Patent Publication Number: US-2023157837-A1

Title: Spinal cervical fusion cage with built-in anchorages

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a spinal cage implant, and, more particularly, to a spinal fusion cage having built-in anchorages. 
     BACKGROUND 
     The spinal column includes a plurality of vertebrae linked to one another by facet joints and having an intervertebral discs located between each pair of adjacent vertebrae. The facet joints and intervertebral discs allow one vertebra to move relative to an adjacent vertebra, providing the spinal column a range of motion. When the facet joints and/or intervertebral discs become diseased, degenerated, damaged, or otherwise impaired the patient may experience pain or discomfort and/or loss of motion, thus prompting surgery to alleviate the pain and/or restore motion of the spinal column. 
     One possible method of treating these conditions is to immobilize a portion of the spine to allow treatment. For example, in a conventional spinal fusion procedure, a surgeon restores the alignment of the spine or the disc space between vertebrae by installing a rigid fixation rod and/or a plate between pedicle screws secured to adjacent vertebrae. Bone graft may be placed between the vertebrae, and the fixation rod cooperates with the screws to immobilize the two vertebrae relative to one another so that the bone graft may fuse with the vertebrae. In some procedures, a degree of mobility of the spine is permitted while also providing sufficient support and stabilization to effect treatment. 
     However, the use of bone screws, rods, and plates, necessitates a substantial amount of hardware left in the body for an extended period of time. In addition to the unavoidable certainty of pain associated with drilling through bone, the hardware involved also incurs a risk of soft tissue injury, infection, dislodgement, fracture, and the like. Thus, there is a need for a spinal cage implant that does not require external bone screws, rods, and/or plates. The present novel technology addresses this need. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a spinal fusion cage for spinal implant surgery, according to the present disclosure. 
         FIG.  2    is perspective view of the spinal fusion cage of  FIG.  1    and including a titanium bead bone infiltration scaffolding defining a contiguous porous network. 
         FIG.  3    is a top plan view of a titanium wire infiltration scaffolding for use with the spinal fusion cage of  FIG.  1   . 
         FIG.  4    is a perspective view of the scaffolding of  FIG.  3   . 
         FIG.  5    is a partial cutaway perspective view of the scaffolding of  FIG.  4    as attached to the cage of  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
       FIGS.  1 - 5    illustrate a first embodiment of the present novel technology, a spinal fusion cage  100  having an apertured generally flat plate member  105  with support members  110  extending therefrom. Herein, ‘generally flat’ may be taken to mean mostly flat but with contouring to match the shape of the plate  105  to the natural vertebra endplate. The generally flat plate  105  may have a central contour or dome shape to fit with the natural vertebra endplate. The fusion cage  100  may be configured for cervical, thoracic, or lumbar use. The plate member  105  is generally rectangular, and more particularly has curved edges mimicking the contours of the vertebrae between which it is to be placed. The plate member  105  includes an aperture array  120  formed therethrough, with the apertures  125  typically being of different sizes, such as including at least two different aperture areas. The pattern of the aperture array  120  may be varied, such as rows of apertures  125  oriented in a grid pattern, random placement of apertures  125 , and the like. 
     The support members  110  extend away from the plate member for engagement with vertebrae in either direction. If the plate member  105  is assumed to be oriented horizontally, the support members  110  extend therefrom both above and below the plate member  105 , typically with a vertical orientation. In other words, the support members  110  orthogonally or generally orthogonally intersect the plate member  105 , with the plate member  105  bisecting the support member(s)  110 . 
     Support members  110  include multiple teeth  130  extending therefrom for lockingly engaging bone to anchor the cage  100  in place between vertebrae. Teeth  130  are typically provided in varying sizes, with some teeth  130  angled to extend toward the plate  105  while some extend away from the plate  105  or parallel therewith. Teeth  130  are typically symmetrical along the direction of elongation, so as to minimize or avoid front/back movement. Support member  110  further includes a middle square pin  131 , which is sufficiently thick so as to resist horizontal movement and/or deformation. The support members or keels  110  extend sufficiently far from the plate  105  and any adjacent filler material  140  so as to be able to penetrate the vertebral end plates of adjacent vertebrae (above and below plate  105 ) and remain embedded in the endplate(s) during vertical movement; the adjacent vertebral end plates are oriented parallel to plate  105 . Teeth  130  are angled to intersect the vertebral end plates at an intersection angle; the intersection angle is typically between 20 and 70 degrees, more typically between 30 and 60 degrees, still more typically between 40 and 50 degrees, and yet more typically 45 degrees, so as to increase resistance to horizontal and vertical movement of the cage  100 . 
     The plate  105  and support members  110  are typically made of a biocompatible structural material, such as titanium or natural or artificial bone, and are more typically provided as a unitary piece. 3D printed bone maybe used to make all or part of the cage  100 . 
     A filler material  140  may be provided to extend from the plate  105  to provide support to adjacent vertebrae (when the cage  100  is emplaced therebetween) as well as to provide a porous scaffold  150  for infiltration and bone growth. In one embodiment, the filler material  140  is a volume of titanium beads  145  defining a porous scaffolding  150  disposed on both sides of the plate  105  and connected together at contact points, such as by a rapid electrical discharge welding process or the like. In this embodiment, the filler material  140  is a porous scaffolding  150  defining a solid portion (an interconnected bead array)  151  and an open cell pore network  153 . The bead size and bead size distribution are variable; variations of bead size and bead size distribution allows for variation and fine-tuning of the porosity and contiguity of the open cell pore network  153 . In other embodiments, the porous scaffolding  150  includes a solid portion  151  made of a twisted, interconnected wire mesh, arrays of twisted and/or curved wire, and the like. 
     In other embodiments, the filler  140  is made of an artificial bone material, such as hydroxyapatite, beta tricalcium phosphate, other morphologies of tricalcium phosphate, bioglass, collagen, chitosan, carbon nanotubes, combinations thereof, and the like. Artificial bone is typically provided as a solution to be 3D printed, such as by a bioprinter. Filler  140 , cage  100 , or both may be made of 3D printed artificial bone. In still other embodiments, the filler  140  is a combination of titanium and artificial bone. In all embodiments, the filler  140  may be infiltrated with bone growth accelerants, antibiotics, antivirals, medicines, pharmaceuticals, minerals, combinations thereof, and the like. In some embodiments, the filler  140  is surrounded by a filler wall  160 . The filler wall  160  is typically made of titanium or like structural material and/or of a resorbable biocompatible material, such as bone, artificial bone, 3D printed bone/artificial bone, bioglass, printed bioglass, combinations thereof, and the like. 
     In operation, the device  100  is surgically placed between adjacent vertebrae once the injured or damaged disc has been removed. The teeth  130  lockingly engage the bone endplate of each respective vertebra, such that the device is essentially self-seating and does not move or shift after being emplaced. Over time, bone grows out and through the porous filler  140 , permanently fusing the adjacent vertebrae. Bone grows inside the 3D printed bone  105 ,  110 ,  140  portions until the implant  100  is completely resorbed and replaced by the patient&#39;s own vertebral bone. 
     While the novel technology has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It is understood that the embodiments have been shown and described in the foregoing specification in satisfaction of the best mode and enablement requirements. It is understood that one of ordinary skill in the art could readily make a nigh-infinite number of insubstantial changes and modifications to the above-described embodiments and that it would be impractical to attempt to describe all such embodiment variations in the present specification. Accordingly, it is understood that all changes and modifications that come within the spirit of the novel technology are desired to be protected.