Abstract: Devices and methods for treating degenerative conditions of the spine or for alleviating pain or discomfort associated with the spinal column are disclosed. In particular, laminoplasty fixation devices and methods are disclosed. Also disclosed, is a vertebral implant comprising a first bone engaging portion configured for securing to a first cut portion of a vertebra and a second bone engaging portion configured for securing to a second cut portion of the vertebra. A body portion is provided for associating the first and second bone engaging portions at a preselected spacing from each other, wherein the implant is adjustable to select said spacing.

Abstract: Methods and devices are disclosed herein that generally involve applying thermal therapy to tissue (e.g., localized cooling or heating of tissue), and in particular applying thermal therapy to the spinal canal, tissue disposed within the spinal canal, and/or nerve roots extending from the spinal canal. In some embodiments, tissue can be cooled or heated by implanting or positioning a thermal device in proximity to the targeted tissue. A number of exemplary thermal devices are disclosed, including bone anchors, inserts for use with bone anchors, K-wires, bone anchor extensions or towers, cross-connectors, spinous process plates, spinal rods, pedicle markers, bone taps, drill bits, bone plugs, bone plates, clamps, interbody or disc implants, thermal pads, and tubing loops. The thermal device can be left in place following surgery to facilitate application of post-surgical thermal therapy. In some embodiments, the thermal device can be removed post-surgery in a minimally- or non-invasive manner.

Abstract: A pedicle screw system that includes a pedicle screw and a collar. The pedicle screw includes an insertion portion, a shaft portion that extends from the insertion portion, and a head portion that is attached to the shaft portion. The head portion has a diameter that is larger than the shaft portion. The collar includes a first aperture and a second aperture. The first aperture and the second aperture are both adapted to receive the head portion. The first aperture includes a first aperture section and a second aperture section. The first aperture section is larger than the head portion. The second aperture section is smaller than the head portion.

Abstract: The present method includes the following steps: removing a portion of a previously implanted spinal arthroplasty device; and attaching a revision component to a remaining portion of the previously implanted spinal arthroplasty device to alter a biomechanical characteristic of the implanted arthroplasty device. Another aspect of the invention provides a method of limiting motion between adjacent vertebrae including the steps of accessing an implanted spinal arthroplasty device comprising a cephalad component fixed to a first vertebra and a caudal component fixed to a second vertebra inferior to the first vertebra, the cephalad and caudal components having a range of motion between them, and attaching a revision component to the cephalad and caudal components to reduce the range of motion. The invention also includes revision devices for revising the biomechanics of implanted spinal arthroplasty devices.

Abstract: A surgical kit for fastening vertebrae via the posterior approach or via the posterolateral approach, comprising: at least one vertebral or pedicle screw, and a fitting tube co-operating with the screw; the fitting tube having two rigid branches, each of the two branches having, on the inside face of its proximal end, at least one shoulder; the kit further comprising a retractable securing insert for securing together the branches; wherein the screw head has at least two longitudinal extensions, extending in the distal direction, each of said extensions being configured to enable said screw head to be inserted into a space of complementary shape formed between the inside surface of the proximal end of one of the rigid branches and the outside surface of the proximal end of said retractable insert, when the retractable insert is fully engaged in the fitting tube.

Abstract: Internal bone fixation devices and methods for using the devices for repairing a weakened or fractured bone are disclosed herein. A device for use in repairing a fractured bone includes a delivery catheter having an elongated shaft with a proximal end, a distal end, and a longitudinal axis therebetween, wherein the delivery catheter has an inner void for passage of at least one reinforcing material and an inner lumen for passage of a light source; a conformable member releasably engaging the distal end of the delivery catheter, wherein the conformable member moves from a deflated state to an inflated state when the at least one reinforcing material is delivered to the conformable member; and an adapter releasably engaging the proximal end of the delivery catheter for receiving the light source and the at least one reinforcing material.

Abstract: Embodiments of the present invention provide methods, apparatuses, and systems for fixing dens fractures. The mode of failure for screw fixation of C2 dens fractures is often via cut-out at the anterior body. In an embodiment, securing a plate, such as a locking plate, to the anterior surface of the vertebra attached directly to an interfragmentary screw may reduce potential for anterior screw cut-out and improve construct strength. Plate supplementation of anterior screw fixation of Type II dens fractures thus improves construct strength and changes the failure mechanism from anterior screw cut-out to posterior displacement of the screw, thus improving clinical outcomes for these fractures.

Abstract: A device and method for anterior atlantoaxial stabilization may include one or more plates having a plurality of openings for receiving screws configured to screw into one or more C1 articular pillars, one or more C2 articular pillars, and the C2 body. A third cross-linking member may couple to first and second plates to provide additional rigidity and/or resistance to rotational forces. The cross-link member may be separate from one or both of the other plates. Alternatively, the cross-link member may be coupled, releasably or otherwise, to one or more of the other plates. Still further, one or more plates may be joined, e.g., via a single screw passing through openings in both plates or by making the device a unitary structure with a single, shared hole for the plates. One or more plates also may deviate from a substantially planar structure to better operatively engage the spinal features.

Abstract: An implant and method for attaching to vertebral members with the implant including a plate and a cage. The plate is configured to be positioned against and anchored to the bodies of the vertebral members. The plate may also extend into the intervertebral space between the vertebral members. The cage extends outward from the plate and is positioned within the intervertebral space. The implant provides a low profile that is positionable between the bodies of the vertebral members and the lamina/pars/facet joint. The implant may be implanted utilizing a lateral access to the spine. The implant and method may further include just the plate without the cage.

Abstract: An implant and method are provided for treating a fractured bone. The implant includes a generally elongated member having a first configuration for introduction between body tissue layers and a second configuration in-situ having a curved portion. The generally elongated member includes a plurality of alternating projections and slots and a plurality of occlusions wherein each of the occlusions is positioned between adjacent projections. The occlusions at least partially occlude an upper and/or lower side of the associated slot. Additionally, the projections may be configured to overlap each other when the implant is deployed in the second configuration. The occlusions and/or overlapping projections promote improved fluid flow and dispersion through the deployed implant and into the fractured bone. Also provided are methods for using the implant to treat a bone fracture.

Abstract: As implant for the stabilization of bones or vertebrae is provided, the implant being a solid body including a longitudinal axis that defines a longitudinal direction and including a flexible section that has a surface and has a length in the longitudinal direction, the flexible section including at least one cavity located near the surface and having a width in the longitudinal direction that is smaller than the length of the flexible section, the at least one cavity being connected to the surface through at least one slit, and a width of the slit in the longitudinal direction being smaller than the width of the cavity.

Abstract: An anterior lumbar interbody graft includes a wedge-shaped body including a hole and recesses formed in the top and bottom surfaces, radiating away from the hole.

Abstract: An implant connector comprises a first surface defining a first cavity configured for disposal of a first implant. A second surface defines a second cavity configured for disposal of a coupling member. A third surface defines a third transverse cavity configured for disposal of a second implant. The third surface includes a projection configured to engage the second implant in a provisional locking orientation. Methods of use are disclosed.

Abstract: A spinal fixation device for securing to a spine includes a body having one or more longitudinal members extending between a pair of wedge members. Each wedge member defines one or more openings therethrough for the reception of a bone screw. The wedge members are disposed on opposite ends of the one or more longitudinal members. One of the wedge members is positionable within a first intervertebral space and the other wedge member is positionable within a second intervertebral space. The one or more longitudinal members define a length that spans one or more vertebrae. The one or more longitudinal members are positionable within the one or more vertebrae when the wedge members are positioned within the respective first and second intervertebral spaces to maintain the body in a minimal profile orientation relative to the spine.

Abstract: A system for anchoring a pedicle screw in a patient's vertebra uses a pedicle screw having a threaded portion sinkable in the vertebral arch. The space between the threaded portion and cortical edge layer of the pedicle is at least partially filled by a spacer that enables an all-round support of the threaded portion at the cortical edge layer. A kit includes a pedicle screw and a spacer which at least partially fills the space between the threaded portion and cortical edge layer of the pedicle. A spacer has an essentially oval cross-section for form-locking fit in a corresponding axial recess sunk in the pedicle and having an axial through-hole to accommodate the threaded portion of a pedicle screw, as well as a spacer in the form of an essentially cylindrical pedicle augmentation in the form of a bone screw or a bone bracket.

Abstract: The present invention describes a system, devices and methods for percutaneous pedicle screw revision procedures. The present invention utilizes a tulip rod stub/connector adapted to be used to extend pedicle screw/rod constructs with minimal disruption to surrounding soft tissue and without having to remove existing hardware.

Abstract: An expandable implant for inserting within a skeletal space is provided, and a method for using the implant to expand the skeletal space. The implant is preferably designed to be inserted into an intervertebral space to replace at least part of an intervertebral disc between adjacent vertebral bodies. The expandable implant contains at least one first expansion compartment and at least one second expansion compartments, which compartments can be inflatable balloons that are inflated by a catheter. Inflating the first expansion compartment expands the implant in a first direction and inflating the second expansion compartment expands the implant in a second direction.

Abstract: A retention member for a spinal plate system where at least one or more segments of the retention member cover the head portion of a bone anchor member to inhibit movement of the bone anchor member that is inserted into the plate. The retention member allows for ease of insertion of the bone anchor member and once the bone anchor member is fully seated the retention member is in place.

Abstract: A bone plate that is configured to operatively attach to bone includes a first segment, a second segment, and a locking mechanism. The first segment includes a compression notch. The first and second segments are positioned along a longitudinal axis and are movable relative to one another. The locking mechanism inhibits relative axial movement of the first and second segments along the longitudinal axis away from one another. The locking mechanism includes first and second grooves disposed on the second segment. The first and second grooves and the compression slot are configured to receive an instrument to move the first segment towards the second segment along the longitudinal axis.

Abstract: An occipital plate for use in an occipitocervical fixation procedure to stabilize the base of a patient's skull with respect to the patient's neck. The occipital plate is made up of a middle portion having left and right sides, and left and right hinged legs extending outward in opposite directions from the left and right sides of the middle portion. Each of the left and right hinged legs uses a hinge mechanism to secure a spinal rod to the occipital plate.

Abstract: Methods for treating a defect in an annulus fibrous are described. The annulus fibrosis has an outer layer, at least one inner layer, and a defect extending through the outer and inner layers. An implant is inserted into the defect in the annulus fibrosis, the implant having at least one aperture. The implant is advanced distally beyond the outer layer in the annulus fibrosis and positioned to occlude the defect. An elongate fixation element is inserted through the at least one aperture, the elongate fixation element having a first end region and a second end region. The elongate fixation element is positioned such that the first end region is within the at least one aperture. The second end region of the elongate fixation element is anchored to the annulus fibrosis. The implant prevents escape of nucleus pulposus through the defect.

Abstract: A spinal stabilization system includes an implant and instrumentation for stabilizing the spine. In one embodiment, the system includes a plate having a side rail and a channel extending adjacent the side rail. A pedicle screw assembly is positioned in the channel in releasable engagement with the side rail. The pedicle screw assembly includes a polyaxial screw seated in a lower housing having a lower locking flange. An upper housing having an upper locking flange secures the plate to the lower housing. The side rail of the plate is releasably engaged between the upper locking flange and the lower locking flange. The upper and lower housings include on-board locking mechanisms for fixing components in the screw assembly. The screw assembly and plate are inserted and oriented by remote manipulation. Minimally invasive techniques for inserting the implant are performed with the instrumentation, and cause minimal disturbance to surrounding tissue.

Abstract: A posterior vertebral plating system comprising a plate and a plurality of attachment members. The plate has a plurality of holes extending through the plate from an upper surface to a lower surface, and the plate is configured to extend along the posterior side of at least two vertebrae adjacent at least one boney structure of each of the vertebrae. The holes are spaced in such a way that a first plurality of holes is positionable over a boney structure of a first vertebra to define a plurality of fixation points to the first vertebra and a second plurality of holes is positionable over boney structure of a second vertebra to define a plurality of fixation points to the second vertebra. The attachment members are insertable through the holes of the plate and into the boney structure of a corresponding vertebra to fix the plate to the vertebra.

Abstract: Devices and methods for treating degenerative conditions of the spine or for alleviating pain or discomfort associated with the spinal column are disclosed. In particular, laminoplasty fixation devices and methods are disclosed. Also disclosed, is a vertebral implant comprising a first bone engaging portion configured for securing to a first cut portion of a vertebra and a second bone engaging portion configured for securing to a second cut portion of the vertebra. A body portion is provided for associating the first and second bone engaging portions at a preselected spacing from each other, wherein the implant is adjustable to select said spacing.

Abstract: A spine stabilization system including a first anchor, a second anchor and a rod for connecting the first and second anchors together. The first anchor includes an anchor body and a hook. A slot is defined between the hook and a first wall of the anchor body, facing the hook, the slot being configured to receive a bony structure. The first anchor further comprises a flexible member having first and second ends, and an intermediate portion therebetween. The anchor body is provided with an exit passage from which the first and second ends extend, and a loop passage going through the first wall and facing the hook, the intermediate portion extending from the loop passage to form a loop going through the slot and around the bony structure.

Abstract: A bone fixation assembly comprises a plate having a top surface and a bottom surface and defining at least one bone screw bore, the bore including a circumferential rib situated between the top and bottom surfaces of the plate and at least one scallop interrupting the circumferential rib. A bone engaging fastener is provided for each bore, the fastener having a shank defining bone engaging threads and an enlarged head. The head defines threads for threaded engagement with the circumferential rib, with a lead thread configured to pass through a scallop to allow the threads to engage the circumferential rib.

Abstract: A functionally dynamic stabilization unit and system for treatment of spinal instability are provided. Each unit, and collectively, the system, is configured to control flexion, extension and translation of the affected unstable vertebral area, thereby stabilizing the vertebral segments by restoring normal function. This is achieved by providing a unit and system that allow for lateral bending, axial compression, rotation, anterior segmental height adjustment, and posterior segmental height adjustment. The unit and system provide sufficient segmental stiffness, while also limiting, or controlling, the range of motion (i.e., sufficient stiffness in the neutral or active zone, while limiting or preventing motion outside of the active zone) to stabilize the vertebral segments. In use, the system mimics the natural movement of the normal spine. Furthermore, the system includes a rigid, fusion-promoting coupler configured for use in an adjacent level, or as a substitute for the functionally dynamic unit.

Abstract: An improved anterior cervical plating system and methods of cervical fusion using such a system are provided. The cervical plating system includes an interlocking mechanism that integrated into each of the plates such that any two plates may cooperatively engage through the interlocking mechanism such that a new cervical plate can be interconnected with a pre-existing plate during revision surgery without removal of the pre-existing plate.

Abstract: Apparatus for use in stabilizing and/or aligning the spinal column utilizes hooks and rods to effectively transfer load from the vertebrae to the apparatus regardless of the angle and the height of the pedicular screws. A screw cap formed of a base having a bore therethrough for receiving the head of the screw, an upright riser formed thereon that is laterally offset from the bore, and a surface for engaging the rod or plate of the stabilizer enables the apparatus to be used for stabilizing and/or aligning vertebral bodies that are out of alignment, of different shape or size, and/or pathology. The apparatus is implanted in a series of steps that are quickly and conveniently performed in the surgical stage and with minimal application of force to align the vertebral bodies, decreasing the likelihood of damaging the nerves populating the surgical stage.

Abstract: Methods and devices are disclosed herein that generally involve applying thermal therapy to tissue (e.g., localized cooling or heating of tissue). In some embodiments, tissue can be cooled or heated by implanting a malleable or deformable thermal device in proximity to the targeted tissue. The thermal device can be left in place following surgery to facilitate application of post-surgical thermal therapy. In some embodiments, the thermal device can be removed post-surgery in a minimally- or non-invasive manner. The thermal device can be connectionless or can include penetrable regions, pre-attached tubing, or detachable connectors to facilitate application of cooling or heating means to the device. Methods are disclosed for utilizing thermal devices and for carrying out various treatment regimens that involve cooling or heating tissue using such devices.

Abstract: Open implant closure structures include a helically wound guide and advancement flange form having splay control surfaces. Multi-start closures and closures with inner set screws have splay control contours for interlocking with cooperating flange forms of bone anchor receivers. Flange form heights, thicknesses and other geometry, such as splay control ramp angle may be varied.

Abstract: A minimally invasive system and method for vertebral body augmentation includes an expandable containment device, a chassis including an interior cavity for at least partially enclosing the expandable containment device, a first guidewire, a working cannula, a second guidewire having at least a partially flexible distal end portion and a sleeve for introducing bone filler material through a cannulated passageway of the sleeve and into an interior cavity of the containment device. The containment device preferably includes a plurality of pores for directing the outflow of bone filler material anteriorly within the vertebral body. The containment device and chassis are left interior to the vertebral body subsequent to height restoration and augmentation of the vertebral body.

Abstract: Methods for altering the natural history of degenerative disc disease and osteoarthritis of the spine are proposed. The methods focus on the prevention, or delayed onset or progression of, subchondral defects such as bone marrow edema or bone marrow lesion, and subchondral treatment to prevent the progression of osteoarthritis or degenerative disc disease in the spine and thereby treat pain.

Abstract: An implant support comprises a first member including a first portion and a second portion configured to engage a bone fastener. The second portion extends in a transverse orientation from the first portion. The members define a longitudinal axis. The second member includes a first portion and a second portion configured to engage the bone fastener. The second portion of the second member extends in a transverse orientation from the first portion. At least one of the members is movable relative to the longitudinal axis between a first configuration and a second configuration such that the longitudinal axis is offset relative to an axis of the bone fastener. Systems and methods are disclosed.

Abstract: Bone implantable devices and methodologies permit careful application of biologically active substances and management of bone growth processes. The device includes a body defining a carrier receiving area for locating adjacent bone. Carrier material is located in the carrier receiving area. Substance is delivered onto carrier material through a port. A pathway delivers substance from the carrier receiving area to the bone surface. The body may be in the form of a spinal fusion cage, facet fusion screw, artificial joint, bone fixation plate, interbody graft, IM nail, hip stem, or other bone-to-bone appliances or bone-to-device appliances. In use, carrier is installed in the carrier receiving area of the device. The device is then implanted adjacent a bone. The substance is applied to the carrier for subsequent delivery to the bone. By doping carrier material after device implantation, inadvertent contact of the substance with non-target bone is more easily eliminated.

Abstract: The present invention includes an apparatus for securing a spinal rod with an anchoring device, the apparatus including a tubular body defining a longitudinal axis from a proximal end to a distal end; a connecting element positioned within the tubular body and along the longitudinal axis, the connecting element engaged by a first internal shaft and a second internal shaft, the tubular body, first internal shaft and second internal shaft coaxial with one another; the first internal shaft rotatably engages the connecting element such that rotation of the first internal shaft results in axial translation of the connecting element; and the second internal shaft engages the connecting element such that rotation of the second internal shaft results in rotation of the connecting element.

Abstract: An anterior cervical plate system is provided. The cervical plate includes a retention ring with a deflectable flange that is upwardly spaced from the top surface of the ring and configured to prevent an inserted bone fastener from backing out of the plate. The plate includes a locking pin having a camming surface and a blocking surface. When the camming surface is moved into position adjacent to the flange, the flange is free to flex out of the way of a bone screw being inserted into or removed from the plate. When the blocking surface is positioned adjacent to the flange, outward deflection of the flange is prevented to retain the bone screw inside the plate. The locking pin is rotated through a camming surface to bring a blocking surface against the flange deflecting the flange onto the head of the bone screw.

Abstract: The present invention relates invention relates to devices and methods for the fixation and stabilization of orthopedic fractures and more specifically to stabilization of compression fractures of spinal vertebrae. The systems comprise cannulated orthopedic screws and mechanical expandable implants introducible through the lumen of such screws. In certain embodiments the cannulated implants are expandable within an intraosseous space to introduce scaffold-like structures such that subsequent introduction of a bone cement forms a composite in situ. The devices and methods are also particularly useful for stabilizing the orthopedic screws.

Abstract: A system for use in stimulating at least one of bone growth, tissue healing and pain control in a patient includes a first screw and a second screw. The first screw has an elongate shaft with opposite ends and a length extending between the ends, an exterior surface and a screw thread formed on the exterior surface of the shaft and extending along at least a portion of the length. The screw thread has an electrically conducting portion and an electrically insulating portion. The electrically conducting portion is located for deposition in a first pre-specified portion of the patient and the electrically insulating portion is located for deposition in a second pre-specified portion of the patient. An electrical power source is adapted to pass electrical current through the patient between the first and second screws. The electrical power source is operatively connected to the first screw for conveying current through the electrically conducting portion of the screw thread to the first pre-specified portion.

Abstract: A spinal implant for connecting to an elongated rod is disclosed. The spinal implant includes a yoke having a first end and a second end, the first end having a first and second rod engaging portion and a channel between the first and second rod engaging portions for encompassing a first bone anchor, and the second end being spaced apart from the first end. An extension rod is also provided which extends from the second end of the yoke parallel to the elongated rod. The first and second rod engaging portions are configured and dimensioned to receive first and second securing member for securing the elongated rod.

Abstract: An embodiment of the invention provides for a system, such as a cervical plate fusion system, that has mechanisms for preventing bone screws from backing out of the plate. The system prevents both counter-rotation of the screw and axial backing out of the screw. Other embodiments are described herein.

Abstract: An apparatus and method of performing a minimally invasive posterior spine fusion. More specifically an apparatus with a handle and a forked head on the distal end of the handle is used to grasp implant material and introduce the material to an implant site. The shaft of the apparatus is shaped so as to allow the affixation of a drill guide and drill while simultaneously holding the implant material in the implant site. After removal of the boring tools and assembly of the fusing element, the apparatus can be selectively removed from the implant site. A method of achieving facet joint fusion with near simultaneous fixation is also disclosed.

Abstract: A method for installing a surgical device on a spine for applying corrective forces thereon comprises installing at least one anchor on a first vertebra and at least another anchor on a second vertebra. At least one connector is installed on at least one of the first and the second vertebrae. A flexible tether is fixed to one of the anchors. The flexible tether is tensioned about a surface of the at least one connector. The flexible tether is fixed to the other one of the anchors to maintain a tension in the flexible tether to apply corrective forces to the vertebrae interconnected by the tether. A method for installing a staple device with rotational joints in the vertebrae is also provided.

Abstract: The disclosure relates generally to embodiments of systems and methods of spinal stabilization. Embodiments include methods that use a dilator to displace tissue proximate to a sleeve. An embodiment of a surgical system can comprise a dilator that may define a working channel from a first opening to a second opening. The dilator can be positioned to displace tissue proximate to the sleeve. The dilator may be shaped to allow a first end of an elongated member to enter the working channel through the first opening and exit the dilator through the second opening to be percutaneously moved to another assembly.

Abstract: Embodiments of bony region stabilization implants including multiple fenestrations and bony ingrowth materials are described generally herein. Other embodiments may be described and claimed.

Abstract: A spinal fixation device is provided having first and second elongate members that are angularly adjustable relative to one another. Each elongate member can include a connecting feature formed on a terminal end thereof, and each connecting feature can be coupled to one another to allow angular movement of the first and second elongate members. The device can also include a locking mechanism that is adapted to couple to the connecting feature on each of the first and second elongate members to lock the elongate members in a fixed position relative to one another.

Abstract: The present invention provides a dynamic stabilization device positionable about a portion of a spinal column. The stabilization device may generally include a first component and a second component, where the first and second components are movably coupled to one another to define an arcuate path of motion. The stabilization device may also include one or more adjustment elements positionable within first and second adjustment openings to affect the path of motion between the first and second components and/or the behavior and characteristics of the movement. In addition, one or more resistive elements may be adjustably positionable within either and/or both of the first and second adjustment openings to provide resistance and/or dampening of the forces experienced as the first and second components move relative to one another. The stabilization device may further define a joint having three degrees of freedom to adapt to movement of a spinal column.

Abstract: Assemblies of one or more implant structures make possible the achievement of diverse interventions involving the fusion and/or stabilization of lumbar and sacral vertebra in a non-invasive manner, with minimal incision, and without the necessitating the removing the intervertebral disc. The representative lumbar spine interventions, which can be performed on adults or children, include, but are not limited to, lumbar interbody fusion; translaminar lumbar fusion; lumbar facet fusion; trans-iliac lumbar fusion; and the stabilization of a spondylolisthesis.

Abstract: An implantable apparatus for use in the correction of skeletal deformities comprising a rod, a pair of spaced apart attachment members, each of the attachment members being attachable to a bone. At least one of the attachment member mounts a rod receiving member, the rod being slidable along a predetermined path with respect to the rod receiving member.

Abstract: A posterior spinal fusion system may include a plurality of cannulas that mate with cages polyaxially coupled to pedicle screws. The cannulas maintain access to the pedicle screws to facilitate percutaneous insertion of a fusion rod into engagement with the cages. Each cannula has a pair of blades that may be held together by an abutment member that at least partially encircles the blades. Each abutment member abuts the skin to define a variable subcutaneous length of the corresponding cannula. Each abutment members is also lockably removable from the corresponding blades to enable the blades to pivot with respect to the connecting element to a position in which they can be withdrawn from the connecting element. The blades of each cannula are spaced apart to provide first and second slots of each cannula, through which the fusion rod can be percutaneously inserted.