Variable Angle Locking Structure for Orthopedic Applications

Abstract

An embodiment includes a bone fixation system that includes: a bone anchor having a tapered head with threads thereon; and a plate including a void that includes one of a countersink or a counterbore; wherein: (a) no portion of the void has threads; (b) the void includes an inner wall; and (c) the inner wall includes a protrusion along its perimeter. Other embodiments are described herein.

Description

Technical Field

[0001] Embodiments of the present invention belong to the field of orthopedic applications. Background Art

[0002] In orthopedics, it is common practice to screw bone screws into bones through holes in a fixing plate. This allows for the stabilization of osteotomies, fractures, bone fragments, etc. Typically, a user may wish to lock the screw to the plate to prevent the screw from backing out of the plate after insertion into the bone. Depending on the patient's anatomy or additional hardware, the required angle at which the locked screw engages the hole in the plate may vary from the normal to the central axis of the hole. Brief Description of the Drawings

[0003] The features and advantages of embodiments of the present invention will become apparent from the appended claims, the following detailed description of one or more example embodiments, and the corresponding drawings. Where appropriate, reference numerals are repeated in the drawings to indicate corresponding or similar elements.

[0004] Figure 1 Including a bone anchor in one embodiment.

[0005] Figure 2A 、 Figure 2B 、 Figure 2C Including a top view, a perspective view, and a cross-sectional view of a bone plate in an embodiment.

[0006] Figure 3A 、 Figure 3B 、 Figure 3C Including a side view, a cross-sectional view, and a top view of a bone plate in an embodiment.

[0007] Figure 4A 、 Figure 4B 、 Figure 4C Including a side view, a cross-sectional view, and a top view of a bone plate in an embodiment.

[0008] Figure 5A 、 Figure 5B 、 Figure 5C Including cross-sectional views of different embodiments of a bone plate. Detailed Description of the Embodiments

[0009] Reference will now be made to the accompanying drawings, where like structures may be provided with like suffix reference numerals. For the sake of more clearly showing the structures of the various embodiments, the drawings included herein are schematic representations of the structures. Thus, the actual appearance of the fabricated structure (e.g., in a photograph) may look different while still including the claimed structure of the illustrated embodiments. Additionally, the drawings may only show the structures that contribute to an understanding of the illustrated embodiments. Additional structures known in the art may not be included to maintain the clarity of the drawings. For example, not every part of the device may necessarily be shown. "An embodiment", "various embodiments", etc. indicate that the embodiments so described may include a particular feature, structure, or characteristic, but not every embodiment must include the particular feature, structure, or characteristic. Some embodiments may have some, all, or none of the features described for other embodiments. "First", "second", "third", etc. describe a common object and indicate different instances of like objects being referenced. Such adjectives do not mean that the objects so described must be in a given order, whether in time, space, ranking, or in any other way. "Connected" may indicate that elements are in direct physical or electrical contact with each other, and "coupled" may indicate that elements cooperate or interact with each other, but they may or may not be in direct physical or electrical contact. A phrase such as "including at least one of A and B" includes the cases of A, B, or A and B.

[0010] One embodiment includes a variable angle locking screw and plate system, where the plate system does not require the plate to include threaded holes or tapered holes. Locking the screw to the plate allows biomechanical loads to be transferred from the screw to the plate in a more efficient manner than in a standard non-locking screw / plate system. Since, for example, reduction of osteotomy or fracture is maintained, load transfer can contribute to the healing process.

[0011] One embodiment includes a bone fixation system that includes a bone anchor 101 and a plate 151. Although Figure 2A the plate in [the figure] shows a single hole, this is for clarity, and embodiments may include 1, 2, 3, 4, 5, 6, or more holes.

[0012] The bone anchor includes a head 102, a body 103, and a long axis 104. The body has an outer diameter 105 orthogonal to the long axis, and the head has an outer diameter 106 orthogonal to the long axis. Although the body is not tapered in Figure 1 [the figure], other embodiments may have a tapered body, where (a) the thread root 107 (where the thread of the body intersects the non-threaded portion) may be tapered, (b) the thread crest (the outermost edge of the thread) may be tapered, (c) both the thread root and the thread crest may be tapered at the same incident angle with respect to the long axis, or (d) the thread root and the thread crest may be tapered at different incident angles with respect to the long axis. In Figure 1 [the figure], the outer diameter of the head diameter 106 is greater than the outer diameter of the body 105.

[0013] The plate includes a hole 152, and the hole includes a long axis 153 that passes through the hole but does not intersect the plate. The hole includes a first opening 154 and a second opening 155. The hole includes a protrusion 156, and the protrusion projects inwardly and toward the long axis from the wall 157 of the hole. The protrusion has a first surface 158 and a second surface 159. At least a portion of the first surface is coplanar with a first plane 160. The first plane 160 intersects the long axis at a first angle 161 of 90 degrees. However, in other embodiments, the first angle is between 85 degrees and 95 degrees, between 75 degrees and 105 degrees, or between 65 degrees and 115 degrees.

[0014] The protrusion 156 includes an inner wall 162 that couples the first surface of the protrusion to the second surface of the protrusion. The inner wall of the protrusion has a first portion 163 that is at a first distance 164 from the long axis 153, and the first distance is orthogonal to the long axis. The inner wall of the protrusion has a second portion 165 that is at a second distance 166 from the long axis, and the second distance is orthogonal to the long axis. Because portion 165 is in a void, groove, or protrusion formed along the wall 162, the second distance is greater than the first distance. In one embodiment, the inner wall of the protrusion has a third portion 167 that is at a third distance 168 from the long axis, and the third distance is orthogonal to the long axis. The third distance is greater than the first distance.

[0015] In one embodiment, the third distance 168 is greater than the second distance 166 ( Figure 2A not shown). Thus, protrusions can be formed at different depths that are not equal to each other. The second distance is measured from the position of the second portion that is farthest from the long axis compared to other positions of the second portion (i.e., the deepest part of the protrusion), and the third distance is measured from the position of the third portion that is farthest from the long axis compared to other positions of the third portion.

[0016] In one embodiment, the inner wall of the protrusion defines the inner perimeter of the protrusion. The inner wall of the protrusion has a fourth portion 169 that is at a first distance 164 from the long axis.

[0017] In one embodiment, the distance 166 is between 0.508 mm and 1.016 mm and is greater than the distance 164 by a difference distance 184, and the difference distance is between 0.127 mm and 0.381 mm.

[0018] In one embodiment, at least a portion of the second surface is coplanar with a second plane 170. The second plane intersects the long axis at a second angle 171 of 90 degrees. However, in other embodiments, the second angle is between 85 degrees and 95 degrees, between 75 degrees and 105 degrees, or between 65 degrees and 115 degrees.

[0019] In Figure 2CIn [the figure], the first surface 158 is at a first distance 172 from the first opening, and the first distance is parallel to the long axis. The second surface is at a second distance 173 from the second opening, and the second distance is parallel to the long axis. The first distance is greater than the second distance. This can allow for a greater clearance for receiving the bone anchor in the plate, thus allowing a greater angle for inserting the anchor into the plate. However, in other embodiments, these distances may be the same.

[0020] In one embodiment, the distance 173 is between 0.254 mm and 1.27 mm, and the distance 172 is between 0.254 mm and 5.588 mm. In one embodiment, the portion 163 of the protrusion projects inward from the wall 157 of the hole and toward the long axis by a distance 185, and the distance 185 is between 0.254 mm and 0.127 mm. In one embodiment, the thickness 186 is between 1.00 mm and 2.75 mm.

[0021] The dimensions used herein are examples, and various embodiments may or may not include such dimensions.

[0022] In one embodiment, the plate 151 does not include threads between the first opening 154 and the second opening 155. The first opening 154 directly engages with the first outer surface 174 of the plate; the second opening 155 directly engages with the second outer surface 175 of the plate; the first outer surface 174 of the plate faces away from the second outer surface 175 of the plate. By avoiding the use of threads, the locking angle can be increased without shearing the protrusion material or generating burrs. In addition, once the screw is locked at an angle in a threaded structure, the threads are damaged and it may be difficult to relock at a different angle. Avoiding threads allows for high-angle and repeated locking. In addition, different from many other conventional locking structures, one is not limited to a single screw design or thread profile.

[0023] In one embodiment, the first opening has a first maximum diameter orthogonal to the long axis ( Figure 2C twice the radius 176 in the example of Figure 2C ), and the second opening has a second maximum diameter orthogonal to the long axis (

[0024] twice the radius 177 in the example of Figure 3BIn this case, the head 102 of the bone anchor includes a maximum diameter 106. The maximum diameter 176' of the plate opening 154 is greater than the maximum diameter 106. Additionally, the protrusion 156 forms a ring surrounding the interior of the hole. This ring has a minimum diameter 164' that is less than the maximum diameter 106. As used herein, the "maximum" diameter can accommodate situations where, for example, the surface is not circular. For example, the opening 154 can be non-circular in some embodiments and thus include more than one diameter such that the "maximum" diameter is the largest of the plurality of diameters.

[0025] In one embodiment, the maximum diameter 106 of the head of the bone anchor is between 5% and 10% greater than the minimum diameter 164' of the ring.

[0026] In Figure 1 this case, at least a portion of the head 102 of the bone anchor is included in the nearest fifth (20%) of the bone anchor, and this portion includes threads. In other words, at least a portion of the bone anchor head has threads. In Figure 1 this case, the body 103 of the bone anchor includes threads. The threads of the body of the bone anchor have a first thread height 178, and the threads of this portion of the head of the bone anchor have a second thread 179 that is less than the first thread height.

[0027] In Figure 1 this case, the threads of the body of the bone anchor have a first crest width 180, and the threads of this portion of the head of the bone anchor have a second crest width 181 that is greater than the first crest width. However, in other embodiments, the widths 180, 181 are equal to each other, and in other embodiments, the width 181 is less than the width 180.

[0028] In Figure 1 this case, the thread height 179 is between 0.0254 mm and 0.3048 mm, and the crest width 181 is between 0.0508 mm and 0.3048 mm.

[0029] In Figure 1 , Figure 3C and Figure 4C this case, the head of the bone anchor has a circular cross-section that is orthogonal to the long axis of the bone anchor; and based on the bone anchor including a tapered portion, the outer diameter of the head is greater than the outer diameter of the body. The tapered portion includes a thread root that tapers outwardly at an angle 182 between 10 degrees and 20 degrees. The threads of this portion of the head of the bone anchor include a thread crest that tapers outwardly at an angle 183 between 10 degrees and 20 degrees. However, in other embodiments, the tapered portion includes a thread root that tapers outwardly at an angle 182 between 10 degrees and 25 degrees, and the threads of this portion of the head of the bone anchor include a thread crest that tapers outwardly at an angle 183 between 10 degrees and 25 degrees.

[0030] One embodiment provides a variable angle locking structure for orthopedic applications by allowing interference between a locking screw and a screw hole. In one embodiment, the locking screw is a double-lead locking screw having a tapered diameter (measured from one or more thread crests) that extends from 2.2 mm to 3.5 mm. However, in other embodiments, the locking screw is a double-lead locking screw having a tapered diameter (measured from one or more thread crests) that extends from 1.6 mm to 7.0 mm. In one embodiment, the threaded portion extends throughout the length of the screw. The small end taper of the screw head is from 12 degrees to 17 degrees and comprises 8% to 80% of the total screw length. The large end taper of the screw head is from 7 degrees to 15 degrees, but not for the entire head. For 5% to 15% of the screw head, the proximal portion of the large end of the screw head is not tapered. The screw has a small end diameter at the thread break 187 that is in the range of 6% smaller to 3% larger than diameter 164’. However, in another embodiment, the screw has a small end diameter at the thread break 187 that is in the range of 10% smaller to 5% larger than diameter 164’.

[0031] In one embodiment, the diameter of the locking threads on the anchor head is in the range of 1% larger to 15% larger than diameter 164’. The difference in diameter provides interference with the protrusion 156, causing hole deformation at the release cuts in portions 165, 167 (and any other release cuts or portions in the protrusion 156).

[0032] In one embodiment, the anchor includes diameter 106, which allows for limited interference with the top surface 174 when locked at an angle of up to 30 degrees with respect to axis 104. However, in another embodiment, the anchor includes diameter 106, which allows for limited interference with the top surface 174 when locked at an angle of up to 50 degrees with respect to axis 104.

[0033] In one embodiment, the space 188 is formed as a counterbore having a diameter 176’ that is 15% to 35% larger than diameter 164’. The hole formed by the sidewall 162 is coaxial with the counterbore and allows for mating with the locking screw. Diameter 164’ provides interference with the tapered head 102 and the locking threads of the head. A radius 189 in the range from 0.0508 mm to 0.381 mm may be present at the bottom of the counterbore to help reduce stress or aid in manufacturability.

[0034] The protrusion 156 includes a thickness 186 that is 40% to 60% less than the lead of the screw 190 (where the lead is the axial advancement of the helix or screw during one full revolution (360°), and where the lead of the screw threads is the axial travel for one revolution).

[0035] The locking hole can have a plurality of release cuts (see, for example, sections 165, 167) radially oriented around the hole. The presence of the cuts (or more generally, voids) allows for deformation of the platform, which aids in the interference fit with the screw.

[0036] In one embodiment, the anchor and the plate are made of the same material. Such material can include, for example, Ti-6Al-4V. However, other biocompatible materials can be used in other embodiments, and the anchor and the plate do not necessarily require the same material.

[0037] The embodiments are applicable to locking bone plates and anchors (such as screws) for foot / ankle treatment. However, other embodiments are generally applicable to orthopedics or medicine (human or animal), including but not limited to applications in the foot and ankle, spine, craniofacial, and / or veterinary fields, etc.

[0038] The embodiments provide a variable angle locking structure that does not use a tapered plate, a threaded plate, or a striated plate.

[0039] In an alternative embodiment, the release cuts or voids of the plate can include 1, 2, 3, 4, 5 or more. One embodiment does not have a countersink on the bottom side (e.g., void 188' is missing). For example, the diameter 164' can range from 1.0 mm to 7.0 mm or greater. Similarly, the anchor can vary from 1.0 mm to 7.0 mm or greater in diameter 106. In one embodiment, the screw is not fully threaded and has a cap at the head of the screw that does not contain threads. In one embodiment, the drive feature of the screw can be any feature that allows for the transmission of torque from the mating member. In one embodiment, the threads of the screw can be embodied as a left-handed thread configuration. In one embodiment, the number of thread pitches can vary from 1 to 4. In one embodiment, the shape of the screw head can be spherical rather than conical.

[0040] One embodiment includes a locking mechanism that uses a combination of "cut-in", "point-loaded threads", and "screw head expansion" for locking, and includes a mechanism that does not use countersunk holes, threaded holes, or tapered hole geometries. Compared to conventional techniques that use a two-component system for locking, the locking mechanism proposed herein provides a higher angle degree without affecting the locking strength. Advantages over conventional systems include the ability to lock at an angle of more than 30 degrees in one direction, which results in a 60-degree locking cone. However, in other embodiments, advantages over conventional systems include the ability to lock at an angle of more than 50 degrees in one direction, which results in a 100-degree locking cone. Additionally, one embodiment allows for multiple locking attempts at different angles (without using additional components such as bushings or locking caps). Instead, such an embodiment only requires locking holes and screws of a specific geometry to achieve the same result.

[0041] One embodiment includes a screw having more than two continuous threads. The screw includes a tapered head and a cylindrical body that make up the total length of the screw 201. Embodiments of the screw can vary in length from 4 mm to 170 mm. In one embodiment, the length is between 8 mm and 50 mm.

[0042] In one embodiment, the screw has a tapered head that tapers down to the cylindrical body of the screw. In this embodiment, the screw is generally cylindrical between the tapered head and the screw tip.

[0043] In one embodiment, the diameter of the screw head is a critical dimension. The diameter 106 of the screw head is essential for allowing the screw to be locked to the plate and preventing the screw from translating through the hole without "biting" or locking interference. The diameter 106 of the screw head can vary from 2.4384 mm to 4.572 mm. In this embodiment, the head diameter is equal to or greater than the diameter 164'. In one embodiment, the diameter 106 is 7% larger than the diameter 164'. However, in other embodiments, the diameter 106 is 4%, 5%, 6%, 8%, 9%, 10% or more larger than the diameter 164'.

[0044] In one embodiment, the thread height 178 (for the threads on the body) ranges from 0.254 mm and 0.762 mm. In one embodiment, the height 178 is 0.381 mm. Figure 1 The thread heights between two threads of the embodiment are the same, but in other embodiments, they can be different, where one thread has a greater height than the other thread.

[0045] In one embodiment, a key feature is that the thread height 181 at the head of the screw is different from the thread height 178 of the body of the screw. The thread height 181 is between 0.0254 mm and 0.3048 mm. In one embodiment, the thread height 181 is 0.1778 mm. The height of the thread 181 in the tapered head 102 allows for an ideal lock into the hole formed by the protrusion 156. If the thread height 181 is too high, the thread may deform and shear from the head of the screw, creating an undesired burr of the loose body. Conversely, if the thread height 181 is too low, the lock may be included by not contributing to the cut in the protrusion 156.

[0046] In one embodiment, a key feature is the smaller head angle 182 (i.e., the angle followed by the root of the thread). This feature is a key embodiment because it contributes to the formation of the thread head geometry. In various embodiments, this angle varies from 10 degrees to 20 degrees and extends from 80% to 100% of the tapered head 102 from the body of the screw 103. However, in other embodiments, this angle varies from 10 degrees to 25 degrees and extends from 80% to 100% of the tapered head 102 from the body of the screw 103. The angle 182 allows the threads on the head to bite into and wedge into the protrusion 156.

[0047] In one embodiment, a key feature is the major head angle 183 (i.e., the angle followed by the crest of the thread). This feature is key in one embodiment because it defines the geometry of the threads on the head. In various embodiments, this angle can range from 10 degrees to 20 degrees. However, in other embodiments, this angle can range from 10 degrees to 25 degrees. In one embodiment, the angle 183 is between 15 degrees and 17 degrees. In one embodiment, this angle is constant throughout the head of the screw. The angle allows the threads on the head to bite into and wedge into the protrusion 156.

[0048] In one embodiment, the front flank angle 191 helps to define the thread geometry and is between 30 degrees and 40 degrees (or between 20 degrees and 50 degrees in other embodiments). In one embodiment, the angle 191 is 35 degrees. In one embodiment, the rear flank angle 192 helps to define the thread geometry and is between 2 degrees and 8 degrees (or between 2 degrees and 30 degrees in other embodiments). In one embodiment, the angle 192 is 3 degrees. In one embodiment, the lead 190 of the screw (i.e., the pitch divided by each unique thread) is between 0.7366 mm and 1.524 mm. In one embodiment, the lead is 0.9906 mm. In one embodiment, the crest width 180 on the body of the screw (or the plane at the thread edge) is between 0.0254 mm and 0.1524 mm.

[0049] In one embodiment, a key feature is that the crest width 181 on the head of the screw is between 0.0508 mm and 0.3048 mm, with a value of 0.2032 mm in one embodiment. This is key because the crest needs to be small enough to generate sufficient stress and / or strain on the protrusion 156, but large enough so that it does not shear and produce a loose body.

[0050] In one embodiment, the thread diameter 105 is the maximum diameter of the threads at the screw body. In one embodiment, the diameters of all unique threads are equal (e.g., if there are two unique threads on the screw, the threads are equal to each other). However, in one embodiment, the diameters of all unique threads can be different. In one embodiment, the diameter 105 is approximately 2.6924 mm.

[0051] In one embodiment, the shank diameter 193 (defined by the diameter resulting from the root of the threads of the screw body) is equal for all unique threads and can be approximately 1.8796 mm. However, in other embodiments, for different unique threads, the diameter 193 can be different. In one embodiment, the tip of the screw can be round or sharp for self-drilling applications. In one embodiment, the root 107 of the thread consists of more than two geometries, such as a radius (e.g., 0.2032 mm) and a plane of 0.0254 mm.

[0052] Regarding the plate, in one embodiment, a key feature includes the use of a countersink. As used herein, a countersink is a cylindrical flat-bottomed hole that enlarges another coaxial hole. The use of the countersink creates a flat platform 158 to which the locking screw can engage. The countersink can have a depth 172 of 0.762 mm, but in other embodiments can range from 0.254 mm to 1.27 mm. In an alternative embodiment (e.g., Figure 5B ), the upper portion of the countersink can have a counterbore with a total angle greater than 90 degrees with respect to the central axis 153. As used herein, a counterbore includes a tapered hole cut into a manufactured object. In an embodiment, a countersink radius 189 may or may not be present and allows for the manufacturability of the platform feature. Such a radius can be, for example, 0.254 mm.

[0053] In one embodiment, hole bosses are key components. For example, in Figure 2A there are three bosses, but in alternative embodiments there can be 1, 2, 4, 5 or more bosses. The bosses are radially oriented from the central axis 153 and include a diameter 166 ranging from 0.508 mm to 1.016 mm, and the bosses project into the protrusion 156. The bosses allow for the deformation of the locking hole to occur without creating a loose body.

[0054] In one embodiment, the protrusion 156 (e.g., the platform) is a protrusion of material that is radially oriented with upper and lower surfaces that can be parallel to each other. In one embodiment, there is no taper, angle, or thread protrusion to the platform (e.g., there is a 90-degree angle between the wall 162 and the surface 158). If the lower side of the locking plate is curved, the platform can increase along the short axis of the locking hole (the hole formed by the protrusion 156). The platform includes a thickness 186 and a length 185.

[0055] In one embodiment, thickness 186 is critical to the function of the locking mechanism and is between 0.254 mm and 5.588 mm, which allows the threads of the locking head to cut into the protrusion without severely deforming the protrusion and allows the screw to pull through the protrusion. In one embodiment, the platform thickness 186 is uniform around the circumference of the hole. In one embodiment, the thickness 186 varies. Such an embodiment may include, for example, steps to vary the thickness.

[0056] In one embodiment, 176’ is 1.0668 mm larger than diameter 164’. The smaller the counterbore diameter, the smaller the angle at which the screw can be locked because the screw will contact the top surface 174. In an alternative embodiment, the presence of a countersink at the top of the counterbore circumvents this consideration.

[0057] In one embodiment, the critical feature is the depth 184 of the protrusions, which can be equal or unequal for each protrusion in the protrusion. Generally, the protrusions will have a depth 184 into the protrusion 156 ranging from 0.127 mm to 0.381 mm. In one embodiment, the depth 184 is 0.3048 mm. If the depth of the protrusion is too shallow, locking will be affected. Similarly, if the depth is too deep, the platform may be subjected to critical forces and the platform will deform excessively and shear from the locking plate.

[0058] In one embodiment, diameter 164’ is a critical feature. The diameter is 7% smaller than the head diameter 106, but can be 2% to 15% smaller. This diameter is critical to the design and allows an optimal interference amount that allows the screw to bite / wedge into the locking hole (the hole defined by the protrusion 156) to form a strong integral structure. In one embodiment, the hole has a diameter of 4.0767 mm.

[0059] In one embodiment, the upper counterbore depth has sidewalls 157 parallel to the axis 153. However, the counterbore can be combined with other features such as a countersink (e.g., Figure 5B ) Figure 5A and Figure 5C illustrates other alternative designs. In one embodiment, the upper counterbore depth 172 is 0.889 mm.

[0060] In one embodiment, there is a lower counterbore, but this feature is optional. One embodiment includes a platform having two parallel planes 160, 170. If there is no lower counterbore, the lower side 175 can have a radius of curvature that is not parallel to the top surface 174 of the platform. The presence of a lower counterbore or void helps provide clearance for the locking screw at a large angle. In one embodiment, the lower counterbore has a diameter 176” of 5.461 mm and a depth 173 of 0.127 mm.

[0061] In some embodiments, a key feature is the distance 185 of the protrusion of the locking hole platform from the counterbore wall 157. In various embodiments, this value can vary from 0.254 mm to 0.762 mm. The protrusion is critical to the locking mechanism because if the protrusion is too small, the angle and locking ability of the screw lock will be affected. Additionally, if the protrusion is too long, the locking screw may translate through the locking hole.

[0062] In one embodiment, the angle of the upper counterbore wall 157 with the central axis 153 can be 0 degrees (parallel), but in other embodiments can be in the range of 0 degrees to 80 degrees. Additionally, the angle of the lower counterbore sidewall with the axis 153 can be 0 degrees, but can be in the range of 0 to 80 degrees.

[0063] The following examples relate to additional embodiments.

[0064] Example 1. A bone fixation system, comprising: a bone anchor; and a plate; wherein the bone anchor: (a)(i) includes a head and a body, the head being coupled to the body, (a)(ii) has a longitudinal axis, (a)(iii) the body has an outer diameter orthogonal to the longitudinal axis, and the head has an outer diameter orthogonal to the longitudinal axis, and (a)(iv) the outer diameter of the head is greater than the outer diameter of the body; wherein: (b)(i) the plate includes a hole, (b)(ii) the hole includes a longitudinal axis passing through the hole but not intersecting the plate, (b)(iii) the hole includes a first opening and a second opening, (b)(iv) the hole includes a protrusion and the protrusion projects inward from the wall of the hole and toward the longitudinal axis, (b)(v) the protrusion has a first surface and a second surface, and (b)(vi) at least a portion of the first surface is coplanar with a first plane, and (b)(vii) the first plane intersects the longitudinal axis at a first angle and the first angle is between 85 degrees and 95 degrees.

[0065] In one embodiment, such a bone anchor can include some so-called "headless" screws. Such screws can have different pitches or leads (e.g., a larger pitch or lead near the distal end and a smaller pitch or lead near the proximal end). However, even if the taper near the proximal end is very small, the screw may still have a certain degree of taper.

[0066] Example 2. The bone fixation system according to Example 1, wherein: the protrusion includes an inner wall that couples the first surface of the protrusion to the second surface of the protrusion; the inner wall of the protrusion has a first portion at a first distance from the longitudinal axis, the first distance being orthogonal to the longitudinal axis; the inner wall of the protrusion has a second portion at a second distance from the longitudinal axis, the second distance being orthogonal to the longitudinal axis; the second distance is greater than the first distance.

[0067] Example 3. The bone fixation system according to Example 2, wherein: the inner wall of the protrusion has a third portion at a third distance from the long axis, the third distance being orthogonal to the long axis; the third distance is greater than the first distance.

[0068] Example 4. The bone fixation system according to Example 3, wherein: the third distance is greater than the second distance; the second distance is measured from the position of the second portion that is farthest from the long axis compared to other positions of the second portion; the third distance is measured from the position of the third portion that is farthest from the long axis compared to other positions of the third portion.

[0069] Example 5. The bone fixation system according to Example 3, wherein: the inner wall of the protrusion defines the inner circumference of the protrusion; the inner wall of the protrusion has a fourth portion at the first distance from the long axis; the first portion is between the second portion and the third portion; the third portion is between the first portion and the fourth portion.

[0070] Example 6. The bone fixation system according to Example 2, wherein the first plane is orthogonal to the long axis.

[0071] Example 7. The bone fixation system according to Example 1, wherein the first plane is orthogonal to the long axis.

[0072] Example 8. The bone fixation system according to Example 1, wherein at least a portion of the second surface is coplanar with a second plane, and (b)(viii) the second plane intersects the long axis at a second angle and the second angle is between 85 degrees and 95 degrees.

[0073] Example 9. The bone fixation system according to Example 8, wherein the second plane is orthogonal to the long axis.

[0074] Example 10. The bone fixation system according to Example 8, wherein the first plane is orthogonal to the long axis.

[0075] Example 11. The bone fixation system according to Example 1, wherein: the first surface is between the second surface and the first opening; the second surface is between the first surface and the second opening; the first surface is at a first distance from the first opening, the first distance being parallel to the long axis; the second surface is at a second distance from the second opening, the second distance being parallel to the long axis; the first distance is greater than the second distance.

[0076] Example 12. The bone fixation system according to Example 1, wherein: the plate does not include threads between the first opening and the second opening; the first opening directly engages with the first outer surface of the plate; the second opening directly engages with the second outer surface of the plate; the first outer surface of the plate is opposite to the second outer surface of the plate.

[0077] Example 13. The bone fixation system according to Example 12, wherein: the first opening has a first maximum diameter orthogonal to the longitudinal axis; the second opening has a second maximum diameter orthogonal to the longitudinal axis; the second maximum diameter is greater than the first maximum diameter.

[0078] Example 14. The bone fixation system according to Example 13, wherein: the head of the bone anchor includes a third maximum diameter; the first maximum diameter is greater than the third maximum diameter; the protrusion forms a ring surrounding the interior of the hole; the ring has a minimum diameter; the minimum diameter of the ring is less than the third maximum diameter.

[0079] Example 15. The bone fixation system according to Example 1, wherein: at least a part of the head of the bone anchor is included in the one-fifth of the proximal end of the bone anchor; the part of the head of the bone anchor includes threads.

[0080] Example 16. The bone fixation system according to Example 15, wherein: the body of the bone anchor includes threads; the threads of the body of the bone anchor have a first thread height; the threads of the part of the head of the bone anchor have a second thread height; the second thread height is less than the first thread height.

[0081] Example 17. The bone fixation system according to Example 16, wherein: the threads of the body of the bone anchor have a first crest width; the threads of the part of the head of the bone anchor have a second crest width; the second crest width is greater than the first crest width.

[0082] Example 18. The bone fixation system according to Example 1, wherein the protrusion forms a ring surrounding the interior of the hole.

[0083] Example 19. The bone fixation system according to Example 1, wherein: the head of the bone anchor has a circular cross-section that is orthogonal to the longitudinal axis of the bone anchor; based on the bone anchor including a tapered portion, the outer diameter of the head is greater than the outer diameter of the body; the tapered portion includes a thread root that tapers outwardly at an angle between 10 degrees and 25 degrees; the head of the bone anchor includes a maximum diameter taken orthogonally to the longitudinal axis of the bone screw; the protrusion forms a ring surrounding the interior of the hole, and the ring includes a minimum diameter; the maximum diameter of the head of the bone anchor is 5% to 10% larger than the minimum diameter of the ring; at least a portion of the head of the bone anchor is included in the one-fifth of the proximal end of the bone anchor, and the portion of the head of the bone anchor includes threads; the threads of the portion of the head of the bone anchor have a thread height between 0.0254 mm and 0.3048 mm; the threads of the portion of the head of the bone anchor have a crest width between 0.0508 mm and 0.3048 mm; the first surface is between the second surface and the first opening, and the second surface is between the first surface and the second opening; the first surface is a first distance from the first opening, the first distance is parallel to the longitudinal axis, and is between 0.254 mm and 1.27 mm; the protrusion includes an inner wall that couples the first surface of the protrusion to the second surface of the protrusion; the inner wall of the protrusion has a first portion at a second distance from the longitudinal axis, the second distance being orthogonal to the longitudinal axis; the inner wall of the protrusion has a second portion at a third distance from the longitudinal axis, the third distance being orthogonal to the longitudinal axis; the third distance is greater than the second distance, and the third distance is between 0.508 mm and 1.016 mm; the third distance is greater than the second distance by a difference distance, and the difference distance is between 0.127 mm and 0.381 mm; the first surface is a fourth distance from the second surface, the fourth distance is parallel to the longitudinal axis, and is between 0.254 mm and 5.588 mm; the first portion of the protrusion projects inwardly from the wall of the hole and toward the longitudinal axis by a fifth distance, the fifth distance being between 0.254 mm and 0.127 mm.

[0084] Example 19.5. The bone fixation system according to Example 19, wherein the threads of the portion of the head of the bone anchor include a thread crest that tapers outwardly at an angle between 10 degrees and 20 degrees.

[0085] Example 20. A bone fixation system comprising: a bone anchor having a tapered head with threads thereon; and a plate including a void, the void including one of a countersink or a counterbore; wherein: no part of the void has threads; the void includes an inner wall; the inner wall includes a protrusion along its perimeter.

[0086] Example 21. The bone fixation system according to Example 20, wherein: the void includes a countersink; the countersink includes a landing, the landing including a surface defined by a plane; the plane is orthogonal to the longitudinal axis of the void; the countersink includes sidewalls that extend parallel to the longitudinal axis of the void.

[0087] Example 22. The bone fixation system of Example 20, wherein: the bone anchor includes a material; the plate includes the material; the bone anchor is integral; the plate is integral.

[0088] Example 23. The bone fixation system of Example 21, wherein: the bone anchor and the protrusion are configured such that: when the bone anchor mates with the plate, the threads of the bone anchor head deform the landing adjacent to at least one of the protrusions; the bone anchor and the protrusion are configured to lock the bone anchor to the plate in response to the threads of the bone anchor head deforming the landing.

[0089] Example 24. The bone fixation system according to Example 23, wherein the plate does not include an elastic member.

[0090] For example, some conventional techniques may use a wire (e.g., a nickel-chromium alloy with shape memory) that moves laterally when the screw is inserted and then rebounds quickly in the middle and above the screw head to prevent the screw from backing out. However, such an elastic member is not included in the embodiments of the plate.

[0091] Example 25. A bone fixation kit comprising: a plate including a void, the void including one of a countersink or a counterbore; wherein: the plate does not include an elastic member; no part of the void has threads; the void includes an inner wall; the inner wall includes a protrusion along its perimeter; the protrusion is configured such that: when the bone anchor mates with the plate, the threads of the bone anchor head will deform the inner wall adjacent to at least one of the protrusions.

[0092] Example 26. The bone fixation kit according to Example 25, wherein: the void includes the countersink; the countersink includes a landing, the landing including a surface defined by a plane; the plane is orthogonal to the longitudinal axis of the void; the countersink includes sidewalls that extend parallel to the longitudinal axis of the void.

[0093] Example 27. The bone fixation kit according to Example 25, including the bone anchor.

[0094] Example 5a. The bone fixation system according to any one of Examples 3-4, wherein: the inner wall of the protrusion defines the inner circumference of the protrusion; the inner wall of the protrusion has a fourth portion at the first distance from the long axis; the first portion is between the second portion and the third portion; the third portion is between the first portion and the fourth portion.

[0095] Example 6a. The bone fixation system according to any one of Examples 1-5, wherein the first plane is orthogonal to the long axis.

[0096] Example 8a. The bone fixation system according to any one of Examples 1-6, wherein at least a portion of the second surface is coplanar with a second plane, and (b)(viii) the second plane intersects the long axis at a second angle and the second angle is between 85 degrees and 95 degrees.

[0097] Example 10a. The bone fixation system according to any one of Examples 1-9, wherein the first plane is orthogonal to the long axis.

[0098] Example 11a. The bone fixation system according to any one of Examples 1-10, wherein: the first surface is between the second surface and the first opening; the second surface is between the first surface and the second opening; the first surface is at a first distance from the first opening, the first distance being parallel to the long axis; the second surface is at a second distance from the second opening, the second distance being parallel to the long axis; the first distance is greater than the second distance.

[0099] Example 12a. The bone fixation system according to any one of Examples 1-11, wherein: the plate does not include threads between the first opening and the second opening; the first opening is directly engaged with the first outer surface of the plate; the second opening is directly engaged with the second outer surface of the plate; the first outer surface of the plate faces away from the second outer surface of the plate.

[0100] Example 15a. The bone fixation system according to any one of Examples 1-14, wherein: at least a portion of the head of the bone anchor is included in the one-fifth closest to the proximal end of the bone anchor; the portion of the head of the bone anchor includes threads.

[0101] Example 18a. The bone fixation system according to any one of Examples 1-17, wherein the protrusion forms a ring surrounding the interior of the hole.

[0102] Example 19a. The bone fixation system according to any one of Examples 1-18, wherein: the head of the bone anchor has a circular cross-section that is orthogonal to the longitudinal axis of the bone anchor; based on the bone anchor including a tapered portion, the outer diameter of the head is greater than the outer diameter of the body; the tapered portion includes a thread root that tapers outwardly at an angle between 10 degrees and 20 degrees; the head of the bone anchor includes a maximum diameter taken orthogonally to the longitudinal axis of the bone screw; the protrusion forms a ring surrounding the interior of the hole, and the ring includes a minimum diameter; the maximum diameter of the head of the bone anchor is 5% to 10% greater than the minimum diameter of the ring; at least a portion of the head of the bone anchor is included in the proximal fifth of the bone anchor, and the portion of the head of the bone anchor includes threads; the threads of the portion of the head of the bone anchor have a thread height that is between 0.0254 mm and 0.3048 mm; the threads of the portion of the head of the bone anchor have a crest width that is between 0.0508 mm and 0.3048 mm; the first surface is between the second surface and the first opening, and the second surface is between the first surface and the second opening; the first surface is a first distance from the first opening, the first distance being parallel to the longitudinal axis and being between 0.254 mm and 1.27 mm; the protrusion includes an inner wall that couples the first surface of the protrusion to the second surface of the protrusion; the inner wall of the protrusion has a first portion that is a second distance from the longitudinal axis, the second distance being orthogonal to the longitudinal axis; the inner wall of the protrusion has a second portion that is a third distance from the longitudinal axis, the third distance being orthogonal to the longitudinal axis; the third distance is greater than the second distance, and the third distance is between 0.508 mm and 1.016 mm; the third distance is greater than the second distance by a difference distance, and the difference distance is between 0.127 mm and 0.381 mm; the first surface is a fourth distance from the second surface, the fourth distance being parallel to the longitudinal axis and being between 0.254 mm and 5.588 mm; the first portion of the protrusion projects inwardly from the wall of the hole and toward the longitudinal axis a fifth distance, the fifth distance being between 0.254 mm and 0.127 mm.

[0103] Example 22a. The bone fixation system according to any one of Examples 20-21, wherein: the bone anchor includes a material; the plate includes the material; the bone anchor is integral; the plate is integral.

[0104] As used herein, integral means formed from a single unit. For example, a plate can be formed by forging, machining of a block of material, additive manufacturing, etc. Such a unit will not include welds or portions joined via an adhesive.

[0105] Example 23a. The bone fixation system according to any one of Examples 20 - 22, wherein: the bone anchor and the protrusion are jointly configured such that: when the bone anchor mates with the plate, the threads of the bone anchor head deform the platform adjacent to at least one of the protrusions; the bone anchor and the protrusion are jointly configured to lock the bone anchor to the plate in response to the threads of the bone anchor head deforming the platform.

[0106] Example 24a. The bone fixation system according to any one of Examples 20 - 23, wherein the plate does not include an elastic member.

[0107] Example 27a. The bone fixation kit according to any one of Examples 25 - 26, including the bone anchor.

[0108] Example 6a’. The bone fixation system according to any one of Example 5a, wherein the first plane is orthogonal to the long axis.

[0109] Example 8a’. The bone fixation system according to any one of Examples 5a - 6a, wherein at least a portion of the second surface is coplanar with a second plane, and (b)(viii) the second plane intersects the long axis at a second angle and the second angle is between 85 degrees and 95 degrees.

[0110] Example 10a’. The bone fixation system according to any one of Examples 5a, 6a, 8a, wherein the first plane is orthogonal to the long axis.

[0111] Example 11a’. The bone fixation system according to any one of Examples 5a, 6a, 8a, 10a, wherein: the first surface is between the second surface and the first opening; the second surface is between the first surface and the second opening; the first surface is a first distance from the first opening, the first distance being parallel to the long axis; the second surface is a second distance from the second opening, the second distance being parallel to the long axis; the first distance is greater than the second distance.

[0112] Example 12a’. The bone fixation system according to any one of Examples 5a, 6a, 8a, 10a, 11a, wherein: the plate does not include threads between the first opening and the second opening; the first opening directly engages with the first outer surface of the plate; the second opening directly engages with the second outer surface of the plate; the first outer surface of the plate is opposite to the second outer surface of the plate.

[0113] Example 15a’. A bone fixation system according to any one of Examples 5a, 6a, 8a, 10a, 11a, 14a, wherein: at least a portion of the head of the bone anchor is included in the proximal fifth of the bone anchor; the portion of the head of the bone anchor includes threads.

[0114] Example 18a’. A bone fixation system according to any one of Examples 5a, 6a, 8a, 10a, 11a, 14a, 17a, wherein the protrusion forms a ring around the interior of the hole.

[0115] Example 19a'. A bone fixation system according to any one of Examples 5a, 6a, 8a, 10a, 11a, 14a, 17a, 18a, wherein: the head of the bone anchor has a circular cross-section that is orthogonal to the longitudinal axis of the bone anchor; based on the bone anchor including a tapered portion, the outer diameter of the head is greater than the outer diameter of the body; the tapered portion includes a thread root that tapers outwardly at an angle between 10 degrees and 20 degrees; the head of the bone anchor includes a maximum diameter taken orthogonally to the longitudinal axis of the bone screw; the protrusion forms a ring surrounding the interior of the hole, and the ring includes a minimum diameter; the maximum diameter of the head of the bone anchor is 5% to 10% greater than the minimum diameter of the ring; at least a portion of the head of the bone anchor is included in the proximal fifth of the bone anchor, and the portion of the head of the bone anchor includes threads; the threads of the portion of the head of the bone anchor have a thread height that is between 0.0254 mm and 0.3048 mm; the threads of the portion of the head of the bone anchor have a crest width that is between 0.0508 mm and 0.3048 mm; the first surface is between the second surface and the first opening, and the second surface is between the first surface and the second opening; the first surface is a first distance from the first opening, the first distance being parallel to the longitudinal axis and between 0.254 mm and 1.27 mm; the protrusion includes an inner wall that couples the first surface of the protrusion to the second surface of the protrusion; the inner wall of the protrusion has a first portion that is a second distance from the longitudinal axis, the second distance being orthogonal to the longitudinal axis; the inner wall of the protrusion has a second portion that is a third distance from the longitudinal axis, the third distance being orthogonal to the longitudinal axis; the third distance is greater than the second distance, and the third distance is between 0.508 mm and 1.016 mm; the third distance is greater than the second distance by a difference distance, and the difference distance is between 0.127 mm and 0.381 mm; the first surface is a fourth distance from the second surface, the fourth distance being parallel to the longitudinal axis and between 0.254 mm and 5.588 mm; the first portion of the protrusion projects inwardly from the wall of the hole and toward the longitudinal axis a fifth distance, the fifth distance being between 0.254 mm and 0.127 mm.

[0116] Example 23a’. The bone fixation system according to any one of Examples 22a, wherein: the bone anchor and the protrusion are jointly configured such that: when the bone anchor mates with the plate, the threads of the bone anchor head deform the platform adjacent to at least one of the protrusions; the bone anchor and the protrusion are jointly configured to lock the bone anchor to the plate in response to the deformation of the platform by the threads of the bone anchor head.

[0117] Example 24a’. The bone fixation system according to any one of Examples 22a and 23a, wherein the plate does not include an elastic member.

[0118] The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. The description and the following claims include terms for descriptive purposes only and should not be construed as limiting, such as left, right, top, bottom, above, below, upper, lower, first, second, etc. For example, the term specifying a relative vertical position refers to the case where the device side of the substrate is the "top" surface of the substrate; the substrate can actually be in any orientation such that the "top" side of the substrate can be lower than the "bottom" side in a standard terrestrial reference system and still fall within the meaning of the term "top". As used herein (including in the claims), the term "on" does not indicate that the first structure "on" the second structure is directly on the second structure and in direct contact with the second structure, unless specifically stated; there may be a third structure or other structures between the first structure and the second structure on the first structure. Embodiments of the devices or articles described herein can be manufactured, used, or transported in multiple positions and orientations. Those skilled in the relevant art will understand that many modifications and variations can be made in accordance with the above teachings. Those skilled in the art will recognize various equivalent combinations and alternatives of the various components shown in the figures. Therefore, the scope of the invention is not limited by this specific embodiment, but by the appended claims.

Claims

1. A bone fixation system, comprising: A bone anchor having a longitudinal axis, the bone anchor comprising: A threaded head including a proximal end having a circular cross-section orthogonal to the longitudinal axis of the bone anchor, and A threaded body extending from the threaded head; and A plate, comprising: A hole extending through the plate along the longitudinal axis of the hole, the hole comprising: A first plate opening; A second plate opening; A side wall extending from the first plate opening into the hole; and A protrusion projecting inwardly from the side wall towards the longitudinal axis of the hole, the protrusion comprising: A first surface extending from the side wall of the hole between the first plate opening and the second plate opening of the hole, the first surface being coplanar with a first plane intersecting the longitudinal axis at a first angle between 85 degrees and 95 degrees, A second surface disposed between the first surface of the protrusion and the second plate opening of the plate, and An inner wall extending parallel to the longitudinal axis of the hole and defining a protrusion thickness, the inner wall coupling the first surface of the protrusion to the second surface of the protrusion, Wherein for all non-zero angles between 30 degrees and 50 degrees between the longitudinal axis of the bone anchor and the longitudinal axis of the hole, the threads of the threaded head of the bone anchor are configured to engage the protrusion in an interference fit, the protrusion having the protrusion thickness so as not to severely deform the protrusion, thereby locking the bone anchor within the hole of the plate.

2. The bone fixation system according to claim 1, wherein: The inner wall of the protrusion has a first portion having a first distance from the longitudinal axis measured orthogonally to the longitudinal axis; and The inner wall of the protrusion has a second portion having a second distance from the longitudinal axis measured orthogonally to the longitudinal axis, the second distance being greater than the first distance.

3. The bone fixation system according to claim 2, wherein: The inner wall of the protrusion has a third portion having a third distance from the longitudinal axis measured orthogonally to the longitudinal axis, the third distance being greater than the first distance.

4. The bone fixation system according to claim 3, wherein: The third distance is greater than the second distance; The second distance is measured from the position of the second portion that is farthest from the longitudinal axis compared to other positions of the second portion; The third distance is measured from the position of the third portion that is farthest from the longitudinal axis of the hole compared to other positions of the third portion.

5. The bone fixation system according to claim 3, wherein: The inner wall of the protrusion defines an inner circumference of the protrusion; The inner wall of the protrusion has a fourth portion having the first distance from the longitudinal axis; The first portion is between the second portion and the third portion; The third portion is between the first portion and the fourth portion.

6. The bone fixation system according to claim 2, wherein the first plane is orthogonal to the longitudinal axis of the hole.

7. The bone fixation system according to claim 1, wherein the first plane is orthogonal to the longitudinal axis of the hole.

8. The bone fixation system according to claim 1, wherein the second surface is coplanar with a second plane that intersects the longitudinal axis of the hole at a second angle between 85 degrees and 95 degrees.

9. The bone fixation system according to claim 8, wherein the second plane is orthogonal to the longitudinal axis of the hole.

10. The bone fixation system according to claim 8, wherein the first plane is orthogonal to the longitudinal axis of the hole.

11. The bone fixation system according to claim 1, wherein: the first surface is a first distance from the first plate opening, the first distance being measured parallel to the longitudinal axis; and the second surface of the protrusion is set at a second distance from the second plate opening, the second distance being less than the distance from the first plate opening of the hole to the second surface of the protrusion, the second distance being measured parallel to the longitudinal axis.

12. The bone fixation system according to claim 1, wherein: the plate does not include threads between the first plate opening and the second plate opening; the first plate opening directly engages the first outer surface of the plate; the second plate opening directly engages the second outer surface of the plate; the first outer surface of the plate faces away from the second outer surface of the plate.

13. The bone fixation system according to claim 2, wherein: the first plate opening has a first maximum diameter measured orthogonally to the longitudinal axis of the hole; the second plate opening has a second maximum diameter measured orthogonally to the longitudinal axis of the hole, the second maximum diameter being greater than the first maximum diameter of the first plate opening.

14. The bone fixation system according to claim 13, wherein: the first maximum diameter of the first plate opening is greater than the maximum diameter of the threaded head of the bone anchor; the protrusion forms a ring surrounding the interior of the hole, the ring having a minimum diameter less than the maximum diameter of the threaded head of the bone anchor.

15. The bone fixation system according to claim 1, wherein: at least a portion of the head of the bone anchor is included in the nearest fifth of the bone anchor; the portion of the head of the bone anchor includes threads.

16. The bone fixation system according to claim 15, wherein: the threads of the threaded body of the bone anchor have a first thread height; the threads of the portion of the head of the bone anchor have a second thread height, the second thread height being less than the first thread height.

17. The bone fixation system according to claim 16, wherein: the threads of the threaded body of the bone anchor have a first crest width, the first crest width being less than the second crest width of the threads of the threaded head of the bone anchor.

18. The bone fixation system according to claim 14, wherein: the bone anchor includes a tapered portion that includes thread roots that taper outwardly at an angle between 10 degrees and 25 degrees; the protrusion forms a ring surrounding the interior of the hole, the ring including a minimum diameter; The maximum diameter of the head of the bone anchor is 5% to 10% larger than the minimum diameter of the ring; At least a portion of the head of the bone anchor is included in the nearest fifth of the bone anchor, and the portion of the head of the bone anchor includes threads; The threads of the portion of the head of the bone anchor have a thread height between 0.0254 mm and 0.3048 mm; The threads of the portion of the head of the bone anchor have a crest width between 0.0508 mm and 0.3048 mm; The first surface is at a distance between 0.254 mm and 1.27 mm measured parallel to the long axis of the hole from the first plate opening; The protrusion includes an inner wall that couples the first surface of the protrusion to the second surface of the protrusion; The inner wall of the protrusion has a second portion of a third distance that is measured orthogonally to the long axis of the hole and is between 0.508 mm and 1.016 mm from the long axis, The third distance is greater than the second distance by a differential distance between 0.127 mm and 0.381 mm; The first surface is at a fourth distance between 0.254 mm and 5.588 mm measured parallel to the long axis of the hole from the second surface; The first portion of the protrusion projects inward from the sidewall of the hole and toward the long axis of the hole by a fifth distance between 0.254 mm and 0.127 mm.

19. A bone fixation system comprising: A bone anchor having a tapered head with threads; And A plate including a void, the void including one of a countersink or a counterbore, and including; A protrusion projecting inwardly toward the long axis of the void, the protrusion including: A first surface coplanar with a first plane A second surface, and An inner wall extending parallel to the long axis of the void and defining a protrusion thickness, the inner wall coupling the first surface of the protrusion to the second surface of the protrusion; Wherein: No portion of the void has threads; The inner wall includes a protrusion along its perimeter; and For all non-zero angles between 30 degrees and 50 degrees between the long axis of the bone anchor and the long axis of the void, the threads of the head of the bone anchor are configured to engage the protrusion in an interference fit, the protrusion having the protrusion thickness such that the protrusion is not severely deformed, thereby locking the bone anchor within the hole of the plate.

20. The bone fixation system according to claim 19, wherein: The void includes the countersink; The countersink includes a platform, the platform including the first surface; and The first plane is orthogonal to the long axis of the void.

21. The bone fixation system according to claim 19, wherein: The bone anchor includes a material; The plate includes the material; The bone anchor is integral; The plate is integral.

22. The bone fixation system according to claim 20, wherein the plate does not include an elastic member.

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