WO2025238592A1

WO2025238592A1 - Bone screw fixation device for cell proliferation, bone integration, and enhanced fixation

Info

Publication number: WO2025238592A1
Application number: PCT/IB2025/055085
Authority: WO
Inventors: Olumide ARUWAJOYE; Brian Butler; Julien Prevost
Original assignee: Warsaw Orthopedic Inc
Current assignee: Warsaw Orthopedic Inc
Priority date: 2024-05-16
Filing date: 2025-05-15
Publication date: 2025-11-20
Anticipated expiration: 2026-11-16

Abstract

A bone screw extending from a distal end portion and a proximal end portion having an optional cannulation is disclosed. The bone screw may include a first threaded section and a second threaded section extending contiguously from the distal end portion toward the proximal end portion defining a dual lead thread pattern. The bone screw may further comprise a third threaded section at distal end portion of the bone screw having a wider thread crest relative to the first and second threaded sections. In some embodiments, the bone screw also comprises a threaded sleeve portion that is configured to receive the shaft of the bone screw. The bone screw also may comprise roughened surface features to provide sufficient osseointegration, cellular attachment, and osteoblast maturation. Methods for manufacturing the bone screw and providing roughened surface features are also disclosed.

Description

BONE SCREW FIXATION DEVICE FOR CELL PROLIFERATION, BONE INTEGRATION, AND ENHANCED FIXATION

FIELD

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63/648,290, filed 16 May 2024, the entire content of which is incorporated herein by reference.

[0002] The present technology is generally to the field of bone screws, and more particularly relates, for example, to a bone screw having multiple threaded sections or assembled from multiple portions and may include roughened surface features adapted for engagement with different regions of bone, and a method for using or forming the same.

BACKGROUND

[0003] Spinal pathologies and disorders such as kyphosis, scoliosis, and other spinal abnormalities, degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, rumor, scoliosis and other curvature abnormalities, kyphosis and fracture may result from factors including trauma, disease and degenerative conditions caused by injury and aging. Spinal disorders typically result in symptoms including deformity, pain, nerve damage, and partial or complete loss of mobility.

[0004] Non-surgical treatments, such as medication, rehabilitation and exercise can be effective, however, may fail to relieve the symptoms associated with these disorders. Surgical treatment of these spinal disorders includes correction, fusion, fixation, discectomy, laminectomy and implantable prosthetics. As part of these surgical treatments, spinal constructs including bone screws are often used to provide stability to a treated region. Such bone screws are traditionally manufactured using a machining technique. However, the present bone screws lack advantageous surface features that facilitate a sufficient osseointegration between the bone screw and the adjacent boney structure. This disclosure describes an improvement over these prior technologies. SUMMARY

[0005] The techniques of this disclosure generally relate to manufacturing of, for example, a bone screw with roughened surface features for osseointegration. In one aspect, the method may comprise: (a) forming a head and shaft by applying a subtractive manufacturing process to a material to provide a flat superior surface and a flat inferior surface, and opposing curved side surfaces normal to the superior and the inferior surface on the shaft, wherein the opposing curved side surfaces comprise a threadform; (b) forming the superior shaft plate and an inferior shaft plate respectively, by an additive manufacturing process, wherein the superior and the inferior shaft plates each comprise a flat surface, a curved surface opposite the flat surface, and a threadform on the curved surface; and (c) attaching the flat surfaces of the superior shaft plate and the inferior shaft plate to the flat superior and inferior surfaces of the shaft.

[0006] In some embodiments, the method may further comprise adding microscale and nanoscale features to the bone screw, the method comprising: masking a first portion of the bone screw with a maskant to obtain a maskant-bone screw assembly with a tight seal formed around the first portion of the bone screw; roughening surface of unmasked portion of the bone screw by grit blasting, chemical etching, or both; and removing the maskant from the bone screw, wherein an anodized finish remains on the first portion of the bone screw and removed from the unmasked portion of the bone screw.

[0007] In another aspect, a bone screw is provided. The bone screw comprises a superior shaft plate and an inferior shaft plate having a flat surface, a curved surface opposite the flat surface, and a threadform on the curved surface, wherein the superior shaft plate and the inferior shaft plate each include lattice structures on exposed surfaces. The bone screw further comprises a shaft extending along a longitudinal axis between a distal end portion and a proximal end portion, the shaft comprising a flat superior surface, a flat inferior surface opposite the superior surface, and opposing curved side surfaces, wherein the curved side surfaces comprise a threadform extending from the distal end portion towards the proximal end portion defining a threaded section, and a head extending from the proximal end portion of the shaft, wherein the shaft is disposed between the superior shaft plate and the inferior shaft plate. The threaded section on the shaft and the threadform on the superior and the inferior shaft plates are aligned to form a continuous helical thread, and wherein the bone screw comprises a passageway extending longitudinally from the head through the shaft defining a cannulation, and wherein the bone screw is coaxial with the longitudinal axis from the distal end portion to the head.

[0008] In another aspect, another embodiment of bone screw is provided. The bone screw comprises a threaded sleeve portion extending along a longitudinal axis between a distal end portion and a proximal end portion, at least a portion of the threaded sleeve having a plurality of minor grooves and a plurality of lattice structures on exposed surfaces thereof, and a sleeve channel extending longitudinally from the distal end portion to the proximal end portion of the threaded sleeve. The bone screw further comprises a shaft extending along a longitudinal axis between a distal end portion and a proximal end portion, the distal end portion having a threadform; and a head extending from the proximal end portion of the shaft. The bone shaft of the bone screw is disposed in the sleeve channel of the threaded sleeve portion, and the shaft and the head comprise a passageway extending longitudinally from the head through the shaft defining a canulation.

[0009] Yet in another aspect, another embodiment of a bone screw is provided. The bone screw comprises a shaft extending along a longitudinal axis between a distal end portion and a proximal end portion, comprising a threaded section extending from the distal end portion towards the proximal end portion, the shaft comprising at least one aperture extending through the shaft in a direction normal to the longitudinal axis; and a head extending from the proximal end portion of the shaft. The bone screw may be coaxial with the longitudinal axis from the distal end portion to the head and the bone screw may comprise a passageway extending longitudinally from the head through the shaft defining a cannulation, and wherein the aperture is in communication with the passageway.

[0010] The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0011] The following drawings are illustrative of particular embodiments of the present disclosure and therefore do not limit the scope of the present invention. The drawings are not to scale and are intended for use in conjunction with the explanations in the following detailed description.

[0012] FIG. 1 is a perspective view of a bone screw of the present disclosure.

[0013] FIG. 2 is an exploded parts view of the bone screw of FIG. 1.

[0014] FIG. 3 is an enlarged perspective view of a shaft endplate in FIG. 2.

[0015] FIG. 4 is a side cross-sectional perspective view of bone screw of FIG. 1.

[0016] FIG. 5 is a rear perspective view of a bone screw of FIG. 1.

[0017] FIG. 6 is a perspective view of another embodiment of a bone screw of the present disclosure.

[0018] FIG. 7 is an exploded parts view of the bone screw of FIG. 6.

[0019] FIG. 8 is a side cross-sectional perspective view of bone screw of FIG. 6.

[0020] FIG. 9 is a side cross-sectional perspective view of sleeve portion of FIG. 6.

[0021] FIG. 10 is an exploded parts view of another embodiment of a bone screw of the present disclosure.

[0022] FIG. 11 is a side perspective view of bone screw of FIG. 10.

[0023] FIG. 12 is a side cross-sectional perspective view of bone screw of FIG. 10.

[0024] FIG. 13 is an enlarged perspective view of additive portion in FIG. 10.

[0025] FIG. 14 a perspective view of another embodiment of additive portion of the present disclosure.

[0026] FIG. 15 is a flow diagram of an illustrative method for adding surface roughness to a bone screw.

DETAILED DESCRIPTION

[0027] Embodiments of the present disclosure relate generally, for example, to spinal stabilization systems, and more particularly, for example, to a bone screw used as spinal stabilization systems. Exemplary embodiments of the devices and methods are described below with reference to the Figures. [0028] The following discussion omits or only briefly describes certain conventional features related to surgical systems for treating the spine, which are apparent to those skilled in the art. It is noted that various embodiments are described in detail with reference to the drawings, in which like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the claims appended hereto. Additionally, any examples set forth in this specification are intended to be non-limiting and merely set forth some of the many possible embodiments for the appended claims. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations.

[0029] Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc. It must also be noted that, as used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless otherwise specified, and that the terms "comprises" and/ or "comprising," when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. [0030] Terms such as “same,” “equal,” “planar,” “coplanar,” “parallel,” “perpendicular,” etc. as used herein are intended to encompass a meaning of exactly the same while also including variations that may occur, for example, due to manufacturing processes. The term “substantially” may be used herein to emphasize this meaning, particularly when the described embodiment has the same or nearly the same functionality or characteristic, unless the context or other statements clearly indicate otherwise. Additionally, it shall be understood that the term “about” encompasses a variation of at least +/- 10% from the example values provide herein.

[0031] The following discussion includes a description of, for example, a bone screw and related methods of manufacturing the bone screw in accordance with the principles of the present disclosure. Alternate embodiments are also disclosed. Reference is made in detail to the exemplary embodiments of the present disclosure, which are illustrated in the accompanying figures. FIGS. 1-14, there are illustrated components of a bone screw, such as, for example a bone screw 100, 200, or 300.

[0032] The following discussion includes a description of a bone screw, a method of manufacturing a bone screw, related components, and method of providing a surface roughening of a bone screw in accordance with the principles of the present disclosure. Alternate embodiments are disclosed. Reference is made in detail to the exemplary embodiments of the present disclosure, which are illustrated in the accompanying figures. Turning to FIGS. 1-5, there are illustrated components of a bone screw 100.

[0033] Bone screw 100 is shown as comprising, for example, a spinal screw, a sacropelvic screw, or a pedicle screw. The spinal screw can include, but is not limited to, screws compatible with the Medtronic ModuLeX™ spinal system, Solera™ spinal system, or Ballast™ spinal system. For example, Ballast™ spinal system includes, for example a shaft designed for sacroiliac fixation in spinal procedures and offers, for example, a universal connection design that allows for different head assemblies and/or tulips to be connected onto a bone screw shaft. However, the present solution is not limited in this regard. Bone screw 100 could include other types of components that can be implanted in a person’s body and/or could stimulate osseointegration. The components of bone screw 100 may be fabricated from various biologically acceptable materials suitable for medical applications, including metals, synthetic polymers, ceramics, bone material and/or their composites. For example, the components, individually or collectively, can be fabricated from materials such as stainless steel alloys, commercially pure titanium, titanium alloys, Grade 5 titanium, superelastic titanium alloys, cobalt-chrome alloys, superelastic metallic alloys (e.g., Nitinol, super elastoplastic metals, such as GUM METAL®), ceramics and composites thereof such as calcium phosphate (e.g., SKELITE™), thermoplastics such as polyaryletherketone (PAEK) including polyetheretherketone (PEEK), polyetherketoneketone (PEKK) and polyetherketone (PEK), carbon-PEEK composites, PEEK-BaSCL polymeric rubbers, polyethylene terephthalate (PET), fabric, silicone, polyurethane, silicone-polyurethane copolymers, polymeric rubbers, polyolefin rubbers, hydrogels, semi-rigid and rigid materials, elastomers, rubbers, thermoplastic elastomers, thermoset elastomers, elastomeric composites, rigid polymers including polyphenylene, polyamide, polyimide, polyetherimide, polyethylene, epoxy, bone material including autograft, allograft, xenograft or transgenic cortical and/or corticocancellous bone, and tissue growth or differentiation factors, partially resorbable materials, such as, for example, composites of metals and calcium-based ceramics, composites of PEEK and calcium based ceramics, composites of PEEK with resorbable polymers, totally resorbable materials, such as, for example, calcium based ceramics such as calcium phosphate, tri-calcium phosphate (TCP), hydroxyapatite (HA)-TCP, calcium sulfate, or other resorbable polymers such as polyketide, polyglycolide, polytyrosine carbonate, poly caprolactone, polylactic acid or polylactide and their combinations.

[0034] In various embodiments, components of the bone screw 100 may have material composites, including the above-mentioned materials, to achieve various desired characteristics such as strength, rigidity, elasticity, compliance, biomechanical performance, durability and radiolucency, or imaging preference. In some embodiments, the bone screw 100 may be fabricated from a heterogenous material such as a combination of two or more of the above-described materials. In various embodiments, bone screw 100 may also have an anodized surface finish. Anodized surface finish on certain portions of the bone screw improves mechanical integrity and human factors feature for easy bone screw identification. [0035] Referring to FIGS. 1 and 2, a perspective and an exploded parts view of an embodiment of bone screw 100 is shown. The bone screw 100 may extend along a longitudinal axis Al and includes a distal end portion lOOd and a proximal end portion lOOp. The bone screw 100 may include a shaft portion 102 adapted for engagement within a bone, and a head portion 101 adapted for coupling with a receiver or an implant (not shown). In various embodiments, the receiver may comprise a screw tulip configured for top loading, or a cap receiver configured for bottom loading. Further details regarding the receiver mechanisms are illustrated and described, for example in U.S. Patent No. 5,643,263 to Simonson, U.S. Patent No. 5,947,967 to Barker, U.S. Patent No. 6,471,703 to Ashman, and U.S. Provisional Patent Application No. 63/497,038 to Gallagher et al., the entire contents of which are incorporated herein by reference. In some embodiments, the receiver may include various bone screw configurations, including but not limited to an interbody screw, a uni-axial screw, a fixed angle screw, a multi-axial screw, a side loading screw, a sagittal adjusting screw, a transverse sagittal adjusting screw, an awl tip, a dual rod multi-axial screw, a midline lumbar fusion screw, or a sacral bone screw. In various embodiments, a multi-axial screw configuration may, for example, comprise bone screw 100 coupled to receiver at head 101, pivoting about the receiver at an angulation from about -40° to about 40°, about -30° to about 30°, about -20° to about 20°, about -10° to about 10°, or from about -5° to about 5° from longitudinal axis Al. In various embodiments, the multi-axial screw configuration may comprise bone screw 100 having 360° directional freedom relative to and about head 101 such that shaft 102 is selectively aligned for ration in a plane relative to receiver. In various embodiments, bone screw 100 may be coupled to the receiver in a top loading configuration, in which bone screw 100 is inserted through aperture of the receiver from distal end portion lOOd to head 101. In some embodiments, bone screw 100 may be coupled to the receiver in a bottom loading configuration, in which head 101 is loaded onto an anchor member of the receiver. Further details regarding bone screw loading are illustrated and described, for example in U.S. Patent No. 8,002,806 to Justis and U.S. Patent No. 11,426,223 to Ballard et al., the entire contents of which are incorporated herein by reference.

[0036] In various embodiments, the bone screw 100 may be fabricated from a monolithic material by one or more subtractive manufacturing process to provide a flat superior surface 109, an inferior surface 110, and two opposing curved side surfaces 112 and 111 having a threadform extending from distal end portion 1 lOd towards proximal end portion lOOp defining a threaded section. In various embodiments, the subtractive manufacturing process may include, not is not limited to machining, cutting, grinding, grinding, electrical discharge machining, milling, lathing, burring sawing, or sanding.

[0037] In some embodiments, the bone screw 100 may also include a distal tip 104 that is configured to penetrate bone at various insertion angles. In various embodiments, the distal tip 104 may be tapered or pointed. In various embodiments, the tip may comprise a flat, pointed, fluted, sharp, or self-tapping tip to facilitate the entry of the screw into boney structure.

[0038] In some embodiments, the bone screw 100 may comprise a superior (inferior) shaft plate 120 (130), each having a flat surface 122 (132), a curved surface 121 (131) opposite the flat surface 122 (132), and a threadform 123 (133) on curved surface 121 (131). In some embodiments, superior shaft plate 120 and inferior shaft plate 130 may comprise same material as shaft 102. As shown in FIG. 2 and more clearly illustrated in FIG. 3, superior shaft plate 120 and inferior shaft plate may comprise a plurality of lattice structures 124 and 134 on exposed surfaces of superior shaft plate 120 and inferior shaft plate 130 that are configured for bony ongrowth and/or through-growth. In various embodiments, lattice structures 124 and 134 may comprise a circular, triangular, diamond, square, rectangular, hexagonal shape, or a combination thereof. In various embodiments, the lattice structure may comprise a trabecular lattice that mimics the bone trabecular bone structure to provide a conduit for bony on growth and through growth.

[0039] In various embodiments, the shaft 102 and superior (inferior) shaft plate 120 (130) may be roughened to stimulate osseointegration for creating a direct structural and functional connection between living bone and the surface of the bone screw. The roughness of the bone screw 100 may be on a micron- or nanoscale-levels. The textured surface features are designed, for example, to mimic a bone remodeling process. The textured surface features may comprise micron scale or microscale valleys or pores that correlate to osteoclastic resorption pits. In some embodiments, nanoscale features such as striations, steps, or nanopores may be formed within the microscale features.

[0040] In various embodiments, different parts of the bone screw including but not limited to, the superior shaft plate, inferior shaft plate, and the shaft may comprise different or varied surface features. In some embodiments, the superior shaft plate and the inferior shaft plate may comprise microscale features while the shaft of the bone screw may comprise both microscale and nanoscale features. This variation in surface features (i.e., varied porosity between shaft and shaft plates) for various embodiments may provide ensures improved fixation to the bony structures and promote bone-growth around the bone screw as well as channel the right tissue response (e.g. mesenchymal stem cells differentiating to osteoblasts) and a nutrient rich environment for bony on growth.

[0041] In various embodiments, shaft 102 may be disposed between superior shaft plate 120 and inferior shaft plate 130 in a configuration such that flat surface 122 of superior shaft plate 120 is in contact with flat superior surface 109 of shaft 102, and flat surface 132 of inferior shaft plat 130 is in contact with flat inferior surface 110 of shaft 102. In some embodiments, superior shaft plate 120 and inferior shaft plate 130 are mechanically attached to shaft 102 by a weld, a thread, and adhesive or a stake forming the bone screw. In various embodiments, superior shaft plate 120 and inferior shaft plate 130 may be fabricated by one or more additive manufacturing method including 3D printing, injection molding, deposition modeling, selective layer sintering, direct metal laser sintering, selective laser melting, electron beam melting, layered object manufacturing or stereolithography. Further details regarding the additive manufacturing for fabricating bone screw are illustrated and described, for example in U.S. Patent No. 11,229,465 to Tempco et al., the entire contents of which are incorporated herein by reference.

[0042] In some embodiments, when superior shaft plate 120 and inferior shaft plate 130 are attached to shaft 102, threadform 123 (133) on superior (inferior) shaft plate may be aligned with threadform 103 on shaft may be aligned to form a continuous helical thread. In various embodiments, the threaded section may comprise a first threaded having a thread pitch Pl section extending from distal end portion lOOd of shaft 102 towards proximal end portion lOOp, and a second threaded section having a thread pitch P2 extending contiguously from first threaded section toward the proximal end portion lOOp of shaft 102. In some embodiments, the first threaded section may include first helical thread having a single thread type extending along shaft 102 into the second threaded section comprising a second helical thread interleaved with the first helical thread defining a dual lead thread pattern. In various embodiments the first helical thread and the second helical thread may have substantially equal thread pitch. In some embodiments, the second threaded section may comprise a finer thread pattern relative to the first threaded section resulting from the dual lead thread pattern, i.e., interleaved second helical thread with first helical thread.

[0043] In various embodiments, bone screw 100, may be provided with a passageway 108 extending longitudinally from head 101 through distal portion lOOd and partially or entirely therethrough defining a cannulation. Referring to FIG. 4, a side cross-sectional perspective view of bone screw 100 is shown. In some embodiments, bone screw 100 may include a straight flute 106 (as shown in FIG. 1) on curved side surfaces 111 and 112 (as shown in FIG. 2) defining a plurality of transverse or lateral passageways/fenestrations 107 that communicate with the longitudinal cannulation defining the fenestration openings. In various embodiments, cannulation 108 and fenestration openings 107 may be used to deliver growth agents such as bone graft materials or, for example, bone cement, from proximal end portion lOOp of bone screw 100 to distal end portion lOOd into areas of the bone axially or laterally adjacent the distal end portion lOOd or other portions of shaft 102.

[0044] In various embodiments, bone screw 100 may comprise an additional threaded section on distal end portion lOOd of shaft 102 that extends along to the first threaded section described above. In some embodiments, the third threaded section may comprise a third helical thread 105 that is interleaved with the first helical thread. In various embodiments, the third helical thread may have a crest thickness that is wider than the first helical thread. In various embodiments, the third threaded portion provides the thicker, wider or blunt start thread at distal lOOd of the bone screw, which prevents the bone screw starting off-axis to the attached receiver or spinal system, and allows the bone screw to engage with the boney structure for sacroiliac fixation.

[0045] Now referring to FIG. 5, a rear perspective view of bone screw 100 is shown. In various embodiments, bone screw 100 may comprise head 101 extending coaxially from proximal end portion lOOp along longitudinal axis Al. In various embodiments, passageway 108 may extend from proximal end portion lOOp through distal end of head 101. In various embodiments, bone screw 100 may include configurations where head 101 is spherical, cylindrical, conical, oval, or of other various shapes or combinations of shapes including ledges, flat surfaces or steps and may further include, for example, screws that do not have a head. In various embodiments, head 101 may include features such as socket 109 that allow for releasable engagement with a driving tool or instrument (not shown) such as, for example, a screwdriver for screwing bone screw 100 into boney structures. In some embodiments, socket 109 may have various shapes such as, for example, oval, hexagonal, rectangular, a cross, i.e., Phillips head, a linear, straight head, or other polygonal shapes to provide engagement between head 101 and the driver tool. In various embodiments, head 101 may be or may not be anodized.

[0046] In various embodiments, bone screw 100 may further comprise roughened surface features on shaft 102, superior shaft plate 120, inferior shaft plate 130, and/or head 101. In some embodiments, roughened surface features may comprise microscale feature, nanoscale feature, or both. In some embodiments, roughened surface features may be applied by grit blasting, chemical etching, or both by the method described in this disclosure. [0047] The surface treatment provided by the present invention may include roughened surface with microscale and nanoscale features that is designed to improve fixation to the adjacent bone. In various embodiments, the first level is the microscale features with dimensions correlating to osteoclastic resorption pits (e.g., 1-1000 microns; valleys/pores are approximately 20-500 pms in diameter and 10-30 pm deep in case of valleys). These microstructures may, for example, provide or improve biomimicry at this level which promote osteointegration and bone growth at this level.

[0048] In various embodiments, different parts of the bone screw including but not limited to, the superior shaft plate, inferior shaft plate, and the shaft may comprise different or varied surface features. In some embodiments, the superior shaft plate and the inferior shaft plate may comprise microscale features while the shaft of the bone screw may comprise both microscale and nanoscale features. This variation in surface features (i.e., varied porosity between shaft and shaft plates) may, for example, improve fixation to the bony structures and promote bone-growth around the bone screw as well as channel the right tissue response (e.g. mesenchymal stem cells differentiating to osteoblasts) and a nutrient rich environment for bony on growth.

[0049] FIGS. 6 and 7 are assembled and exploded perspective views, respectively, of a second example of bone screw 200 that may be manufactured by the methods described in this disclosure. Bone screw 200 may have the same, similar and/or substantially the same features and functionality, as well as fabricated using the similar and/or substantially the same method as explained above with respect to bone screw 100. For example, bone screw 200 may a shaft 202 extending longitudinally along Bl from distal end portion 200d towards proximal end portion 200p and head 201 extending from proximal end portion 200p. As seen best in FIGS. 6 and 7, bone screw 200 may comprise a shaft 202 extending along a longitudinal axis Bl between a distal end portion 200d and proximal end portion 200p. In various embodiments, distal end portion 200d may comprise a tip 204 that is configured to penetrate the bone having similar and/or substantially the same features and functionality as tip 104 of bone screw 100. In some embodiments, bone screw 200 may comprise a head 201 extending from proximal end portion 200p of shaft 202 having similar and/or substantially the same features and functionality as head 101 of bone screw 100 (FIG. 5). As seen best in FIG. 8, in some embodiments, head 201 and shaft 202 may be provided with a passageway 208 extending longitudinally from head 201 through distal portion 200d and partially or entirely therethrough defining a cannulation. In some embodiments, shaft 202 may comprise plurality of micropores (not shown) that are in communication with passageway 208 and configured to deliver growth agents such as bone graft materials from passageway 208 through the micropores.

[0050] In various embodiments, bone screw 200 may comprise a modular threaded sleeve portion 210 extending along a longitudinal axis B2 between distal end portion 210d and proximal end portion 21 Op. In some embodiments, sleeve portion 210 may comprise channel 214 extending through longitudinal axis B2 that is configured to receive shaft 202 of bone screw, i.e., shaft 202 of bone screw may be disposed in channel 214. As best seen in FIG. 6, in a combined configuration sleeve portion 210 and shaft portion 202 are axially aligned such that longitudinal axis Bl and longitudinal axis B2 are coaxial. Similarly, in a combined configuration, distal end portions 200d and 21 Od, and proximal end portions 200p and 21 Op may refer to same positions along bone screw 200.

[0051] In various embodiments, sleeve portion 210 may comprise a threaded section comprising threadform 211 extending from distal end portion 210d towards proximal end portion 21 Op, and a second threaded section extending contiguously from the first threaded section towards to proximal end portion 21 Op. In some embodiments, the first threaded section may include a first helical thread having a single thread type extending into the second threaded section, and the second threaded section may comprise a second helical thread interleaved with the first helical thread to define the second threaded section. In various embodiments, the first helical thread and the second helical thread may have a substantially equal thread pitch. In various embodiments, bone screw 200 may comprise an additional threaded section on distal end portion 200d of shaft 202 that extends along to the first threaded section of sleeve portion 210 described above. In some embodiments, the third threaded section may comprise a third helical thread 205 positioned at tip 204 of shaft 202 that is interleaved with the first helical thread. In various embodiments, the third helical thread may have a crest thickness that is wider than the first helical thread for sacroiliac fixation. In this configuration, the third helical thread 205 of the shaft is in an alignment with the threadform 211 of the sleeve portion 210 such that when the bone screw 200 is inserted into the surgical area, the continuous threadform allows for a facile insertion of bone screw 200 and sleeve portion 210.

[0052] In various embodiments, as seen in FIG. 6, length of sleeve portion 210 may be substantially smaller than length of shaft 202 such that sleeve portion 210 partially encloses shaft 202. In this configuration, shaft 202 may have additional helical thread at the proximal end of shaft 202 that is aligned with threadform 211 to form a continuous helical thread. [0053] In various embodiments, sleeve portion 210 may comprise a plurality of minor craters or grooves 212 on surface exposed surface of sleeve portion 210 that are configured to increase friction between the sleeve and adjacent bony surface. In various embodiments, sleeve portion 210 may comprise a plurality of lattice spaces 213 on expose surface of sleeve portion 210 thereof defining a plurality of transverse or lateral passageways that communicate with channel 214 that are configured for bony ongrowth and/or through-growth and delivery of growth agents. In various embodiments, micropores on shaft 202 that are in communication with passage 208 may be in communication with lattice spaces 213 and may be used to deliver growth agents such as bone graft materials or, for example, bone cement, from proximal end portion 200p of bone screw 200 to distal end portion 200d into areas of the bone axially or laterally adjacent sleeve portion 210. In various embodiments, lattice spaces 213 may comprise a circular, triangular, diamond, square, rectangular, or hexagonal shape. As seen in FIG. 7, in some embodiments, shaft 202 may comprise one or more keyed slot 206 along shaft 202 that may be used to mate and align the position of one or more inner notch 215 extending through the inner walls of sleeve portion 210 to prevent independent rotational movement of sleeve portion 210, and to align threads 211 of sleeve 210 with the threads of shaft 202 for a continuous threadform. As best seen in FIGS. 7 and 9, in some embodiments, sleeve portion 210 may comprise a spring tab 216 having a protrusion 217 in channel 214 that is configured to contact with shaft portion 202 and provide friction, stability, and alignment of shaft 202 and sleeve 210 such that in a combined configuration, there is no movement of sleeve portion 210 along body of shaft 202. In various embodiments, sleeve portion 210 may be attached to shaft 202 by a weld, a thread, and adhesive or a stake forming bone screw 200. [0054] In various embodiments, channel portion 214 may comprise cross-section having a circular, oval, elliptical, or polygonal geometry. In some embodiments, generally a circular cross-section may comprise an inner diameter that is uniform throughout channel 214. In some embodiments, a polygonal cross-section geometry may comprise a regular geometry defined by a longest length between two vertices through the center (i.e., longitudinal axis B2) of the polygonal cross-section. In some embodiments, sleeve channel 214 may comprise a hexagonal cross-section. In various embodiments, shaft 202 may comprise cross-section having the same shape as channel 214 and a slightly smaller outer diameter as an inner diameter of channel 214 such that shaft 202 may be inserted into channel 214 of sleeve portion 210.

[0055] In some embodiments, channel portion 214 may comprise a frustoconical crosssection having a first inner diameter at distal end portion 21 Od and a slightly larger second inner diameter at proximal end portion 21 Op. In this configuration, corresponding shaft 202 may comprise a frustoconical cross-section having a first outer diameter that is slightly smaller than the first inner diameter of channel 214 and a second outer diameter that is slightly smaller than the second inner diameter of channel 214. In various embodiments, base of frustoconical cross-section of sleeve 214 and shaft 202 may comprise a non-circular geometry including, but not limited to a polygonal geometry having first and second diameters defined as longest length between two vertices through the center (i.e., longitudinal axis B2).

[0056] In various embodiments, sleeve portion 210 may further comprise roughened surface features including microscale feature, nanoscale feature, or both. In some embodiments, roughened surface features may be applied by grit blasting, chemical etching, or both by the method described in this disclosure. In various embodiments, sleeve portion 210 may be fabricated by one or more additive manufacturing method including 3D printing, injection molding, deposition modeling, selective layer sintering, direct metal laser sintering, selective laser melting, electron beam melting, layered object manufacturing or stereolithography.

[0057] Now referring to FIGS. 10 and 11, an exploded perspective view (FIG. 10) and side view (FIG. 11) of a third example of bone screw 300 that may be manufactured by the methods described in this disclosure are shown. Bone screw 300 may have the same, similar and/or substantially the same features and functionality, as well as fabricated using the similar and/or substantially the same method as explained above with respect to bone screw 100 and 200. For example, bone screw 300 may a shaft 302 extending longitudinally along Cl from distal end portion 300d towards proximal end portion 300p and head 301 extending from proximal end portion 300p. As seen best in FIGS. 10 and 11, bone screw 300 may comprise a shaft 302 extending along a longitudinal axis Cl between a distal end portion 300d and proximal end portion 300p. In various embodiments, distal end portion 300d may comprise a tip 304 that is configured to penetrate the bone having similar and/or substantially the same features and functionality as tip 104 (204) of bone screw 100 (200). In some embodiments, bone screw 300 may comprise a head 301 extending from proximal end portion 300p of shaft 302 having similar and/or substantially the same features and functionality as head 101 (201) of bone screw 100 (200).

[0058] As seen best in FIG. 11 and 12, in some embodiments, head 301 and shaft 302 may be provided with a passageway 308 extending longitudinally from head 301 through distal portion 300d and partially or entirely therethrough defining a cannulation. In some embodiments, bone screw 300 may comprise at least one aperture 307 extending through shaft 302 in a direction normal or transverse to longitudinal axis Cl that is in communication with passageway 308 configured to deliver growth agents such as bone graft materials or, for example, bone cement, from proximal end portion 300p of bone screw 300 to distal end portion 300d into areas of the bone axially or laterally adjacent the distal end portion 300d or other portions of shaft 302. In some embodiments, aperture 307 may have a generally rectangular shape but other shapes such as circular, oval, elliptical or polygonal shapes may be contemplated. In some embodiments, aperture 307 may be configured to receive an additive portion 310 comprising a roughened and porous surface that may be disposed in aperture 307 at both aperture ends. In various embodiments, the additive portion may be substantially same shape and size as the aperture. In some embodiments, the additive portion may be mechanically attached to shaft 302 by a weld, a thread, and adhesive or a stake forming the bone screw. [0059] In various embodiments, additive portion may be fabricated by one or more additive manufacturing method including 3D printing, injection molding, deposition modeling, selective layer sintering, direct metal laser sintering, selective laser melting, electron beam melting, layered object manufacturing or stereolithography to provide to provide macroscale roughened features such as valleys, pits, or pores in the size ranging from 0.01 pm- 10 mm. In various embodiments, the microscale features may comprise valleys or pores with dimensions correlating to osteoclastic resorption pits (e.g., 1-1000 microns; valleys/pores are approximately 20-500 pms in diameter and 10-30 pm deep in case of valleys). These microstructures may, for example, provide or improve biomimicry at this level which promote osteointegration and bone growth at this level.

[0060] As shown best in FIG. 13, additive portion 310 may include roughened surface 311 with microscale and/or nanoscale features that resemble a 3-dimensional mesh-like network present in the additive portion that are designed to improve fixation to the adjacent bone. In various embodiments, the mesh-like structure may comprise pores or spaces within the network that extend through main body 313 of additive portion 310 and are in communication with passageway 308 of bone screw such that when growth agents such as bone graft materials are delivered from proximal end portion 300p of bone screw 300 to distal end portion 300d, growth agents may be released into areas of the bone laterally adjacent to shaft 302 by the spaces of the roughened features 311. In various embodiments additive portion 310 may comprise threadform with thread 312 that aligns with thread of threadform 303 to form a continuous helical thread along shaft 302 of bone screw 300.

[0061] Now referring to FIG. 14, another embodiment of additive portion 320 is shown. In various embodiments, additive portion 320 may comprise plurality of pores 321 on the surface of additive portion 320 that extends through body 323. In various embodiments, additive portion 320 may comprise an attachment feature 324 that may conform with the shape of the inner wall of passageway 308 such that pores 321 are in communication with passageway 308 of bone screw 300 such that when growth agents such as bone graft materials are delivered from proximal end portion 300p of bone screw 300 to distal end portion 300d, growth agents may be released into areas of the bone laterally adjacent to shaft 302 by pores 321 when additive portion 320 is dispose in aperture 307. In various embodiments additive portion 320 may comprise threadform with thread 322 that aligns with thread of threadform 303 to form a continuous helical thread along shaft 302 of bone screw 300.

[0062] In various embodiments, bone screw 300 may comprise a first threaded section comprising threadform 303 having a thread pitch P3 extending from distal end portion 300d towards proximal end portion 300p, and a second threaded section having a thread pitch P4 extending contiguously from the first threaded section towards to proximal end portion 300p. In some embodiments, the first threaded section may include first helical thread having a single thread type extending along shaft 302 into the second threaded section comprising a second helical thread interleaved with the first helical thread defining a dual lead thread pattern. In some embodiments, the second threaded section may comprise a finer thread pattern relative to the first threaded section resulting from the dual lead thread pattern, i.e., interleaved second helical thread with first helical thread.

[0063] In various embodiments, the first helical thread and the second helical thread may have substantially equal thread pitch. In some embodiments, the second threaded section may comprise a finer thread pattern relative to the first threaded section. In various embodiments, bone screw 300 may comprise an additional threaded section on distal end portion 300d of shaft 302 that extends along to the first threaded section described above. In some embodiments, the third threaded section may comprise a third helical thread 305 that is interleaved with the first helical thread. In various embodiments, the third helical thread may have a crest thickness that is wider than first helical thread for sacroiliac fixation.

[0064] In various embodiments, bone screw 300 may further comprise roughened surface features on shaft 302, threadforms 303 and 305. In some embodiments, roughened surface features may comprise microscale feature, nanoscale feature, or both. In some embodiments, roughened surface features may be applied by grit blasting, chemical etching, or both by the method described in this disclosure.

[0065] Another aspect of the present disclosure is related to a method of manufacturing of embodiments of bone screw of present disclosure. In various embodiments, the method may comprise forming a head and shaft of bone screw by applying a subtractive manufacturing process to a material. In various embodiments, the subtractive manufacturing process may be applied to provide a flat superior surface and a flat inferior surface and opposing curved side surfaces having a threadform as exhibited by bone screw 100. In various embodiments, the subtractive manufacturing process may include, not is not limited to machining, cutting, grinding, grinding, electrical discharge machining, milling, lathing, burring sawing, or sanding. In some embodiments, the material may comprise various biologically acceptable materials suitable for medical applications, including metals, synthetic polymers, ceramics, bone material and/or their composites. For example, the components, individually or collectively, can be fabricated from materials such as stainless steel alloys, commercially pure titanium, titanium alloys, Grade 5 titanium, superelastic titanium alloys, cobalt-chrome alloys, superelastic metallic alloys (e.g., Nitinol, super elastoplastic metals, such as GUM METAL®), ceramics and composites thereof such as calcium phosphate (e.g., SKELITE™), thermoplastics such as polyaryletherketone (PAEK) including polyetheretherketone (PEEK), poly etherketoneketone (PEKK) and poly etherketone (PEK), carbon-PEEK composites, PEEK-BaSO4 polymeric rubbers, polyethylene terephthalate (PET), fabric, silicone, polyurethane, silicone-polyurethane copolymers, polymeric rubbers, polyolefin rubbers, hydrogels, semi-rigid and rigid materials, elastomers, rubbers, thermoplastic elastomers, thermoset elastomers, elastomeric composites, rigid polymers including polyphenylene, polyamide, polyimide, polyetherimide, polyethylene, epoxy, bone material including autograft, allograft, xenograft or transgenic cortical and/or corticocancellous bone, and tissue growth or differentiation factors, partially resorbable materials, such as, for example, composites of metals and calcium-based ceramics, composites of PEEK and calcium based ceramics, composites of PEEK with resorbable polymers, totally resorbable materials, such as, for example, calcium based ceramics such as calcium phosphate, tri-calcium phosphate (TCP), hydroxyapatite (HA)-TCP, calcium sulfate, or other resorbable polymers such as polyketide, polyglycolide, polytyrosine carbonate, polycaprolactone, polylactic acid or polylactide and their combinations. In some embodiments, the method may further include applying a drilling or boring process along a longitudinal axis of head and shaft to provide a cannulated passageway.

[0066] In some embodiments, the method may further comprise forming a superior and inferior shaft plates by an additive manufacturing process including 3D printing, injection molding, deposition modeling, selective layer sintering, direct metal laser sintering, selective laser melting, electron beam melting, layered object manufacturing or stereolithography. In various embodiments, the additive manufacturing step may be carried out to provide a flat surface on the shaft plate, and an opposing curved surface having a threadform. During the additive manufacturing process, the method may include providing lattice spaces on exposed surfaces of the superior shaft plate and the inferior shaft plate. In various embodiments, the shaft plates and body of bone screw including shaft and head may comprise same material. After forming the shaft plates by additive manufacturing process, the method may comprise attaching the flat surfaces of the superior shaft plate and the inferior shaft plate to the flat superior and inferior surface of the shaft. In various embodiments, the method may include anodizing head, the shaft or both prior to the attaching step. In various embodiments, the attaching step may be conducted by welding, threading, adhesive or staking. In some embodiments, the attaching step may comprise aligning the threadform on the side surfaces of the shaft and the threadforms on the superior and the inferior shaft plates thereby forming a contiguous helical threadform.

[0067] After manufacturing the bone screw, a surface roughing process may be performed to create micro- and nanoscale valleys on an exposed surface of the bone screw. The surface rouging process can include, but is not limited to, grit blasting and/or chemical etching. Illustrative surface roughing processes that can be used here are described in U.S. Patent No. 8,814,939 to Ulrich, Jr. et al., and U.S. Patent No. 2012/0316650 to Ullrich, Jr. et al., the entire contents of which are incorporated herein by reference. The surface treatment of the present disclosure may comprise subtractive process that provide a microscopic-roughened surface with nanoscale features that is designed to improve fixation to the adjacent bone. The first, microscopic roughening produces microscale valley features with dimensions correlating to osteoclastic resorption pits (e.g., 1-1000 microns; valleys are approximately 20-500 pms in diameter and 10-30 pm deep in case of valleys). The number of valleys may, for example, improve or provide biomimicry at this level. The second, nano-level provides nanoscale features (e.g., 1-1000 nm) which consists of nano striations or steps superimposed within those microfeatures. The nanoscale striations/steps have a high aspect ratio, for example, with a length typically greater than 100 nm but a width less than 100 nm. They are not depressions into the material rather ridges with peaks. It is a combination of the two textures that constitute a biomimic surface which promotes an increase in bone formation while maintaining the structural integrity of the bone screw.

[0068] Now referring to FIG. 15, a flow diagram of an illustrative method 1500 for adding surface roughness to a bone screw (e.g., bone screws 100, 200, or 300). The method 1500 may begin with 1501 and continues to 1502 where the main body of the bone screw is manufactured from a monolithic material by one or more subtractive manufacturing process including, not is not limited to machining, cutting, grinding, grinding, electrical discharge machining, milling, lathing, burring sawing, or sanding. Next, the additive portion is manufactured using various additive manufacturing processes including, but not limited to 3D printing, injection molding, deposition modeling, selective layer sintering, direct metal laser sintering, selective laser melting, electron beam melting, layered object manufacturing or stereolithography as shown in block 1503. Next, in block 1504, the additive portion is attached to the bone screw by a weld, a thread, adhesive, or stake.

[0069] The method 1500 continues to 1505 where the first portion of the bone screw is masked to obtain a maskant-bone screw assembly with a tight seal formed around the first portion of the bone screw. In some embodiments, the first portion may comprise a head of the bone screw. The tight seal may comprise a vapor and/or watertight seal. In various embodiments, the maskant may comprise a cap mask as described in U.S. Provisional Patent Application No. 63/497,038 to Gallagher et al., the entire contents of which are incorporated by reference. In various embodiments, the method may comprise optionally masking an internal feature of the bone screw using an insert mask. This masking may be achieved by: stretching the insert mask; pulling the insert mask through an aperture formed in the bone screw; and releasing the insert mask so that the insert mask at least partially un-stretches and seals the aperture. Masking of certain features of bone screw is performed to maintain mechanical integrity of the bone screw post-surface roughening process.

[0070] After the masking steps of 1505, the unmasked portion of the bone screw may be roughened by grit blasting, chemical etching, or both as described in block 1506. In various embodiments, the unmasked portion may comprise body of the bone screw including but not limited to the shaft, additive portion, threadform, tip, and the neck. The roughening process creates microscale features on a surface of the unmasked portions of the bone screw After surface roughening process, additional masking of the additive portion may be applied as described in block 1507. After masking the additive portion, the exposed surface and features of the bone screw, i.e., shaft, thread, tip, and the neck may undergo additional surface roughening process to impart nanoscale features within or around the microscale features in block 1508 and thereby producing different porosity/feature dimensions on the screw body (having both micro- and nanoscale features) compared to the additive portion (having only microscale features) in an integrally formed bone screw. After removing the maskant in block 1509, the bone screw may be routed for subsequent post-processing in 1510.

[0071] It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. For example, features, functionality, and components from one embodiment may be combined with another embodiment and vice versa unless the context clearly indicates otherwise. Similarly, features, functionality, and components may be omitted unless the context clearly indicates otherwise. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques).

[0072] Without excluding further possible embodiments, certain example embodiments are summarized in the following example clauses:

[0073] Example 1. A bone screw comprising: a superior shaft plate having a flat surface, a curved surface, and a threadform on the curved surface, wherein the superior shaft plate and comprises a lattice structure; a shaft extending along a longitudinal axis between a distal end portion and a proximal end portion, the shaft comprising a flat superior surface, and a curved side surface having a threadform defining a threaded section, and a head extending from the proximal end portion of the shaft.

[0074] Example 2. The bone screw of example 1, wherein the bone screw further comprises an inferior shaft plate having a flat surface, a curved surface, and a threadform on the curved surface; wherein the inferior shaft plate comprises a lattice structure, wherein the threaded section on the shaft and the threadform on the superior and the inferior shaft plates are aligned to form a continuous helical thread. 1 [0075] Example 3. The bone screw of example 1 or example 2, wherein the bone screw comprises a passageway extending longitudinally from the head through the shaft defining a cannulation.

[0076] Example 4. The bone screw of any one of examples 1-3, wherein the threaded section comprises a first threaded section extending from the distal end portion of the shaft towards the proximal end portion, and a second threaded section extending contiguously from the first threaded section toward the proximal end portion of the shaft, wherein the first threaded section includes a first helical thread having a single thread type extending along the shaft into the second threaded section, wherein the second threaded section comprises a second helical thread interleaved with the first helical thread defining a dual lead thread pattern, and wherein the first helical thread and the second helical thread have a substantially equal thread pitch.

[0077] Example 5. The bone screw of example 4, wherein the second threaded section comprises a finer thread pattern relative to the first threaded section.

[0078] Example 6. The bone screw of any one of examples 1-5, further comprising a receiver configured to couple to the head of the bone screw.

[0079] Example 7. The bone screw of example 6, wherein the receiver comprises a screw tulip.

[0080] Example 8. The bone screw of clause 6 or example 7, wherein the receiver is coupled to the bone screw in a uni-axial configuration.

[0081] Example 9. The bone screw of clause 6 or example 7, wherein the receiver is coupled to the bone screw in a multi-axial configuration, wherein the bone screw pivots about the receiver, and wherein the bone screw pivots at an angulation from about -40° to about 40° from the longitudinal axis.

[0082] Example 10. The bone screw of any one of examples 6-9, wherein the receiver is coupled to the bone screw by bottom loading configuration.

[0083] Example 11. The bone screw of any one of examples 6-9, wherein the receiver is coupled to the bone screw by top loading configuration. [0084] Example 12. The bone screw of example 1, wherein the shaft further comprises a plurality of lateral fenestrations on the curved side surfaces in communication with the passageway.

[0085] Example 13. The bone screw of any one of examples 1-12, wherein the shaft comprises a material selected from metals, synthetic polymers, ceramics, bone material, and their composites.

[0086] Example 14. The bone screw of any one of examples 1-13, wherein the superior and the inferior shaft plates comprise the same material as the shaft.

[0087] Example 15. The bone screw of any one of examples 1-14, wherein the shaft, the superior shaft plate, and the inferior shaft plate further comprise roughened surface features.

[0088] Example 16. The bone crew of example 15, wherein the roughened surface features comprise microscale features.

[0089] Example 17. The bone crew of example 15 or clause 16, wherein the roughened surface features comprise nanoscale features.

[0090] Example 18. The bone screw of any one of examples 15-17, wherein the superior shaft plate and the inferior shaft plate comprise different surface features compared to the shaft.

[0091] Example 19. The bone screw of any one of examples 15-18, wherein roughened surface features are formed by grit blasting and/or chemical etching.

[0092] Example 20. The bone screw of any one of example 1-19, wherein the lattice structures comprise a circular, triangular, diamond, square, rectangular, or hexagonal shape, or a combination thereof.

[0093] Example 21. The bone screw of any one of examples 1-19, wherein the lattice structure comprises a trabecular lattice.

[0094] Example 22. The bone screw of any one of examples 1-21, wherein the superior shaft plate and the inferior shaft plate are mechanically attached to the shaft by a weld, a thread, and adhesive or a stake.

[0095] Example 23. The bone screw of any one of examples 1-22, wherein the bone screw comprises a flat, pointed, fluted, sharp, or self-tapping tip. [0096] Example 24. The bone screw of any one of example s 4-23, comprising a third threaded section on the distal end portion of the shaft extending along the shaft into the first threaded section, wherein the third threaded section comprises a third helical thread interleaved with the first helical thread, and wherein the third helical thread has a crest thickness that is wider than the first helical thread.

[0097] Example 25. A bone screw comprising: a threaded sleeve portion extending along a longitudinal axis between a distal end portion and a proximal end portion, at least a portion of the threaded sleeve having a plurality of minor grooves and a plurality of lattice structures on exposed surfaces thereof, and a sleeve channel extending longitudinally from the distal end portion to the proximal end portion of the threaded sleeve, a shaft extending along a longitudinal axis between a distal end portion and a proximal end portion, the distal end portion having a threadform; and a head extending from the proximal end portion of the shaft, wherein the shaft is disposed in the sleeve channel of the threaded sleeve portion, and wherein the shaft and the head comprise a passageway extending longitudinally from the head through the shaft defining a canulation.

[0098] Example 26. The bone screw of example 25, wherein the threaded sleeve portion comprises a first threaded section extending from the distal end portion toward proximal end portion, wherein a second threaded section extend continuously from the first threaded section toward the proximal end portion, wherein the first threaded section includes a first helical thread having a single thread type extending along the shaft into the second threaded section, and wherein the second threaded section comprises a second helical thread interleaved with the first helical thread to define the second threaded section, wherein the first helical thread and the second helical thread have a substantially equal thread pitch.

[0099] Example 27. The bone screw of example 25 or example 26, wherein the sleeve channel comprises a circular cross-section having an inner diameter.

[0100] Example 28. The bone screw of any one of examples 25-27, wherein the sleeve channel comprises a regular polygonal cross-section having an inner diameter defined by a longest length between two vertices through center of the polygonal cross-section.

[0101] Example 29. The bone screw of example 28, wherein the sleeve channel comprises a hexagonal cross-section. [0102] Example 30. The bone screw of any one of examples 25-29, wherein the shaft comprises an outer diameter that is slightly smaller than the inner diameter of the channel. [0103] Example 31. The bone screw of any one of examples 25-30, wherein the shaft comprises same cross-section shape as the channel.

[0104] Example 32. The bone screw of example 25 or example 26, wherein the sleeve channel comprises a frustoconical cross-section having a first inner diameter at the distal end portion a second inner diameter at the proximal end portion.

[0105] Example 33. The bone screw of any one of examples 25, 26, or 32, wherein the shaft comprises a frustoconical cross-section having a first outer diameter that is slightly smaller than the first inner diameter of the channel at the distal end portion, and a second outer diameter that is slightly smaller than the second inner diameter of the sleeve channel at the proximal end portion.

[0106] Example 34. The bone screw of any one of examples 25-33, wherein the shaft further comprises micropores in communication with the passageway.

[0107] Example 35. The bone screw of any one of examples 25-34, wherein the threaded sleeve portion comprises microscale surface features.

[0108] Example 36. The bone screw of any one of examples 25-35, wherein the threaded sleeve portion comprises nanoscale surface features.

[0109] Example 37. The bone screw of any one of examples 25-36, wherein the threaded sleeve portion is attached to the shaft by a weld, a thread, adhesive or a stake.

[0110] Example 38. The bone screw of any one of examples 26-37, comprising a third threaded section on the distal end portion of the shaft extending along the shaft into the first threaded section of the threaded portion, wherein the third threaded section comprises a third helical thread interleaved with the first helical thread of the threaded sleeve portion, and wherein the third helical thread has a crest that is wider than the first helical thread.

[0111] Example 39. A bone screw comprising: a shaft extending along a longitudinal axis between a distal end portion and a proximal end portion, comprising a threaded section extending from the distal end portion towards the proximal end portion, the shaft comprising at least one aperture extending through the shaft in a direction normal to the longitudinal axis; and a head extending from the proximal end portion of the shaft, wherein the bone screw is coaxial with the longitudinal axis from the distal end portion to the head, wherein the bone screw comprises a passageway extending longitudinally from the head through the shaft defining a cannulation, and wherein the aperture is in communication with the passageway, and wherein the aperture is configured to receive an additive portion comprising roughened and porous surfaces, wherein the additive portion is substantially the same shape and size as the aperture.

[0112] Example 40. The bone screw of example 39, wherein the additive portion comprises a threadform aligned with the threaded section on the shaft to form a continuous helical thread.

[0113] Example 41. The bone screw of example 39 or example 40, wherein the threaded section comprises a first threaded section extending from the distal end portion of the shaft towards the proximal end portion, and a second threaded section extending contiguously from the first threaded section toward the proximal end portion, wherein the first threaded section includes a first helical thread having a single thread type extending along the shaft into the second threaded section, wherein the second threaded section comprises a second helical thread interleaved with the first helical thread to define the second threaded section, and wherein the first helical thread and the second helical thread have a substantially equal thread pitch.

[0114] Example 42. The bone screw of any one of examples 39-41, wherein the shaft comprises microscale features.

[0115] Example 43. The bone screw of example any one of examples 39-42, wherein the shaft comprises nanoscale surface features.

[0116] Example 44. The bone screw of any one of examples 39-43, wherein the additive portion is mechanically attached to the shaft by a weld, a thread, adhesive or a stake.

[0117] Example 45. The bone screw of any one of examples 41-44, comprising a third threaded section on the distal end portion of the shaft extending along the shaft into the first threaded section, wherein the third threaded section comprises a third helical thread interleaved with the first helical thread, and wherein the third helical thread has a crest thickness that is wider than the first helical thread. [0118] Example 46. A method for manufacturing a bone screw, comprising the steps of: forming a head and shaft by applying a subtractive manufacturing process to a material to provide a flat superior surface and a flat inferior surface, and opposing curved side surfaces normal to the superior and the inferior surface on the shaft, wherein the opposing curved side surfaces each comprise a threadform; forming the superior shaft plate and an inferior shaft plate respectively, by an additive manufacturing process, wherein the superior and the inferior shaft plates each comprise a flat surface, a curved surface opposite the flat surface, and a threadform on the curved surface; and attaching the flat surfaces of the superior shaft plate and the inferior shaft plate to the flat superior and inferior surfaces of the shaft.

[0119] Example 47. The method of example 46, comprising anodizing the head and the shaft of the bone screw prior to the attaching step.

[0120] Example 48. The method of example 46 or clause 47, comprising applying a drilling process to provide a cannulated passageway extending longitudinally from the head through the shaft of the bone screw.

[0121] Example 49. The method of any one of examples 46-48, wherein the forming the shaft step comprises applying subtractive manufacturing processing step to a material selected from metals, synthetic polymers, ceramics, bone material, and their composites.

[0122] Example 50. The method of any one of examples 46-49, wherein the subtractive manufacturing comprises at least one of: milling, lathing, burring, sawing, or sanding.

[0123] Example 51. The method of any one of examples 46-50, wherein the forming the superior shaft plate and the inferior shaft plate is conducted by the additive manufacturing process comprising at least one of 3D printing, injection molding, deposition, or layering.

[0124] Example 52. The method of any one of examples 46-51, wherein the forming the superior shaft plate and the inferior shaft plate comprises providing lattice structures on exposed surfaces thereof.

[0125] Example 53. The method of any one of examples 46-52, wherein the forming the superior shaft plate and the inferior shaft plate comprises applying the additive manufacturing process to the same material as the shaft.

[0126] Example 54. The method of any one of examples 46-53, wherein the attaching process in step (c) is conducted by welding, threading, adhesive or staking. [0127] Example 55. The method of clause 54, wherein the attaching step comprises aligning the threadforms on the side surfaces of the shaft and the threadforms on the superior and the inferior shaft plates thereby forming a contiguous helical threadform.

[0128] Example 56. The method of any one of examples 46-55, further comprising adding surface roughness to the bone screw, the steps comprising: masking a first portion of the bone screw with a maskant to obtain a maskant-bone screw assembly with a tight seal formed around the first portion of the bone screw; roughening surface of unmasked portion of the bone screw by grit blasting, chemical etching, or both; and removing the maskant from the bone screw, wherein an anodized finish remains on the first portion of the bone screw and removed from the unmasked portion of the bone screw.

[0129] Example 57. The method of example 56, wherein the maskant comprises a cap mask.

[0130] Example 58. The method of example 56 or example 57, wherein the first portion comprises a head of the bone screw, and the unmasked portion comprises body of the bone screw.

[0131] Example 59. The method of any one of examples 56-58, wherein the roughening process creates microscale features on the unmasked portion of the bone screw.

[0132] Example 60. The method of example 59, wherein the roughening further creates nanoscale features within or around the microscale features.

[0133] Example 61. The method of any one of examples 56-60, wherein the masking the first portion of the bone screw maintains mechanical integrity of the bone screw.

Claims

What is claimed is:

1. A bone screw comprising: a superior shaft plate (120) having a flat surface (122), a curved surface (121), and a threadform on the curved surface (123), wherein the superior shaft plate comprises a lattice structure (124) on exposed surfaces; a shaft (102) extending along a longitudinal axis between a distal end portion (lOOd) and a proximal end portion (lOOp), the shaft comprising a flat superior surface (109), and a curved side surface having a threadform (103) extending from the distal end portion towards the proximal end portion defining a threaded section; and a head (101) extending from the proximal end portion of the shaft, wherein the shaft is disposed between the superior shaft plate and the inferior shaft plate, wherein the bone screw comprises a passageway (108) extending longitudinally from the head through the shaft defining a cannulation,

2. The bone screw of claim 1 , wherein the bone screw further comprises an inferior shaft plate (130) having a flat surface (132), a curved surface (131), and a threadform on the curved surface (133); wherein the inferior shaft plate comprises a lattice structure (134), wherein the threaded section on the shaft and the threadform on the superior and the inferior shaft plates are aligned to form a continuous helical thread.

3. The bone screw of claim 1, wherein the threaded section comprises a first threaded section extending from the distal end portion of the shaft towards the proximal end portion, and a second threaded section extending contiguously from the first threaded section toward the proximal end portion of the shaft, wherein the first threaded section includes a first helical thread having a single thread type extending along the shaft into the second threaded section, wherein the second threaded section comprises a second helical thread interleaved with the first helical thread defining a dual lead thread pattern, and wherein the first helical thread and the second helical thread have a substantially equal thread pitch.

4. The bone screw of claim 3, wherein the second threaded section comprises a finer thread pattern relative to the first threaded section.

5. The bone screw claim 1, further comprising a receiver configured to couple to the head of the bone screw in a uni-axial configuration.

6. The bone screw of claim 5, wherein the receiver is coupled to the bone screw in a multi-axial configuration, wherein the bone screw pivots about the receiver, and wherein the bone screw pivots at an angulation from about -40° to about 40° from the longitudinal axis.

7. The bone screw of claim 1, wherein the lattice structures comprise a circular, triangular, diamond, square, rectangular, hexagonal shape, or a combination thereof.

8. The bone screw of claim 1, wherein the lattice structure comprises a trabecular lattice.

9. The bone screw of claim 1, wherein the shaft, the superior shaft plate, and the inferior shaft plate further comprise roughened surface features.

10. The bone crew of claim 9, wherein the roughened surface features comprise microscale and nanoscale features.

11. The bone screw claim 10, wherein the superior shaft plate and the inferior shaft plate comprise different surface features compared to the shaft.

12. The bone screw of claim 9, wherein roughened surface features are formed by grit blasting and/or chemical etching.

13. The bone screw of claim 1, wherein the superior shaft plate and the inferior shaft plate are mechanically attached to the shaft by a weld, a thread, and adhesive or a stake.

14. The bone screw of claim 1, wherein the bone screw comprises a flat, pointed, fluted, sharp, or self-tapping tip.

15. The bone screw of claim 3, comprising a third threaded section on the distal end portion of the shaft extending along the shaft into the first threaded section, wherein the third threaded section comprises a third helical thread interleaved with the first helical thread, and wherein the third helical thread has a crest thickness that is wider than the first helical thread.