US20230240722A1 - Expandable articulating intervertebral implant with limited articulation - Google Patents

Abstract

An artificial functional spinal unit including an expandable intervertebral implant that can be inserted via a posterior surgical approach and used with one or more facet replacement devices to provide an anatomically correct range of motion is described. Lordotic and non-lordotic expandable, articulating implants and cages are described, along with embodiments of facet replacement devices and instruments for insertion. Methods of insertion are also described.

Description

PRIORITY
• This application is a continuation of U.S. patent application Ser. No. 11/134,079 entitled “Expandable Articulating Intervertebral Implant with Limited Articulation” filed May 20, 2005 which is a continuation of U.S. Pat. No. 7,753,958 entitled “Functional Spinal Units” to Charles R. Gordon, Corey T. Harbold, and Heather S. Hanson, issued on Jul. 13, 2010 which is a continuation-in-part of PCT Application No. US2004/025090 entitled “Artificial Spinal Unit Assemblies” to Charles Gordon and Corey Harbold, filed on Aug. 4, 2004 which is a continuation-in-part of U.S. Pat. No. 7,909,869 entitled “Artificial Spinal Unit Assemblies” to Charles Gordon and Corey Harbold, issued on Mar. 22, 2011 which is a continuation-in-part of U.S. Pat. No. 7,316,714 entitled “Artificial Functional Spinal Unit Assemblies” to Charles Gordon and Corey Harbold, issued on Jan. 8, 2008, which is a continuation-in-part of U.S. Pat. No. 7,204,853 entitled “Artificial Functional Spinal Unit Assemblies” to Charles Gordon and Corey Harbold issued on Apr. 17, 2007.
BACKGROUND1. Field of the Invention
• Embodiments of the invention generally relate to functional spinal implant assemblies for insertion into an intervertebral space between adjacent vertebrae of a human spine, and reconstruction of the posterior elements to provide stability, flexibility, and proper biomechanical motion. More specifically, embodiments of the invention relate to artificial functional spinal units including an expandable artificial intervertebral implant that can be inserted via a posterior surgical approach and used in conjunction with one or more facet replacement devices to approach an anatomically correct range of motion. Embodiments of the invention may also be inserted via an anterior surgical approach.
2. Description of Related Art
• The human spine is a complex mechanical structure including alternating bony vertebrae and fibrocartilaginous discs that are connected by strong ligaments and supported by musculature that extends from the skull to the pelvis and provides axial support to the body. The intervertebral discs provide mechanical cushion between adjacent vertebral segments of the spinal column and generally include three basic components: the nucleus pulposus, the annulus fibrosis, and two vertebral end plates. The end plates are made of thin cartilage overlying a thin layer of hard cortical bone that attaches to the spongy, cancellous bone of the vertebral body. The annulus fibrosis forms the disc's perimeter and is a tough outer ring that binds adjacent vertebrae together. The vertebrae generally include a vertebral foramen bounded by the anterior vertebral body and the neural arch, which consists of two pedicles and two laminae that are united posteriorly. The spinous and transverse processes protrude from the neural arch. The superior and inferior articular facets lie at the root of the transverse process.
• The human spine is a highly flexible structure capable of a high degree of curvature and twist in nearly every direction. However, genetic or developmental irregularities, trauma, chronic stress, and degenerative wear can result in spinal pathologies for which surgical intervention may be necessary. In cases of deterioration, disease, or injury, a spinal disc may be removed from a human spine. A disc may become damaged or diseased, reducing intervertebral separation. Reduction of the intervertebral separation may reduce a height of the disc nucleus, which may cause the annulus to buckle in areas where the laminated plies are loosely bonded. As the overlapping laminated plies of the annulus begin to buckle and separate, circumferential or radial annular tears may occur. Such disruption to the natural intervertebral separation may produce pain, which may be alleviated by removal of the disc and maintenance of the natural separation distance. In cases of chronic back pain resulting from a degenerated or herniated disc, removal of the disc becomes medically necessary.
• In some cases, a damaged disc may be replaced with a disc prosthesis intended to duplicate the function of a natural spinal disc. U.S. Pat. No. 4,863,477 to Monson, which is incorporated herein by reference, discloses a resilient spinal disc prosthesis intended to replace the resilience of a natural human spinal disc. U.S. Pat. No. 5,192,326 to Bao et al., which is incorporated herein by reference, describes a prosthetic nucleus for replacing just the nucleus portion of a human spinal disc. U.S. Patent Application Publication No. 2005/0021144 to Malberg et al., which is incorporated herein by reference, describes an expandable spinal implant.
• In other cases, it may be desirable to fuse adjacent vertebrae of a human spine together after removal of a disc. This procedure is generally referred to as “intervertebral fusion” or “interbody fusion.” Intervertebral fusion has been accomplished with a variety of techniques and instruments. It is generally known that the strongest intervertebral fusion is the interbody fusion (between the lumbar bodies), which may be augmented by a posterior or facet fusion. In cases of intervertebral fusion, either structural bone or an interbody fusion cage filled with bone graft material (e.g., morselized bone) is placed within the space where the spinal disc once resided. Multiple cages or bony grafts may be used within that space.
• Cages of the prior art have been generally successful in promoting fusion and approximating proper disc height. Cages inserted from the posterior approach, however, are limited in size by the interval between the nerve roots. Therefore, a fusion implant assembly that could be expanded from within the intervertebral space could reduce potential trauma to the nerve roots and yet still allow restoration of disc space height. It should be noted, however, that fusion limits overall flexibility of the spinal column and artificially constrains the natural motion of the patient. This constraint may cause collateral injury to the patient's spine as additional stresses of motion, normally borne by the now-fused joint, are transferred onto the nearby facet joints and intervertebral discs. Thus, an implant assembly that mimics the biomechanical action of the natural disc cartilage, thereby permitting continued normal motion and stress distribution, would be advantageous.
• A challenge of instrumenting a disc posteriorly is that a device large enough to contact the end plates and slightly expand the space must be inserted through a limited space. This challenge is often further heightened by the presence of posterior osteophytes, which may cause “fish mouthing” of the posterior end plates and result in very limited access to the disc. A further challenge in degenerative disc spaces is the tendency of the disc space to assume a lenticular shape, which requires a relatively larger implant than often is easily introduced without causing trauma to the nerve roots. The size of rigid devices that may safely be introduced into the disc space is thereby limited.
• The anterior approach poses significant challenges as well. Though the surgeon may gain very wide access to the interbody space from the anterior approach, this approach has its own set of complications. The retroperitoneal approach usually requires the assistance of a surgeon skilled in dealing with the visceral contents and the great vessels, and the spine surgeon has extremely limited access to the nerve roots. Complications of the anterior approach that are approach-specific include retrograde ejaculation, ureteral injury, and great vessel injury. Injury to the great vessels may result in massive blood loss, postoperative venous stasis, limb loss, and intraoperative death. The anterior approach is more difficult in patients with significant obesity and may be virtually impossible in the face of previous retroperitoneal surgery.
• Despite its difficulties, the anterior approach does allow for the wide exposure needed to place a large device. In accessing the spine anteriorly, one of the major structural ligaments, the anterior longitudinal ligament, must be completely divided. A large amount of anterior annulus must also be removed along with the entire nucleus. Once these structures have been resected, the vertebral bodies are over distracted in order to place the device within the disc and restore disc space height. Failure to adequately tension the posterior annulus and ligaments increases the risk of device failure and migration. Yet in the process of placing these devices, the ligaments are overstretched while the devices are forced into the disc space under tension. This over distraction can damage the ligaments and the nerve roots. The anterior disc replacement devices currently available or in clinical trials may be too large to be placed posteriorly, and may require over distraction during insertion in order to allow the ligaments to hold them in position.
SUMMARY
• In an embodiment, an intervertebral implant may include first and second members having outer surfaces that engage vertebrae of a human spine. The implant may include an insert positioned between inner surfaces of the first and second members before insertion of the implant between the vertebrae. The implant may include an expansion member that increases a separation distance between the first member and the second member. A portion of the expansion member may engage the insert to increase a range of angular motion between the first and second members after insertion of the implant between the vertebrae. In one embodiment, the insert includes a convex spherical surface that contacts the inner surface of the first or second member. In another embodiment, the insert includes a convex ellipsoidal surface that contacts the inner surface of the first or second member.
• In an embodiment, an insert for an intervertebral implant may be rotatable. The insert may include protrusions, such as radial arms. In certain embodiments, the protrusions may be generally aligned along a longitudinal axis of the implant. The implant may further include an expansion member that engages at least one of the protrusions to rotate the insert. Rotation of the insert may increase a height of the implant. In some embodiments, an implant may provide for a functional spinal unit (e.g., an implant having a first member that articulates relative to a second member). In other embodiments, an implant may provide for fusion of the vertebrae.
• In some embodiments, the insert may have an inclined surface that engages the first or second member. In one embodiment, the insert includes a plurality of cam ramps. In certain embodiments, the insert may comprise platforms. Engagement of the platforms with the first or second member may maintain the implant at an increased height. In other embodiments, one or both of the first and second members may include an inclined surface that engages a portion of an insert. In some embodiments, the inclined portions are angled such that an anterior height of the implant differs from a posterior height of the implant after rotation of the insert.
• In an embodiment, an implant may include a spacer that is inserted between the first and second members. The spacer may maintain the implant at a desired height. In some embodiments, the spacer may include a lip that facilitates insertion (e.g., guides the spacer into position in the implant). In certain embodiments, the spacer may include a protrusion that engages a portion of the implant to provide a tactile sensation when the spacer is fully installed.
• An implant may include aligning elements to maintain alignment of a first member and a second member during use. In certain embodiments, an implant may include stabilizers coupled to a first member that engage a second member to inhibit separation of the first member from the second member. In certain embodiments, the stabilizers may be angled with respect to a top surface of the first member.
• In an embodiment, an implant may include a rotating insert whose axis of rotation is generally aligned along a longitudinal axis of the implant. The insert may include a spiral cam. In one embodiment, the spiral cam is lockable to maintain an expanded height of the implant.
• In an embodiment, a facet replacement device may include two or more pedicle screws and an elongated member. The elongated member may include retaining portions that inhibit translation of at least one end of the rod during use. In certain embodiments, the retaining portions may include rings placed over the elongated member. In one embodiment, the elongated member includes a reduced diameter portion at a junction between the elongated member and a pedicle screw. The retaining portions may allow a limited range of translation and/or angulation of the elongated member with respect to the pedicle screws.
• In some embodiments, resilient members may be provided between retaining portions on an elongated member and pedicle screws. The resilient members may cushion engagement between the retaining portions and the screws. In one embodiment, the resilient members are O-rings that partially reside in a head of a pedicle screw.
• In another embodiment, a facet replacement device may include pedicle screws having head posts and an elongated member having apertures for receiving the posts. The apertures may allow a limited range of motion of the pedicle screws relative to the elongated member. In one embodiment, the elongated member may be a flat plate. In another embodiment, the elongated member may have a T-shaped cross section. In certain embodiments, resilient members may be provided in the apertures to cushion engagement between the elongated member and the screws.
• In an embodiment, a surgical instrument may include a shaft and a driver rotatably coupled to the shaft. The driver may engage an insert of the implant while the implant is between two vertebrae of a human spine. The driver may be operable to actuate the insert to spread two or more endplate engaging members of the implant apart while the implant is between the vertebrae. The driver may be operated using a thumbwheel or similar device. In certain embodiments, the instrument may include a protector that protects portions of the driver and/or the thumbwheel from damage during use.
• In some embodiments, an instrument may include an inserter that can be movably coupled to a shaft for an implant holder or expansion driver. The inserter may be used to insert a spacer between endplate engaging members of the implant. Engagement of the inserter on the shaft may guide the spacer to a desired location for insertion between the endplate engaging members.
• In an embodiment, a holding device may be used to hold an implant or a spacer. The holding device may include a pair of opposing holding arms that engage surfaces of the implant or spacer. In some embodiments, a holding device may inhibit movement of an implant while a driver is actuated to expand the implant. In certain embodiments, a holding device may be operated using a control member, such as a thumbwheel or lever. In one embodiment, a holding device may include a shape memory alloy portion that allows release of the holding device when the device reaches a certain temperature. In another embodiment, an instrument may include a slide that is selectively positioned to inhibit release of the holding device.
• In an embodiment, a method of performing a minimally invasive surgical procedure may include removing a portion of a disc between two vertebrae of a human spine, placing an implant in a disc space between the vertebrae using a posterior approach, spreading end plate engaging members of the implant in the disc space until the implant reaches an expanded height, and fixing to the height of the implant at the expanded height. The maximum disc space height between the vertebrae at any time during the procedure may be less than or equal to the expanded height of the implant. In some embodiments, fixing the height of the implant may include inserting one or more spacers between the end plate engaging members.
BRIEF DESCRIPTION OF THE DRAWINGS
• Advantages of the present invention will become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings in which:
• FIG.1 depicts a top view of an embodiment of a cylindrical, expandable implant.
• FIG.2A is a side cross-sectional view of the embodiment depicted inFIG.1.
• FIG.2B is a side cross-sectional view of the implant embodiment depicted inFIG.1.
• FIG.3A is a cross-sectional view of an embodiment of an expandable implant in extension.
• FIG.3B is a cross-sectional view of an embodiment of an expandable implant in flexion.
• FIG.4A is a cross-sectional view of an embodiment of an expandable implant prior to expansion.
• FIG.4B is a cross-sectional view of an embodiment of an expandable implant following expansion.
• FIG.4C is a cross-sectional view of an embodiment of an expandable implant employing buttress screws to secure the device between vertebrae.
• FIG.4D is a cross-sectional view of an embodiment of an expandable implant employing an expansion plate with a securing keel to secure the device between vertebrae.
• FIG.4E is a side perspective of an embodiment of an expandable implant employing a securing keel.
• FIG.5 is a side perspective view illustrating placement of an expandable implant in an intervertebral space.
• FIG.6A depicts a top view of an embodiment of a c-shaped, expandable implant.
• FIG.6B is a top view of an embodiment of a c-shaped expandable implant, illustrating insertion of expansion screws to expand the implant.
• FIG.6C is a top view of an embodiment of a c-shaped, expandable implant, illustrating insertion of a non-threaded expansion member to expand the implant.
• FIG.6D is a top view of an embodiment of a c-shaped, expandable implant with a posteriorly positioned expansion opening.
• FIG.7A is a cross-sectional view of an embodiment of an expandable, articulating implant including an insert with stops.
• FIG.7B is a cross-sectional view of the embodiment depicted inFIG.7A showing articulation of the implant.
• FIG.8A is a top view of an embodiment of a c-shaped, expandable implant, illustrating the insertion of an expansion plate to expand the implant.
• FIG.8B is a side cross-sectional view of an embodiment of a c-shaped, expandable implant, illustrating the insertion of an expansion plate to expand the implant.
• FIG.8C is a side cross-sectional view of an embodiment of an expandable implant, featuring stabilizers.
• FIG.8D is a side cross-sectional view of an embodiment of an expandable implant in flexion, featuring stabilizers.
• FIG.9A is a top view of an embodiment of an expandable cage.
• FIG.9B is a side cross-sectional view of an embodiment of an expandable cage prior to expansion.
• FIG.9C is a side cross-sectional view of an embodiment of an expandable following expansion.
• FIG.9D is a side cross-sectional view of an embodiment of an expandable cage with a larger upper surface area prior to expansion.
• FIG.9E is a side cross-sectional view of an embodiment of an expandable cage with a larger upper surface area following expansion.
• FIG.9F is a cross-sectional view of an embodiment of a cage that is expandable in two directions.
• FIG.10A is a posterior view of an embodiment of a c-shaped lordotic expandable implant.
• FIG.10B is a top view of an embodiment of a c-shaped lordotic expandable implant.
• FIG.11A is a lateral view of an embodiment of a c-shaped lordotic expandable implant prior to expansion.
• FIG.11B is a lateral view of an embodiment of a c-shaped lordotic expandable implant following expansion.
• FIG.12A is a side cross-sectional view of an embodiment of an expandable lordotic cage prior to expansion.
• FIG.12B is a side cross-sectional view of an embodiment of an expandable lordotic cage following expansion.
• FIG.13A is a lateral view of an embodiment of a c-shaped lordotic expandable implant with an inclined expansion member.
• FIG.13B is a side cross-sectional view of an embodiment of an expandable lordotic cage with an inclined expansion member.
• FIG.14A is a perspective view of an embodiment of an expandable, articulating implant with a spiral cam.
• FIG.14B is a cross-sectional view of the implant embodiment depicted inFIG.14A prior to expansion.
• FIG.14C is a cross-sectional view of the implant embodiment depicted inFIG.14A following expansion.
• FIG.15A is a top view of an embodiment of a c-shaped expandable, articulating implant with a round insert.
• FIG.15B a side cross-sectional view of an embodiment of a c-shaped implant with an expansion member/advancing element combination prior to expansion.
• FIG.15C is a side cross-sectional view of an embodiment of a c-shaped implant with an expansion member/advancing element combination following expansion.
• FIG.16A is a perspective view of an embodiment of an expandable, articulating implant before expansion.
• FIG.16B is a perspective view of an embodiment of an expandable, articulating implant following expansion.
• FIG.17 is a perspective view of an embodiment of a portion of an implant with a double-wedged expansion member.
• FIG.18A is a cross-sectional view of an embodiment of an expandable, articulating implant with a wedged insert.
• FIG.18B is a top view of an embodiment of a spacer.
• FIG.19A is a perspective view of an embodiment of an expandable cage with an elongated insert.
• FIG.19B is a cross-sectional view of the expandable cage embodiment depicted inFIG.19A.
• FIG.19C is a view of the inferior surface of the upper body of the cage depicted inFIG.19A.
• FIG.20A is a perspective view of an embodiment of a cage including a cam and cam ramps.
• FIG.20B is a view of the inferior surface of the upper body of the embodiment of the cage depicted inFIG.20A.
• FIG.20C illustrates the use of an advancing element to advance the cam onto the cam ramp of the cage embodiment depicted inFIG.20B.
• FIG.20D is a cross-sectional view of an embodiment of an articulating cage including a cam and cam ramps.
• FIG.21A depicts a perspective view of an embodiment of an expandable, articulating cage with toothed engaging surfaces.
• FIG.21B depicts a perspective view of the cage depicted inFIG.21A (without the toothed to engaging surface) after expansion.
• FIG.22 depicts a perspective view of an embodiment of an insert with four cam ramps.
• FIG.23 depicts a perspective view of an embodiment of a portion of a cage with cam ramps and stabilizers.
• FIG.24A depicts a perspective view of an embodiment of a spacer coupled to an insert of an implant.
• FIG.24B depicts a perspective view of an embodiment of a spacer with a protrusion.
• FIG.24C depicts a perspective view of an embodiment of a spacer with a protrusion and a lip.
• FIG.24D depicts a perspective view of an embodiment of an insert with a recess for accepting a protrusion of a spacer.
• FIG.24E depicts a cross-sectional view of an embodiment of a spacer with a lip coupled to an insert in an expandable cage.
• FIG.25 depicts a perspective view of an embodiment of insertion of a spacer into an expanded cage.
• FIG.26A depicts a perspective view of an embodiment of insertion of a spacer into an expanded cage.
• FIG.26B depicts a perspective view of an embodiment of the cage depicted inFIG.26A after insertion of the spacer.
• FIG.26C depicts a perspective view of an embodiment of the cage depicted inFIG.26A after insertion of the spacer.
• FIG.27 depicts a perspective view of an embodiment of an expanded cage with a large profile spacer.
• FIG.28A is a side view of an embodiment of a facet replacement device, featuring a rod with two washer-type heads.
• FIG.28B is a side view of an embodiment of a portion of a facet replacement device, featuring a rod with a single washer-type head.
• FIG.28C is a cross-sectional view of an embodiment of a pedicle screw featuring a locking screw head.
• FIG.28D is a cross-sectional view of an embodiment of a pedicle screw featuring a head-locking insert that allows translation and rotation of a rod.
• FIG.29A is a side view of an embodiment of a portion of a facet replacement device, featuring a rod having a ball joint.
• FIG.29B is a side view of an embodiment of a portion of a facet replacement device featuring a retaining plate.
• FIG.29C is a top view of an embodiment of a portion of a facet replacement device featuring a retaining plate.
• FIG.29D is a top view of an embodiment of a portion of a facet replacement device featuring a combination multi-axial pedicle screw and retaining bar with post-type pedicle screw system.
• FIG.29E is a side view of an embodiment of a post-type pedicle screw.
• FIG.29F illustrates attachment of the retaining bar to the post-type pedicle screw.
• FIG.30 is a posterior view of a portion of a human spine after reconstruction and implantation of an embodiment of an artificial functional spinal unit including an expandable implant and a facet replacement device.
• FIG.31A is a perspective view of an embodiment of a portion of a facet replacement device.
• FIG.31B is a cross-sectional view of the facet replacement device depicted inFIG.31A.
• FIG.31C is a cross-sectional view of the facet replacement device depicted inFIG.31A.
• FIG.31D is a perspective view of an embodiment of a reduced diameter portion of a rod resting in a pedicle screw head of a facet replacement device.
• FIG.32 is a perspective view of an embodiment of a portion of a facet replacement device with a retainer to limit the motion of a rod.
• FIG.33A is a perspective view of an embodiment of a portion of a facet replacement device designed to couple to a plate with a T-shaped cross section.
• FIG.33B is a cross-sectional view of the facet replacement device depicted inFIG.33A.
• FIG.34A is a perspective view of an embodiment of a portion of a facet replacement device including a pedicle screw with a ball joint.
• FIG.34B is a cross-sectional view of the facet replacement device depicted inFIG.34A.
• FIG.34C is a cross-sectional view of the facet replacement device depicted inFIG.34A.
• FIG.35 is a perspective view of an instrument for installing and expanding an implant.
• FIG.36 is a detail view of a distal end of an instrument for installing and expanding an implant.
• FIG.37 is a detail view of a proximal end of an instrument for installing and expanding an implant.
• FIG.38 is a perspective view of an expandable implant held by an instrument including a holding device and expansion driver.
• FIG.39 is a perspective view of an instrument for installing an expandable implant including a spacer.
• FIG.40 is a perspective top view of an expandable implant held by an instrument with a partially inserted spacer.
• FIG.41 is a perspective bottom view of an expandable implant with a partially inserted spacer.
• FIG.42 is a perspective view of a holding device including opposing arms with ball detent mechanisms.
• FIG.43 is a perspective view of a holding device including opposing arms coupled by a coil spring.
• FIG.44 is a perspective view of a holding device including opposing spring arms.
• FIG.45 is a perspective view of a holding device with shape memory alloy arms.
• FIG.46 is a perspective view of an implant held in a holding device including upper and lower holding arms.
• FIGS.47A-47D illustrate use of an instrument to expand an implant and install a spacer.
• FIG.48 is a perspective view of a distal end of an instrument including a holding device with a slide.
• FIG.49 is a perspective view of an instrument with a holding device coupled to a control member.
• FIG.50A is a side view of a dual rod instrument during guided advancement of a spacer.
• FIG.50B is a side view of a dual rod instrument with one rod positioned to impact the spacer between upper and lower bodies of an implant.
• FIG.51 is a cross-sectional view of an instrument including a driving portion that directly engages an insert for expanding an implant.
• FIGS.52A and52B are side views of an instrument including multiple rods with threaded ends.
• FIG.53 is a schematic end view of a head of a fastener for a spinal system.
• FIG.54 is a schematic end view of a driver for a fastener of a spinal system.
• While the invention may be susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. The drawings may not be to scale. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but to the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.
DETAILED DESCRIPTION
• As used herein, “implant” generally refers to an artificial intervertebral implant or cage. The shape and/or size of an implant or other device disclosed herein may be chosen according to factors including, but not limited to, the surgical approach employed for insertion (e.g., anterior or posterior), the intended position in the spine (e.g., cervical or lumbar), and a size of the patient. For example, cervical implants may range from about 6 mm to about 11 mm in height, and lumbar implants may range from about 10 mm to about 18 mm in height. Heights outside these ranges may be used as required by a patient's anatomy. In general, implants with a substantially round cross section may range from about 14 mm to about 26 mm in diameter, and implants with a substantially square cross section may range from a size of about 14 mm square to a size of about 26 mm square. Implants that are substantially rectangular or trapezoidal may range from about 8 mm to about 12 mm along short side of the implant to about 24 mm to about 30 mm along a long side of the implant. As used herein, “c-shaped” implants generally refer to implants with an arcuate shape. Some c-shaped implants may be slightly curved (e.g., “banana-shaped”), while other c-shaped implants may have a higher degree of curvature (e.g., more closely approximating a “c”).
• It is to be understood that implants described herein may include features not necessarily depicted in each figure. In some embodiments, an endplate engaging surface of any implant may have regularly or irregularly spaced protrusions of uniform or various shapes and sizes to facilitate retention of the implant in a desired position between vertebrae. For example, an endplate engaging surface of an implant may include teeth or ridges. In some embodiments, members of an implant may include one or more openings to accommodate packing of bone graft material and/or to allow for bone ingrowth. In certain embodiments, one or more surfaces of an implant may include material, such as osteoconductive scaffolding, to enhance integration of the implant in a patient's spine. In some embodiments, a substance to be delivered to a patient's body may be included in a portion of the implant for delivery to the insertion site. In certain embodiments, implants depicted herein may include features allowing the implant to provide a desired lordotic angle (e.g., up to about 15°) between vertebrae.
• As used herein, an “expandable” implant generally refers to an implant designed such that a height of the implant and/or a separation distance between two parts of the implant may be increased. In some embodiments, an implant may be expanded after insertion of the implant in a human spine. In certain embodiments, a height of an implant may be decreased after the implant has been expanded during insertion in a human spine. In other embodiments, expansion of an implant may be substantially irreversible after insertion in a human spine.
• As used herein, an “articulating” implant generally refers to an implant designed such that at least two members of the implant are capable of undergoing rotational motion with respect to each other in at least one direction after insertion in a human spine. In some embodiments, one or more members of an articulating implant may be capable of rotating in more than one direction with respect one or more other members of the implant after insertion in a human spine to allow, for example, anterior-posterior rotation and/or lateral bending. In some embodiments, rotation may occur about fixed axes. In certain embodiments, an axis of rotation may change as one member of an implant rotates relative to another member of the implant. In some embodiments, one or more members of an articulating implant may be capable of translating with respect to one or more other members of the implant. As used herein, an articulating implant may also be described as “functional” or “dynamic”.
• Implant embodiments depicted herein may be expandable and/or articulating. In certain embodiments, expansion of an implant after insertion in a human spine may allow articulation of the implant. That is, the implant may not display articulating motion before expansion of the implant in a human spine. In other embodiments, expansion of an implant after insertion in a human spine may allow an increased range of motion (increased articulation) between at least two members of the implant. As used herein, “insertion” of an implant in a human spine may refer to assembly, insertion, positioning, and/or expansion of the implant.
• As used herein “facet replacement device” generally refers to a facet replacement device. For simplicity, a portion of a facet replacement device may generally be referred to as a facet replacement device. The facet replacement devices disclosed herein generally allow for rotational and/or translational motion of one or more portions of the facet replacement device including, but not limited to, a plate or elongated member (e.g., rod, bar, rail). Pedicle screws of facet replacement devices disclosed herein may retain multi-axial character after insertion of the facet replacement device. As used herein, “pedicle screw” refers to a portion of a facet replacement device that couples to bone. As used herein, “pedicle screw head” refers to a portion of a facet replacement device that accepts an elongated member. As used herein, “pedicle screw” and “pedicle screw head” may be separate components that may be assembled for use in a facet replacement device.
• As used herein, “coupled” includes a direct or indirect coupling unless expressly stated otherwise. For example, a control member may be directly coupled to a driver or indirectly coupled by way of an intermediate shaft. As used herein, “member” includes an individual member or a combination of two or more individual members. A “member” may be straight, curved, flexible, rigid, or a combination thereof. A member may have any of various regular and irregular forms including, but not limited to, a rod, a plate, a disk, a cylinder, a disk, or a bar.
• An implant may be constructed of one or more biocompatible metals having a non-porous quality (e.g., titanium) and a smooth finish. In some embodiments, an implant may be constructed of ceramic and/or one or more other suitable biocompatible materials, such as biocompatible polymers. Biocompatible polymers include, but are not limited to, polyetheretherketone resin (“PEEK”). In certain embodiments, an implant may be constructed of a combination of one or more biocompatible metals and one or more ceramic and/or polymeric materials. For example, an implant may be constructed of a combination of biocompatible materials including titanium and PEEK.
• FIG.1 depicts a top view of an embodiment of an expandable, articulating implant.Implant100 may be substantially cylindrical.FIGS.2A and2B depict a side cross-sectional view ofimplant100. In some embodiments,implant100 may includeupper body102 andlower body104. As used herein, “body” may be of unitary construction or may include two or more members. References to “upper body” and “lower body” are chosen for convenience of description of the figures. In some embodiments, an implant may be inserted in a human spine with the “upper body” superior to the “lower body”. In some embodiments, an implant may be inserted in a human spine with the “lower body” superior to the “upper body”. In certain embodiments, upper and lower bodies of an implant may be substantially interchangeable. Similarly, “inferior” and “superior” surfaces are also named for convenience of description and may assume “superior” and “inferior” positions, respectively, upon insertion.
• Implant100 may includeupper body102 andlower body104 in a substantially planar configuration. In some embodiments,superior surface106 ofupper body102 andinferior surface108 oflower body104 may include (e.g., be coupled to) osteoconductive scaffolding110 (e.g., an osteoconductive mesh structure). Vertebral bone from a patient's spine may grow throughosteoconductive scaffolding110 after insertion ofimplant100. In some embodiments,osteoconductive scaffolding110 may include spines and/or barbs that project into and secure against the bony endplates of the adjacent vertebral bodies upon expansion of the implant, reducing the possibility of subluxation and/or dislocation.
• In some embodiments, a shape ofrecess116 and insert118 may be substantially the same as a shape ofupper body102 and/orlower body104. In certain embodiments, a shape ofinsert118 may be different from a shape ofupper body102 and/orlower body104. For example, a shape ofinsert118 may be oval or round, andupper body102 and/orlower body104 may be c-shaped.Implant100 may includeexpansion member124.Expansion member124 may be inserted intoopening126 to elevateinsert118 fromrecess116.
• In some embodiments, at least a portion ofinferior surface112 ofupper body102 may be concave. In certain embodiments,superior surface114 oflower body104 may includerecess116. Recess116 may include, but is not limited to, a channel or groove. In some embodiments,recess116 may have a rectangular cross section that extends alonglower body104 in the medial-lateral direction. In certain embodiments, a shape ofrecess116 may be substantially the same as a shape ofupper body102 and/orlower body104.Insert118 may be positioned inrecess116 onsuperior surface114 oflower body104. In some embodiments,inferior surface120 ofinsert118 may be substantially flat. In some embodiments, at least a portion ofsuperior surface122 ofinsert118 may be convex. A convex portion ofsuperior surface122 ofinsert118 may articulate with a concave portion ofinferior surface112 ofupper body102, allowing rotation ofupper body102 with respect tolower body104.
• In some embodiments, one or more expansion members may be used to increase a height of an implant and/or increase a separation distance between two or more members of an implant by engaging a portion (e.g., an insert) of the implant. In some embodiments, an expansion member may be a part of the implant. That is, the expansion member may remain coupled to the implant after insertion of the implant in a human spine. For example, expansion members may include, but are not limited to, screws, plates, wedges, and/or a combination of two or more of these elements. In some embodiments, an expansion member may be a tool, instrument, or driver that is used to expand the implant during insertion but does not remain as part of the implant following insertion. In certain embodiments, an expansion member may be used to elevate an insert with respect to the lower body of the implant, thereby increasing a height of the implant and/or increasing a separation distance between two or more members of the implant. In certain embodiments, an expansion member may be used to translate and/or rotate an insert with respect to a body of the implant (e.g., upper body, lower body), thereby increasing a height of the implant and/or increasing a separation distance between two or more members of the implant.
• As depicted inFIGS.2A and2B,expansion member124 may be a screw.Expansion member124 may be inserted throughopening126 and belowinsert118 to elevate the insert fromlower body104. In some embodiments, opening126 may be threaded to accept a threaded expansion member. In certain embodiments, opening126 may include features (e.g., notches) to allow stepwise insertion of an expansion member. For example, an expansion member may enter opening126 in a ratcheting motion. In some embodiments, a void space may be created betweeninsert118 and the bottom ofrecess116 adjacent to the expansion member.
• FIGS.3A and3B depict side cross-sectional views ofimplant100 after insertion of expansion member124 (e.g., after expansion of the implant) such that concaveinferior surface112 ofupper body102 is able to articulate with convexsuperior surface122 ofinsert118.FIG.3A depictsimplant100 withupper body102 rotated with respect tolower body104 to undergo extension.FIG.3B depictsimplant100 withupper body102 rotated with respect tolower body104 to undergo flexion. In some embodiments,stabilizers128 may be used to maintain alignment ofupper body102 andlower body104 during insertion, expansion, and/or articulation ofimplant100.Stabilizers128 may include, but are not limited to, cables, retaining pegs, elastomeric bands, springs, and/or combinations thereof.
• FIGS.4A and4B illustrate the expansion ofimplant100 in more detail. As shown inFIG.4A, prior to expansion ofimplant100,upper body102 may rest uponlower body104.Inferior surface120 ofinsert118 may rest upon the bottom ofrecess116, which extends along a portion oflower body104. In some embodiments, a surface ofinsert118 may have angledportion130. In some embodiments, an angled portion may be a wedge-shaped portion. In certain embodiments, an angled portion may include a curved surface or other surface to facilitate elevation ofinsert118 fromlower body104.Angled portion130 may facilitate the lifting ofinsert118, allowingexpansion member124 to engageinferior surface120 ofinsert118. Following insertion of expansion member124 (e.g., following expansion to a desired intervertebral disc height132),inferior surface120 ofinsert118 may rest upon the expansion member withupper body102 raised abovelower body104, as depicted inFIG.4B.
• After expansion ofimplant100, the implant may be secured in place in a human spine with one or more fasteners (e.g., one or more buttress screws).FIG.4C illustrates anembodiment utilizing fastener134.Lower body104 may includeportion136 with one ormore openings138 defined therethrough. One ormore fasteners134 may be inserted throughportion136 and secured into a vertebral body. In some embodiments,fastener134 may be a screw (e.g., a buttress screw).
• In some embodiments, an implant may be secured in place with a portion of an expansion member. As shown inFIG.4D,expansion member140 may includeportion142 with one ormore openings138 defined therethrough. In some embodiments,portion142 may be a keel. Afterexpansion member140 is impacted into place, one ormore screws134 may be inserted throughportion142 and secured into a vertebral body.Expansion member140 andlower body104 may also include complementaryengaging portion144 to secureexpansion member140 withlower body104.
• FIG.4E illustratesimplant100 secured between vertebrae of a human spine. One end ofportion142 may be secured ontolower body104 ofimplant100.Portion142 may be rotated after placement of the device in the intervertebral space. After rotation ofportion142, the portion is secured to the vertebral body above or belowimplant100 with one or more fasteners134 (e.g., screws).FIG.5 depictsimplant100 following insertion in a spinal column. In some embodiments,implant100 may be posteriorly inserted and expanded throughvoid space146 created by removal of a facet joint.
• FIG.6A depicts a top view of an embodiment of a c-shaped expandable implant.Implant148 may includeinsert118. In some embodiments, insert118 may be substantially the same as a shape of an upper body and/or lower body ofimplant148. In certain embodiments, a shape ofinsert118 may be different from a shape ofupper body102 and/orlower body104. For example, a shape ofinsert118 may be oval or round, andupper body102 and/orlower body104 may be c-shaped.Implant148 may include two ormore expansion members124.Expansion members124 may be inserted intoopenings126 to elevateinsert118 fromrecess116.
• FIGS.6B and6C illustrate the insertion of expansion members into c-shaped implants. In the embodiment depicted inFIG.6B,expansion members124 forimplant148 may be screws. One ormore expansion members124 may be inserted through one ormore openings126. In some embodiments, one ormore openings126 may be threaded. In certain embodiments, as shown inFIG.6C,implant150 may includeexpansion member152.Expansion member152 may be an elongated or curved member sized and/or shaped for insertion throughopening126. In some embodiments,expansion member152 may have an angled or wedge portion. Opening126 may be non-threaded.Expansion member152 may be impacted or driven throughopening126 intorecess116 to engageinsert118. Recess116 may be an arcuate channel or a groove shaped and/or sized to facilitate insertion ofexpansion member152 before or afterimplant150 has been positioned between vertebrae of a human spine. A shape ofexpansion member152 may be complementary to a shape ofrecess116.Engaging insert118 withexpansion member152 may elevate the insert from the lower body ofimplant150, increasing a separation distance between the upper body and the lower body of the implant. In some embodiments,member154 may be used to retainexpansion member152 inrecess116.Member154 may be, for example, a cap or set screw that fits throughopening126 into a portion (e.g., a threaded portion) ofrecess116.
• FIG.6D depicts an alternative embodiment for posteriorly securing an expansion member in a c-shaped implant.Expansion member156 may be an expansion plate.Expansion member156 may be inserted throughopening126 ofimplant158.Expansion member156 may be inserted posteriorly throughopening126 to slidingly engageinsert118 inimplant158 in the medial-lateral direction. After expansion,member160 may be inserted inrecess116. In some embodiments,member160 may be a retainer plate. In some embodiments,member160 may substantially fillrecess116. In certain embodiments,member160 may include a securing device such as, for example, a screw.
• FIGS.7A and7B depict a cross-sectional view of another embodiment of an expandable, articulating implant.Implant162 may includeupper body102,lower body104, insert164,expansion member152, and setscrew166 or similar device.Insert164 may include one or more stops168. In some embodiments, stop168 may be a lip or ledge around a circumference ofinsert164. In certain embodiments, insert164 may includeangled portion130. In certain embodiments,expansion member152 may includeangled portion170. Before insertion ofexpansion member152 intorecess116,inferior surface112 ofupper body102 may rest onsuperior surface114 oflower body104.
• Withinsert164 positioned inrecess116 oflower body104,expansion member152 may be inserted intorecess116.Angled portion170 ofexpansion member152 may engageangled portion130 ofinsert164 and expandimplant162. In some embodiments, setscrew166 may be used to inhibit backout ofexpansion member152 after insertion of the expansion member. In certain embodiments, setscrew166 may be used to advanceexpansion member152 as well as to inhibit backout of the expansion member.
• After expansion ofimplant162, a separation distance betweeninferior surface112 ofupper body102 andsuperior surface114 oflower body104 may allow articulation of the upper body with convexsuperior surface122 ofinsert164.FIG.7A depictsimplant162 after expansion. As depicted inFIG.7A,upper body102 is substantially parallel tolower body104.FIG.7B depictsimplant162 following articulation ofupper body102 with respect tolower body104. As depicted inFIG.7B, stops168 may limit an angular range of motion ofupper body102 with respect tolower body104. In some embodiments, a shape and/or thickness ofstops168 may limit a range of rotation ofupper body102 with respect tolower body104 to less than about 20°. For example, a range of rotation ofupper body102 may be limited to less than about 5°, less than about 10°, or less than about 15°. A range of rotation may depend upon, for example, a shape (e.g., round, ellipsoidal, etc.) of the convex portion ofsuperior surface122 ofinsert164.
• FIGS.8A and8B depict different cross-sectional views of an embodiment of an expandable, articulating c-shaped implant. As shown inFIG.8A,implant172 depictsrecess116 designed to acceptarcuate expansion member152.Implant172 may have opening126 on an end (e.g., a short side) of the implant.Expansion member152 may be impacted into place throughopening126 to elevateinsert118 fromlower body104 afterimplant172 has been positioned in an intervertebral space.Recess116, as well asexpansion member152, may have substantially the same shape (e.g., substantially the same curvature) as a portion of the upper body and/or the lower body ofimplant172. In some embodiments, a portion ofinsert118 may be oval or round (e.g., ellipsoidal, spherical) to allow improved biomechanical motion of the implant. In some embodiments, a bottom ofrecess116 may include a feature (e.g., an integral part of the lower body or an element coupled to a portion of the lower body) designed to retainexpansion member152 in position after expansion. For example, as depicted inFIG.8B,surface174 ofrecess116 may includelip176 or other feature designed to retainexpansion member152 in the recess. During insertion ofimplant172, a surgeon may forceexpansion member152 overlip176 into place. Passage ofexpansion member152 overlip176 and into place may allow the surgeon to feel whenexpansion member152 has been properly inserted. In some embodiments,lip176 may inhibit dislocation of the implant (e.g., backout of expansion member152).
• FIGS.8C and8D depict cross-sectional views of an embodiment of an expandable, articulating implant.Implant178 may includestabilizers180.Stabilizers180 may be coupled tolower body104 and may extend from the lower body intoopenings182 inupper body102.Stabilizers180 and/oropenings182 may be of various sizes and/or shapes. For example,Stabilizers180 may be substantially round andopenings182 may be substantially oval, allowing to torsional mobility ofupper body102. In some embodiments,stabilizers180 may be captive.Stabilizers180 may inhibit dislocation ofupper body102 fromlower body104 during flexion, extension, and/or torsional motion ofimplant178. As shown inFIG.8D, whenimplant178 is flexed or extended,stabilizers180 may inhibit dislocation ofupper body102 fromlower body104.
• The disclosed techniques of expanding an implant by insertion of an expansion member may also be employed to expand a PLIF or TLIF cage.FIGS.9A-9C depict views of an embodiment of an expandable cage.FIG.9A depicts a top view ofcage184.FIG.9B depicts a cross-sectional view ofcage184 before expansion. In some embodiments,cage184 may includecage element186 and insert188.Insert188 may be positioned incage element186. In certain embodiments,cage element186 may includeosteoconductive scaffolding110. For example,cage element186 may includeosteoconductive scaffolding110 oninferior surface190. An osteoconductive substance may be placed inosteoconductive scaffolding110 to promote bone growth intocage184. In some embodiments,cage element186 may include opening192 throughsuperior surface194.
• In some embodiments, insert188 may includemember196 havinginferior surface198 andsuperior surface200. In some embodiments,member196 may be substantially planar (e.g., a plate). In certain embodiments,osteoconductive scaffolding202 may be coupled tosuperior surface200 ofmember196.Member196 may includeangled portion130.Angled portion130 may facilitate expansion of cage184 (e.g., elevation of insert188) upon insertion ofexpansion member204.Expansion member204 may be inserted into opening206 ofcage element186 and advanced (e.g., impacted, driven) to engageangled portion130 ofmember196.FIG.9C depicts a cross-sectional view of expandedcage184. In some embodiments,lip176 may inhibit dislocation ofexpansion member204 after expansion ofcage184. In certain embodiments,lip176 and/or one or more other features may secureexpansion member204 incage element186 in such a way that a surgeon may sense tactilely when the expansion member is fully inserted incage184.
• FIGS.9D and9E depict cross-sectional views of an embodiment of an expandable cage.FIG.9D depictscage208 before expansion.Insert210 ofcage208 may includeosteoconductive scaffolding212 coupled tosuperior surface214 ofmember216. In some embodiments,osteoconductive scaffolding212 may have a T-shaped cross-section, such that the osteoconductive scaffolding rests uponsuperior surface218 ofcage element220, providing an increased surface area between the osteoconductive scaffolding and the bony endplates within the intervertebral space.
• In some embodiments, expandable cages may be expanded in two or more dimensions.FIG.9F depicts an embodiment of a cage that may be expanded in two dimensions.Cage222 may includecage element186 and inserts188.Cage element186 may include opening224 throughinferior surface190 as well as opening192 throughsuperior surface194. Twoinserts188 may be positioned incage element186. Asexpansion member204 is inserted intocage element186 betweeninserts188, the inserts may be forced throughopenings192,224 to engage the bony endplates within the intervertebral space.
• FIGS.10A,10B,11A, and11B depict an embodiment of a lordotic, c-shaped expandable, articulating implant. The lumbar spine is lordotic, thus the anterior disc height is naturally larger than the posterior disc height. Therefore, an expandable implant for the lumbar spine may advantageously expand into a lordotic position.FIG.10A depicts a posterior view ofimplant226.FIG.10B depicts a top view ofimplant226.FIGS.11A and11B depict cross-sectional views ofimplant226 before and after expansion of the implant, respectively.
• Implant226 may includeupper body228 andlower body230.Lower body230 may include two or more members. In some embodiments, members oflower body230 may be coupled (e.g., hinged). Portions ofupper body228 andlower body230 may be substantially parallel before expansion ofimplant226. In some embodiments,superior surface106 ofupper body228 andinferior surface108 oflower body230 may includeosteoconductive scaffolding110. In certain embodiments, at least a portion ofinferior surface112 ofupper body228 may be substantially concave.
• Lower body230 may includelower portion232 andupper portion234. In some embodiments,lower portion232 andupper portion234 oflower body230 may be coupled withhinge236.Hinge236 may effectively fix posterior disc height238 (shown inFIG.11B). In certain embodiments,inferior surface240 ofupper portion234 may be substantially flat. In certain embodiments, at least a portion ofsuperior surface242 ofupper portion234 may be convex.Lower portion232 andinferior surface240 ofupper portion234 may be substantially parallel prior to expansion. In some embodiments,lifting mechanism244 may be located proximateanterior end246 oflower portion232. Following insertion ofimplant226 in an intervertebral space,lifting mechanism244 may be engaged to increase a height ofanterior end246 ofimplant226. Increasing a height ofanterior end246 ofimplant226 may provide a desiredanterior disc height248 and proper lordosis. As depicted inFIGS.11A and11B,anterior end246 ofupper portion234 may includenotch250.Notch250 may engagelifting mechanism244 to secure a height ofanterior end246 ofimplant226 following expansion.
• In some embodiments, at least a portion ofinferior surface112 ofupper body228 may be concave. A concave portion ofinferior surface112 ofupper body228 may articulate with a convex portion ofsuperior surface242 ofupper portion234. When viewed in the medial or lateral direction, as shown inFIGS.11A and11B,upper body228 may includeextension252 for coupling toelongated member254. In some embodiments,elongated member254 may coupleupper body228 toupper portion234 oflower body230, thus reducing a possibility of dislocation.FIG.11B depicts the posterior placement ofhinge236 and anterior placement of liftingmechanism244, withelongated member254 positioned throughupper body228 andupper portion234 oflower body230.
• A lifting mechanism may also be used to achieve desired lordosis with expandable PLIF and TLIF cages, as shown inFIGS.12A and12B.FIGS.12A and12B depict side cross-sectional views ofcage256 before and after expansion, respectively.Cage256 may includeupper body258 andlower body260. In some embodiments, hinge262 may posteriorly coupleupper body258 tolower body260. In certain embodiments, hinge262 may fixposterior disc height238 after expansion ofcage256.Superior surface264 ofupper body258 andinferior surface266 oflower body260 may includeosteoconductive scaffolding110.Lifting mechanism244 may be engaged to expandcage256. In some embodiments,lifting mechanism244 may engage notch250 after expansion, reducing the possibility for dislocation after insertion and expansion ofcage256. A height oflifting mechanism244 may be chosen to achieve a desired anterior disc height248 (e.g., to achieve proper lordosis).
• FIG.13A depicts a cross-sectional view of an expandable, articulating lordotic implant.FIG.13B depicts a cross-sectional view of an embodiment of an expandable lordotic cage.Implant268 inFIG.13A andcage270 inFIG.13B both includeexpansion member272 to achieve proper lordosis. In some embodiments,expansion member272 is generally wedge-shaped. In certain embodiments,posterior end274 ofexpansion member272 may includeangled portion276.Angled portion276 may facilitate expansion ofimplant268 andcage270.Protrusion280 may be located onsuperior surface278 of the anterior end ofexpansion member272. As show inFIG.13A,expansion member272 may be inserted betweenupper portion234 andlower portion232 oflower body230.Protrusion280 may engage notch250 to secure a height ofimplant268 andcage270 following expansion.Lip176 or other feature may be located on an anterior end ofsuperior surface282 oflower portion232 to reduce the potential of dislocation ofexpansion member272.
• FIG.14A depicts a perspective view of an embodiment of an expandable, articulating implant.Implant284 may be of any size and/or shape known in the art.FIGS.14B and14C depict cross-sectional views ofimplant284 before and after expansion, respectively.Implant284 may includeupper body286,lower body288, andelongated member290. In some embodiments,lower body288 may includechannel294.Lower body288 may includeopenings296 on opposing walls for receivingelongated member290. In certain embodiments,elongated member290 may traverse a portion (e.g., a length) ofimplant284.
• In some embodiments,elongated member290 may includecam portion298. In certain embodiments,cam portion298 may include a spiral cam portion.Cam portion298 may include an arcuate surface that resides withinchannel294 oflower body288. In some embodiments,cam portion298 may be coupled toelongated member290. In certain embodiments,cam portion298 may form an integral part ofelongated member290. In some embodiments,cam portion298 may wrap partially around elongatedmember290 with increasing thickness. In some embodiments, as depicted inFIG.14B,implant284 may be in an unexpanded position whencam portion298 rests at the bottom ofchannel294. Whenelongated member290 is rotated,cam portion298 may spin upward to expandimplant284.FIG.14C depicts a cross-sectional view of expandedimplant284.
• Superior surface300 ofupper body286 may contact the bony surface of a human vertebra after insertion ofimplant284 in a human spine. In some embodiments, an inferior surface ofupper body286 may articulate with the arcuate surface ofcam portion298. In certain embodiments,upper body286 may move back and forth against the arcuate surface ofcam portion298. This movement may allow biomechanical motion in a human spine in which implant284 has been inserted and expanded. In some embodiments,elongated member290 may be held in place inopenings296 to fix a height ofimplant284 after expansion. For example, a ratcheting device or fastener (e.g., a set screw) may be used to fix a position ofelongated member290. In certain embodiments,superior surface300 ofupper body286 and/orinferior surface302 oflower body288 may be coupled to osteoconductive scaffolding.
• FIGS.15A-15C depict an embodiment of a c-shaped expandable, articulating implant.FIG.15A depicts a top view ofimplant304 withinsert306. In some embodiments, a portion ofinsert306 may be substantially round, providing a close approximation to natural biomechanical motion.FIGS.15B and15C illustrate side cross-sectional views ofimplant304 before and after expansion, respectively.Expansion member308 may be inserted throughopening310. In some embodiments, opening310 may be threaded. Advancingelement312 may be inserted inopening310 following insertion ofexpansion member308. Advancingelement312 may be used to advanceexpansion member308 into position belowinsert306. In some embodiments, advancingelement312 may remain inrecess314 to inhibit dislocation ofexpansion member308 after expansion ofimplant304. Use of advancing element312 (e.g., a set screw) to advanceexpansion member308 into place may reduce impaction during positioning of the expansion member. Reducing impaction during positioning ofexpansion member308 may reduce stress on portions of a patient's body during the insertion procedure. It should be noted that the expansion member/advancing element combination may be employed with any of the disclosed implants, including cages.
• FIGS.16A and16B depict perspective views of an embodiment of a c-shaped expandable, articulating implant before and after expansion, respectively. As shown inFIG.16A,implant316 may includeinsert306 andexpansion member308. Insertion ofexpansion member308 is achieved by movement of advancingelement312 throughopening310 in an end ofimplant316. Advancingexpansion member308 with advancingelement312 or other device (e.g., a threaded driver) rather than impacting the expansion member may allow a smaller expansion member to be used. Using a smaller expansion member may require a shorter access to the implant, allowing an implant to be positioned in a final TLIF position and then expanded. For example, a smaller expansion member may require a shorter access to the implant. Raisinginsert306 withexpansion member308 may increase a height ofimplant316. Increasing a height ofimplant316 may increase a range of articulation of the implant after insertion of the implant in a human spine.
• FIG.17 depicts a perspective view of an embodiment of a portion of an expandable implant.Implant318 may includeexpansion member320.Expansion member320 may be advanced with advancingelement322. As depicted inFIG.17, advancingelement322 may be a screw. In some embodiments, advancingelement322 may engageexpansion member320 from a side (e.g., anterior side, posterior side) ofimplant318. In some embodiments,expansion member320 may include two angled portions.Angled portion324 may engage a portion of implant318 (e.g., an insert or a portion of an upper body or a lower body). Advancingelement322 may engageangled portion326, thus allowing a component of the force from the advancing element to increase a height ofimplant318. Accessingexpansion member320 from a longer side (e.g., posterior side) of implant318 (PLIF approach) may advantageously require a smaller incision and/or cause less tissue damage during insertion of the implant than accessing the expansion member from shorter end of the implant (TLIF approach).
• FIG.18A depicts an embodiment of a c-shaped expandable, articulating implant designed to accept a spacer between an upper body and a lower body of the implant after expansion.Upper body328 ofimplant330 may includeupper portion332 andlower portion334.Upper portion332 andlower portion334 may both have substantially the same c-shape. In some embodiments,superior surface336 ofupper portion332 may contact a bony surface of a vertebral body after insertion ofimplant330 in a human spine. At least a portion ofinferior surface338 ofupper portion332 may be concave. At least a portion ofsuperior surface340 oflower portion334 may be convex. In some embodiments,inferior surface338 ofupper portion332 may articulate withsuperior surface340 oflower portion334.
• In some embodiments,inferior surface342 oflower portion334 may includeangled portion344. As depicted inFIG.18A,angled portion344 may be a downward projecting ramp. In certain embodiments,angled portion346 ofexpansion member348 may engageangled portion344 oflower portion334 during insertion of the expansion member. After expansion ofimplant330,spacer350 may be inserted in gap352 betweenlower portion334 ofupper body328 andlower body354. In some embodiments,spacer350 may be a shim. In certain embodiments, a superior surface oflower body354 may include one or more guides356.Guides356 may include, but are not limited to, protrusions, keyways, rails, grooves, ridges, notches, and/or combinations thereof.Guides356 may align spacer350 during insertion of the spacer. In some embodiments, guides356 may inhibit dislocation ofspacer350 after insertion of the spacer.
• FIG.18B depicts a top view of an embodiment ofspacer350. In some embodiments,spacer350 may have substantially the same shape and/or profile asupper body328 and/orlower body354 ofimplant330. In certain embodiments,spacer350 may be sized such that the spacer is substantially flush with an outside edge ofimplant330. In other embodiments,spacer350 may protrude from implant330 (e.g., from a side surface of implant330) to facilitate alignment and placement of the spacer in the implant. In some embodiments,spacer350 may include one or more guides358.Guides358 may include, but are not limited to, grooves, keyways, rails, ridges, protrusions, notches, and/or combinations thereof.Guides358 onspacer350 may be complementary to guides on a portion (e.g., upper body, lower body) of an implant. A height of a spacer may be chosen to provide a desired expanded height of an implant.
• A height of a spacer may be, for example, 2 mm, 3 mm, 4 mm, or greater. Spacer height may be chosen to achieve a desired height of an implant in a patient's spine. In some embodiments, a spacer with a variable thickness may be used to provide lordosis to an implant. In some embodiments, a spacer may be constructed of biocompatible metal (e.g., titanium). In certain embodiments, a spacer may be constructed of the same material as an implant into which the spacer is to be inserted. In other embodiments, a spacer may include elastomeric material (e.g., silicone) to absorb shock and/or allow additional bending.
• FIG.19A depicts a perspective view of an embodiment of an expandable implant with an elongated, rotating insert following expansion.Implant360 may includeupper body362,lower body364, insert366, and advancingelement368. Intended placement ofimplant360 in the spine may determine a shape ofupper body362 and lower body364 (e.g., c-shaped, round).Superior surface370 oflower body364 may includerecess372. In some embodiments,recess372 may be a channel.Insert366 may be positioned inrecess372.Insert366 may remain inrecess372 during insertion and expansion ofimplant360. In some embodiments,inferior surface374 ofinsert366 may be substantially flat.Insert366 may have an elongated shape with one or moreangled portions376 on superior surface378 of the insert.
• As advancingelement368 is advanced,angled portions376 may engageextensions450 of upper body460. Advancement of advancingelement394 and rotation ofinsert366 may increase a separation distance between upper body460 and lower body462.
• FIG.19B depicts a cross-sectional view ofimplant360 before expansion. During expansion, angledportions376 on superior surface378 ofinsert366 may engageangled portions380 extending downward frominferior surface382 ofupper body362. As advancingelement368 is advanced intorecess372 inlower body364, insert366 rotates inrecess372 onsuperior surface370 oflower body364. In some embodiments, insert366 remains inrecess372 and is not elevated during insertion and expansion ofimplant360 in a human spine. Asinsert366 is rotated,angled portions380 ofupper body362 slide up theangled portions376 ofinsert366, and the upper body is elevated abovelower body364 to increase a height ofimplant360 and/or to increase a separation distance between the upper body and the lower body. The elongated nature ofinsert366 may result in a more stable expanded implant than an insert of a shorter length. As shown inFIG.19B,angled portions376 and/orangled portions380 do not include a platform portion. Thus,implant360 may have a variable expansion height. An expansion height ofimplant360 may be secured with advancingelement368 or with a spacer of a desired height.
• FIG.19C depicts a view of an inferior side ofupper body362 withinsert366 positioned on retainingpost384.Insert366 may rotate around retainingpost384. In certain embodiments, retainingpost384 may limit a height ofimplant360 and/or limit a separation distance betweenupper body362 andlower body364.
• FIG.20A depicts a perspective view of an embodiment of a c-shaped expandable implant with a cam device.Implant386 may includeupper body388,lower body390, insert392, and advancingelement394. In some embodiments, advancingelement394 may be an expansion member. In some embodiments, insert392 may be a cam. As with all of the disclosed embodiments, the placement ofimplant386 in the spine will determine a shape ofupper body388 andlower body390. In some embodiments,lower body390 may includerecess398 insuperior surface396. In certain embodiments, insert392 may be positioned inrecess398.
• In some embodiments, as shown inFIG.20B, insert392 may have a generally cylindricalcentral portion400 with opening402 defined therethrough. In certain embodiments, insert392 may include one ormore projections404 extending radially fromcentral portion400. In some embodiments,projections404 may be arms.Insert392 may be positioned inrecess398 inlower body390 on a projection (not shown) extending upward from a superior surface of the lower body such that the projection fits in opening402 ofcentral portion400 of the insert. The projection may align and/or retaininsert392 in a desired position.
• In some embodiments,upper body388 may include one or more angled portions or cam ramps406 that extend downward frominferior surface408 of the upper body. In certain embodiments, cam ramps406 may be positioned such thatprojections404 ofinsert392 engage the cam ramps ascentral portion400 of the insert is rotated around the projection oflower body390, increasing a separation distance betweenupper body388 andlower body390.
• In certain embodiments, insert392 may be rotated via the insertion of advancing element394 (e.g., a screw), as shown inFIG.20C. In some embodiments,stabilizers412 may extend downward frominferior surface408 ofupper body388 or upward from a superior surface oflower body390. In some embodiments,stabilizers412 may be, for example, retaining pegs.Stabilizers412 may be of various shapes or sizes as required to limit separation ofupper body388 andlower body390 as desired. Whenupper body388 is placed overlower body390, a large diameter portion (e.g., T-shaped, circular, ellipsoidal, rectangular) ofstabilizers412 may be held inopenings414 inlower body390. In certain embodiments,stabilizers412 may be inserted throughinferior surface416 oflower body390 and then coupled (e.g., spot welded) to inferior surface408 (e.g., openings in the inferior surface) ofupper body388.
• As depicted inFIG.20A, expansion ofimplant386 may increase a separation distance betweenupper body388 andlower body390 to formgap418 between the upper body and the lower body. The force of advancingelement394 onprojections404 ofinsert392 may inhibit the insert from rotating after expansion, thus inhibitingimplant386 from undesirably returning to an unexpanded position. In some embodiments, a spacer may be placed ingap418 betweenupper body388 andlower body390 to remove the force on advancingelement394 and to ensure thatimplant386 remains in an expanded position.
• The cam device employed in the embodiment illustrated inFIGS.20A-C, as with all the disclosed embodiments of expandable implants, may also be employed in an articulating, or functional, implant.FIG.20D depicts a cross-sectional view of an embodiment of an expandable, articulating implant with a cam insert.Insert392 ofimplant422 may be positioned inrecess398 oflower body390. Projection424 (e.g., a post) may extend upward from the superior surface oflower body390.Insert392 may rotate aboutprojection424.
• Superior surface426 ofupper portion432 ofupper body388 may contact the bony surface of an adjacent vertebral body after insertion. At least a portion ofinferior surface428 ofupper portion432 may be concave. At least a portion ofsuperior surface430 oflower portion434 may be convex. A convex portion oflower portion434 may be, for example, circular or ellipsoidal in shape. In some embodiments, a circular convex portion may allow biomechanical motion that mimics motion of the human spine. In certain embodiments, an ellipsoidal convex portion may allow translation as well as rotation between, for example, an upper portion and a lower portion of an upper body of an implant. In some embodiments,upper portion432 andlower portion434 ofupper body388 may articulate with respect to each other (e.g., may form a functional joint). In certain embodiments, cam ramps406 may extend downward frominferior surface436 oflower portion434 intolower body390. Advancingelement394 may push againstprojections404 ofinsert392, thereby rotating the insert and causing the projections to engagecam ramps406. Asprojections404 ofinsert392 engagecam ramps406 and the projections travel up the cam ramps,lower portion434 andupper portion432 ofupper body388 may be elevated with respect tolower body390. As with the other disclosed embodiments, stabilizers (e.g., captive pegs) may also be employed to inhibit separation ofupper body388 fromlower body390.
• After expansion ofimplant422,gap418 may exist betweenlower portion434 ofupper body388 andlower body390. A spacer (e.g., a shim) may be placed ingap418 to inhibitimplant422 from returning to an unexpanded position. A spacer may be of various desirable shapes and/or sizes. For example, one side of a spacer may be thicker than another side of the spacer to achieve a desired lordotic angle of the implant. In some embodiments,implant422 may be inserted in a spine upside down (e.g.,upper body388 oriented inferior to lower body390) such that an axis of rotation of the implant is located closer to the inferior body after insertion.
• FIGS.21A and21B depict a perspective view of embodiments of c-shaped expandable, articulatingimplant422 depicted inFIG.20D.FIGS.21A and21B depict retention ofstabilizers412 inlower body390. As shown inFIG.21A,superior surface426 ofupper portion432 ofupper body388 andinferior surface416 oflower body390 may includeteeth438.Teeth438 may be of any regular or irregular desired size, shape, and/or spacing to promote retention ofimplant422 between vertebrae after insertion. In some embodiments,teeth438 may be randomly spaced protrusions or barbs. In certain embodiments,upper body388 and/orlower body390 may include openings to allow for bone ingrowth into an interior portion ofimplant422.
• FIG.21A depictsimplant422 before expansion. In some embodiments, no visible gap may exist between upper body388 (or upper portion432) andlower body390 ofimplant422. Thus, a height ofimplant422 before expansion may be a minimal height of the implant (e.g., the implant may not be able to articulate before expansion). In some embodiments, a visible gap may exist between upper body388 (or upper portion432) andlower body390 ofimplant422. Thus, a separation distance between upper body388 (or upper portion432) andlower body390 ofimplant422 may increase during expansion.FIG.21B depicts fully expanded implant422 (teeth are not shown for clarity) after advancement of advancingelement394. In some embodiments, advancingelement394 may be a screw (e.g., a set screw). In certain embodiments, advancingelement394 may be positioned on a side (e.g., posterior side) of implant422 (e.g., for a TLIF application). In certain embodiments, advancingelement394 may be positioned on an end of implant422 (e.g., for a PLIF application).
• Implant422 may be fully expanded whenplatform440 of cam ramps406 rests on a superior surface of insert392 (e.g., on a superior surface ofprojections404 of the insert). In some embodiments, articulation ofupper portion432 withlower portion434 may be determined by a degree of convex curvature ofinferior surface428 ofupper portion432 andsuperior surface430 oflower portion434 and/or a relative height (and depth) of complementary convex/concave contacting surfaces of the upper portion and the lower portion. In certain embodiments,stabilizers442 may be used to alignupper portion432 withlower portion434 ofupper body388 and/or to retain the upper portion on the lower portion and/or to limit articulation between the upper portion and the lower portion. As depicted inFIG.21B,stabilizers442 may be coupled tolower portion434 ofupper body388 and reside inopenings444 ofupper portion432. In some embodiments,stabilizers442 may be coupled toupper portion432.
• FIG.22 depicts an embodiment of a portion of an expandable implant. In the embodiment depicted inFIG.22,insert446 includes fourcam ramps448. In other embodiments, an insert may include fewer (e.g., 2 or 3) or more (e.g., 5 to 12 or more) cam ramps. In contrast to the embodiment depicted inFIG.21, in which the cam ramps are a part of the upper body of the implant and are stationary during expansion of the implant, cam ramps448 may rotate as advancingelement394 rotatesinsert446. In some embodiments, advancingelement394 may rotateinsert446 until an inferior surface ofextensions450 ofupper body452 rest on a superior surface (e.g., a platform) of cam ramps448, as depicted inFIG.22. Thus, the portion of the insert depicted inFIG.22 may be used without a spacer to achieve a fixed separation distance between an upper body and a lower body of an implant. In some embodiments, a spacer may be used to provide extra stability and/or to reduce force exerted oncam ramps448 ofinsert446. In certain embodiments, a spacer may be used to achieve a separation distance less than the fixed separation distance determined by a cumulative height of cam ramps448 andextensions450 ofupper body452.
• In some embodiments, one or more cam ramps may be positioned on an inferior surface of an upper body or a superior surface of a lower body of an implant.FIG.23 depicts an embodiment of an upper body of an implant.Upper body464 may include cam ramps406. Advancement of an insert up a curved and/or inclined surface of cam ramps406 may determine an expansion height of an implant (e.g., a separation distance between an upper body and a lower body of the implant).Stabilizers466 may allowupper body464 and a lower body of the implant to remain coupled during and after expansion of the implant. In some embodiments,stabilizers466 may limit a height of an implant and/or a separation distance between an upper body and a lower body of the implant. Opening468 ofupper body464 may allow bone graft material to be packed inside the implant.
• In some embodiments, a spacer and an insert may include complementary portions that allow a spacer to be coupled to an implant (e.g., reversibly or irreversibly locked into place between an upper body and a lower body of the implant).FIG.24A depicts a perspective view of an embodiment ofspacer470 coupled to insert472.FIG.24B depicts a perspective view ofspacer470.FIG.24C depicts a perspective view of anotherspacer474.Spacers470,474 may includeprotrusion476. In some embodiments,protrusion476 ofspacers470,474 may be press fit or loose fit into a recess of a member of an implant (e.g., an insert). Fitting (e.g., snapping)protrusion476 into a recess may advantageously provide a tactile indication to a surgeon that spacer470,474 is properly placed and secured in an implant.
• Spacers may have various features designed to facilitate insertion in an implant, retention in an implant, and/or removal from an implant. For example,spacer470 shown inFIG.24B may includerecess478. Recess478 may allowspacer470 to be grasped for insertion in an implant and/or for removal from an implant.Spacer474 shown inFIG.24C may includelip480.Lip480 may facilitate (e.g., guide) insertion ofspacer474 into a gap in an implant. In some embodiments,lip480 may promote retention ofspacer474 in a gap between an upper body and a lower body of an implant. In some embodiments, a spacer may include a lip around a superior and/or inferior surface of the entire spacer. In certain embodiments, a spacer may include a lip around a superior and/or inferior surface of a portion (e.g., one side) of a spacer. In some embodiments, a lip may be an external lip or an internal lip. In certain embodiments, a lip on an inferior surface of an upper body or a superior surface of a lower body of an implant may be used together with or instead of a lip on a spacer.
• FIG.24D depicts a perspective view of an embodiment of an insert.Insert472 may includerecess482. Recess482 may be complementary to a protrusion of a spacer (e.g.,protrusion476 ofspacers470,474). As depicted inFIG.24A,protrusion476 ofspacer470 may fit securely inrecess482 ofinsert472, inhibiting backout of the spacer after the spacer has been fully inserted.FIG.24E depicts a perspective cross-sectional view ofspacer474 withlip480 used to maintain a separation distance betweeninsert472 and an upper body of an implant.
• FIG.25 depicts a perspective view of an embodiment of an expanded c-shaped implant during insertion of a spacer.Implant484 may includeupper body486 andlower body488.Spacer490 may be inserted ingap492 betweenupper body486 andlower body488. Opening494 inupper body486 may allow bone graft material to be packed insideimplant484.
• FIG.26A depicts a perspective view of an embodiment of an expanded c-shaped articulating implant during insertion of a spacer.Implant496 may includeupper body498 andlower body500.Upper body498 may includeupper portion502 andlower portion504.Spacer506 may be inserted ingap508 betweenlower body500 andlower portion504 ofupper body498. In some embodiments,stabilizers510 may extend fromlower portion504 throughopenings512 inupper portion502 ofupper body498. A size and/or shape ofstabilizers510 and/oropenings512 may allow a desired amount of articulation betweenupper portion502 andlower portion504 of upper body498 (e.g., about a convex portion of the superior surface of lower portion).
• FIGS.26B and26C depict perspective views ofimplant496 afterspacer506 has been fully inserted.FIG.26B depictsimplant496 withupper portion502 angled relative to lowerportion504 ofupper body498. Superior surface oflower portion504 may include a convex portion (e.g., substantially ellipsoidal or round) that articulates with a concave portion of inferior surface ofupper portion502 to allow translation, rotation, anterior/posterior bending, and/or lateral bending ofupper portion502 relative tolower portion504 ofupper body498, subject to size, shape, and orientation ofstabilizers510 andopenings512.FIG.26C depictsimplant496, with details ofstabilizers510 andopenings512 visible.Stabilizers510 may be shaped and oriented such thatupper portion502 is angled ontolower portion504 during assembly ofimplant496. Angled portions ofstabilizers510 andopenings512 may allow desired ranges of translational and/or rotational motion ofupper portion502 relative tolower portion504 while inhibiting separation of the upper portion from the lower portion.
• FIG.27 depicts a perspective view of an embodiment of a c-shaped expandable implant with a spacer.Implant514 may includespacer516 betweenupper body518 andlower body520.Spacer516 may have a larger profile thanupper body518 andlower body520 ofimplant514. Thus, a portion ofspacer516 may protrude from a circumference ofimplant514. A spacer with a larger profile than an upper body and/or lower body of an implant may provide torsional support and/or facilitate insertion of the spacer during a surgical procedure.
• FIG.28A depicts a side view of an embodiment of a facet replacement device.Facet replacement device522 may includeupper pedicle screw524 andlower pedicle screw526.Rod528 may be retained inhead530 ofupper pedicle screw524 andhead532 oflower pedicle screw526.Rod528 may have washer-type ends534 that allow for posterior compression, but not extension.
• FIG.28B depicts a side view of an embodiment of a facet replacement device.Facet replacement device536 may includerod538.Rod538 may include a single washer-type end540 onlower end542.Head544 ofupper pedicle screw546 may have threaded lockingscrew548, as shown in the cross section inFIG.28C. Threaded lockingscrew548 may holdrod538 in place and inhibithead544 of pedicle screw546 from swiveling while allowingrod538 to rotate and translate through the head of the pedicle screw.
• FIG.28D depicts a cross-sectional view of an embodiment of a head-locking insert that may be used in conjunction with a pedicle screw having a locking-type head. In some embodiments, insert550 may have a similar shape to head544 ofpedicle screw546.Insert550 may be of solid construction, with opening554 defined therethrough. In some embodiments, opening554 may substantially align with the opening defined throughhead544 ofpedicle screw546. Asset screw556 is engaged intohead544 ofpedicle screw546, force is applied to the top ofinsert550 and is transferred to the bottom of the head. The force locks head544 ofpedicle screw546, as with conventional locking pedicle screws; however, the force is not transferred torod538. With no force transferred torod538, the rod may rotate in and translate throughhead544 of the pedicle screw. Alternatively, a shorter insert550 (e.g., threaded only part way into head544) may be used to inhibit a transfer of force to the bottom of the head such that the pedicle screw head undergoes multi-axial motion while retaining the rod in the head.
• FIG.29A depicts a side view of an embodiment of a facet replacement device.Facet replacement device558 may includeupper pedicle screw560 andlower pedicle screw562.Rod564 may be retained within heads of pedicle screws560,562. Both pedicle screws560,562 may be secured with lockingscrews566 that inhibit heads568,570 of the pedicle screws from swiveling while allowing rotation and/or translation ofrod564.Rod564 may includerod members572,574 coupled via ball joint576. Ball joint576 may allow for a generally upward rotation, away from the bony surfaces of the vertebrae to which pedicle screws560,562 are secured, but inhibit a generally downward rotation, which would bring the ball joint in contact with the vertebrae to which the pedicle screws are secured.
• FIGS.29B and29C depict side and top views, respectively, of an embodiment of a facet replacement device.Facet replacement device578 may includeupper pedicle screw580 andlower pedicle screw582 having post-type heads584,586. Rather than the previously described rod, retainingplate588 may be included.Elongated openings590 may be defined through retainingplate588 positioned on the post-type heads584,586 of pedicle screws580,582. Post-type heads584,586 may be allowed to move inelongated openings590, providing a limited range of motion. Employingcushioning pads592 made of rubber or other elastomeric biocompatible material may dampen movement of retainingplate588. Post-type heads584,586 may also include threaded orlockable caps594 to inhibit dislocation of retainingplate588 from the post-type heads.
• FIG.29D illustrates a pedicle screw havingpost-type head584 used in conjunction with a pedicle screw having a locking ornon-locking type head598. Retainingplate588 may be formed withrod600 on one end, which may be slidingly positioned throughpedicle screw head598.
• As shown inFIGS.29E and29F,post-type heads604 ofpedicle screws606 used in conjunction with retainingplate588 may also exhibit multi-axial motion.Post-type head604 may be coupled topedicle screw606 with ball joint608.FIG.29F shows spacer610 disposed below retainingplate588.Spacer610 may allow for rotation of ball joint608.
• FIG.30 depictsfacet replacement device558 ofFIG.29A in place on the spinal column. Note thatimplant612 has been posteriorly placed within the intervertebral space through the void created by the surgical removal of the natural facet joint. In addition, ball joint576 may rotate in the posterior (upward) direction during posterior compression to inhibit impact upon the bony surfaces of the spine.
• FIG.31A depicts a perspective view of a portion of an embodiment of a facet replacement device.Facet replacement device614 may includepedicle screw head616,pedicle screw618,lower saddle620,upper saddle622, and setscrew624.Rod626 may be positioned betweenlower saddle620 andupper saddle622. Setscrew624 may securelower saddle620,upper saddle622, androd626 inpedicle screw head616 offacet replacement device614. In some embodiments, a diameter of a portion ofrod626 held betweenlower saddle620 andupper saddle622 may substantially the same diameter as other portions of the rod. For example,rod626 may be of substantially constant diameter. In certain embodiments, a portion ofrod626 held betweenlower saddle620 andupper saddle622 may be reduced in diameter relative to other portions of the rod.FIG.31B depicts a cross-sectional view of reduceddiameter portion628 ofrod626 positioned inpedicle screw head616 offacet replacement device614.
• FIGS.31B and31C depict perspective cross-sectional views offacet replacement device614. As shown inFIGS.31B and31C,rod626 may have reduceddiameter portion628 positioned betweenlower saddle620 andupper saddle622. Reduceddiameter portion628 ofrod626 may be secured in opening630 formed bylower saddle620 andupper saddle622.Rod626 may be retained in a desired position betweenlower saddle620 andupper saddle622 by O-rings632. As depicted inFIG.31B, O-rings632 may reside ingrooves634 inrod626. A position ofgrooves634 inrod626 may be chosen to allow translation of the rod throughopening630 with O-rings632 positioned ingrooves634. O-rings632 may be made of any biocompatible elastomeric material including, but not limited to, silicone.Grooves634 may have any desirable cross-sectional shape including, but not limited to, rectangular, square, arcuate, or v-shaped.
• As depicted inFIGS.31B and31C, opening630 formed bylower saddle620 andupper saddle622 may have a diameter that exceeds a diameter of the portion of rod626 (e.g., reduceddiameter portion628 held between the upper saddle and the lower saddle. With a diameter of opening630 that exceeds a diameter ofrod626 held in the opening, the rod may be able to move relative topedicle screw head616 offacet replacement device614. In some embodiments,rod626 may be able to translate and/or rotate with respect topedicle screw head616. In certain embodiments,rod626 may be able to rotate about axes parallel and/or perpendicular to a longitudinal axis of the rod. As depicted inFIG.31B, rotation ofrod626 about an axis perpendicular to a longitudinal axis of the rod may result in tilting or angulation of the rod relative topedicle screw head616. In some embodiments, movement ofrod626 in opening630 may be cushioned by O-rings632.
• FIG.32 depicts a perspective view of a portion of an embodiment of a facet replacement device that may be used in a 2-level spinal stabilization procedure.Facet replacement device636 may includepedicle screw head616,pedicle screw618, lower saddle (not shown),upper saddle622, and setscrew624.Retainer638 may holdrod626 in opening630 formed by the lower saddle andupper saddle622. Opening630 may be sized as noted with respect to facet replacement device614 (FIG.31) to allow rotational and/or translational motion ofrod626 in the opening. O-ring632 may cushion movement ofrod626 inopening630.Rod626 used withfacet replacement device636 may have a substantially uniform diameter. That is,facet replacement device636 does not require a portion ofrod626 to have a reduced diameter. Therefore,pedicle screw head616 may be placed at any desired position along a length ofrod626. Adjustable positioning ofpedicle screw head616 along a length of a rod of uniform diameter may allow the use of thefacet replacement device636 in a two-level or multi-level spinal stabilization procedure.
• Retainer638 may be a c-shaped element withopening640. A diameter ofrod626 may exceed a length ofopening640. Thus, afterretainer638 has been snapped ontorod626, the retainer may remain securely on the rod. Rotational motion ofrod626 in opening630 may be limited by relative diameters ofrod626 andopening630. Translational motion ofrod626 throughopening630 may be limited by placement ofretainers638 on either side ofpedicle screw head616.
• FIG.33A depicts a perspective view of an embodiment of a portion of a facet replacement device including a plate rather than a rod.Facet replacement device642 may includepedicle screw618,pedicle screw head644, andfastener646. In some embodiments,fastener646 may be, for example, a screw.Plate648 may be coupled betweenpedicle screw head644 andfastener646. In some embodiments,plate648 may have a T-shaped cross section. In certain embodiments, a T-shaped cross section may provide a lower profile than a rod, advantageously requiring less space at a surgical site. Size, thickness, and dimensions of a T-shaped cross section may vary as needed for strength, stability, and surgical access. For example,stem portion650 ofplate648 may be of various heights.
• FIG.33B depicts a cross-sectional view offacet replacement device642 includingplate648.Plate648 may be coupled topedicle screw head644 betweenlip652 of the pedicle screw head andlip654 offastener646. In some embodiments,fastener646 may have a threaded portion that engages a threaded portion inside pedicle screw head644 (threaded portions not shown). In some embodiments,spacer656 may be positioned betweenpedicle screw head644 andfastener646. In certain embodiments,spacer656 may fit inside opening658 in plate648 (e.g., between the plate and fastener646). A diameter ofopening658 may be sized such thatplate648 can rotate and/or translate relative topedicle screw head644. In some embodiments,spacer656 may be a bushing or an O-ring.Spacer656 may be made of elastomeric materials such as, but not limited to, silicone.Spacer656 may cushion and/or dampen movement ofplate648 relative topedicle screw head644 and/orfastener646 to allow smoother biomechanical motion after insertion in a human spine.
• FIG.34A depicts a perspective view of an embodiment of a portion of a facet replacement device with a pedicle screw that retains mobility after a rod is secured.Facet replacement device660 may includepedicle screw head662,pedicle screw664,upper saddle666, and setscrew624.Ball joint668 ofpedicle screw664 may rest inbase670 ofpedicle screw head662. A portion ofrod626 may contact ball joint668 ofpedicle screw664. In some embodiments,rod626 may have a reduced diameter portion that resides inpedicle screw head662 and contacts ball joint668 ofpedicle screw664. In other embodiments,rod626 may have a substantially constant diameter.
• In some embodiments, an outside portion ofupper saddle666 and an inside portion ofpedicle screw head662 may be complementarily threaded (not shown), such that the upper saddle may be threaded into the head. In certain embodiments,pedicle screw head662 may be threaded such thatupper saddle666 may be threaded a limited distance into the head (e.g.,upper saddle666 does not contact base670). Setscrew624 may inhibit backout ofupper saddle666 frompedicle screw head662. A length of threading inpedicle screw head662 may be chosen such thatupper saddle666 may be fully secured in the head without tighteningrod626 onto ball joint668. Thus, withrod626 fully secured inhead662, the rod andpedicle screw664 both retain rotational mobility. In some embodiments, O-rings632 may be positioned onrod626 on both sides ofupper saddle666. Translation ofrod626 inpedicle screw head662 may be limited by the placement of O-rings632 on the rod and/or by a retainer.
• FIGS.34B and34C depict cross-sectional views offacet replacement device660. As shown inFIGS.34B and34C, reduceddiameter portion628 ofrod626 may be held loosely betweenupper saddle666 and ball joint668 ofpedicle screw664. With threading (not shown) insidepedicle screw head662 extending only partially down toward the base of the pedicle screw head,upper saddle666 may securerod626 in the pedicle screw head without causing the rod to bear down on ball joint668 ofpedicle screw664. Withrod626 and ball joint668 able to move freely, the rod may retain rotational (and/or translational) mobility after insertion offacet replacement device660 in a human spine.
• In some embodiments, instruments may be used to install elements of an implant in a spine. Instruments may also be used to position (e.g., rotate, translate, expand) elements of an implant in vivo. In certain embodiments, a single instrument may be used to perform multiple steps of a spinal procedure. For example, an instrument may be used to position an implant in an intervertebral space and to actuate an expansion member to expand the implant in the intervertebral space.
• FIG.35 depictsinstrument700 for use in installing and expanding an implant.Instrument700 may haveproximal end702 anddistal end704.Instrument700 may includeouter shaft706,driver708, holdingdevice710, and handle712. As used herein, “shaft” includes elongated members having various regular and irregular cross-sections, including, but not limited to, round, square, rectangular, hexagonal, or irregular. A shaft may be solid or hollow.
• Instrument700 may includethumbwheel714.Thumbwheel714 may be coupled todriver708.Thumbwheel714 may act as a control member fordriver708. As used herein, “control member” includes any element that is operable by a user to control position, orientation, or motion of another element. Other examples of control members include, but are not limited to, a knob, a lever, or a button. In some embodiments, a control member may be operated using a tool.
• In one embodiment,thumbwheel714 may be fixedly coupled todriver708 such thatdriver708 rotates asthumbwheel714 is rotated. In another embodiment,thumbwheel714 may be threadably coupled todriver708 such thatdriver708 translates along its axis whenthumbwheel714 is rotated.
• FIG.36 depicts a detail view ofdistal end704 ofinstrument700.Holding device710 may hold an implant during insertion of the implant between two vertebrae. As used herein, “holding device” includes any element or combination of elements that may be used to hold, support, or grip another element, such as an implant, spacer, or insert. Examples of holding devices include, but are not limited to, a clamp, a clip, or a threaded rod. In some embodiments, a holding device may include one or more opposing holding elements. For example, as shown inFIG.36, holdingdevice710 may include holdingarms716. Holdingarms716 may be hinged tobase718.Base718 may be coupled toouter shaft706. Holdingarms716 may be coupled tospring clip720.Spring clip720 may maintain holdingarms716 in a closed position (as shown inFIG.36) unless at least a predetermined amount of separation force is applied toinstrument700 and an implant.
• Lobes722 on holdingarms716 may engage complementary surfaces (e.g., notches, grooves) on an implant or spacer. Engagement between lobes and complementary surfaces on an implant or spacer may promote engagement between an instrument and an implant or a spacer. Holding arms may include other engaging elements, such as tabs, grooves, or pins. In certain embodiments, the inner surfaces of holding arms on a holding device may be flat. The inner surfaces of holding arms may be textured or smooth.
• In some embodiments,spring clip720 may be at least partially made of a shape memory alloy.Spring clip720 may be actuated by allowing the spring clip to reach a predetermined temperature. Whenspring clip720 is actuated, the spring clip may urge holdingarms716 outwardly from a closed position. In one embodiment,spring clip720 may be actuated by body heat. In another embodiment,spring clip720 may be actuated by electrical current carried by insulated conductors in or on the instrument.
• Base718 of holdingdevice710 may allow for passage ofdriver708.Driver708 may includeinner shaft724 anddriver head726.Inner shaft724 may be coupled with thumbwheel714 (shown inFIG.35).Driver head726 may have any of various forms suitable for actuating (e.g., rotating, advancing) a portion of an expansion member or insert. In one embodiment, a driver head may include external threads that can engage internal threads on a portion of an implant. Other examples of driver head types include, but are not limited to, slotted, Phillips, square, hexagonal, or hexalobular. In some embodiments, the driver head may engage a set screw in the implant.
• FIG.37 depicts a detail view ofproximal end702 ofinstrument700. Handle712 may includegrip portion728 andend portion730.End portion730 may include a surface suitable for receiving impact by another instrument.Slot732 may be provided betweengrip portion728 andend portion730.Thumbwheel714 may partially reside inslot732. In certain embodiments, surfaces ofthumbwheel714 may have knurls, ribs, or similar characteristics to facilitate rotation of the thumbwheel.
• Handle712 may protect portions of the instrument from damage during use. For example, handle712 may protect against damage to threads oninner shaft724 when another instrument is used to strikeinstrument700. In one embodiment, a transverse cross section ofhandle712 atslot732 may be generally rectangular, as shown inFIG.37. A rectangular cross section atslot732 may allow a user to access a sufficient portion ofthumbwheel714 to turn the thumbwheel, but still protectthumbwheel714 and inner shaft724 (shown inFIG.35) from damage. A transverse cross section of handle atslot732 may be shapes other than rectangular, such as square, oval, hexagonal, or irregular.
• Although the protecting portions ofinstrument700 shown inFIG.37 are an integral part ofhandle712, a protector in other embodiments may be a separate component from the handle. In certain embodiments, a protector may be removable from an instrument so that a user may access a driver and/or control member.
• FIG.38 depictsimplant484 held byinstrument700 afterdriver708 has been operated to expand the implant. Whenimplant484 is initially coupled to holdingdevice710,lobes722 of holdingarms716 may engage in holdingrecesses733 on either side oflower body488. Engagement oflobes722 in holdingrecesses733 may help maintain a position of the implant during insertion and/or expansion of the implant. Engagement oflobes722 within holdingrecesses733 may placeimplant484 in a desired alignment for insertion between the vertebrae and engagement with an expansion tool. The location of holdingrecesses733 may be selected according to the approach to be used (e.g., TLIF, PLIF) and the location of an expansion member of the implant. For example, for a TLIF implant, holding recesses may, in some embodiments, be located near both longitudinal ends of the implant.
• In some embodiments,driver head726 may engage an insert (e.g., insert472 depicted inFIG.24D) of an implant. In other embodiments,driver head726 may engage a set screw (e.g., advancingelement394 depicted inFIG.21B) of an implant, which may in turn actuate (e.g., translate or rotate) an insert. Actuation ofdriver708 may expandimplant484 to the expanded position shown inFIG.38. Afterimplant484 has been expanded,instrument700 may be pulled away from the surgical site with enough force to overcome the closing force of holdingdevice710, thereby spreading holdingarms716 apart to allow separation ofinstrument700 fromimplant484 and removal of the instrument from the site. In another embodiment, a release mechanism can be used to spread holdingarms716 apart.
• In some embodiments, an inserter for a spacer may be used in combination with an implant holder and/or a driver for an expansion member. In some embodiments, an inserter may include a guide that engages a portion of an implant holder. The guide may be used to position the spacer near a desired location near the implant and/or to insert the spacer in the implant. Examples of guides include, but are not limited to, a fork, a hook, a ring, a spring clip, a tab, a rail, or a groove. In some embodiments, an inserter may be used to guide a spacer to a location near an implant, such as at a gap between an upper body and a lower body of the implant. In certain embodiments, an inserter may be advanced on a shaft to fully insert a spacer between upper and lower bodies of an implant.
• FIG.39 depictsinstrument736 includinginserter738 for holdingspacer470.Inserter738 may includeinserter shaft740,inserter handle portion742,spacer holding device744, and guidefork746.Guide fork746 may engageouter shaft706.Inserter handle portion742 may includebend748. Bend748 may allow a proximal portion ofinserter handle portion742 to be positioned close to handle712 soinserter handle portion742 may be manipulated in a relatively small incision.
• In the embodiment shown inFIG.39,inserter738 may be easily separated fromouter shaft706. Thus, the surgeon could first insert and expand the implant, then introduceinserter738 into the incision. In other embodiments, an inserter may be permanently coupled to the rest of an instrument.
• FIG.40 depicts a detail view ofimplant484 held byinstrument736, as seen from the upper side of the implant.FIG.41 depicts a detail view ofimplant484 held byinstrument736, as seen from the lower side of the implant. InFIGS.40 and41,spacer470 is partially inserted betweenupper body486 andlower body488 ofimplant484.
• In the embodiment shown inFIG.40,spacer holding device744 includes holdingarms716 that are fixed with respect tobase718. Each of holdingarms716 may includeball detent mechanism750.FIG.42 depicts a detail view ofball detent mechanisms750. Detent springs752 may provide a desired amount of clamping force onspacer470. In other embodiments, a spacer holding device may include hinged arms that are similar to those of holdingdevice710 shown inFIG.36.
• Referring again toFIG.36, it is noted thatspring clip720 may serve as a biasing element to maintain a holding force on the implant. As used herein, a “biasing element” includes any element that biases a member of a device toward one position. A biasing element may be a separate element of a holding device or integral to another element of the device (e.g., a holding arm). Biasing elements include, but are not limited, resilient members such as metal springs or elastomeric bands. Additional embodiments of holding devices with biasing elements are described below.
• FIG.43 depicts holdingdevice710 including holdingarms716 hinged to base718 and connected bycoil spring754. In one embodiment,coil spring754 is spot welded to the holding arms.FIG.44 depicts an alternate embodiment of holdingdevice710 that includesspring arms755. In certain embodiments,spring arms755 may be made of 302, 314, or 316 stainless steel.FIG.45 depicts a holdingdevice710 having holdingarms716 made of a shape memory alloy. Holdingarms716 may be actuated by allowing the holding arms to reach a predetermined temperature. When holdingarms716 are actuated, the holdingarms716 may move outwardly from a closed position. Holdingarms716 may be actuated using body heat, insulated electrical current, or another heat source.
• FIG.46 depicts an alternate embodiment of a holding device.Holding device710 may engage a top surface ofimplant484.Notches756 inimplant484 may allow the outer surfaces of holdingarms716 to be flush with the outer surfaces ofupper body486 andlower body488, facilitating insertion ofimplant484 between the vertebrae. In another embodiment, a holding device may engage top and bottom surfaces of a spacer for an expandable implant.
• FIGS.47A-47D depict a top view of an expandable implant during expansion of the implant and insertion of a spacer between upper and lower bodies of the implant.FIG.47A depictsimplant484 oninstrument700 before expansion ofimplant484.Driver head726 ofdriver708 may be advanced into a tapped through hole inlower body488 ofimplant484 until the tip ofdriver head726 engagesinsert472. Advancement ofdriver head726 may rotateinsert472 to expandimplant484 between the vertebrae (seeFIG.47B).Holding device710 may exert sufficient force onimplant484 to maintain the implant in a fixed position during actuation ofdriver708.
• Guide fork746 of inserter738 (shown inFIG.39) may be placed onouter shaft706.Inserter738 may be advanced onouter shaft706 to move spacer470 into position between the upper body and the lower body of implant484 (FIG.47C).Inserter738 may be advanced untilspacer470 is fully installed between the upper and lower bodies of implant484 (FIG.47D). Oncespacer470 is fully installed,instrument700 andinserter738 may be withdrawn from the surgical site, either together or one at a time.
• In certain embodiments, an instrument may include a movable element for maintaining a holding device in a closed position.FIG.48 depicts a distal end ofinstrument758 includingslide760.Slide760 may includeprojections762.Projections762 may definenotches764 at a distal end ofslide760.Bottom surfaces766 ofnotches764 may act as stops against axial motion of holdingdevice710.Spring clip720 may bias holding arms outwardly from the closed position shown inFIG.48. Whenprojections762 are adjacent to holdingarms716 of holding device710 (as shown inFIG.48, for example), the projections may inhibit outward rotation of the holding arms, thereby keeping the holding device in a closed position. Whenslide760 is retracted from holding arms716 (e.g., by moving the slide proximally with respect to the holding device), the holding arms may move apart under the force ofspring clip720 to allow release of an implant from the instrument.
• Other arrangements may be used to maintain a holding device in a closed position. For example, a slide may include a cylindrical sleeve that passes over the outer sides of a holding device. The inner wall of the sleeve may inhibit the holding arms from moving out of a closed position.
• In some embodiments, a holding device for an implant or spacer may be coupled to a control member, such as a thumbwheel or lever. The control member may be operated to selectively hold and release the implant or spacer.FIG.49 depicts a perspective view ofinserter768 including holdingdevice710. Holdingarms716 of holdingdevice710 may be coupled tocoil spring754 in a similar manner as described above relative toFIG.43.Coil spring754 may bias holdingarms716 into a closed position on a spacer.Cable770 may extend betweenthumbwheel714 and holdingarms716 throughhollow shaft772.Thumbwheel714 may be operated to drawcable770 away fromdistal end704 ofinstrument768.Cable770 may act against the force ofcoil spring754 to open holdingarms716, thereby allowing the spacer to be released from the holding device.Inserter768 may includeguide fork746.Guide fork746 may slidably engage a portion of an implant holder (e.g., the outer shaft shown inFIG.35) to facilitate positioning of the spacer prior to release of the spacer. In another embodiment, a control member may be connected to a locking slide to selectively lock and release a holding device.
• FIGS.50A and50B depictinstrument774 including a pair of rods for insertingimplant776 havingspacer778.Bottom rod780 andtop rod782 ofinstrument774 may be commonly supported onbase member784.Bottom rod780 may include threadedportion781. Threadedportion781 may engage in a tapped hole inlower body786 ofimplant776. In one embodiment,tab787 onspacer778 may engage a channel or groove intop rod782 to help guide and/or alignspacer778.Top rod782 may be used to guidespacer778 to a gap betweenupper body788 andlower body786, as shown inFIG.50A. Oncespacer778 is in position for insertion betweenupper body788 andlower body786 ofimplant776,top rod782 may be repositioned inbase member784 such that a distal end oftop rod782 is behindspacer778, as shown inFIG.50B.Top rod782 can be used to advancespacer778 betweenupper body788 andlower body786. In certain embodiments,top rod782 may be used toimpact spacer778 betweenupper body788 andlower body786.
• FIG.51 depicts alternative embodiment of aninstrument790 includingdriver708 withdriver head726.Driver head726 may include threadedportion792. In one embodiment, threadedportion792 may be threaded into a tapped through opening in an upper or lower body of an implant. As threadedportion792 ofdriver head726 is advanced through the opening, a distal tip ofdriver head726 may actuate (e.g., translate, rotate) an insert.Instrument790 may includeouter shaft706 and holdingdevice710. In certain embodiments, holdingdevice710 ofinstrument790 may be shaped to match a contour of an implant or a spacer. In one embodiment, holdingdevice710 may have an arcuate shape.Driver head726 may be actuated bythumbwheel714.Instrument790 may includeremovable cover794.Removable cover794 may protectthumbwheel714 from damage during use.
• FIGS.52A and52B depict an alternate embodiment of an instrument for placing and expanding an implant and inserting a spacer.Instrument796 may includebase member798.Base member798 may carryholder rod800,driver rod802, andinserter rod804.Holder rod800 may threadably engage a tapped hole inlower body786 to supportimplant806.Driver rod802 may threadably engage throughhole808 inlower body786.Driver rod802 may be advanced to actuateinsert810 to increase a separation distance betweenlower body786 andupper body788, thereby expandingimplant806.Spacer812 may be threadably coupled toinserter rod804.Inserter rod804 may be guided onbase member798 to advancespacer812 betweenlower body786 andupper body788.Holder rod800,driver rod802, andinserter rod804 may be rotated to disengage the rods fromimplant806. The rods may be removable frombase member798. In some embodiments,inserter rod804 may be loaded into an open channel inbase member798.
• It will be understood that any or all of the threaded tips onrods800,802, and804 may be replaced by other holding devices including, but not limited to, the holding devices shown inFIGS.36-44. It will be further understood that in other embodiments, an instrument may omit one or more of the implant holder, the expansion driver, or the spacer inserter. For example, an instrument may include only an implant holder and an expansion driver, or only an implant holder and a spacer inserter.
• In an embodiments, a driver for components of a spinal system may include a feature for locking with an element of a spinal system.FIG.53 depicts a schematic view of a proximal end ofhead816 onfastener818 for a spinal system.Head816 may includeside hole820. A fastener for a spinal system may include, but is not limited to, a set screw, a pedicle screw, or a threaded top for a polyaxial screw.FIG.54 depicts a schematic view of a distal end ofdriver822.Driver822 may includesleeve824 havingsocket826.Driver822 may includelock element828.Lock element828 may retractably extend intosocket826.Button830 on sleeve may be manually operated to retractlock element828 fromsocket826. Whensleeve824 ofdriver822 is placed onhead816 offastener818,lock element828 ofdriver822 may engage inside hole820.
• Engagement oflock element828 inside hole820 may inhibit axial separation ofdriver822 fromhead816 offastener818. A locking element may reduce a risk of a fastener disengaging from a tool during use. In certain embodiments,lock element828 may be used to capture a break-off head of a top for a polyaxial screw. In certain embodiments,driver822 may be coupled with a detachable handle. In some embodiments,driver822 may be used with a power tool (e.g., a drill).
• In an embodiment, an implant (e.g., for an expanse cage, dynamic cage) may be placed in a human spine using a posterior approach to a diseased lumbar disc. In some embodiments, the surgeon may use the same approach as is typically used in a microdiscectomy, TLIF, or minimally invasive posterior exposure. Such procedures involve removing some of the lamina and the medial facet joint. More bone, including the spinous process and the entire facet may be removed if indicated.
• The vital structures involved with the posterior approach are the nerve roots. The exiting root is the root that leaves the spinal canal just cephalad (above) the disc, and the traversing root leaves the spinal canal just caudad (below) the disc. The thecal sac houses the other nerve roots that exit lower. The triangle between the exiting nerve root and the traversing nerve root (Pambin's or Cambin's triangle) is the extent of the access to the disc. The triangle may be enlarged by retracting the traversing nerve root medially. If retraction is done too vigorously, however, retraction injuries may occur and serious complications such as nerve root sleeve tear may result, causing spinal fluid leakage, nerve root injury, avulsion and even spinal cord injury.
• After the lamina has been removed and the traversing root retracted medially, the posterior annulus may be exposed. While the root is retracted gently, the surgeon may create an annulotomy. Pituitary forceps may be used to remove disc material. Successively larger forceps may be used until an adequate amount of disc is removed. Care should be taken not to penetrate the anterior annulus and enter the retroperitoneal space. After adequate disc material has been removed, the end plates may be prepared using osteotomes to remove posterior ostephytes and cutting curettes to decorticate the end plates. The object of end plate preparation is to remove the cartilaginous tissue and score the cortical bone without completely removing the cortical strength.
• Once the end plates have been prepared, a trial may be placed in the disc space. The trial should be snug without significantly distracting the end plates. An unexpanded implant of approximately the same size as the trial may then be inserted into the disc space. Once positioned anterior to the nerve roots, the implant may be expanded. In some embodiments, a spacer may be introduced following expansion of the implant. The spacer may include a protrusion, groove, or similar element that snaps or locks into place to provide a tactile sensation as the spacer reaches a fully inserted position. A tactile sensation may provide the surgeon with positive feedback that the spacer is in place. In certain embodiments, the implant may be further rotated within the space after the spacer is introduced, according to the preference of the surgeon.
• An expandable implant (e.g., an expanse cage or dynamic device) may allow a larger device to be placed into the disc from a posterior approach without over distracting the nerve roots or the ligaments. In some embodiments, the implant may be expanded without any over distraction. This advantage may allow the surgeon to tension the annulus, avoid resection of the anterior longitudinal ligament, and decompress the nerve roots without requiring over distraction and the attendant possibility of injury to the nerves and ligaments. For reasons outlined above, many patients are not suitable candidates for an anterior approach. In one embodiment, an implant of less than about 12 mm in width is placed posteriorly without over distraction. In another embodiment, an implant of less than about 10 mm in width is placed posteriorly without overdistraction.
• In an embodiment, an expandable implant may expand throughout its entire width. In some embodiments, an expandable implant may be used for posterior disc height restoration without increasing lordosis. In other embodiments, an expandable implant may be used for posterior disc height restoration with increasing lordosis. In certain embodiments, an implant may be placed using a TLIF approach. Although some of the description herein relates to a PLIF or TLIF approach, it will be understood that implants as described herein may be placed using an anterior approach.
• In this patent, certain U.S. patents, U.S. patent applications, and other materials (e.g., articles) have been incorporated by reference. The text of such U.S. patents, U.S. patent applications, and other materials is, however, only incorporated by reference to the extent that no conflict exists between such text and the other statements and drawings set forth herein. In the event of such conflict, then any such conflicting text in such incorporated by reference U.S. patents, U.S. patent applications, and other materials is specifically not incorporated by reference in this patent.
• Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.

Claims (12)

1.-157. (canceled)

158. An intervertebral implant for a human spine, comprising:

a lower body comprising a superior surface and an inferior surface, wherein the inferior surface of the lower body is configured to engage a first vertebra of a human spine;

an upper body comprising an inferior surface and a superior surface, wherein the superior surface of the upper body is configured to engage a second vertebra of a human spine;

an insert positioned between the superior surface of the lower body and the inferior surface of the upper body before insertion of the intervertebral implant between the first vertebra of a human spine and the second vertebra of a human spine; and

an expansion member configured to engage the insert to increase a separation distance between the upper body and the lower body after insertion of the intervertebral implant between the first vertebra and the second vertebra of a human spine;

wherein the insert is moved in a substantially linear direction and both the upper body and lower body are moved at an oblique angle with respect to the insert.

159. The intervertebral implant ofclaim 158, wherein the insert comprises generally upwardly projecting protrusions and the upper body comprises recesses in which the protrusions of the insert are positioned, wherein the protrusions and the recesses are configured to secure the upper body and the lower body together to inhibit dislocation of the upper body from the lower body after insertion of the intervertebral implant between the first vertebra and the second vertebra of a human spine.

160. The intervertebral implant ofclaim 158, further comprising a cage comprising a first opening in a superior surface of the cage and a second opening in the inferior surface of the cage;

wherein the upper body is inserted and maintained at least partially in the first opening of the cage and the second member is inserted and at least partially maintained in the second opening of the cage, wherein the upper body is expanded above the superior surface of the cage and the inferior surface of the lower body is expanded below the inferior surface of the cage.

161. The intervertebral implant ofclaim 160, wherein prior to expansion, at least a portion of the superior surface of the upper body rests upon at least a portion of the superior surface of the cage and at least a portion of the inferior surface of the lower body rests on at least a portion of the inferior surface of the cage.

162. The intervertebral implant ofclaim 160 wherein the cage comprises a superior structure and an inferior structure, and further wherein at least one of the superior and inferior structures is configured to maintain at least a portion of the expandable element within the cage.

163. An intervertebral implant for a human spine, comprising:

a lower body comprising a superior surface and an inferior surface, wherein the inferior surface of the lower body is configured to engage a first vertebra of a human spine;

an upper body comprising an inferior surface and a superior surface, wherein the superior surface of the upper body is configured to engage a second vertebra of a human spine;

an insert comprising an elongated body having a substantially flat inferior surface, a substantially flat superior surface, and a first angled portion; and

an expansion member configured move the insert, wherein the expansion member is configured to be positioned between the upper body and the lower body;

wherein insert is configured such that the substantially flat superior and inferior surfaces of the elongated body of the insert move in a substantially linear direction and both the upper and lower bodies are moved at least partially at an oblique angle with respect to the insert to increase a separation distance between the superior surface of the upper body and the inferior surface of the lower body.

164. The intervertebral implant ofclaim 163, wherein the first angled portion of the insert engages an angled portion on the upper member to increase a separation distance between the superior surface of the upper body and the inferior surface of the lower body.

165. An intervertebral implant for a human spine, the intervertebral implant comprising:

a first body comprising a first surface and a second surface, wherein the first surface of the first body is configured to engage a first vertebra of a human spine;

a second body comprising a first surface and a second surface, wherein the second surface of the second body is configured to engage a second vertebra of a human spine; and

an expansion member comprising an elongated body having a substantially flat first surface, a substantially flat second surface, and a first angled portion at an insertion end of the elongated body, wherein the expansion member is configured to be positioned between the first body and the second body such that applying a force to a trailing end of the elongated body opposite the insertion end of the elongated body is configured to advance the first angled portion and the substantially flat first and second surfaces of the expansion member in a substantially linear direction between, and at least partially oblique to, at least a portion of the second surface of the first body and at least a portion of the first surface of the second body after insertion of the first and second bodies in a human spine so as to increase a separation distance between the first surface of the first body and the second surface of the second body.

166. An intervertebral implant for a human spine, comprising:

a first member comprising a first inferior surface and a first superior surface, where the first superior surface comprises a substantially planar surface configured to contact and support a first vertebra of a human spine;

a second member comprising a second inferior surface and a second superior surface, where the second inferior surface comprises a substantially planar surface configured to contact and support a second vertebra of a human spine;

a cage comprising a first opening in a superior surface of the cage and a second opening in an inferior surface of the cage, wherein the first member is inserted at least partially into the first opening and the second member is inserted at least partially in the second opening; and

an expansion element that is inserted between the first inferior surface of the first member and the second superior surface of the second member, wherein insertion of the expansion member expands the first and second members relative to one another to increase a separation distance between the first superior surface of the first member and the second inferior surface of the second member, wherein the first superior surface is expanded above the superior surface of the cage and the second inferior surface is expanded below the inferior surface of the cage, such that the distance between the first superior surface and the second inferior surface is greater than the distance between the superior surface and the inferior surface of the cage, and wherein the first superior surface supports at least a portion of the first vertebra above the superior surface of the cage and the second inferior surface supports at least a portion of the second vertebra below the inferior surface of the cage;

wherein portions of the first and second members are maintained within the first and second openings, respectively, of the cage.

167. The intervertebral implant ofclaim 166, wherein prior to expansion, at least a portion of the superior surface of the upper body rests upon at least a portion of the superior surface of the cage and at least a portion of the inferior surface of the lower body rests on at least a portion of the inferior surface of the cage.

168. The intervertebral implant ofclaim 166 wherein the cage comprises a superior structure and an inferior structure, and further wherein at least one of the superior and inferior structures is configured to maintain at least a portion of the expandable element within the cage.

Images