion 22′ utilizing a rotating motion that alternates direction instead of utilizing unidirectional rotation. A rotating motion may advantageously allow the surgeon to keep their same hand position on a hand operated drill which may not be possible when using a hand drill for unidirectional rotation. This may permit more accurate formation of threaded holes in bone using a hand operated drill.
The devices disclosed herein are intended for uses related to orthopedic medicine. Accordingly, embodiments of tool 20, 20′ should be made of materials compatible with the environment of orthopedic surgery, such as stainless steel or other hard materials that can be effectively sterilized and can efficiently cut bone tissue. Cutting edges should be made so as to minimize or eliminate the chance of leaving rough edges in or on bone tissue or otherwise causing cuts, abrasions or punctures outside of the intended preparation of a hole in bone, or other tissue damage.
While the disclosure has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the claims are desired to be protected. Features described or shown with respect to one particular embodiment may be used or included with other embodiments consistent with this disclosure.
