Locking structures for affixing bone anchors to a bone plate, and related systems and methods

Abstract

A bone plate includes an upper surface, an opposed lower surface configured to face a bone, and at least one aperture extending through the bone plate from the upper to the lower surface along a central aperture axis. The aperture is defined by an interior surface of the bone plate. The interior surface defines a plurality of columns sequentially located about a circumference of the interior surface and a plurality of recesses located circumferentially between the columns. Each of the columns is configured to undergo deformation at least in a radial direction perpendicular to the central aperture axis responsive to engagement with a head of a locking bone screw that is receivable within the at least one aperture so as to lock the head to the bone plate. The plurality of columns comprises at least five columns.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No. 15/926,390, filed on Mar. 20, 2018, in the name of Bosshard, et al., the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein.

TECHNICAL FIELD

The present invention relates to bone plates and bone anchors for coupling to the bone plates, and particularly relates to locking structures defined within an aperture of a bone plate for locking with a head of a bone anchor.

BACKGROUND

Bone plate systems for the internal fixation of bone fractures are well known. Conventional bone plate systems are particularly well-suited to promote the healing of a fracture. A bone anchor, such as a bone screw, is inserted through a bone plate aperture or hole and is threaded into bone to compress, neutralize, buttress, tension bend, and/or bridge the fracture ends together. To transfer loads from one fractured bone part, over a plate, and onto another fractured bone part without drawing the bone against the plate, and to avoid loosening or backing out the bone screws with respect to the plate (which can lead to poor alignment and poor clinical results), bone screws that are capable of locking with the bone plate can be employed. One known embodiment of such a screw employs a screw head with external threads for engaging with a corresponding thread on the inner surface of a bone plate aperture to lock the screw to the plate. These screws (which are hereinafter referred to as “locking screws” or “locking compression screws”), which can include standard-type locking screws that are configured to lock within an aperture substantially only at a “nominal” orientation whereby the central screw axis is substantially aligned with the central aperture axis, as well as “variable-angle” (VA) locking screws, which are configured to lock within an aperture at either a nominal orientation or an “angulated” orientation whereby the central screw axis is oriented at an acute angle with respect to the respective central aperture axis.

SUMMARY

According to an embodiment of the present disclosure, a bone plate includes an upper surface configured to face away from a bone, an opposed lower surface configured to face the bone, and at least one aperture extending through the bone plate from the upper surface to the lower surface along a central aperture axis. The at least one aperture is defined by an interior surface of the bone plate. The interior surface further defines a plurality of columns sequentially located about a circumference of the interior surface and a plurality of recesses located circumferentially between the columns. Each of the columns is configured to undergo deformation at least in a radial direction perpendicular to the central aperture axis responsive to engagement with a head of a locking bone screw that is receivable within the at least one aperture so as to lock the head to the bone plate. The plurality of columns comprises at least five columns.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of illustrative embodiments of the present application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the locking structures of the present application, there is shown in the drawings illustrative embodiments. It should be understood, however, that the application is not limited to the precise arrangements and instrumentalities shown. In the drawings:

FIG. 1 is a perspective view of a bone fixation system including a bone plate defining apertures with locking screws received therein, according to an embodiment of the present disclosure;

FIG. 2 is a sectional perspective view of an aperture of the bone plate shown in FIG. 1;

FIG. 3A is a top plan view of the aperture shown in FIG. 2;

FIG. 3B is a top plan view of an aperture, according to another embodiment of the present disclosure;

FIG. 4 is a sectional side view of the aperture taken along section line 4-4 in FIG. 3A;

FIG. 5 is a sectional side view of the aperture taken along section line 5-5 in FIG. 3A;

FIG. 6 is a sectional side view of enlarged portion B of the aperture shown in FIG. 4;

FIG. 7 is a sectional side view of the bone fixation system taken along section line 7-7 in FIG. 1;

FIG. 8 is a side view of the head portion of a standard-type locking screw configured to be locked within an aperture of a bone plate at a nominal orientation;

FIG. 9 is a sectional side view of the head of the standard-type locking screw of FIG. 8 locked within an aperture of the bone plate of FIG. 7;

FIG. 10 is a side view of the head portion of a variable-angle locking screw configured to be locked within an aperture of a bone plate at either a nominal or angulated orientation;

FIG. 11 is a sectional side view of the head of the variable-angle locking screw of FIG. 10 locked within an aperture of the bone plate of FIG. 7 at a nominal orientation;

FIG. 12 is a sectional side view of the head of the variable-angle locking screw of FIG. 10 locked within an aperture of the bone plate of FIG. 7 at an angulated orientation;

FIG. 13 is a perspective view of an aperture of a bone plate, with locking structures within the aperture, according to another embodiment of the present disclosure;

FIGS. 14 and 15 are top and bottom views, respectively, of the aperture of FIG. 13;

FIG. 16 is a sectional side view of the aperture of FIG. 13;

FIG. 17 is a section view of a variable-angle locking screw locked within the aperture of FIG. 16 at a nominal orientation;

FIG. 18 is a section view of the variable-angle locking screw locked within the aperture of FIG. 16 at an angulation of about 5 degrees;

FIG. 19 is a section view of the variable-angle locking screw locked within the aperture of FIG. 16 at an angulation of about 10 degrees;

FIG. 20 is a section view of the variable-angle locking screw locked within the aperture of FIG. 16 at an angulation of about 15 degrees;

FIG. 21 is a perspective view of an aperture of a bone plate, with locking structures within the aperture, according to another embodiment of the present disclosure;

FIG. 22 is a top plan view of the aperture shown in FIG. 21;

FIG. 23 is a sectional side view of the aperture taken along section line 23-23 in FIG. 22;

FIG. 24 is a perspective view of an aperture of a bone plate, with locking structures within the aperture, according to another embodiment of the present disclosure;

FIG. 25 is a top plan view of the aperture shown in FIG. 24;

FIG. 26 is a sectional side view of the aperture taken along section line 26-26 in FIG. 25; and

FIG. 27 is a top plan view of an aperture, according to an embodiment of the present disclosure, in which the aperture is intersected by an additional aperture so as to define a “combi-hole”.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present disclosure can be understood more readily by reference to the following detailed description taken in connection with the accompanying figures and examples, which form a part of this disclosure. It is to be understood that this disclosure is not limited to the specific devices, methods, applications, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the scope of the present disclosure. Also, as used in the specification including the appended claims, the singular forms “a,” “an,” and “the” include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise.

The term “plurality”, as used herein, means more than one. When a range of values is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. All ranges are inclusive and combinable.

VA locking screws have a tendency to cause cross-threading within an aperture of a bone plate in which they are inserted. Cross-threading can be caused by the external threads on the screw head not fitting within and thus cross-threading the internal threading of the aperture. Cross-threading is problematic because it reduces the interference fit (also referred to as the “form-fit”) between the internal threading of the aperture and the screw head threads, which can result in a reduction of stability between the screw head and the aperture of the bone plate. The embodiments disclosed herein pertain to locking structures employed within the apertures of a bone plate, which structures are configured to lock with the heads of both standard-type and VA locking screws in a manner inhibiting or at least reducing cross-threading.

Referring to FIG. 1, a bone fixation system 2 includes a bone plate 4 having one or more apertures 6 defined therein. The apertures 6 are configured to receive anchor members, such as locking screws 8, for example, that are configured to affix the bone plate 4 to one or more portions of bone. The apertures 6 have locking structures therein that are configured to deform around the heads of the locking screws 8 in a manner providing enhanced locking engagement between the locking screws 8 and the bone plate 4, as set forth in more detail below. The bone plate 4 can be a bridge plate, as shown, although other bone plate types and configurations are within the scope of the present disclosure.

The bone plate 4 can include a body 9 that defines a first end 10 and a second end 12 spaced from each other along a longitudinal direction X and a first lateral side 14 and a second lateral side 16 spaced from each other along a lateral direction Y that is substantially perpendicular to the longitudinal direction X. The bone plate 4 can also define an upper plate surface 18 configured to face away from the bone and an opposed lower plate surface 20 configured to face the bone. The upper and lower plate surfaces 18, 20 are spaced from each other along a vertical direction Z substantially perpendicular to each of the longitudinal direction X and the lateral direction Y.

It is to be appreciated that, as used herein, the terms “longitudinal”, “longitudinally”, and derivatives thereof refer to the longitudinal direction X; the terms “lateral”, “laterally”, and derivatives thereof refer to the lateral direction Y; and the terms “vertical”, “vertically”, and derivatives thereof refer to the vertical direction Z.

The plate body 9 and the locking screws 8 can each comprise one or more biocompatible materials, such as titanium, titanium alloys (e.g., titanium-aluminum-niobium (TAN) alloys, such as Ti-6Al-7Nb), stainless steel, cobalt base alloys, composite materials, and polymeric materials and/or ceramic materials, by way of non-limiting examples. Preferably, the screw 8 material is harder than the plate body 9 material, which provides for beneficial locking characteristics between the locking screws 8 and the bone plate 4, as described in more detail below. In one example embodiment, the plate body 9 primarily or entirely comprises titanium and the locking screws 8 primarily or entirely comprise TAN.

Referring now to FIG. 2, the apertures 6 extend vertically from the upper plate surface 18 to the lower plate surface 20 along a central aperture axis 22. In the depicted embodiment, the central aperture axis 22 is oriented along the vertical direction Z, although in other embodiments the central aperture axis 22 can be offset and angulated from the vertical direction Z. Each of the apertures 6 can be defined by an interior surface 24 of the plate body 9. Within the apertures 6, the interior surface 24 can define a plurality of locking structures, such as columns 26, that are configured to deform around the head of a locking screw 8 in a manner locking the screw head in position within the aperture 6.

Within each (or at least some of) the apertures 6, the columns 26 are sequentially located about a circumference of the interior surface 24 so as to define a plurality of recesses 28 sequentially located circumferentially between the columns 26. The columns 26 extend vertically between the upper and lower plate surfaces 18, 20 and are configured to deform at least in a radial direction R that is oriented perpendicular to the central aperture axis 22 responsive to engagement with an outer surface of a head of one of the locking screws 8. In this manner, the radial deformation of one or more of the columns 26 provides a form-fit and a compression fit (i.e., a “press-fit”) between the plate body 9 and the screw head within the aperture 6, which form-fit and press-fit preferably locks the head (and thus the screw 8) to the plate body 9 at a fixed orientation, as described in more detail below. It is to be appreciated that, as used herein, the terms “radial”, “radially”, and derivatives thereof refer to the radial direction R.

Referring now to FIG. 3A, the columns 26 and recesses 28 can be evenly spaced about the circumference of the interior surface 24 within the aperture 6. However, in other embodiments, the columns 26 and/or recesses 28 can be un-evenly spaced about the circumference of the aperture 6. As depicted in FIG. 3A, the aperture 6 can include nine (9) columns 26, although fewer than nine (9) columns 26 or more than nine (9) columns 26 can be employed in the aperture 6. For example, each aperture 6 can include five (5) or fewer columns 26, six (6) columns 26, seven (7) columns 26, eight (8) columns 26, or ten (10) or more columns 26. For example, FIG. 3B shows an embodiment of an aperture 26 with six (6) columns 26. In further embodiments, each aperture 6 can include between ten (10) and twenty (20) columns 26 or more than twenty (20) columns 26.

Referring now to FIGS. 4 and 5, the interior surface 24 can include an upper relief surface 34 extending from the upper plate surface 18 toward the lower plate surface 20 and a lower relief surface 36 extending from the lower plate surface 20 toward the upper plate surface 18. The lower relief surface 36 and the upper relief surface 34 can each define a respective relief angle in a range of about 1 degree to about 60 degrees from the central aperture axis 22. In the illustrated embodiment, the relief angle of the lower relief surface 36 is about 15 degrees and the relief angle of the upper relief surface 34 is about 45 degrees. The upper relief surface 34 can define an upper end 38 of the columns 26 and the lower relief surface 36 can define a lower end 40 of the columns 26. The upper relief surface 34 can be configured to accommodate (i.e., house or provide space for) an angulated screw head, and the lower relief surface 36 can be configured to accommodate the shaft of an angulated screw 8.

Each column 26 can define a first surface 42 substantially facing the central aperture axis 22, and a pair of side surfaces 44 located on adjacent circumferential sides of the first surface 42. The first surface 42 can also be referred to as an “innermost surface” of the column 26. Each side surface 44 of the column 26 can define at least a portion of the circumferentially adjacent recess 28. Each recess 28 can extend from the first surface 42 of one adjacent column 26 to the first surface 42 of the other adjacent column 26. The recesses 28 can extend continuously in a circumferentially arcuate manner between adjacent columns 26, although other recess configurations are within the scope of the present disclosure.

Within one or more of the apertures 6, the first surfaces 42 of the columns 26 can collectively define segments of a first shape, such as a first inverted frusto-conical shape. The nadirs 46 (i.e., the lowest point) of the recesses 28 can collectively define segments of a second shape, such as a second inverted frusto-conical shape that is wider than the first inverted frusto-conical shape. In the illustrated embodiments, the first and second inverted frusto-conical shapes have a common cone angle, although in other embodiments the first and second inverse cone shapes can have different cone angles. In yet other embodiments, the first and second shapes can be circular, elliptical, parabolic, or other types of geometries.

In the illustrated embodiment, the first inverse cone shape causes each first surface 42 within the aperture 6 to have a concave profile in a horizontal reference plane P1 (i.e., a plane extending along the longitudinal and lateral directions X, Y). It is to be appreciated, however, that in other embodiments, the first surfaces 42 within an aperture 6 can be convex in the horizontal reference plane P1. In such embodiments, the apices of the first surfaces 42 of the columns 26 can collectively define the first inverted cone shape. In yet other embodiments, the first surfaces 42 within an aperture 6 can have a linear profile in the horizontal reference plane P1.

Referring again to the illustrated embodiment, the interior surfaces 24 of the apertures 6 can initially be formed to define an inverted cone shape with a tool, such as a conical drill bit and/or milling cutter, by way of non-limiting examples. The recesses 28 can be subsequently formed, such as with a milling cutter that removes plate body 9 material sequentially about the circumference of the aperture 6 so as to form the recesses 28 and the distinct columns 26 therebetween. The upper and lower relief surfaces 34, 36 can be formed with one or more angle or dovetail mills, by way of non-limiting example.

With continued reference to FIGS. 4 and 5, the first surfaces 42 of each of the columns 26 within an aperture 6 can taper radially inwardly from the upper plate surface 18 to the lower plate surface 20 at a first angle A1 in a range of about 3 degrees to about 30 degrees relative to the central aperture axis 22, and preferably in a range of about 10 degrees to about 15 degrees relative to the central aperture axis 22. Additionally, the nadirs 46 of the recesses 28 within an aperture 6 can taper radially inwardly from the upper plate surface 18 to the lower plate surface 20 at a second angle A2 in a range of about 3 degrees to about 30 degrees relative to the central aperture axis 22, and preferably in a range of about 10 degrees to about 15 degrees relative to the central aperture axis 22. The radius of each recess 28 can be the same at any vertical location within the recess 28; although in other embodiments the radius of each recess 28 can vary. Additionally, as shown, the first surfaces 42 of the columns 26 can increase in circumferential width moving vertically from the lower plate surface 20 toward the upper plate surface 18 (and thus decrease in circumferential width moving vertically from the upper plate surface 18 toward the lower plate surface 20). As depicted, the first and second angles A1, A2 can be substantially equivalent, although in other embodiments they can be offset.

One or more of the apertures 6 can include internal threading 50 for engaging external threads on the outer surface of a screw head. The internal threading 50 preferably helically traverses each column 26 in the aperture 6 such that each column 26 defines one or more thread portions 52 of the internal threading 50. The threading 50 can be configured to terminate between the upper and lower ends 38, 40 of the columns 26. In this manner, each column 26 can define an upper column portion 60 encompassing the one or more thread portions 52 and a lower column portion 62 devoid of the internal threading 50. Stated differently, the lower column portions 62 can have no threading, at least prior to engagement with the head of a locking screw 8.

Referring now to FIG. 6, the thread portions 52 can include a thread root 54 recessed radially outward from the first surface 42 of the respective column 26. The thread portions 52 of the columns 26 can define a third or thread angle A3 in a range of about 30 degrees to about 90 degrees, preferably in the range of about 55 degrees to about 65 degrees, and more preferably at about 60 degrees. The thread portions 52 can define a thread pitch in a range of about 0.1 mm to about 1.6 mm, and more preferably at about 0.8 mm, by way of non-limiting examples. The threading 50 is preferably a right-hand thread, although left-hand threading 50 is within the scope of the present disclosure. The threading 50 can be dual-lead, as shown, although single-lead or triple-lead threading 50 is also within the scope of the present disclosure.

In the present embodiment, the one or more thread portions 52 of each column 26 is tapered along a threading profile 58 that extends substantially linearly along the roots 54 and is oriented such that the threading profile 58 and the central aperture axis 22 are each coextensive in a common vertical reference plane. The threading profile 58 can be angled radially inwardly from the upper plate surface 18 to the lower plate surface 20 at a fourth angle A4 or “threading slope” in a range of about 4 degrees to about 40 degrees relative to the central aperture axis 22, and preferably in a range of about 11 degrees to about 30 degrees relative to the central aperture axis 22, and more preferably at about 20 degrees relative to the central aperture axis 22. The fourth angle A4 can be referred to as the “internal threading slope.” In the present embodiment, the threading slope A4 preferably exceeds the first angle A1, causing the internal threading 50 to terminate at a location between the upper and lower ends 38, 40 of the columns 26, as described above.

Referring now to FIG. 7, the apertures 6 can be configured to provide enhanced affixation with multiple types of locking screws 8, including standard-type locking screws 8a and VA locking screws 8b, so as to allow a physician to implant the bone plate 4 to one or more bones or bone segments as desired. As shown, the bone plate 4 can be coupled to a long-bone 100 via locking screws 8a, 8b in a manner affixing fractured segments 102, 104 of the bone together. The apertures 6 described herein can lock with standard-type locking screws 8a at a nominal orientation whereby the central screw axis 64 is substantially aligned with the central aperture axis 22, as well as VA locking screws 8b at either a nominal orientation or an “angulated” orientation whereby the central screw axis 64 is oriented at an acute angle A5 with respect to the respective central aperture axis 22. The acute angle A5 can also be referred to as the “angle of angulation” or simply the “angulation.” Both types of locking screws 8a, 8b and their locking functionalities are described more fully in U.S. Pat. No. 9,314,284, issued Apr. 19, 2016, in the name of Chan et al. (the “Chan Reference”), the entire disclosure of which is incorporated by reference herein.

With reference to FIGS. 8 through 12, engagement between the columns 26 and standard-type locking screws 8a (FIGS. 8 and 9) and VA locking screws 8b (FIGS. 10 through 12) will now be described.

Referring now to FIG. 8, a standard-type locking screw 8a can have a screw head 32a defining a conical outer surface 66a defining external screw head threads 68a. The external screw head threads 68a have a first threading profile 70 measured at the thread roots and a second threading profile 72 measured at the thread crests. As depicted, the standard-type locking screw 8a has conical first and second threading profiles 70, 72 that are parallel; additionally the profiles 70, 72 taper downwardly so as to provide the screw head 32a with a locking functionality as the screw head 32 advances within the aperture 6.

Referring now to FIG. 9, the internal threading 50 of the aperture 6 is configured to engage the external screw head threads 68a in an interconnecting manner so as to substantially induce a form-fit interaction therebetween (i.e., the apices of the external screw head threads 68a extend within the troughs of the internal threading 50 of the aperture 6, and vice versa). The columns 26 are configured to provide plastic deformation between the columns 26 and the screw head 32a. A first or primary measure of the plastic deformation is plastic deformation of the columns 26 from engagement with the screw head 32a. A second or secondary measure of the plastic deformation (i.e., plastic deformation of the screw head 32a, such as at least at the screw head threads 68a) can accompany the first measure of plastic deformation. Preferably, the first measure of plastic deformation at least exceeds the second measure of plastic deformation. More preferably, the second measure of plastic deformation is eliminated or at least minimized in favor of the first measure of plastic deformation. Stated differently, it is preferred that the screw head 32a deforms the columns 26 as opposed to the columns 26 deforming the screw head 32a. In this regard, the material of the plate body 9 is preferably selected so that the locking screw 8a comprises a material harder than the plate body 9 material. It is to be appreciated, however, that in operation a minor amount of plastic deformation of the screw head 32a (i.e., the second measure of plastic deformation) can occur. The geometry of the columns 26 as described herein provides the benefit of increasing the first measure of plastic deformation while decreasing the second measure of plastic deformation.

With continued reference to the plastic deformation, although the following description is made in reference to a single column 26, it is to be appreciated that additional columns 26 (and preferably each of the columns 26) within the aperture 6 will undergo the same or at least a substantially similar plastic deformation.

The internal threading slope A4 provides that, after the form-fit interaction is induced, further advancement of the screw head 32a causes the screw head threads 68a to press within the troughs of the internal thread portions 52 of the column 26 in a manner plastically deforming the engaged body 9 material at or adjacent the internal thread portions 52 and tightening the form-fit. Stated differently, the first measure of plastic deformation can commence at the internal aperture threading 50, which is further induced by the screw 8a material being harder than the plate body 9 material.

Yet further advancement of the screw head 32a within the aperture 6 causes the screw head threads 68a to engage the unthreaded lower column portion 62. The columns 26 are configured such that, as the screw head threads 68a engage the unthreaded lower column portion 62, the screw head threads 68a commence “thread-forming” the lower column portion 62 via plastically radially deforming the lower column portion 62 substantially without removing (e.g., shearing) body 9 material therefrom. In this manner, the first measure of plastic deformation continues within the lower column portion 62. The plastic deformation of the columns 26 can provide a tight locking press-fit between the plate body 9 and the screw head 32a within the aperture 6, locking the standard-type locking screw 8a to the plate body 9 at the nominal orientation. It is to be appreciated that the design of the columns 26 preferably avoids, or at least reduces, the occurrence of cross-threading because the thread forming of the columns 26 occurs in situ through engagement with the screw head threads 68a.

The columns 26 and the internal threading 50 are configured such that the first measure of plastic deformation occurs substantially in the radial direction R. However, it is to be appreciated that a minor degree of the first measure of plastic deformation can occur in a circumferential direction (i.e., the columns 26 can expand circumferentially into the recesses 28), and another minor degree of plastic deformation within portions of the columns 26 can occur vertically. It is also to be appreciated that a measure of elastic deformation beneficially accompanies the plastic deformation, so that the columns 26 reactively press radially inward against the screw head 32a, increasing the locking press-fit therebetween.

Referring now to FIGS. 10 and 11, the columns 26 provide a similar locking function with the screw head 32b of a VA locking screw 8b at a nominal orientation. As shown in FIG. 10, the screw head 32b of the VA locking screw 8b can have a generally spherical outer surface 66b that defines external screw head threads 68b. The external screw head threads 68b of the VA locking screw 8b have a first threading profile 74 measured at the thread roots and a second threading profile 76 measured at the thread crests. As depicted, the threading profiles 74, 76 of the VA locking screw 8b are generally spherical, which provides the screw head 32b with a locking functionality as it advances within the aperture 6.

As shown in FIG. 11, similarly to the manner set forth above, as the screw head 32b of the VA locking screw 8b advances within the aperture 6, the screw head threads 68b commence a form-fit interaction with the column thread portions 52, which interaction leads to at least the first measure of plastic deformation (primarily in the radial direction R) as the head 32b advances further. Yet further screw head 32b advancement causes thread-forming of the unthreaded lower column portion 62 via plastic deformation thereof (primarily in the radial direction R) substantially without removing body material from the column 26, avoiding or reducing cross-threading. It is to be appreciated that the generally spherical profiles of the screw head 32b and the screw head threads 68b of the VA locking screw 8b can provide an increased plastic deformation relative to that of the standard-type locking screw 8a. It is also to be appreciated that a measure of elastic deformation beneficially accompanies the plastic deformation, so that the columns 26 reactively press radially inward against the nominal screw head 32b, increasing the locking press-fit therebetween.

Referring now to FIG. 12, the locking function of the columns 26 will now be discussed with reference to the VA locking screw 8b inserted along an angulated orientation within the aperture 6. In FIG. 12, the angulation is shown at about 15 degrees, whereby the relief angle allows the lower relief surface 36 to house a portion of the shaft of the screw 8b. As the angulated screw head 32b advances within the aperture 6, the head threads 68b commence a form-fit interaction with the column thread portions 52, which interaction is enabled at least in part by the pitch, thread angle, and/or the slope A4 of the column thread portions 52 and the pitch, thread angle, and/or the generally spherical profile of the head threads 68b as well as the particular angulated orientation. The form-fit interaction leads to at least the first measure of plastic deformation (primarily in the radial direction R) as the screw head 32b advances. Yet further screw head 32b advancement at the angulated orientation causes thread forming of the unthreaded lower column portion 62 via plastic deformation thereof (primarily in the radial direction R), which, as described above, can occur substantially without removing body material from the column 26. It is to be appreciated that, as above, a measure of elastic deformation beneficially accompanies the plastic deformation, so that the columns 26 reactively press radially inward against the angulated screw head 32b, increasing the locking press-fit therebetween.

Another embodiment of the locking structures will now be described with reference to FIGS. 13 through 20. For the sake of brevity, the following description will focus mainly on the differences between the present embodiments and the embodiments described above with reference to FIGS. 1 through 12.

Referring now to FIG. 13, the locking structures include a plurality of columns 126 and a plurality of recesses 128 sequentially located about the circumference of the interior surface 24 of the aperture 6. The columns 126 extend vertically between the upper and lower plate surfaces 18, 20 and are configured to deform primarily in the radial direction R responsive to engagement with a head of a locking screw. As described above, compression of the columns 126 around the screw head forms a tight press-fit therebetween, locking the screw head within the aperture 6 at a fixed orientation with respect to the bone plate 4.

Referring now to FIG. 14, the columns 126 and recesses 128 can be evenly spaced about the circumference of the interior surface 24, as shown; although un-even spacing can be employed in other embodiments. The interior surface 24 can define fifteen (15) columns 126 and fifteen (15) recesses 128, although less than fifteen (15) or more than fifteen (15) columns 126 and recesses 128 can also be employed.

In the present embodiment, the recesses 128 can each extend purely vertically, or at least substantially vertically, between an upper relief surface 34 and a lower relief surface 36 defined by the interior surface 24, as shown in FIG. 16. In this manner, the nadirs 146 of the recesses 128 can be parallel with the central aperture axis 22; additionally, the radius of each recess 128 in a horizontal reference plane can be the same at any vertical location within the recess 128. In other embodiments, the recesses 128 can be angled with respect to the central aperture axis 22, similar to the manner described above with reference to FIG. 4. The recesses 128 can optionally be sized and located such that, in a horizontal reference plane, each column 126 is thicker at its first or innermost surface 142 that at a radially outward location of its side surfaces 144. In the present embodiment, the upper relief surface 34 can define a relief angle in a range of about 0 degrees to about 85 degrees and the lower relief surface 36 can define a relief angle in a range of about 0 degrees to about 60 degrees.

Referring now to FIG. 15, in one example of the present embodiment, the aperture 6 can include fifteen (15) recesses 128 with central recess axes 129 spaced at 24 degree intervals a about the central aperture axis 22. In this example, the central recess axes 129 are located radially outward of the first surfaces 142 of the columns 126, and are spaced from the central aperture axis 22 by a radial distance R1 in a range of about 1.8 mm to about 2.7 mm and preferably about 2.25 mm. Also in this example, each recess 128 defines a recess radius R2 in a range of about 0.2 mm to about 0.6 mm and preferably about 0.4 mm.

Referring now to FIG. 16, the upper relief surface 34 can define upper ends 138 of the columns 126 and the lower relief surface 36 can define lower ends 140 of the columns 126, as described above. The first surface 142 of each column 126 extends between the upper and lower ends 138, 140 and substantially faces the central aperture axis 22. The side surfaces 144 of each column 126 can define at least portions of the circumferentially adjacent recesses 128. The aperture 6 can also include a second upper relief surface 139, which can be a countersink, for example.

In the present embodiment, the internal aperture threading 150 can extend from a location within the upper relief surface 34 to a location within the lower relief surface 36. In this manner, the internal aperture threading 150 can helically traverse one or more of the columns 126 from its upper end 138 to its lower end 140. The threading 150 can include thread crests 156 that define the first surface 142 of each columns 126 and roots 154 recessed radially outward from the first surface 142. The internal threading 150 can define a thread angle A3 in a range of about 30 degrees to about 90 degrees, preferably in the range of about 55 degrees to about 65 degrees, and more preferably at about 60 degrees. The thread portions 52 can define a thread pitch in a range of about 0.1 mm to about 1.6 mm, and more preferably at about 0.8 mm, by way of non-limiting examples. The threading 150 is preferably a right-hand thread, although left-hand threading 150 is within the scope of the present disclosure. The threading 150 can be dual-lead, as shown, although single-lead threading 150 is also within the scope of the present disclosure. The first and second upper relief surfaces 34, 139 can provide that the top of the internal threading 150 is recessed from the upper plate surface 18, which enhances the smoothness of the upper plate surface 18 and can eliminate soft tissue irritation from un-used apertures 6. The first upper relief angle also facilitates smoother initial engagement between the screw head thread 68 and the lead of the internal threading 150.

The internal threading 150 can define a first threading profile 158 extending along the thread roots 154 and a second threading profile 159 extending along the thread crests 156. As shown, the first and second threading profiles 158, 159 can be substantially parallel, providing the threads of the internal threading 150 with substantially equivalent thread depths. However, in other embodiments, the first and second threading profiles 158, 159 can be non-parallel, and the thread depths of the internal threading 150 can vary. With continued reference to FIG. 16, the first and second threading profiles 158, 159 can extend at respective angles A4, A5 each in a range of about 5 degrees to about 60 degrees from the central aperture axis 22, preferably from about 10 degrees to about 20 degrees, and more preferably about 15 degrees.

The first surfaces 142 of the columns 126 (along second threading profile 159) can collectively define segments of a first shape, such as an inverted frusto-conical shape. The nadirs 146 of the recesses 128 can collectively define segments of a second shape, such as cylindrical shape. The columns 126 and recesses 128, respectively, can be configured to collectively define other shapes, as described above with reference to FIGS. 4 and 5. Additionally, the first surfaces 142 of the columns 126 of the present embodiment have a concave profile in a horizontal reference plane, although in other embodiments the first surfaces 142 can have convex or linear profiles in a horizontal reference plane.

With reference to FIGS. 17 through 20, engagement between the apertures 6 and a VA locking screw 8b at various angulations will now be described. The VA locking screw 8b of the present embodiment can be configured similarly to that described above.

Referring now to FIG. 17, at a nominal orientation, the internal threading 150 of the aperture 6 is configured to engage the screw head threads 68b in an interconnecting manner so as to substantially induce a form-fit interaction therebetween (i.e., the apices of the external screw head threads 68a extend within the troughs of the interior aperture threading 150, and vice versa). The threading profiles 158, 159 of the internal threading 150 and the threading profiles 74, 76 of the screw head threads 68b provide that, after the form-fit interaction is induced, further advancement of the screw head 32b causes the screw head threads 68b to press within the troughs of the internal threading 150 of the column 126 to lock the screw head 32b to the plate 4 substantially without deformation.

Referring now to FIGS. 18 through 20, the columns 126 are configured such that, at varying angulations, such as at 5 degrees (FIG. 18), at 10 degrees (FIG. 19), and at 15 degrees (FIG. 20), as the angulated screw head 32b advances within the aperture 6, the screw head threads 68b commence a form-fit interaction with the column threading 150. This initial form-fit interaction is enabled at least in part by the pitch, thread angle, and/or the threading profiles 158, 159 of the internal threading 150 and the pitch, thread angle, and/or the generally spherical profiles 74, 76 of the screw head threads 68b, as well as the angulation. After the form-fit interaction is induced, further advancement of the angulated screw head 32b causes the screw head threads 68b to elastically and plastically deform the columns 126, primarily at the internal threading 150. This compresses the columns 126 and causes the columns 126 to exert a reactive compressive force against the screw head 32b, together providing a locking compression fit between the columns 126 and the screw head 32b. The columns 126 are configured so that the angulated screw head 32b can be fully seated within the aperture 6 substantially without cross-threading the columns 150, although some minor cross-threading may occur in some instances. The columns 126 are also configured such that, even at increased angulations, the columns 126 deform primarily in the radial direction R, although some circumferential and/or vertical deformation can also occur. It is to be appreciated, however, that as the angulation increases, the extent of circumferential and/or vertical deformation can also increase. The foregoing modes of deformation of the columns 126 allows VA locking screws 8b to be inserted at angulated orientations substantially without cross-threading the internal threading 150 or the screw head threads 68b.

Referring now to FIGS. 21 through 23, in another embodiment, the locking structures in the apertures 6 can include columns 226 that are circumferentially thinner than the columns 26, 126 of the previous embodiments and recesses 228 that are circumferentially wider than the recesses 28, 128 of the previous embodiments. The recesses 228 can define nadirs 246 that extend circumferentially between adjacent columns 226 at a substantially constant radius R3 measured from the central aperture axis 22 in any horizontal reference plane intersecting the nadirs 246. The nadirs 246 can collectively define an inverted frusto-conical shape. The columns 226 can each define an innermost first surface 242 and side surfaces 245 that extend radially between the first surface 242 and the adjacent nadirs 246. The side surfaces 245 can each be substantially planar and can be oriented at an angle A6 in a range of about 10 degrees to about 45 degrees with respect to each other, and preferably at an angle A6 in a range of about 20 degrees to about 30 degrees with respect to each other. The first surface 242 can decrease in circumferential width moving vertically from the upper plate surface 18 toward the lower plate surface 20. The columns 226 can define internal aperture threading 250 with threading characteristics (e.g., thread angle, pitch, threading profile(s), and lead type (i.e., single-, double-, or triple-lead)) similar to those described above. In the lower region of the aperture 6, the crests 256 of the internal aperture threading 250 can define substantially pointed tips.

The columns 226 are configured such that, when a locking screw 8a, 8b is inserted in the aperture 6 at a nominal orientation, the screw head threads 68a, 68b engage the internal aperture threading 250 in an interconnecting manner so as to substantially induce a form-fit interaction therebetween. After the form-fit interaction is induced, further advancement of the screw head 32a, 32b causes the screw head threads 68a, 68b to press within the troughs of the internal aperture threading 250 of the columns 226 to lock the screw head 32a, 32b to the plate 4 substantially without deformation. At angulated orientations of the VA locking screw 8b, advancement of the screw head 32b within the aperture 6 commences a form-fit interaction with the internal aperture threading 250, and further advancement causes the screw head threads 68b to elastically and plastically deform the columns 226, primarily at the internal aperture threading 250, in a manner providing a locking compression fit between the columns 226 and the screw head 32b, similar to the manner described above, substantially without cross-threading.

Referring now to FIGS. 24 through 26, the apertures 6 can define columns 326 and recesses 328 that are similar to those described above with reference to FIGS. 21 through 23. However, the columns 326 of the present embodiment can be unthreaded (i.e., can be devoid of threading). Side surfaces 345 of each column 326 can be substantially planar and can be oriented at an angle A6 in a range of about 10 degrees to about 45 degrees with respect to each other, and preferably at an angle A6 in a range of about 20 degrees to about 30 degrees with respect to each other. The first surfaces 342 of the columns 326 can each decrease in circumferential width moving vertically from the upper plate surface 18 toward the lower plate surface 20 so as to taper to a single edge in a lower region of the aperture 6. In this embodiment, as the screw head 32a, 32b advances within the aperture 6 (whether at nominal or angulated orientations), the screw head threads 68a, 68b plastically and elastically deform the columns 326 radially and in a thread-forming manner so as to provide a locking compression fit between the columns 326 and the screw head 32a, 32b.

It is to be appreciated that, in further embodiments, the columns 26, 126, 226, 326 described herein can be defined by an insert disposed within an aperture 6 in a bone plate 4. In such embodiments, the columns 26, 126, 226, 326 of the insert, the screw head, and the plate 4 itself can each be configured to deform plastically in a manner locking the screw 8 to the plate 4.

Referring now to FIG. 27, the bone plate 4 can be configured such that one or more of the apertures 6 is intersected by another structure, such as another aperture 206, by way of non-limiting example. As shown, an aperture 6 can be intersected by a second aperture 206 in a manner collectively defining a “combi-hole” 106. It is to be appreciated that other aperture configurations are also within the scope of the present disclosure.

Although the disclosure has been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present disclosure is not intended to be limited to the particular embodiments described in the specification. As one of ordinary skill in the art will readily appreciate from that processes, machines, manufacture, composition of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure.

Claims

1. A bone plate, comprising: an upper surface configured to face away from a bone and an opposed lower surface configured to face the bone; andat least one aperture extending through the bone plate from the upper surface to the lower surface along a central aperture axis, the at least one aperture defined by an interior surface of the bone plate, the interior surface further defining a plurality of columns sequentially located about a circumference of the interior surface and a plurality of recesses located circumferentially between the columns, wherein each of the columns is configured to undergo deformation at least in a radial direction perpendicular to the central aperture axis responsive to engagement with a head of a locking bone screw receivable within the at least one aperture so as to lock the head to the bone plate, and the plurality of columns comprises at least five columns.

2. The bone plate of claim 1, wherein the deformation includes plastic deformation, and the columns are configured such that the plastic deformation reduces cross-threading of the columns.

3. The bone plate of claim 1, wherein the plurality of columns comprises at least nine columns.

4. The bone plate of claim 1, wherein the columns are evenly spaced about the circumference of the interior surface.

5. The bone plate of claim 1, wherein each column defines a first surface substantially facing the central aperture axis, and a pair of side surfaces located on adjacent circumferential sides of the first surface, the pair of side surfaces at least partially defining a respective pair of the recesses on the adjacent circumferential sides of the first surface.

6. The bone plate of claim 5, wherein at least one of the first surfaces of the plurality of columns has a convex profile in a reference plane orthogonal to the central aperture axis.

7. The bone plate of claim 5, wherein at least one of the first surfaces of the plurality of columns has a concave profile in a reference plane orthogonal to the central aperture axis.

8. The bone plate of claim 5, wherein the first surfaces of each of the columns taper radially inwardly from the upper surface to the lower surface at an angle in a range of about 3 degrees to about 30 degrees to the central aperture axis.

9. The bone plate of claim 5, wherein the at least one aperture includes internal threading that helically traverses the plurality of columns such that each column defines one or more thread portions of the internal threading, and the one or more thread portions of at least some of the columns are configured to undergo at least some of the deformation when the head of the locking bone screw is inserted.

10. The bone plate of claim 9, wherein the internal threading is tapered along a taper axis that extends along roots of the internal threading and is oriented such that the taper axis and the central aperture axis are each coextensive in a common reference plane, and the taper axis is angled radially inwardly from the upper surface to the lower surface at an angle in a range of about 4 degrees to about 40 degrees to the central aperture axis.

11. The bone plate of claim 10, wherein the internal threading is configured such that each column defines an upper column portion defining the one or more thread portions and a lower column portion having no threading, the lower column portion is configured to be deformed by external threads of the screw head, and the deformation occurs substantially without removal of material from the respective column.

12. The bone plate of claim 1, wherein the interior surface of the aperture further defines a lower relief surface extending upward from the lower surface of the bone plate toward the upper surface and the relief surface defines a portion of each of the columns.

13. The bone plate of claim 12, wherein the internal threading helically traverses the columns from an upper end of each column to the lower relief surface.

14. The bone plate of claim 1, wherein the recesses are each angled radially inwardly from the upper surface to the lower surface at an angle in a range of about 0 degrees to about 30 degrees to the central aperture axis.

15. The bone plate of claim 1, wherein the recesses are each oriented substantially parallel to the central aperture axis.

16. The bone plate of claim 1, wherein the at least one aperture intersects another aperture, and the at least one aperture and the another aperture collectively define a combi-hole.

17. A system for affixation to one or more portions of bone, the system comprising: the bone plate of claim 1; andone or more locking bone screws that are each insertable within the at least one aperture at one or more of a nominal angle and a variable angle.

18. The system of claim 17, wherein the one or more locking bone screws includes one or more variable angle bone screws.

19. The system of claim 18, wherein the one or more locking bone screws comprises a plurality of locking bone screws, and the plurality of locking bone screws includes locking bone screws having different shapes, different sizes, or different shapes and different sizes.

20. The system of claim 17, wherein the one or more locking bone screws are made from a first material, and the bone plate is made from a second material, wherein the first material is harder than the second material.