Patent Publication Number: US-2022226124-A1

Title: Transversely expandable minimally invasive intervertebral cage

Description:
TECHNICAL FIELD 
     The present invention relates to the fusion of vertebral bodies. More specifically, the present invention relates to devices and associated methods for fusion of vertebral bodies that provide robust spinal support in a less invasive manner. 
     BACKGROUND 
     The concept of intervertebral fusion for the cervical and lumbar spine following a discectomy was generally introduced in the 1960s. It involved coring out a bone graft from the hip and implanting the graft into the disc space. The disc space was prepared by coring out the space to match the implant. The advantages of this concept were that it provided a large surface area of bone to bone contact and placed the graft, under loading forces that allowed osteoconduction and induction enhancing bone fusion. However, the technique is seldom practiced today due to numerous disadvantages including lengthy operation time, destruction of a large portion of the disc space, high risk of nerve injury, and hip pain after harvesting the bone graft. 
     Presently, at least two devices are commonly used to perform the intervertebral portion of an intervertebral body fusion: the first is the distraction device and the second is the intervertebral body fusion device, often referred to as a cage. Cages can be implanted as standalone devices or as part of a circumferential fusion approach with pedicle screws and rods. The concept is to introduce a distraction device that will distract a collapsed disc in a generally axial direction, decompress the nerve root, and allow load sharing to enhance bone formation, and then implant an intervertebral fusion device that is small enough to allow implantation with minimal retraction and pulling on nerves. 
     In a typical intervertebral body fusion procedure, a portion of the intervertebral disc is first removed from between the vertebral bodies. This can be done through either a direct open approach or a minimally invasive approach. Disc shavers, pituitary rongeours, curettes, and/or disc scrapers can be used to remove the nucleus and a portion of either the anterior or posterior annulus to allow implantation and access to the inner disc space. The distraction device is inserted into the cleared space to enlarge the disc space such that the vertebral bodies are separated in a generally axial direction by actuating the distraction device. Enlarging the disc space is important because it also opens the foramen where the nerve root exists. It is important that during the distraction process one does not over-distract the facet joints. An intervertebral fusion device is next inserted into the distracted space and bone growth factor, such as autograft, a collagen sponge with bone morphogenetic protein, or other bone enhancing substance may be inserted into the space within the intervertebral fusion device to promote the fusion of the vertebral bodies. 
     Intervertebral distraction and fusion can be performed through anterior, posted or, oblique, and lateral approaches. Each approach has its own anatomical challenges, but the general concept is to fuse adjacent vertebra in the cervical thoracic or lumbar spine. Devices have been made from various materials. Such materials include cadaveric cancellous bone, carbon fiber, titanium and polyetheretherketone (PEEK). Devices have also been made into different shapes such as a bean shape, football shape, banana shape, wedge shape and a threaded cylindrical cage. 
     As with all minimally invasive surgeries, a primary goal is to provide equivalent or near equivalent treatment as more invasive surgical techniques but with less discomfort, recovery time, etc. for the patient. One problem with minimally invasive intervertebral fusion procedures is that the limited size of the surgical access limits the size of the implant(s) that can be inserted. While devices that are vertically expandable in a generally axial direction have addressed some of these issues by being able to be inserted through a smaller opening and then made taller in a generally axial direction within the disc space, such devices are still limited in the transverse footprint that can be covered within the disc space which can affect the stability of the device within the disc space and limits the area for bone grown. 
     SUMMARY 
     Disclosed herein are systems and methods for intervertebral body fusion that provide more robust support within the disc space. Intervertebral body fusion devices can have a unitary monolithic body including a plurality of body segments interconnected with each other by flexure members. Devices be configured to be inserted through an opening in a compressed configuration and then expanded within the disc space to an expanded configuration. In the expanded configuration, devices can have a greater mediolateral or transverse to the disc space footprint. This wider footprint provides greater support for the vertebrae relative to the size of the opening through which the device is inserted. 
     In one embodiment, an expandable intervertebral body fusion device includes a unitary monolithic body having a plurality of body segments connected to each other with flexure members and an opening defined between the plurality of body segments. The device body can include an anterior body segment, a posterior body segment and one or more mediolateral body segments extending between the anterior body segment and the posterior body segment along both a lateral side and a medial side of the anterior body segment and the posterior body segment. A threaded opening can be formed in one or more of the anterior body segment and the posterior body segment. The body is configured to be mediolaterally expanded from a compressed configuration to an expanded configuration by interaction of an expansion tool with the threaded opening causing the one or more mediolateral body segments on the lateral side and the one or more mediolateral body segments on the medial side to generally move away from each other and expand the opening between the plurality of body segments such that the body forms a greater mediolateral footprint in the expanded configuration than in the compressed configuration. 
     In one embodiment, a transversely expandable intervertebral body fusion device for a disc space between adjacent vertebra of a spine of a human patient includes a unitary monolithic body configured in size and shape to be implantable in the disc space. The body can have at least four body segments each connected to adjacent body segments by one or more flexure members with the body segments surrounding and collectively defining an opening within a transverse plane bisecting the body. The body segments can include an anterior body segment, a posterior body segment and at least one mediolateral body segment extending between the anterior body segment and the posterior body segment along each of a lateral side and a medial side of the body. A threaded opening can be formed in at least one of the anterior body segment and the posterior body segment. The body can be configured to be mediolaterally expanded from a transversely compressed configuration to a transversely expanded configuration by interaction of an expansion tool with the threaded opening causing the at least one mediolateral body segments on each side to generally move transversely away from each other, thereby expanding the opening of the body and forming a perimeter defined by an outer edge of the body that presents a mediolateral footprint in the expanded configuration that is greater than in the compressed configuration. 
     The above summary is not intended to describe each illustrated embodiment or every implementation of the subject matter hereof. The figures and the detailed description that follow more particularly exemplify various embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Subject matter hereof may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying figures, in which: 
         FIGS. 1A-1D  depict an expandable intervertebral body fusion device in a collapsed configuration according to an embodiment. 
         FIGS. 2A-2D  depict the expandable intervertebral body fusion device of  FIGS. 1A-1D  in an expanded configuration. 
         FIGS. 3A-3C  depict a portion of the expandable intervertebral body fusion device of  FIGS. 2A-2D . 
         FIG. 4  depicts a schematic representation of an expandable intervertebral body fusion device according to an embodiment being inserted between vertebrae of a patient. 
         FIGS. 5A-5B  depict a schematic representation of an expandable intervertebral body fusion device according to an embodiment inserted between vertebrae of a patient in a compressed and an expanded configuration. 
         FIGS. 6A-6B  depict an expandable intervertebral body fusion device and a corresponding insertion device according to an embodiment. 
         FIGS. 7A-7F  depict portions of an insertion device for an expandable intervertebral body fusion device according to an embodiment. 
         FIGS. 8A-8C  depict portions of an insertion device for an expandable intervertebral body fusion device according to an embodiment. 
         FIGS. 9A-91  depict portions of an insertion device and an expandable intervertebral body fusion device according to an embodiment 
     
    
    
     While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims. 
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A-1D and 2A-2D  depict an expandable intervertebral body fusion device  100  according to an embodiment.  FIGS. 1A-1D  depict the device  100  in a collapsed configuration and  FIGS. 2A-2D  depict the device  100  in an expanded configuration. In practice, the device  100  is inserted into the disc space through a minimally invasive access in the collapsed configuration and then expanded inside of the disc space. In embodiments, the device  100  is inserted between adjacent vertebrae  10  on its side as depicted in  FIG. 4  such that when it is expanded in the disc space rather than expanding vertically it expands horizontally/transversely to the disc space to enable the device to take up a larger footprint within the disc space as can be seen contrasting  FIG. 5A  and  FIG. 5B . The device is therefore able to occupy more lateral to medial and anterior to posterior space within the disc space relative to the size of the access that has heretofore been possible. In one embodiment in its insertion and un-expanded state the device is 8 mm in height, 11.5 mm in width and 26 mm in length. The device can have many heights from 8 mm up to 16 mm. In embodiments, the width can go from 8-12 mm and the length from 22 mm-32 mm. When the device is expanded, the height remains the same but the width can double or nearly double (from 11.5 to 22 mm or 47%) and the length goes from 26 mm to 20 mm (16% decrease). The device can have many lordotic angles from 0 to 15 degrees or higher; the most common being 0, 6, 12 degrees. The horizontal top and bottom of the device can have different shapes to better fit the endplates such as football shaped or domed. Also, the different segments of the device separated by flexures could be tailored or cut by wire EDM or 3D printed to create different horizontal expanded states such as oval, elliptical, circular, bean shaped, banana shaped or many other polygons and non-polygon shapes. The mean disc height at the L3-4 level is 11.3 mm+/−1.8 mm, L4-5 11.3+/−2.1 mm and L5-S1 10.7+/−2.1 mm. The average circumference of the L4 endplate is about 141 mm and surface area 1,492 mm 2  above. The device can have difference foot prints to try to fill the endplate or disc space circumference. Referring now to  FIGS. 1A-1D , device  100  can include a device body  102 . Generally, device body  102  can be unitarily formed as a single monolithic construct, although multiple component embodiments are also contemplated. Device body  102  can include upper  104   a  and lower  104   b  bearing surfaces. As noted above, device  100  can be inserted generally on its side such that bearing surfaces  104   a ,  104   b  interface with and bear the forces of the adjacent vertebrae  10  (see  FIGS. 4 and 5A-5B ). In embodiments, the larger threaded opening  126  are positioned dorsal or posterior and the smaller opening  124  is positioned ventral or anterior. Device body  102  can include a plurality of mediolateral body segments  106  unitary connected to each other by flexure  108  comprising a thin, flexible strip of material. As can be seen in, e.g.,  FIGS. 1C-1D , mediolateral body segments  106  and flexures  108  can perform a continuous, unitary out perimeter surface  110 . Device body  102  can further include an anterior body segment  112  and posterior body segment  114 . Anterior and posterior body segments  112 ,  114  can also be connected with mediolateral body segments by flexures  108 . Device body  102  further defines an open interior  116  between the body segments. 
     In the depicted embodiment, the device  100  includes three mediolateral body segments  106  on each side such that the device includes a total of eight body segments. In some embodiments, a device having eight body segments may be generally octagonally shaped in the expanded configuration as depicted in  FIGS. 2A-2D . In other embodiments, device may have greater or fewer mediolateral body segments on each side. 
     Device body  102  can further include a plurality of locking flexures  118  disposed in the open interior  116 . As can be seen in, e.g.,  FIGS. 1C-1D , locking flexures  118  can extend from a lock base  120  that is recessed with respect to bearing surfaces  104   a ,  104   b . As will be described in more detail below, each locking flexure  118  corresponds with locking projection  122  extending from an adjacent body segment  106 . 
     Each of anterior body segment  112  and posterior body segment  114  can include a threaded opening that aids in insertion and expansion of device. In one embodiment, anterior body segment  112  includes an anterior threaded opening  124  configured to interface with a stabilizing element for inserting the device  100  into the disc space. Posterior body segment  114  can include a posterior threaded opening  126  that is larger than anterior opening  124  and can be configured to interface with an expansion element that is rotated to expand device body  112 , which will be described in more detail below. In other embodiments, anterior opening  124  may interface with the expansion elements while posterior opening  126  interfaces with the stabilizing element. In some embodiments, anterior body segment  112  can be tapered to facilitate insertion of the device  100  into the disc space through the minimally invasive access opening. 
       FIGS. 2A-2D  depict device  100  in an expanded configuration. As the device  100  is expanded, the mediolateral body segments  106  on opposing sides of the device body  102  are moved away from each other causing the device to expand medially and laterally within the disc space. When the device  100  is expanded, the locking flexures  118  interface and lock with the locking projections  122  to prevent external forces from causes the device to compress from the expanded position following expansion. As can be seen in more detail in  FIGS. 3A-3C , each locking flexure  118  includes a pointed tip  128  that interfaces with a notch  130  in locking projections to lock the components together. 
     As noted above, in one embodiment device  100  is inserted between adjacent vertebrae  10  on its side, as shown in  FIG. 4 , with bearing surfaces  104   a ,  104   b  configured to interface with the vertebrae.  FIGS. 5A-5B  depict how the device  100  can be inserted in a collapsed configuration and then expanded within the disc space to occupy a greater footprint within the disc space. Note that these figures show one particular access approach and device orientation relative to the disc space, but that other access approaches and device orientations are possible.  FIGS. 6A-6B  depict device  100  with an insertion device  200  used to insert and expand device  100  within the disc space according to an embodiment. As will be described in more detail below, insertion device  200  generally includes a stabilizing component  204  and an expansion component  202 . Expansion component  202  includes a knob  209  configured to be rotated to secure the expansion component  202  to intervertebral device  100  and a dial  208  configured to be rotated to expand intervertebral device  100 , as discussed in more detail below. 
     Stabilizing component  204  includes a handle  206  configured to be rotated to secure the component to device  100 .  FIGS. 7A-7E  depict further detail regarding the components of insertion device  200 . 
     Expansion component  202  includes a body  224 , a shaft  222  extending from the body  224 , a flange  226  at the distal end of shaft  222  and a distal threaded tip  228 . Shaft  222  and body  224  include internal lumens that enable passage of shaft body  214  of stabilizing component  204  to pass through expansion component  202 . Distal tip  228  is sized to be rotatingly received by posterior or proximal threaded opening  126  of device. Flange  226  is wider than shaft  222  and threaded tip  228  to prevent expansion component  204  from being over-inserted when attached to expandable device  100 . Knob  209  and dial  208  are selectively attachable to expansion component  202  via, for example, a rotational coupling with knob  209  and with a screw  220  for dial  208 . Dial  208  can also include a threaded portion  221  configured to interface with a proximal threaded portion  212  of shaft  210 . A lock  230  can be selectively insert into a lock aperture  232  through body  224  of expansion component  202  to lock rotation of stabilizing component  204  with respect to expansion component  202 , as will be discussed in more detail below. Lock  230  can be selectively held in place with screw  234 . 
     Stabilizing component  204  includes a shaft  210  extending from handle  206 . Shaft  210  includes a proximal threaded portion  212  configured to interface with dial  208 , a shaft body  214  configured to be extended through the expansion component  202 , an implant extension  216  configured to extend through the implantable device  100  during implantation, and a threaded tip  218 . Shaft  210  further includes a lock slot  236  configured to interface with lock  230 . 
     Lock  230  includes a handle  238  and a lock body  240 . Lock body  240  is configured to be inserted through lock aperture  232  in body  224  of stabilizing component  202 . Lock body  240  further includes a recessed portion  242  having a reduced diameter that interfaces with the lock slot  236  in shaft body  214  of shaft  210 . Recessed portion  242  of lock body  240  further includes a cutout  244  that allows for limited rotation of shaft body  214  when lock  230  is engaged with shaft  210 . 
       FIGS. 8A-8C  further depict the interrelation of the components of inserter  200 . Dial  208  is threaded onto proximal threaded portion  212  of stabilizing component  204 . Shaft  210  of stabilizing component is inserted through expansion component  202  with implant extension  216  and threaded tip  218  extending distally from expansion component  202 . Proximal end of expansion component  202  is secured to dial  208  with screw  220 . Lock  230  can be selectively inserted into aperture  232  and through lock slot  236  in shaft  210 . 
       FIGS. 9A-91  depict further details regarding the interaction between inserter  200  and expandable device  100 . First, the distal tip  228  of the expansion component  202  is engaged with the posterior threaded opening  126  of implantable device  100  and the knob  209  is rotated to secure the tip  228  to the opening  126 . If not already done so prior to attaching expansion component  202 , stabilizing component  204  is inserted through stabilizing component  202  to the distal side of the expandable device  100 . The implant extension  216  can be extended through the body of the implant  100  to engage the threaded tip  218  of the stabilizing component  204  to interface with the distal threaded opening  124  of the implant. Handle  206  can be rotated to secure the tip  218  to the opening  124 . Lock  230  can now be inserted through slot  232  in expansion component and across slot  236  in shaft  214  of stabilizing component. 
     The dial  208  of the expansion component  202  can now be rotated to expand the implant  100  within the disc space. Dial  208  is rotated while the user holds the knob  209  such that the dial rotates relative to knob  209 . Lock  230  prevents shaft  214  from rotating such that stabilizing component  204  maintains device  100  in a stable position. Dial  208  therefore rotates shaft  222  and distal tip  228  about shaft  214  of stabilizing component  204 . This rotation pushes on the proximal or anterior end of device  100  while the distal or posterior end of the device is maintained stable, causing the distance between the anterior and posterior ends of the device to shorten and the device  100  to expand laterally outwardly. As described, above, device expands from the collapsed configuration shown in, e.g.,  FIGS. 1A, 5A and 6A , to the expanded configuration shown in, e.g.,  FIGS. 2A, 5B and 6B  to cover a wider footprint in the disc space. Implant is therefore able to provide more robust and stable support in the disc space that is laterally wider than the access opening through which the implant is implanted. 
     As can be seen in  FIGS. 9E-9H , the slot  236  in shaft  210  of stabilizing component  204  can also serve to limit an amount that expansion component  202  can be rotated to expand device  100 . Referring to  FIGS. 9E and 9G , initially the lock  230  is positioned in at a proximal end of slot  236 . As the dial  208  is rotated to rotate the shaft  222  to expand the device  100 , the dial  208  travels linearly along the threaded portion  212  of the stabilizing component and the lock  230 , which is inserted through a locking tube  231  of expansion component that enables shaft  222  to be rotated, is advanced linearly along slot  236 . In the fully expanded position, as shown in  FIG. 9H , the lock  230  abuts a distal end of the slot  236  such that further rotation of dial  208  with not cause any further linear advancement of shaft  222 . The length of the slot  236  can be predetermined based on a desired or actual maximum expansion of the implanted device  100 . 
     Referring to  FIG. 9I , the stabilizing component  204  can be removed by rotating handle  206  to disengage the threaded tip  218  from the device and withdrawing the shaft  210  from the expansion component  202 . The hollow expansion component  202  can then serve as a funnel to infuse one or more of, for example, bone puddy, demineralized bone matrix, and bone chips into the now empty opening in the device  100  to aid the fusion process. Finally, the expansion component  202  can be disengaged from the implant  100  and removed, leaving the implant in the disc space with, e.g., bone graft in the interior of the device  100 . 
     The typical height opening after a discectomy available to insert the implant can be from 4-14 mm depending on how collapsed the disc space is. One would need disc space distractors either a mechanical device or a lollipop sizer to expand the disc space. The typical width of the surgical path into the disc space after retracting the nerve root could be 10-12 mm. Through a transforaminal interbody approach (TLIF: transforaminal interbody fusion) where you remove the superior and inferior facet you may be able to get an additional 1-2 mm more of working room. 
     In another embodiment, device can be inserted into the disc space and expanded vertically to expand the disc space, with the flexures locking the device at the expanded height and maintaining the expanded disc space. 
     Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions. 
     Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted. 
     Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended. 
     Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein. 
     For purposes of interpreting the claims, it is expressly intended that the provisions of 35 U.S.C. § 112(f) are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim.