Patent Description:
Spinal pathologies and disorders such as kyphosis, scoliosis and other curvature abnormalities, degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, tumor, 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.

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 fasteners are often used to provide stability to a treated region. Such bone fasteners are traditionally manufactured using a medical machining technique. This disclosure describes an improvement over these prior technologies.

From <CIT> a bone screw according to the preamble of claim <NUM> and a method for fabricating an implant receiver for a bone screw according to the preamble of claim <NUM> is known. Further bone screws and relating methods are known from <CIT>, <CIT>, <CIT> and <CIT>.

The object of the present invention is providing an improved bone screw having an improved implant receiver and providing a method for fabricating an improved implant receiver for a bone screw. This object is solved by a bone screw according to claim <NUM> and by a method for fabricating an implant receiver for a bone screw according to claim <NUM>. Further embodiments are subject of the dependent claims.

The exemplary embodiments of a surgical system and related methods of use disclosed are discussed in terms of medical devices for the treatment of musculoskeletal disorders and more particularly, in terms of a variable structured spinal implant.

The methods of use described herein aid to understand the invention.

The term "embodiment" used in the present specification does not necessarily indicate ways of carrying out the invention claimed but also examples which aid understanding the invention. According to this, the additive manufacturing apparatus described herein does not form part of the claimed invention.

According to the invention, the spinal implant system includes a spinal implant comprising a variable structured implant receiver.

The spinal implant system of the present invention comprises an implant receiver that is manufactured by combining traditional manufacturing methods and additive manufacturing methods. A layer is applied by additive manufacturing in areas where the implant receiver can benefit from materials, surface texture, and/or other properties that can be associated with using additive manufacturing.

In some embodiments, the implant receiver includes a hybrid configuration that combines a manufacturing method, such as, for example, one or more traditional manufacturing features and materials and a manufacturing method, such as, for example, one or more additive manufacturing features and materials. In some embodiments, the spinal implant system of the present disclosure comprises an implant receiver that promotes bony in-growth by adding a layer thereto by additive manufacturing. In some embodiments, the implant receiver includes a variable structure, such as, for example, any combination of solid, roughened surfaces, porous surfaces, honeycomb filled, structure having a trabecular configuration, or other porous or roughened configurations. In some embodiments, the implant receiver of the present disclosure aids in the promotion of bony fusion. In some embodiments, the porous layer is disposed about all or only a portion of a base, for example, disposed about an outer diameter of the base. In some embodiments, this configuration optimizes bony in-growth with the screw head of a pedicle screw to promote fusion. In some embodiments, this configuration resists and/or prevents toggle. In some embodiments, the spinal implant system of the present disclosure comprises a modular screw system including screw shaft assemblies and implant receiver/head assemblies that may be joined together during manufacturing or intra-operatively, such as, for example, during a surgical procedure in an operating room.

In some embodiment, the implant receiver includes a porous or surface textured layer at a bone interface portion of the implant receiver. In some embodiments, the porous layer is configured to enhance the implant-bone interface. In some embodiments, the porous layer is applied by an additive manufacturing and other components of the bone screw are manufactured by a traditional manufacturing method. In some embodiments, the variable structure bone screw provides for the mechanical strength of the bone screw and the added porous layer enhances the implant-bone interface.

In some embodiments, additive manufacturing includes <NUM>-D printing. In some embodiments, additive manufacturing includes fused deposition modeling, selective laser sintering, direct metal laser sintering, selective laser melting, electron beam melting, layered object manufacturing and stereolithography. In some embodiments, additive manufacturing includes rapid prototyping, desktop manufacturing, direct manufacturing, direct digital manufacturing, digital fabrication, instant manufacturing and on-demand manufacturing. In some embodiments, the spinal implant system comprises one or more components, as described herein, of a spinal implant being manufactured by a fully additive process and grown or otherwise printed. In some embodiments, the implant receiver and/or head assembly of the present disclosure includes a non-solid portion, for example, a porous layer that is applied to a base of the implant receiver and/or head assembly via additive manufacturing, for example, <NUM>-D printing. In some embodiments, this configuration avoids compromising the integrity of a spinal construct and promotes bone fusion.

In some embodiments, the spinal implants, surgical instruments and/or medical devices of the present disclosure may be employed to treat spinal disorders such as, for example, degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, scoliosis and other curvature abnormalities, kyphosis, tumor and fractures. In some embodiments, the spinal implants, surgical instruments and/or medical devices of the present disclosure may be employed with other osteal and bone related applications, including those associated with diagnostics and therapeutics. In some embodiments, the spinal implants, surgical instruments and/or medical devices of the present disclosure may be alternatively employed in a surgical treatment with a patient in a prone or supine position, and/or employ various surgical approaches to the spine, including anterior, posterior, posterior mid-line, lateral, postero-lateral, and/or antero-lateral approaches, and in other body regions such as maxillofacial and extremities. The spinal implants, surgical instruments and/or medical devices of the present disclosure may also be alternatively employed with procedures for treating the lumbar, cervical, thoracic, sacral and pelvic regions of a spinal column. The spinal implants, surgical instruments and/or medical devices of the present disclosure may also be used on animals, bone models and other non-living substrates, such as, for example, in training, testing and demonstration.

The present disclosure may be understood more readily by reference to the following detailed description of the embodiments taken in connection with the accompanying drawing figures, which form a part of this disclosure.

The following discussion includes a description of a spinal implant, a method of manufacturing a spinal implant, related components and methods of employing the surgical system 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 <FIG>, there is illustrated an illustrative system shown to improve the understanding of the principles of the present disclosure, and turning to <FIG>, there are illustrated components of an inventive spinal implant system <NUM> including spinal implants, surgical instruments (not claimed) and medical devices.

Spinal implant system <NUM> includes a spinal implant comprising a bone fastener, such as, for example, a bone screw <NUM>. Bone screw <NUM> includes an implant receiver and/or head assembly having a variably structured configuration that facilitates bone growth through bone screw <NUM> and/or fixation of bone screw <NUM> with tissue. Bone screw <NUM> comprises a screw shaft <NUM> and an implant receiver <NUM>. Receiver <NUM> includes a body <NUM> that defines an implant cavity <NUM> and a base <NUM>. Base <NUM> includes a layer <NUM> applied by an additive manufacturing process.

In various embodiments, body <NUM> has an even, uninterrupted edge surface. Body <NUM> may also include an even, solid surface relative layer <NUM>, as described herein, which provides a variable configuration bone screw <NUM>.

In some embodiments, body <NUM> is fabricated by a first manufacturing method. The manufacturing method can include a traditional machining method, subtractive, deformative or transformative manufacturing methods. In some embodiments, the traditional manufacturing method may include cutting, grinding, rolling, forming, molding, casting, forging, extruding, whirling, grinding and/or cold working. In some embodiments, the traditional manufacturing method includes components being formed by a medical machining process. In some embodiments, medical machining processes can include use of computer numerical control (CNC) high speed milling machines, Swiss machining devices, CNC turning with living tooling and/or wire EDM 4th axis. In some embodiments, the manufacturing method includes a finishing process, such as, for example, laser marking, tumble blasting, bead blasting, micro blasting and/or powder blasting.

In some embodiments, body <NUM> includes a pair of spaced apart arms <NUM>, <NUM>. Arms <NUM>, <NUM> define implant cavity <NUM> therebetween. Implant cavity <NUM> is configured for disposal of a component of a spinal construct, such as, for example, a spinal rod (not shown). In various embodiments, arms <NUM>, <NUM> each extend generally parallel to an axis X1. In some embodiments, arm <NUM> and/or arm <NUM> may be disposed at alternate orientations, relative to axis X1. For example, arm <NUM> and/or arm <NUM> may be disposed transverse, perpendicular and/or other angular orientations, such as acute or obtuse, coaxial and/or may be offset or staggered relative to axis X1. Arms <NUM>, <NUM> each include an outer surface, which may be arcuate, extending between a pair of side edges or surfaces.

In various embodiments, at least one of the outer surfaces and the side surfaces of arms <NUM>, <NUM> have at least one recess or cavity therein configured to receive an insertion tool, compression instrument, and/or instruments for inserting and tensioning bone screw <NUM>. In some embodiments, arms <NUM>, <NUM> are connected at proximal and distal ends thereof such that receiver <NUM> defines a closed spinal rod slot.

Cavity <NUM> may be substantially U-shaped. In some embodiments, all or only a portion of cavity <NUM> has alternate cross section configurations, such as, for example, closed, V-shaped, W-shaped, oval, oblong triangular, square, polygonal, irregular, uniform, non-uniform, offset, staggered, and/or tapered.

Receiver <NUM> includes an inner surface <NUM>. In various embodiments, portion of surface <NUM> includes a thread form located adjacent arm <NUM> and adjacent arm <NUM>. The thread form is configured for engagement with a coupling member, such as, for example, a setscrew (not shown), to retain the spinal rod within cavity <NUM>. In some embodiments, surface <NUM> may be disposed with the coupling member in alternate fixation configurations, such as, for example, friction fit, pressure fit, locking protrusion/recess, locking keyway and/or adhesive. In some embodiments, all or only a portion of surface <NUM> may have alternate surface configurations to enhance engagement with the spinal rod and/or the setscrew, such as, for example, rough, arcuate, undulating, mesh, porous, semi-porous, dimpled and/or textured. In some embodiments, receiver <NUM> may include alternate configurations, such as, for example, closed, open and/or side access.

In some embodiments, receiver <NUM> includes a surface configured for disposal of a part, such as, for example, a crown (not shown). The crown is configured for disposal within implant cavity <NUM>. In some embodiments, the crown includes a curved portion configured for engagement with the spinal rod.

Base <NUM> includes porous layer <NUM> to enhance fixation and/or facilitate bone growth, as described herein. Layer <NUM> is applied with a second manufacturing, as described herein. In some embodiments, the manufacturing method can include an additive manufacturing method by disposing a material onto a surface <NUM> of a wall <NUM>, as described herein. All or a portion of base <NUM> is configured to interface bone. Layer <NUM> is provided to increase a base <NUM>-to-bone interface.

Base <NUM> having layer <NUM> enhances fixation and/or facilitates bone growth, as described herein. In some embodiments, tissue becomes imbedded with layer <NUM> to promote bone growth, enhance fusion of bone screw <NUM> with vertebral tissue, and/or prevent toggle of bone screw <NUM> in one or multiple motion planes.

Body <NUM> is in various embodiments manufactured by a traditional manufacturing process (not including additive manufacturing, for instance), and layer <NUM> is applied to surface <NUM> by an additive manufacturing process. Having body <NUM> and the other components of bone screw <NUM> manufactured by traditional manufacturing processes maintains the mechanical performance characteristics of bone screw <NUM>, while also enhancing bone growth and fusion.

Base <NUM> of receiver <NUM> includes wall <NUM>. Wall <NUM> includes an inner surface <NUM> that defines a cavity <NUM>, and outer surface <NUM>. Cavity <NUM> is configured for disposal of a head <NUM> of screw shaft <NUM>. In various embodiments, wall <NUM> includes an even, uninterrupted configuration and includes an even, solid surface <NUM> relative to the surface of layer <NUM>. Surface <NUM> is configured for providing a fabrication platform for forming layer <NUM> thereon using a second manufacturing method such as, for example, an additive manufacturing method, as described herein. In some embodiments, an overall width of wall <NUM> including layer <NUM> (e.g., outside diameter, or maximum width) is the same as a width of a traditional receiver. In some embodiments, receiver <NUM> has a solid configuration relative to the layer <NUM>. In some embodiments, receiver <NUM> is connectable with a bone screw shaft.

Layer <NUM> is applied to at least a portion of an outer circumference of surface <NUM>. Layer <NUM> includes a portion <NUM> and a portion <NUM>, as shown in FGIS. <NUM> and <NUM>. Portion <NUM> includes a first thickness t1 and portion <NUM> includes a second thickness t2, as shown in <FIG>. In some embodiments, portion <NUM> includes a tapered portion <NUM> that connects portion <NUM> and portion <NUM>. In some embodiments, layer <NUM> has various configurations along surface <NUM>, such as, a non-solid configuration, such as, for example, a porous structure and/or a trabecular configuration.

In some embodiments, additive manufacturing includes <NUM>-D printing, as described herein. In some embodiments, additive manufacturing includes fused deposition modeling, selective laser sintering, direct metal laser sintering, selective laser melting, electron beam melting, layered object manufacturing and stereolithography. In some embodiments, additive manufacturing includes rapid prototyping, desktop manufacturing, direct manufacturing, direct digital manufacturing, digital fabrication, instant manufacturing or on-demand manufacturing.

In some embodiments, layer <NUM> is applied by additive manufacturing, as described herein, and mechanically attached to surface <NUM> by, for example, welding, threading, adhesives and/or staking. In some embodiments, layer <NUM> has a porous configuration, a lattice, a trabecular configuration and/or a roughened surface to promote bone growth through the layer. In some embodiments, additive manufacturing includes heating a material in a selective material formation onto a portion of the outer surface of the implant receiver.

In various embodiments, the non-solid configuration provides one or a plurality of pathways to facilitate bone through growth within, and in some embodiments all of the way through, from one surface to an opposite surface of bone screw <NUM>. In some embodiments, one or more portions, layers and/or substrates of layer <NUM> may be disposed side by side, offset, staggered, stepped, tapered, end to end, spaced apart, in series and/or in parallel. In some embodiments, layer <NUM> is disposed about an entire outer circumference of receiver <NUM>. In some embodiments, layer <NUM> disposed about an outer circumference of a lower portion near base <NUM> of receiver <NUM>, as shown in <FIG>.

In some embodiments, layer <NUM> defines a thickness, which may be uniform, undulating, tapered, increasing, decreasing, variable, offset, stepped, arcuate, angled and/or staggered. In some embodiments, layer <NUM> includes one or more layers of a matrix of material. In some embodiments, layer <NUM> includes one or a plurality of cavities, spaces and/or openings. In some embodiments, layer <NUM> forms a rasp-like configuration. In some embodiments, layer <NUM> is configured to engage tissue, such as, for example, cortical bone and/or cancellous bone, such as, to cut, shave, shear, incise and/or disrupt such tissue. In some embodiments, all or a portion of layer <NUM> may have various configurations, such as, for example, cylindrical, round, oval, oblong, triangular, polygonal having planar or arcuate side portions, irregular, uniform, non-uniform, consistent, variable, horseshoe shape, U-shape or kidney bean shape. Layer <NUM> may be rough, textured, porous, semi-porous, dimpled, knurled, toothed, grooved and/or polished to facilitate engagement and cutting of tissue.

In some embodiments, the non-solid configuration is configured as a lattice extending along surface <NUM>. In some embodiments, the lattice may include one or more portions, layers and/or substrates. Disclosures herein involving a porous, or other particular type of non-solid structure, are meant to disclose at the same time analogous embodiments in which other non-solid structure in addition or instead of the particular type of structure.

In some embodiments, layer <NUM> is fabricated according to instructions received from a computer and processor based on the digital rendering and/or data of the selected configuration, via the additive manufacturing process. See also, the examples and disclosure of the additive and three-dimensional manufacturing systems and methods shown and described in commonly owned and assigned <CIT>; and the examples and disclosure of the additive and three dimensional manufacturing systems and methods shown and described in commonly owned and assigned <CIT> and <CIT>.

In one embodiment, one or more manufacturing methods for fabricating layer <NUM> and other components of bone screw <NUM>, such as, for example, screw shaft <NUM> and receiver <NUM> include imaging patient anatomy with imaging techniques, such as, for example, x-ray, fluoroscopy, computed tomography (CT), magnetic resonance imaging (MRI), surgical navigation, bone density (DEXA) and/or acquirable <NUM>-D or <NUM>-D images of patient anatomy. Selected configuration parameters of screw shaft <NUM>, receiver <NUM> and layer <NUM> and/or other components of bone screw <NUM> are collected, calculated and/or determined. Such configuration parameters can include one or more of patient anatomy imaging, surgical treatment, historical patient data, statistical data, treatment algorithms, implant material, implant dimensions, porosity and/or manufacturing method. In some embodiments, the configuration parameters can include implant material and porosity of layer <NUM> determined based on patient anatomy and the surgical treatment. In some embodiments, the implant material includes a selected porosity of layer <NUM>, as described herein.

In some embodiments, the processor can instruct motors (not shown) that control movement and rotation of components, for example, a build plate <NUM>, receiver <NUM> and/or laser emitting devices, as described herein. In some embodiments, layer <NUM> is applied by utilizing a radiation source to melt and solidify a material M onto surface <NUM> into a desired three-dimensional shape based on the selected configuration parameters, as described herein. In some embodiments, the radiation source includes a laser device <NUM>, as shown in <FIG>, which comprises a carbon dioxide laser. In some embodiments, laser device <NUM> may include a beam of any wavelength of visible light or UV light. In some embodiments, alternative forms of radiation, such as, for example, microwave, ultrasound or radio frequency radiation are provided. In some embodiments, laser device <NUM> is configured to be focused on a portion of surface <NUM> to sinter material M deposited thereon, as shown in <FIG>. In some embodiments, laser device <NUM> emits a beam having a diameter between about <NUM> and about <NUM>. In some embodiments, the diameter of the beam may be between about <NUM> and about <NUM>. In some embodiments, the diameter of the beam is adjustable to customize the intensity of the sintering.

Build plate <NUM> includes a surface that defines one or a plurality of openings <NUM>. Each opening <NUM> is configured for disposal of receiver <NUM> to orient base <NUM> as a fabrication platform for forming layer <NUM> thereon with an additive manufacturing method, as described herein. Surface <NUM> extends from opening <NUM> to orient surface <NUM> for selective laser melting with a powder bed process by the radiation source.

Build plate <NUM> is mounted with a platform <NUM> such that build plate <NUM> can be moved relative to an enclosure in one or more directions to generate layer <NUM> on surface <NUM>, layer by layer, based on the digital rendering and/or data. In some embodiments, build plate <NUM> can be translated vertically, horizontally or diagonally, rotated, pivoted, raised and/or lowered to generate the distal portion. In some embodiments, build plate <NUM> can be moved relative to the enclosure slidably, continuously, incrementally, intermittently, automatically, manually, selectively and/or via computer/processor control. In some embodiments, an apparatus comprising an additive manufacturing device that employs selective laser melting with a powder bed process to create 3D objects is provided. See, for example, the Lasertec <NUM> SLM additive manufacturing machine manufactured by DMG MORI Co. located at <NUM>-<NUM>-<NUM> Meieki, Nakamura-ku, Nagoya City <NUM>-<NUM>, Japan.

In some embodiments, the selected configuration parameters of layer <NUM> and/or other components of bone screw <NUM> are patient specific. In some embodiments, the selected configuration parameters of layer <NUM> and/or other components of bone screw <NUM> are based on generic or standard configurations and/or sizes and not patient specific. In some embodiments, the selected configuration parameters of layer <NUM> and/or other components of bone screw <NUM> are based on one or more configurations and/or sizes of components of a kit of spinal implant system <NUM> and not patient specific.

Screw shaft <NUM> defines an even, uninterrupted edge surface and includes an even, solid surface relative to the surface of layer <NUM>. Shaft <NUM> is configured to penetrate tissue, such as, for example, bone. In some embodiments, shaft <NUM> includes an outer surface having an external thread form. In some embodiments, the external thread form may include a single thread turn or a plurality of discrete threads. Head <NUM> includes a tool engaging portion configured to engage a surgical tool or instrument, as described herein. In some embodiments, the tool engaging portion includes a hexagonal cross-section to facilitate engagement with a surgical tool or instrument, as described herein. In some embodiments, the tool engaging portion may have alternative cross-sections, such as, for example, rectangular, polygonal, hexalobe, oval, or irregular. In some embodiments, head <NUM> includes a plurality of ridges to improve purchase of head <NUM> with the crown. Head <NUM> is configured for attachment with receiver <NUM>, as described herein.

In some embodiments, the external thread form is fabricated to include a fine, closely-spaced and/or shallow configuration to facilitate and/or enhance engagement with tissue. In some embodiments, the external thread form is fabricated to be continuous along shaft <NUM>. In some embodiments, the external thread form is fabricated to be intermittent, staggered, discontinuous and/or may include a single thread turn or a plurality of discrete threads. In some embodiments, shaft <NUM> is fabricated to include penetrating elements, such as, for example, a nail configuration, barbs, expanding elements, raised elements, ribs, and/or spikes. In some embodiments, the external thread form is fabricated to be self-tapping or intermittent at a distal tip. In some embodiments, the distal tip may be rounded. In some embodiments, the distal tip may be self-drilling. In some embodiments, the distal tip includes a solid outer surface.

Surface <NUM> facilitates engagement of head <NUM> with base <NUM> via a pressure and/or force fit connection. In some embodiments, surface <NUM> facilitates a non-instrumented assembly with receiver <NUM> and head <NUM> via an expandable ring. In some embodiments, receiver <NUM> may be disposed with head <NUM> in alternate fixation configurations, such as, for example, friction fit, pressure fit, locking protrusion/recess, locking keyway and/or adhesive. In some embodiments, receiver <NUM> is configured for rotation relative to head <NUM>. In some embodiments, receiver <NUM> is configured for rotation in range of <NUM> degrees relative to head <NUM> to facilitate positioning of shaft <NUM> with tissue. In some embodiments, receiver <NUM> is configured for selective rotation in range of <NUM> degrees relative to and about head <NUM> such that shaft <NUM> is selectively aligned for rotation in a plane relative to receiver <NUM>.

In some embodiments, receiver <NUM> is manually engageable with screw shaft <NUM> in a non-instrumented assembly, as described herein. In some embodiments, manual engagement and/or non-instrumented assembly of receiver <NUM> and screw shaft <NUM> includes coupling without use of separate and/or independent instrumentation engaged with screw shaft <NUM> components to effect assembly. In some embodiments, manual engagement and/or non-instrumented assembly includes a practitioner, surgeon and/or medical staff grasping receiver <NUM> and screw shaft <NUM> and forcibly assembling the components. In some embodiments, manual engagement and/or non-instrumented assembly includes a practitioner, surgeon and/or medical staff grasping receiver <NUM> and screw shaft <NUM> and forcibly snap fitting the components together, as described herein. In some embodiments, manual engagement and/or non-instrumented assembly includes a practitioner, surgeon and/or medical staff grasping receiver <NUM> and screw shaft <NUM> and forcibly pop fitting the components together and/or pop fitting receiver <NUM> onto screw shaft <NUM>, as described herein. In some embodiments, a force in a range of about <NUM> to about <NUM> N is required to manually engage receiver <NUM> and screw shaft <NUM> and forcibly assemble the components. For example, a force in a range of about <NUM> to about <NUM> N is required to snap fit and/or pop fit assemble receiver <NUM> and screw shaft <NUM>. In some embodiments, a force in a range of about <NUM> to about <NUM> N is required to manually engage receiver <NUM> and screw shaft <NUM> and forcibly assemble the components. For example, a force in a range of about <NUM> to about <NUM> N is required to snap fit and/or pop fit assemble receiver <NUM> and screw shaft <NUM>. In some embodiments, screw shaft <NUM> is manually engaged with base <NUM> and/or receiver <NUM> in a non-instrumented assembly, as described herein, such that removal of receiver <NUM> and screw shaft <NUM> requires a force and/or a pull-out strength of at least about <NUM> N. In some embodiments, this configuration provides manually engageable components that are assembled without instrumentation, and subsequent to assembly, the assembled components have a selected pull-out strength and/or can be pulled apart, removed and/or separated with a minimum required force. In some embodiments, spinal implant system <NUM> comprises a spinal implant kit, as described herein, which includes a plurality of screw shafts <NUM> and/or receivers <NUM>.

In some embodiments, bone screw <NUM> can include various configurations, such as, for example, a posted screw, a pedicle screw, a bolt, a bone screw for a lateral plate, 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, midline lumbar fusion screw and/or a sacral bone screw.

In assembly, operation and use, spinal implant system <NUM> is employed to treat an affected section of vertebrae. A medical practitioner obtains access to a surgical site including the vertebrae in any appropriate manner, such as through incision and retraction of tissues. The components of spinal implant system <NUM> including bone screw <NUM> are employed to augment a surgical treatment. Bone screw <NUM> can be delivered to a surgical site as a pre-assembled device. In some embodiments, bone screw <NUM> can be delivered to a surgical site assembled in situ. Spinal implant system <NUM> may be completely or partially revised, removed or replaced.

Surgical system <NUM> may be used with surgical methods or techniques including open surgery, mini-open surgery, minimally invasive surgery and percutaneous surgical implantation, whereby the vertebrae is accessed through a mini-incision, or sleeve that provides a protected passageway to the area. Once access to the surgical site is obtained, a surgical treatment, for example, corpectomy and/or discectomy, can be performed for treating a spine disorder.

Bone screw <NUM> is connected with a surgical instrument, such as, for example, a driver (not shown) and is delivered to the surgical site. Bone screw <NUM> is manipulated including rotation and/or translation for engagement with cortical bone and/or cancellous bone. Receiver <NUM> is manually engaged with screw shaft <NUM> in a non-instrumented assembly, as described herein. Bone screw <NUM> including base <NUM> having layer <NUM> enhances fixation and/or facilitates bone growth, as described herein. In some embodiments, tissue becomes imbedded with layer <NUM> to promote bone growth, enhance fusion of bone screw <NUM> with vertebral tissue, and/or prevent toggle of bone screw <NUM> components. In some embodiments, the layer is disposed about at least a portion of an outer circumference of the base.

Claim 1:
A bone screw (<NUM>) comprising a screw shaft (<NUM>) having a head (<NUM>) and having an external thread form and an implant receiver (<NUM>), wherein the implant receiver comprises:
a body (<NUM>) formed by a first manufacturing method, the body (<NUM>) including a base (<NUM>), wherein the base (<NUM>) includes a wall (<NUM>), wherein the wall (<NUM>) includes an outer surface (<NUM>) and an inner surface (<NUM>) that defines a cavity (<NUM>) configured for disposal of the head (<NUM>) of the screw shaft (<NUM>), and the body (<NUM>) including an implant cavity (<NUM>) having spaced-apart walls defining a cavity (<NUM>) configured for disposal of a spinal implant,
characterized in that
the implant receiver further comprises at least one layer (<NUM>) being formed onto at least a portion of the outer surface (<NUM>) of the base (<NUM>) of the body (<NUM>) by a second manufacturing method including an additive manufacturing method,
the body (<NUM>) includes a first portion defining the cavity (<NUM>) and a second portion including the base (<NUM>), the at least one layer (<NUM>) being disposed about at least a portion of an outer circumference of the second portion, and
the at least one layer (<NUM>) includes along the base (<NUM>) a portion (<NUM>) having a first thickness (t1) and a portion (<NUM>) having a second thickness (t2) with the first thickness (t1) being greater than the second thickness (t2).