Patent ID: 12220323

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments are disclosed herein; however, it is to be understood that the disclosed embodiments are merely examples and that the systems and methods described below can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present subject matter in virtually any appropriately detailed structure and function. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the concepts.

The terms “a” or “an”, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms “including” and “having,” as used herein, are defined as comprising (i.e., open language).

With reference to the figures, the disclosure provides an expandable spacer/implant or device100having an adjustable height. Device100is inserted between two adjacent bony surfaces to facilitate separation of the bones, and if desired, to promote the fusion of bony surfaces. Although intended to be useful with any adjacent bony surface in which fusion is desired, device100is advantageously applied to insertion between two adjacent vertebral bodies in any section of the spine, including the cervical, thoracic, lumbar, and sacral vertebral sections. More than one device100may be implanted within the body, for example between successive or separated vertebrae, or positioned between the same adjacent vertebrae. The use of multiple devices100is particularly advantageous for patients whose back pain is not limited to a localized area, or for patients whose localized damage has progressed to other areas of the spine.

Device100and methods for its insertion can be used in a treatment protocol for any of a wide variety of conditions in a patient involving diseased or damaged bony structures. The patient can be a human being. Additionally, it is contemplated that device100may be useful in veterinary science for any animal having adjacent bony structures to be fused. Devices100can expand to roughly twice its fully reduced insertion height. When in this collapsed configuration, device100can be inserted into a space through a small incision and narrow pathways, using appropriate minimally-invasive techniques, and can be positioned within the space between adjacent bones, and there expanded to a desired therapeutic height. The incision may be short, for example about one centimeter in length, which is smaller than device100in an expanded configuration. If the desired position and/or expansion are not achieved, device100can be collapsed, repositioned, and re-expanded in situ.

Although device100is exemplified herein for use in the spine, device100is contemplated for fusion of any bony structures. While devices100are described herein using several varying embodiments, devices100are not limited to these embodiments. An element of one embodiment may be used in another embodiment, or an embodiment may not include all described elements.

Interbody devices have been used to provide support and stability in the anterior column of the spinal vertebrae when treating a variety of spinal conditions, including degenerative disc disease and spinal stenosis with spondylolisthesis. Clinical treatment of spinal pathologies with anterior vertebral body interbody devices relies on precise placement of interbodies to restore normal anterior column alignment. Iatrogenic pathologies may result from both the surgical access window to the disc space, failure to precisely place the interbody on hard cortical bone often found on the apophyseal ring of the vertebral body, or failure to precisely control and restore normal anatomical spinal alignment. Device100provides for the precise placement of interbody support that both increases interbody contact with hard cortical bone and provides precise control of anterior column alignment while reducing the profile of the access window to the disc space.

More particularly, in order to improve the access profile of the interbody while maximizing cortical bone contact surface area, device100enters the disc space with a narrow profile and articulates to increase surface area contact on the anterior apophyseal ring. The orientation and position of the interbody in its final implanted position may be optimized by pre-/intra-op scans or normal population statistics that determine bone mineral density maps of the vertebral body. Robotic and navigation guidance may be used to correctly orient the interbody.

In an embodiment, device100can be implanted as follows:

1. A determination is made on final optimal implant location to optimize bone mineral density of the contacted bone/implant interface.

2. Robotic/navigation is used to determine the potential trajectories that will allow for this optimal implant location to be achieved.

3. A cannula is docked on the disc space through Kambin's triangle, or the anatomical area that is bordered by the disc space, exiting nerve root, and traversing nerve root.

4. The expandable interbody is inserted in the non-articulated orientation, which can be seen inFIGS.3and9;

5. The expandable interbody is fully articulated into the articulated orientation that fully maximizes surface contact area with the anterior apophyseal ring of the vertebral body (FIG.4).

6. The expandable interbody is expanded to precisely restore normal spinal alignment (FIGS.7-8).

The articulation of the interbody can be accomplished through several methods. In one embodiment, the articulation mechanism consists of an articulation point at the end of a threaded shaft. The articulation mechanism is a hinge joint where the threaded shaft is pinned to the male interior rampslide.

With reference to the drawings, device100is expanded using a slide system which causes the separation of endplates120and122, which are each positioned within the body to contact a separate side of a bone joint relative to the other endplate. When positioned within the spine, one endplate will be a superior endplate contacting a more superior vertebra, and the other endplate will be an inferior endplate, contacting a more inferior vertebra. An orientation of device100may be determined by the side of the body from which implantation is approached. As will be explained in greater detail elsewhere herein, an actuating shaft136forms an angle with respect to the endplates, and it is desired that the shaft lie along the vertebral bone surface, or otherwise does not interfere with movement of the joint or other body tissue.

In particular, and with reference toFIG.2, device100includes first and second slides102,104which are mutually slidingly engaged. In the embodiment shown, each of the first and second slides102,104are provided with a mating dovetail portion106,108, respectively which maintains a back-to-back connection and orientation between slides102,104as they are slid along their longitudinal axes with respect to each other. A length or longitudinal axis extends along a direction of insertion of device100, described further elsewhere herein. A height of device100extends transverse to the longitudinal axis.

Slides102and104cooperate to cause endplates120,122to change a distance from each other when slides102and104are slid relative to each other. With reference toFIG.2, slide104forms one or more ramps110A which each engage a mating cam110B, having a surface which corresponds to ramp110A, on endplate122. Likewise, and with additional reference toFIG.2A, slide104forms one or more ramps110C which each engage a mating cam110D on endplate120. In a similar fashion, slide102forms one or more ramps112A which each engage a mating cam112B on endplate122, and one or more ramps112C which each engage a mating cam112D on endplate120.

Cams110B and112B are angled in opposite directions, and cams110D and112D are likewise angled in opposite directions. In this manner, as slides102and104are moved in opposing directions towards a more overlapping relationship, cams110B,112B,110D, and112D slide along and up ramps110A,112A,110C, and112C, respectively, driving endplates120,122apart. Similarly, as slides102and104are moved in opposing directions towards a less overlapping relationship, cams110B,112B,110D, and112D slide along and down ramps110A,112A,110C, and112C, respectively, enabling endplates120,122to move together, for example by pressure applied by body tissue. Cams110B,112B,110D, and112D each have an inclined cam surface which corresponds to the inclination of a surface of a mating ramp110A,112A,110C, and112C.

Dovetail portions106and108on slides102and104cooperate to maintain contact between slides102and104during relative movement along the longitudinal axis. This contributes to stability and reliability of device100. In an alternative embodiment, dovetail portions106and108do not prevent slides102and104from separating along a direction transverse to the longitudinal axis. For example, dovetail portions106and108can have the form of a protrusion and a groove. In a further embodiment, dovetail portions106and108are absent, and slides102and104are confined in movement by being bounded by cams110B,112B,110D, and112D, and through a mutual connection established through dovetail surfaces150and152of collar138and the proximal end154of slide104. It should further be understood that while the dovetail examples in the drawings illustrate a male component on one part, and a female component on another part, the relative placement of these components can be reversed.

A vertical surface160(FIGS.7and10) can be formed adjacent to any or all of ramps110A,112A,110C, and112C to provide room for entry of cams110B,112B,110D, and112D, and to further prevent relative movement of slides102,104when device100has been reduced to the lowest desired height profile.

In addition, when slides102,104are slid to be relatively less overlapping along a longitudinal direction, cams110B,112B,110D, and112D are more completely overlapping and nesting against ramps110A,112A,110C, and112C, so that endplates120,122are disposed more closely to each other, reducing an overall height profile of device100. As slides102,104are displaced to be relatively more overlapping, cams110B,112B,110D, and112D are less completely overlapping/nesting against ramps110A,112A,110C, and112C, so that endplates120,122are disposed farther from each other, increasing an overall height profile of device100.

With further reference toFIG.2in particular, a series of components connected to slides102and104enable the aforedescribed relative sliding displacement of slides102,104. More particularly, a threaded shaft136is connected at one end of slide102, and a collar138, driven by a nut140engaged with shaft136, is connected to slide104. Collar138is free to rotate and slide along shaft136, and is pushed along a longitudinal axis of shaft136by the rotation of nut140. Shaft136is pivotably engaged with slide102by a pin144which passes through a clevis142mounted to an end of slide102, and through a bore146formed in an end of shaft136. Collar138includes a collar dovetail portion150, and slide104includes a mating slide dovetail end portion152disposed at a proximal end154. As shown in the drawings, collar138is slidable about a sleeve162(FIG.2) associated with nut140. In alternative embodiments, sleeve162is omitted, or collar138forms a different engagement with nut140.

Shaft136can be pivotally connected to slide102by means other than a clevis and pin, for example through any known hinge mechanism, including barrel, flush, living, piano, gate, butt, butterfly, pivot, or spring hinge, as examples, although other hinge structures can be used which enable shaft to form a changeable angle with respect to slide102, and which can be formed in a space efficient manner.

Endplates120,122can be provided with cutout portions156,156A (FIGS.2A and8), respectively, to provide room for clevis142. Similarly, other areas of endplates120,122can be provided with a relief158(FIG.2A) or removed material to accommodate a cam, as shown at110B inFIG.2, or to provide room for other structures when device100is at various height configurations, as needed.

In an insertion orientation, collar138is disengaged from slide dovetail end portion152, and shaft136is pivoted about pin144to be longitudinally aligned with slides102,104, as shown inFIG.3. In this configuration, which has the smallest end-on profile, device100can be inserted into the body to an implantation site through a correspondingly small opening with a minimum of tissue disruption. Specifically, when collar138is disengaged, endplates can be urged towards each other, longitudinally offsetting slides102,104, while producing a longer profile along the longitudinal axis, but the smallest height profile. In an embodiment, the height profile is not greater than the width and thickness of stacked endplates120and122. As can be seen inFIGS.1,3and9-10, slides102,104nest completely within endplates120,122.

While device100is positioned within the body, shaft136is pivoted about pin144, and collar138is rotated, so that collar dovetail portion150is aligned parallel with slide dovetail end portion152, as can be seen inFIG.4. Collar138can then be driven along shaft136by rotation of nut140, until collar dovetail portion150is aligned with slide dovetail end portion152, after which the respective dovetail portions can be mated, as can be seen inFIGS.1and5. Nut140can then be threaded further along shaft136, causing collar138to advance along shaft136, to the point of creating contact between collar138and slide102, thereafter, as nut140is turned further, this contact and interference causes dovetail portions150and152to slide relative to each other, thereby driving slide104relative to slide102, through the sliding connection of dovetail portions150,152. Accordingly, as shaft136is affixed to slide102, and collar138is affixed to slide104, advancement of collar138along shaft136causes slides102and104to move in opposite directions, resulting in a change of height of device100as described above.

Endplates120and122each have parallel sets of spaced apart cams (two each of110D,112D,110B,112B), which cooperate with a matching number of ramps (two each of110A,110C,112A,112C) on slides102,104, to create stability with respect to side-to-side and end-to-end rocking, and which are matched in size to produce relatively parallel movement of endplates120,122as they are moved closer together and farther apart.

In one embodiment of the disclosure, dovetail portions150,152, and collar138are not present. In this embodiment, nut140bears directly upon an end of slide104. In lieu of a dovetail portion150, slide104can be provided with a ramped surface at a proximal end of slide104, and in one variation the ramp has a similar angle as dovetail150. In this embodiment, shaft136is maintained at an angle at which nut140bears upon this angled proximal end. As nut140is rotated, an interference is created between the nut and/or a collar if present and slide104, causing slide104to be driven with respect to slide102as otherwise described herein.

Advantages of the disclosure include, at least:

1. A small insertion profile: the disclosure enables, for example, an 8.5 mm insertion profile into the disc space, reducing the required skin, fascia, muscle, and ligamentous disruption. Smaller profiles can be achieved, including profiles as small as 6 mm, for example, or profiles substantially larger than 8.5 mm.

2. Controlled lordosis: the disclosure enables controlled lordosis through placement of device100in an articulated position in the disc space. With the spacer placed horizontally across the disc space, and due to the fact that the spacer has a relatively small depth, the spacer can be used as a fulcrum to increase lordosis as it is expanded. It is generally accepted that placing the spacer on the anterior apophyseal ring provides the most leverage for continuously increasing lordosis as it is expanded in height. However, more posterior placement can also be utilized as this can allow for increased anterior height when leveraging using the same height spacer. Alternatively, two devices100can be placed between the same vertebrae, one in the anterior aspect of the vertebral body and one in the posterior aspect of the vertebral body, to further control and adjust sagittal balance by then allowing independent expansion of the anterior and posterior aspects of the vertebral body.

3. Reduced endplate disruption: due to the ability of device100to expand a correct, therapeutic extent in situ, the disclosure reduces the need for traditional trialing through the insertion of interbody implants of various sizes, the latter potentially causing or contributing to vertebral endplate disruption and further trauma to the body.

With reference toFIGS.11-12, a driving tool400forms a cannula. Indicia402indicates an insertion depth of tool400into the body. Positioning is carried out using imaging, and can further be carried out using a robotics system. The bore404of tool400enables the insertion of surgical instruments in order to cut, excise, or cauterize body tissue, and to otherwise facilitate a surgical procedure to implant device100. Bore404is further sized to enable passage of device100. To minimize the required size of bore404, device100is configured in the smallest height profile, and with threaded shaft136disengaged from slide104and extending linearly along a longitudinal axis of device100, as shown inFIGS.3and9.

After device100exits tool400within the body, it may be manipulated into a position upon the vertebral endplate300, for example upon the apophyseal ring302, using surgical tools passed through tool400. Additionally, shaft136can be angled to enable engagement of dovetail portions150,152, coupling slides102and104as described elsewhere herein. After dovetail portions150,152are engaged, a driving tool (not shown) can be passed through tool400and engaged with nut140to rotate nut140, causing relative sliding of slides102,104, and expanding a height of device100, as can be seen inFIGS.13-14. At a later date, if needed, tool400can be reinserted into the body to change reposition device100, change a height of device100by rotating nut140, and/or device100can be removed from the body if therapeutically beneficial.

Different devices100may include ramps110A,110C,112A,112C and/or cams110B,110D,112B,112D of differing height and length relative to other devices100, to enable expansion at different rates or extents, as indicated for therapeutic treatment. Fewer or a greater number of ramps and/or cams can be provided. Endplates102,104may additionally, or alternatively, be resilient, so that they may conform to bony surfaces, forming a more stable support platform. Accordingly, endplates102,104can be fabricated from a polymeric material, a naturally resilient material, or a resilient metal, for example a shape memory alloy, or any other resilient biocompatible material of sufficient strength and durability for separating bones within the body.

Device100can be inserted at a contracted height transforaminally, for example, and are capable of articulating into anterior placement. Once placement is achieved, device100is capable of expanding for disc height restoration. Additionally, device100can be positioned anteriorly, and can be expanded through a continuous range to provide axial balance and greater endplate contact area. Additionally, device100enables superior sagittal correction, through the use of a relatively smaller insertion window, decreasing the need for bone damage. Thus, device100provides the benefits of an ALIF device through a familiar posterior approach, decreasing surgery time and associated blood loss, as well as eliminating the need for an access surgeon.

In accordance with the disclosure, during implantation of intervertebral spacers from a posterior approach, there is a need to avoid damaging nerve roots. A prior art spacer dimensioned to separate bones can block a view of nerve roots as it is inserted, and due to its large size, poses a greater risk of contacting nerve roots during insertion into the body. As a result, the medical practitioner must more often retract nerve roots, with attendant danger of tissue damage. Devices100of the disclosure form a smaller dimension during implantation, relative to a final dimension for spacing bones. Accordingly, nerve roots can be visualized and avoided during insertion, and nerve root manipulation can be avoided or minimized.

As devices100of the disclosure can be articulated during implantation, they can be inserted between bones by being passed through a minimally invasive entry, for example through an incision approximating the smallest collapsed dimension, for example transverse to the longitudinal dimension. This enables exceptional anterior placement without impaction, as well as facilitating implantation from other approaches. Devices100of the disclosure further develop a good bone contact area, as an implant with a larger footprint may be inserted through a reduced size incision, due to the overall dimensions of device100being reduced during insertion.

Devices100of the disclosure enable a continuous expansion and distraction over a range of displacements according to predetermined dimensions of a specific spacer design. This provides the ability to distract vertebral bodies or other bones to a desired height or separation. Endplates120,122can be shaped to form planes or surfaces which converge relative to each, to provide for proper lordosis, and can be provided with openings190through which bone may grow, and into which bone graft material may be placed. Devices100of the disclosure may be used to distract, or force bones of a joint apart, or may be used to maintain a separation of bones created by other means, for example by a retractor. Endplates may additionally be curved to conform to the surface of body tissue, for example the surface of cortical bone, of the vertebra to be contacted, for improved fixation and load bearing.

Devices100of the disclosure may be further secured in connection with the body by passage of elongated fasteners through an endplate120,122. A blocking mechanism can be used to prevent backing out of an elongated fastener.

Devices100of the disclosure may be fabricated using any biocompatible materials known or hereinafter discovered, having sufficient strength, flexibility, resiliency, and durability for the patient, and for the term during which the device is to be implanted. Examples include but are not limited to metal, such as, for example titanium and chromium alloys; polymers, including for example, PEEK or ultra high molecular weight polyethylene (UHMWPE); and ceramics. There are many other biocompatible materials which may be used, including other plastics and metals, as well as fabrication using living or preserved tissue, including autograft, allograft, and xenograft material.

Portions or all of device100may be radiopaque or radiolucent, or materials having such properties may be added or incorporated into device100to improve imaging of the device during and after implantation.

Devices100may be formed using titanium, or a cobalt-chrome-molybdenum alloy, Co—Cr—Mo, for example as specified in ASTM F1537 (and ISO 5832-12). The smooth surfaces may be plasma sprayed with commercially pure titanium, as specified in ASTM F1580, F1978, F1147 and C-633 (and ISO 5832-2). Alternatively, part or all of devices100may be formed with a polymer, for example ultra-high molecular weight polyethylene, UHMWPE, for example as specified in ASTM F648 (and ISO 5834-2). In one embodiment, PEEK-OPTIMA (a trademark of Invibio Ltd Corp, United Kingdom) may be used for one or more components of devices100of the disclosure. For example, polymeric portions can be formed with PEEK-OPTIMA, which is radiolucent, whereby bony ingrowth may be observed. Other polymeric materials with suitable flexibility, durability, and biocompatibility may also be used.

In accordance with the invention, implants of various sizes may be provided to best fit the anatomy of the patient. Components of matching or divergent sizes may be assembled during the implantation procedure by a medical practitioner as best meets the therapeutic needs of the patient, the assembly inserted within the body using an insertion tool. Devices100of the invention may also be provided with an overall angular geometry, for example an angular mating disposition of endplates, to provide for a natural lordosis, or a corrective lordosis, for example of from 0° to 12° for a cervical application, although much different values may be advantageous for other joints. Lordotic angles may also be formed by shaping one or both endplates to have relatively non-coplanar surfaces.

Expanded implant heights, for use in the cervical vertebrae for example, may typically range from 7 mm to 12 mm, but may be larger or smaller, including as small as 5 mm, and as large as 16 mm, although the size is dependent on the patient, and the joint into which an implant of the invention is to be implanted. Devices100may be implanted within any level of the spine, and may also be implanted in other joints of the body, including joints of the hand, wrist, elbow, shoulder, hip, knee, ankle, or foot.

In accordance with the invention, a single device100may be used, to provide stabilization for a weakened joint or joint portion. Alternatively, a combination of two, three, or more of any of device100may be used, at a single joint level, or in multiple joints. Moreover, implants of the disclosure may be combined with other stabilizing means.

Additionally, devices100of the disclosure may be fabricated using material that biodegrades in the body during a therapeutically advantageous time interval, for example after sufficient bone ingrowth has taken place. Further, implants of the disclosure are advantageously provided with smooth and or rounded exterior surfaces, which reduce a potential for deleterious mechanical effects on neighboring tissues.

Any surface or component of a device100of the disclosure may be coated with or impregnated with therapeutic agents, including bone growth, healing, antimicrobial, or drug materials, which may be released at a therapeutic rate, using methods known to those skilled in the art.

Devices of the disclosure provide for adjacent vertebrae to be supported during flexion/extension, lateral bending, and axial rotation. In one embodiment, device100is indicated for spinal arthroplasty in treating skeletally mature patients with degenerative disc disease, primary or recurrent disc herniation, spinal stenosis, or spondylosis in the lumbosacral spine (LI-SI). Degenerative disc disease is advantageously defined as discogenic back pain with degeneration of the disc confirmed by patient history and radiographic studies, with or without leg (radicular) pain. Patients are advantageously treated, for example, who may have spondylolisthesis up to Grade 1 at the involved level. The surgery position device100may be performed through an Anterior, Anterolateral, Posterolateral, Lateral, or any other approach.

In a typical embodiment, devices100of the disclosure have an uncompressed height, before insertion, of 7 to 13 mm, and may advantageously be provided in cross-sections of 8×22, 8×26, 8×30, 8×34, 10×27 mm, 12×32 mm and 12×37 mm, with 4, 8, 12, 15, 20, 25, or 30 degree lordotic angles, although these are only representative sizes, and substantially smaller or larger sizes can be therapeutically beneficial. In one embodiment implants in accordance with the instant disclosure are sized to be inserted using an MIS approach, for example using a reduced incision size, for example less than about 5 cm, and advantageously less than about 1 cm, with fewer and shorter cuts through body tissue. Device100may advantageously be used in combination with other known or hereinafter developed forms of stabilization or fixation, including for example rods and plates, or intradiscal fixation, potentially connecting device100to one or more of the adjacent vertebrae.

Devices100of the disclosure can be inserted into the body, advantageously in a contracted or non-expanded configuration, through a transforaminal approach, and can articulate in attachment to an inserter tool, for example as shown inFIGS.11-14or another tool, for example for anterior placement. Once placement is achieved, device100is capable of expanding for disc height restoration. To maintain an engagement device100and an insertion tool, a driving end (not shown) of the tool can be engaged with device100.

All references cited herein are expressly incorporated by reference in their entirety. There are many different features to the present disclosure and it is contemplated that these features may be used together or separately. Unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. Thus, the disclosure should not be limited to any particular combination of features or to a particular application of the disclosure. Further, it should be understood that variations and modifications within scope of the disclosure might occur to those skilled in the art to which the disclosure pertains. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope of the present disclosure are to be included as further embodiments of the present disclosure.