Patent Application
20110106157
The present invention generally relates to bone screws that are used to attach one or more implants to bone or bony tissue, and more particularly relates to a self-locking interference bone screw.
Various types of fasteners are used to engage implants or other devices to bone. In the spinal field, bone screws are commonly used to attach plates, rods and/or other types of implants or devices to one or more vertebrae. In some instances, bone screws can become unthreaded or disengaged following attachment of an implant to bone or one or more vertebrae. This unthreading or disengagement can result in failed surgical procedures and/or interference with patient anatomy surrounding the implantation site, which can in turn result in trauma to adjacent tissue and patient discomfort and can sometimes present a need for additional surgical procedures.
Thus, there remains a need for improved bone screws and methods for using the same.
One non-limiting embodiment of the present invention is directed to a bone screw structured to engage with an implant such as, for example, a bone plate, rod, or interbody stabilization device. In a more particular form, the bone screw is configured to engage with a passage in the implant such that an interference fit is provided between the bone screw and the implant, thereby reducing the likelihood of the bone screw becoming disengaged from the implant and/or bone. However, in other embodiments, different forms and applications of the bone screw are envisioned.
Another embodiment of the present invention is directed to a bone screw that includes an elongate shank extending along a longitudinal axis from an enlarged proximal head portion to a distal tip. The elongate shank includes a first portion having a first non-tapered, linear external profile and a second portion having a first tapered external profile that increases toward the proximal head portion. The second portion is positioned between the first portion and the head portion, and terminates distally of the proximal head portion.
In another embodiment, a stabilization system includes a bone screw and an implant including at least one passage extending therethrough. The bone screw includes an elongate shank extending along a longitudinal axis from an enlarged proximal head portion to a distal tip. The elongate shank includes a first portion having a first non-tapered, linear external profile and a second portion having a first tapered external profile that increases toward the proximal head portion. The second portion is positioned between the first portion and the head portion, and terminates distally of the proximal head portion. The passage of the implant is configured to engage with at least the second portion of the elongate shank of the bone screw to provide an interference fit between the bone screw and the implant.
In yet another embodiment, a bone screw includes an elongate shank extending along a longitudinal axis from an enlarged proximal head portion to a distal tip. The elongate shank includes a first threaded portion and a second portion positioned adjacent to and proximal of the first threaded portion. The second portion defines a distal facing annular shoulder. In one form of this embodiment, the annular shoulder extends radially beyond an external profile of the first threaded portion. In another form of this embodiment, the second portion is also threaded.
Other embodiments include unique methods, systems, devices, kits, assemblies, equipment, and/or apparatus involving a bone screw and/or an implant.
Further embodiments, forms, features, aspects, benefits, objects and advantages of the present invention shall become apparent from the detailed description and figures provided herewith.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is hereby intended, and that alterations and further modifications to the illustrated devices and/or further applications of the principles of the invention as illustrated herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
The present invention is generally directed to a variety of unique bone screws which, in one form, may be used to engage with and attach an implant to bone or bony tissue, although it should be appreciated that alternative uses for the bone screws described herein are contemplated. In one form, the bone screws are configured to be engaged within a passage of an implant such that an interference fit is provided between the bone screw and the implant. More particularly, the sidewall of the implant passage or the external surface of the bone screw is provided with a surface hardness that is greater than the other, and one or both of the passage and the bone screw include a geometrical configuration that causes the sidewall of the passage or the bone screw, whichever has the lower surface hardness, to become deformed. This deformation results in the interference fit between the bone screw and the implant, and thereby reduces the likelihood of the bone screw from becoming disengaged from the implant and/or the bone.
Referring now to
In one embodiment, the distal tip 14 of the elongate shank portion 12 is configured to penetrate bone. For example, in the illustrated embodiment, the distal tip 14 is tapered or pointed to facilitate entry into bone. However, in other embodiments, the distal tip 14 may define a blunt or rounded end. The elongate shank portion 12 also includes a cutting flute 20 extending proximally from the distal tip 14 to provide the bone screw 10 with self-cutting or self-tapping capabilities, although other embodiments were the cutting flute 20 is not provided are also contemplated. In still other embodiments, the bone screw 10 may be provided with an axial passage (not shown) extending from the proximal end portion 16 and partially or entirely therethrough to define a cannulation opening, and may be further provided with transverse passages that communicate with the axial passage to define fenestration openings. The cannulation and fenestration openings may be used to deliver material such as, for example, bone cement from the proximal end portion 16 of the bone screw 10 and into areas of the bone axially or laterally adjacent the distal tip 14 or other portions of the elongate shank portion 12.
In the illustrated embodiment, the head portion 18 is enlarged relative to the elongate shank portion 12 and is generally structured to bear against an implant, although other configurations of the head portion 18 are contemplated. For example, in one non-illustrated form, the head portion 18 may be the same size as or smaller than the elongate shank portion 12. The bone screw 10, and particularly the head portion 18, preferably includes features that allow for releasable engagement with a driving tool or instrument (not shown) such as, for example, a screwdriver. More particularly, in the illustrated form, the head portion 18 includes a receptacle 22 that is sized and shaped to receive a distal end portion of a driver tool. The receptacle 22 may be non-circular such as, for example, hexagonal or rectangular shaped to provide non-rotational engagement between the head portion 18 and the driver tool to facilitate driving engagement of the bone screw 10 into bone. More particular examples of non-circular configurations for the receptacle 22 include, but are not limited to, slotted, Phillips, hexagonal, Torx, spline drive, and double hex configurations. Alternatively, the head portion 18 may define external surface features configured for engagement by the distal end portion of a driver tool.
The bone screw 10 also includes a threading 24 that extends along the elongate shank portion 12 from the distal tip 14 toward the proximal end portion 16. In the illustrated embodiment, the threading 24 terminates distally of the head portion 18. Similarly, the elongate shank portion 12 includes a non-threaded, reduced diameter neck portion 30 positioned between the threading 20 and the head portion 18. However, in other non-illustrated forms, it is contemplated that the threading 24 may continue up to the head portion 18 and/or extend around all or a portion of the head portion 18 to the proximal end portion 16. The threading 24 includes a single thread lead in the form of a helical thread pattern that wraps around the elongate shank portion 12 along the longitudinal axis L. The threading 24 defines a thread root 26 in proximity to the longitudinal axis L, and a thread crest 28 distanced from the longitudinal axis L and radially spaced from the thread root 26. The elongate shank portion 12 includes an inner thread root diameter di measured across the thread roots 26, and an outer thread diameter do measured across the thread crests 28. In one form, the thread crests 28 may be tapered to facilitate self-tapping, or may be truncated and substantially flat. It should further be appreciated that the profile of the thread crests may be the same, or may vary along the length of the elongate shank portion 12.
In the illustrated embodiment, the depth of the threading 24 between the thread root 26 and the thread crest 28 is constant and uniform along the length of the elongate shank portion 12. However, in alternative embodiments, it is contemplated that the depth of the threading 24 may vary along one or more portions of the elongate shank portion 12. In addition, the pitch P of the threading 24 is constant and uniform along the length of the elongate shank portion 12, although in alternative embodiments it is contemplated that the pitch P of the threading 24 may vary along one or more portions of the elongate shank portion 12.
While not previously discussed, it should be appreciated that the external profile of the elongate shank portion 12 may vary along its length. More particularly,
As illustrated in
The fourth portion 38 is positioned proximally of the third portion 36 and includes an external profile having a tapered shape that increases toward the proximal end portion 16. Similarly, it should be appreciated that the outer thread diameter do of the threading 24 along the fourth portion 38 increases toward the proximal end portion 16. The fourth portion 38 terminates adjacent to or merges into the fifth portion 40 which has an external profile having a linear shape. More particularly, the outer thread diameter do of the threading 24 along the fifth portion 40 is constant, and generally corresponds to the largest outer thread diameter do of the threading 24 along the fourth portion 38. However, in other forms, it is contemplated that the outer thread diameter do of the threading 24 along the fifth portion 40 may be larger or smaller than the largest outer thread diameter do of the threading 24 along the fourth portion 38. In the illustrated form, the threading 24 terminates at the proximal end of the fifth portion 40. In addition, the neck portion 30 is positioned between the fifth portion 40 and the proximal head 18 and includes a linear external profile having a reduced diameter relative to the external profile of the fifth portion 40.
In the illustrated embodiment, the external profiles of the second portion 34 and the fourth portion 38 are generally defined by a linear taper that widens toward the proximal end portion 16. However, in one or more alternative forms, it is contemplated that the external profiles of the second portion 34 and the fourth portion 38 may be defined by a curved taper. In addition, in the illustrated embodiment, the taper rate of the external profile of the second portion 34 is more gradual than the taper rate of the external profile of the fourth portion 38. However, in alternative forms, the tapers along the external profiles of the second portion 34 and the fourth portion 38 may be the same, or the taper rate of the external profile of the fourth portion 38 may be more gradual than the taper rate of the external profile of the second portion 34. Moreover, while not previously discussed, it should be appreciated that the difference between the inner thread root diameter di and the outer thread diameter do along the elongate shank portion 12 is generally constant, although other forms are also contemplated wherein the difference between the inner thread root diameter di and the outer thread diameter do changes along one or more portions of the elongate shank portion 12. Stated alternatively, in
With reference to
The passage 52 is generally configured to receive and engage with the bone screw 10 such that an interference fit between the bone screw 10 and the implant 42 is provided. For example, in the illustrated form, the fourth portion 38 and the fifth portion 40 of the elongate shank portion 12 generally provide an external configuration that creates an interference fit between the bone screw 10 and the implant 42 as the bone screw 10 is axially inserted into the passage 52. For example, the fourth portion 38 and/or the fifth portion 40 may be provided with an external diameter that is greater than the internal diameter of the passage 52 of the implant 42. Similarly, since the passage 52 and/or the implant 42 are constructed of a material that has a different hardness than the bone screw 10 (see discussion above), engagement of the distal portion of the fourth portion 38 with the passage 52 of the implant 42 may begin deformation of one of the bone screw 10 and the passage 52. This deformation continues until the bone screw 10 is seated within the passage 52 of the implant 42, and ultimately results in an interference fit between the bone screw 10 and the implant 42 that reduces the likelihood that the bone screw 10 will become disengaged from the implant 42. Further details regarding the relationship, including the interference fit, between the bone screw 10 and the implant 42, as well as between other bone screws and implants, are provided in commonly-owned U.S. patent application Ser. No. 12/508,669, the contents of which are incorporated herein by reference in their entirety.
Other alternative embodiment bone screws are also contemplated for providing an interference fit with an implant. For example, one alternative embodiment bone screw 60 is illustrated in cross section view in
The second portion 64 and the threading 24 terminate at the distal end of the third portion 66. The third portion 66 is non-threaded and includes an external profile having a linear shape. Moreover, in the illustrated form, the third portion 66 includes a reduced diameter relative to the largest outer thread diameter do of the threading 24 along the second portion 64. In this embodiment, an interference fit between the bone screw 60 and an implant can be provided as the tapered external profile along the second portion 64 and the proximal end of the second portion 64 are advanced through a passage in the implant.
Another alternative embodiment bone screw 70 is illustrated in
The second portion 74 terminates at a distal end of the third portion 76. The third portion 76 is positioned proximally of the second portion 74 and includes a threading 82 and an external profile having a tapered shape that increases toward the proximal end portion 16. Similarly, it should be appreciated that the outer thread diameter do of the threading 82 along the third portion 76 increases toward the proximal end portion 16. In addition, the pitch Pi of the threading 80 is different than the pitch P2 of the threading 82. More particularly, the pitch P2 of the threading 82 is greater than the pitch Pi of the threading 80. In an alternative embodiment, it is contemplated that the threading 80 and the threading 82 could be replaced by a single threading that includes a continuous helical thread that is provided with different pitches along the second portion 74 and the third portion 76. In the illustrated form, the threading 80 and the threading 82 generally include a constant depth along the second portion 74 and the third portion 76, respectively. However, it should be appreciated that alternative forms in which the depth of the threading 80 and/or the threading 82 changes along one or more portions of the second portion 74 and/or the third portion 76, respectively, are also contemplated. Moreover, in addition to having different pitches, it should be appreciated that the threading 80 and the threading 82 could be provided with other different or varying aspects such as, for example thread angle and crest width, among other possibilities.
The third portion 76 terminates adjacent to or merges into the fourth portion 78 which has an external profile having a linear shape. More particularly, the fourth portion 78 generally has a constant diameter that generally corresponds to the largest outer thread diameter do of the threading 82 along the third portion 76. However, in other forms, it is contemplated that the diameter of the fourth portion 78 may be larger or smaller than the largest outer thread diameter do of the threading 82 along the third portion 76. In the illustrated form, the threading 82 extends partially into the fourth portion 78, such that the fourth portion 78 includes both threaded and non-threaded sections. However, in other forms, it is contemplated that the threading 82 may terminate distally of the fourth portion 78 such that it only has a non-threaded configuration.
Another alternative embodiment bone screw 90 is illustrated in
The second portion 94 terminates at a distal end of the third portion 96. The third portion 96 is positioned proximally of the second portion 94 and includes a threading 100 and an external profile having a tapered shape that increases toward the proximal end portion 16. Similarly, it should be appreciated that the outer thread diameter do of at least a portion of the threading 100 along the third portion 96 increases toward the proximal end portion 16. In addition, the threading 100 only extends along a portion of the second portion 96 such that the second portion 96 is provided with a non-threaded portion positioned proximally of the threading 100. Thus, it should be appreciated that the tapered external profile of the third portion 96 is defined by both a non-threaded section and the threading 100. Moreover, in the illustrated form, the crest width cw of the crests 102 of the threading 100 increases toward the proximal end portion 16. However, in another form, it is contemplated that another aspect of the threading 100 could change along the third portion 96.
The third portion 96 terminates adjacent to or merges into the fourth portion 98 which is non-threaded and has an external profile having a linear shape. More particularly, the fourth portion 98 generally has a constant diameter that corresponds to the diameter of the third portion 96 at its proximal end adjacent to the fourth portion 98. However, in other forms, it is contemplated that the diameter of the fourth portion 98 may be larger or smaller than the diameter of the third portion 96 at its proximal end.
Another alternative embodiment bone screw 110 is illustrated in
The second portion 114 terminates at a distal end of the third portion 116. The third portion 116 is positioned proximally of the second portion 114 and includes an external profile having a tapered shape that increases toward the proximal end portion 16. The third portion 114 is non-threaded and includes a plurality of engagement features 124 positioned thereon that are adapted to engage with an internal passage of an implant. More particularly, as illustrated in
The third portion 116 terminates adjacent to or merges into the fourth portion 118 which has an external profile having a linear shape. More particularly, the fourth portion 118 generally has a constant diameter that corresponds to the diameter of the third portion 116 at its proximal end adjacent to the fourth portion 118. However, in other forms, it is contemplated that the diameter of the fourth portion 118 may be larger or smaller than the diameter of the third portion 116 at its proximal end. The fourth portion 118 also includes a helical cutting flute 122 that extends from adjacent to the proximal end of the third portion 116 toward the proximal end portion 16. In a non-illustrated form, it is contemplated that the cutting flute 122 could also extend along at least a portion of the third portion 116. Moreover, in other non-illustrated forms, it is contemplated that the fourth portion 118 could be provided with more than one cutting flute 122, or that the cutting flute 122 could have a non-helical configuration such as, for example, a cutting flute that extends longitudinally along the fourth portion 118. In addition, in one or more forms, it is contemplated that the cutting flute 122 may not be provided on the fourth portion of the bone screws 110, 130, 140 and 150.
Another alternative embodiment bone screw 150a is illustrated in
Another alternative embodiment bone screw 160 is illustrated in
The second portion 164 terminates at a distal end of the third portion 166. The third portion 166 is non-threaded and is positioned proximally of the second portion 164. The third portion 166 also includes an external profile having a tapered shape that increases toward the proximal end portion 16. The third portion 166 terminates adjacent to or merges into the fourth portion 168 which has an external profile having a linear shape. More particularly, the fourth portion 168 generally has a constant diameter that corresponds to the diameter of the third portion 166 at its proximal end adjacent to the fourth portion 168. However, in other forms, it is contemplated that the diameter of the fourth portion 168 may be larger or smaller than the diameter of the third portion 166 at its proximal end.
In this embodiment, it is contemplated that the threading 170 and the third portion 166 can both be configured to provide an interference fit with an implant as the bone screw 160 is advanced through a passage of the implant. For example, the threading 170 can be provided with an outer thread diameter do that is sized to initially modify or be modified by the passage of the implant. Additionally, the third portion 166 can be sized such that it also modifies or is modified by the passage of the implant as the bone screw 160 is advanced therethrough.
Another alternative embodiment bone screw 180 is illustrated in
The second portion 184 terminates at a distal end of the third portion 186. The third portion 186 includes an external profile having a non-tapered, linear shape, although other shapes for the external profile of the third portion 186 are contemplated. The third portion 186 also includes a threading 192 that can be provided with a self tapping leading thread positioned adjacent to the proximal end of the second portion 184. The threading 192 also has a constant outer thread diameter do and a constant inner thread root diameter di. However, in alternative embodiments, it is contemplated that one or both of the outer thread diameter do and the inner thread root diameter di of the threading 192 may be varied along the length of the third portion 186. The outer thread diameter do and inner thread root diameter di of the threading 192 are generally larger than the outer thread diameter do and the inner thread root diameter di, respectively, of the threading 190. Similarly, the third portion 186 defines an annular surface or shoulder 188 which faces the second portion 184 and, while not-illustrated, could be provided with a chamfered radial edge. In the illustrated embodiment, the shoulder 188 extends radially beyond the threading 190 of the second portion 184. Stated alternatively, the inner thread root diameter di of the threading 192 is larger than the outer thread diameter do of the threading 190. Moreover, in the illustrated form, the threading 190 and the threading 192 are provided with different thread profiles, although it is also contemplated that the threading 190, 192 could have identical thread profiles. More particularly, the threading 190 has a greater lead than the threading 192. However, it is also contemplated that additional aspects, such as pitch, depth, crest width or thread angle, could be varied between the threading 190 and the threading 192.
It is contemplated that, among other alternatives, the bone screw 180 can be used with an implant that has a passage provided with a tapered portion that widens toward the end at which the bone screw 180 is initially advanced. Thus, as the bone screw 180 is continually advanced into the passage, the annular shoulder 188 and the threading 192 of the third portion 186 engage with the tapered portion of the passage and modify, or are modified by, the passage to provide an interference fit between the bone screw 180 and the implant.
It should be understood that the bone screws described herein may be anchored within any number of vertebral bodies, including a single vertebral body or two or more vertebral bodies. In one embodiment, the bone screws are anchored within the pedicle region of a vertebral body. However, it should be understood that the bone screws may be anchored to other portions or regions of a vertebral body. It should also be understood that the bone screws described herein may be anchored to a posterior, anterior, lateral, posterolateral or anterolateral aspect of a vertebral body. It should further be understood that the bone screws described herein may be attached to any region of the spinal column, including the cervical, thoracic, or lumbar regions of spinal column. It should likewise be understood that the bone screws described herein may be attached to bone structures other than vertebral bodies, such as, for example, bones associated with the arm or leg.
Any theory, mechanism of operation, proof, or finding stated herein is meant to further enhance understanding of the present invention and is not intended to make the present invention in any way dependent upon such theory, mechanism of operation, proof, or finding. It should be understood that while the use of the word preferable, preferably or preferred in the description above indicates that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the application, that scope being defined by the claims that follow. In reading the claims it is intended that when words such as “a,” “an,” “at least one,” “at least a portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and/or “a portion” is used the item may include a portion and/or the entire item unless specifically stated to the contrary.
While the application 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 selected embodiments have been shown and described and that all changes, modifications and equivalents that come within the spirit of the application as defined herein or by any of the following claims are desired to be protected.
