Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Application 61/479,206, filed Apr. 26, 2011. 
    
    
     FIELD 
     The present disclosure relates generally to spinal fusion devices. More specifically, example embodiments are directed to a stand alone interbody spacer. 
     BACKGROUND 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     The spine is a flexible column formed of a plurality of bones called vertebrae. The vertebrae include a hollow cavity and essentially stack one upon the other, forming a strong column for support of the cranium and trunk of the body. The hollow core of the spine houses and protects the nerves of the spinal cord. The different vertebrae are connected to one another by means of articular processes and intervertebral, fibrocartilaginous bodies. Each vertebra includes upper and lower endplates formed from harder compact bone than the softer cancellous bone of the interior of the vertebra. 
     The intervertebral bodies, also known as intervertebral discs, include a fibrous ring filled with pulpy material. The discs function as spinal shock absorbers and also cooperate with synovial joints to facilitate movement and maintain flexibility of the spine. When one or more discs degenerate through accident or disease, nerves passing near the affected area may be compressed and consequently irritated. The result may be chronic and/or debilitating neck and/or back pain due to these spinal disorders. 
     Various methods and apparatus have been designed to relieve such back pain, including spinal fusion using an interbody spacer and suitable graft using techniques such as anterior interbody fusion, posterior interbody fusion, or transforaminal interbody fusion surgical techniques. The implants used in-these techniques are placed in the intervertebral disc space between adjacent vertebrae of the spine. Bone graft material may be placed within the spacers to facilitate bone growth between the adjacent vertebrae. Many times an exterior plate and/or screws are used in conjunction with the implant to hold the adjacent vertebrae while the fusion occurs. 
     Ideally, the interbody spacer should stabilize the intervertebral space and allow fusion of the adjacent vertebrae. Moreover, during the time it takes for fusion to occur, the interbody spacer should have sufficient structural integrity to withstand the stress of maintaining the space without substantially degrading or deforming and have sufficient stability to remain securely in place prior to actual bone in-growth fusion. 
     One significant challenge to providing fusion stability (prior to actual bone ingrowth fusion) is preventing spinal extension during patient movement. Distraction of the vertebral space containing the fusion graft may cause the interbody spacer to shift or move disrupting bone ingrowth fusion and causing pain. An exterior plate is often used with the interbody spacer to hold the adjacent vertebrae while the fusion occurs. There remains a need for an interbody spacer capable of holding the adjacent vertebrae steady during fusion without the use of external plates. 
     SUMMARY 
     An interbody spacer system includes a cage and at least one first fixation blade. The cage includes an anterior wall and a posterior wall connected by a pair of side walls. The at least one first fixation blade partially extends around an outer surface of a first of the pair of side walls and is positionable between a first configuration for insertion into a disk space between two vertebrae and a second configuration for attachment to a first of the vertebrae. 
     In other features, the system includes a shaft extending through a portion of the cage and coupled to the first fixation blade. The shaft rotates the first fixation blade from the first configuration to the second configuration. A second fixation blade partially extends around an outer surface of a second of the pair of side walls, positionable between the first configuration for insertion into the disk space and a second configuration for attachment to a second of the vertebrae. A recessed portion of the first side wall receives the first fixation blade in the first configuration. The first fixation blade and outer surface of the first side wall are flush in the first configuration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top perspective view of an exemplary stand alone interbody spacer according to the principles of the present disclosure. 
         FIG. 2  is a bottom perspective view of the stand alone interbody spacer of  FIG. 1  according to the principles of the present disclosure. 
         FIG. 3  is a lateral side view of the stand alone interbody spacer of  FIG. 1  according to the principles of the present disclosure. 
         FIG. 4  is a top view of the stand alone interbody spacer of  FIG. 1  according to the principles of the present disclosure. 
         FIG. 5  is a posterior side view of the stand alone interbody spacer of  FIG. 1  according to the principles of the present disclosure. 
         FIG. 6  is an exploded perspective view of the stand alone interbody spacer of  FIG. 1  according to the principles of the present disclosure. 
         FIGS. 7A-7C  are perspective views illustrating deployment of a fixation blade of the stand alone interbody spacer of  FIG. 1 . 
         FIGS. 8A-8C  are anterior side views illustrating deployment of a fixation blade of the stand alone interbody spacer of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical “or.” It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
     Embodiments of the invention will now be described with reference to the Figures, wherein like numerals reflect like elements throughout. Embodiments of the invention may include several novel features, no single one of which is solely responsible for its desirable attributes or which is essential to practicing the invention described herein. The words proximal and distal are applied herein to denote specific ends of components of the instrument described herein. For example only, a proximal end refers to the end of an instrument nearer to an operator of the instrument when the instrument is being used. A distal end refers to the end of a component further from the operator and extending towards the surgical area of a patient and/or the implant. Similarly, the words left and right, top and bottom, and upper and lower may denote opposite sides of a component. 
     Referring now to  FIGS. 1-6 , an exemplary stand alone interbody fixation system  100  for spinal surgeries includes a cage  102  and an attachment member  104 . The cage  102  may include a substantially annular shape formed by an anterior wall  106 , lateral walls  108  and  110 , and a posterior wall  112  that form a substantially hollow interior  114 . A plurality of grooves  115  on upper and lower surfaces of the cage  102  may improve attachment of the cage  102  to the vertebrae. The attachment member  104  may include one or more fixation blades  116   a - b  (collectively blades  116 ) coupled to a shaft  118  at a hub  119 . The shaft  118  may extend through into at least one of the walls  106 - 112 . For example, in the present example, the shaft  118  extends through the anterior wall  106 , a portion of the hollow interior  114 , and into the posterior wall  112 . One or more of the blades  116  may be positioned exterior to the walls  106 - 112 . The blades  116  may rotate about the shaft  118  to engage vertebrae above and below the cage  102 . 
     Other typical stand alone interbody fixation systems may include interior blades within the hollow interior of a cage. Because these interior blades must fit within the hollow interior of the cage, the dimensions must be limited to the dimensions of the interior sides of the various walls comprising the cage. Further, because the interior blades fill a portion of the hollow interior, less volume is available for packing of bone graft material. 
     The exterior blades  116  provide a larger radius of travel or arc length than prior stand alone interbody spacer systems having blades that deploy from the hollow interior  114 . For example, in the cervical region of the spine, vertebrae and intervertebral disc space are substantially smaller than in lower regions of the spine. Therefore, spacers with internal blades are substantially limited in terms of arc length and engagement with the adjacent vertebrae. By positioning the blades external to the spacer/cage, the blades may include radial lengths greater than internal blades. Although the exterior blades  116  of the present example are substantially formed in right angles, other blade configurations may include curved blades, helical blades, and additional toothed and spiked blades. 
       FIG. 6  illustrates an exploded perspective view of the system  100  showing additional features for coupling the cage  102  and the attachment member  104 . The anterior wall  106  of the cage  102  may include an anterior aperture  120 . The anterior aperture  120  may also include a keyed portion  122  that engages portions of the shaft  118  to lock the system  100  in one or more configurations. For example, the hub  119  may include posterior projections  123  configured to snap into the keyed portion  122 . The posterior wall  112  of the cage may include a posterior aperture  124 . The posterior aperture  124  may include a slot  126  for guiding the shaft  118  through the posterior wall  112 . The attachment member  104  may be rotated from a non-deployed first configuration to a deployed second configuration by rotating the shaft  118  as illustrated in  FIGS. 7A-7C  and  8 A- 8 C. For example, a deployment instrument (not shown) may engage a driving feature  127  of the hub  119 . 
     The cage  102  may include nesting features for receiving the attachment member  104  within portions of the walls  106 - 112  in the first configuration. For example, in  FIG. 6 , the side walls  108  and  110  include recessed portions  128  and  130  configured to partially engage the attachment member  104 . The blades  116  of the attachment member  104  may comprise an anterior member  132  extending substantially parallel with the anterior wall  106  and including the hub  119 . A first arm  134  may extend posteriorly from the anterior member  132  and proximate to the first side wall  108  to form the first blade  116   a . A second arm  136  may extend posteriorly from the anterior member  132  and proximate to the second side wall  110  to form the second blade  116   b . First recessed portion  128  may permit nesting of the first arm  134  such that the outer surfaces of the first arm  134  and the side wall  108  are substantially flush with one another. Likewise, second recessed portion  130  may permit nesting of the second arm  136  such that the outer surfaces of the second arm  136  and the side wall  110  are flush with one another. Thus, the attachment member  104  may form a substantially unitary, U-shaped construction that surrounds the cage  102 . Posterior ends of the blades  116  may include piercing members  138  such as spikes, claws, and the like for piercing the endplates of the vertebrae. 
     Referring now to  FIGS. 7A-7C  and  8 A- 8 C, the system  100  may be deployed by rotating the shaft  118  within the cage  102 . In  FIGS. 7A and 8A , the system  100  is in a first non-deployed configuration with the first and second arms  134  and  136  nesting within the first and second recessed portions  128  and  130  respectively. The system  100  includes a slim profile for insertion into the intervertebral space. The deployment instrument (not shown) may engage the recess  127  of the hub  119  and apply a torque to rotate the attachment member  104  and deploy the system  100 . As the shaft  118  rotates within the apertures  120  and  124  in  FIGS. 7B and 8B , the first arm  134  may disengage the first recessed portion  128  and the second arm  136  may disengage the second recessed portion  130 . 
     Rotation of the arms  134  and  136  positions the piercing members  138  closer to the endplates and begins engage the piercing members  138  with the endplates of the vertebrae. In  FIGS. 7C  and  8 C, the system  100  is in a fully deployed configuration with the first and second arms  134  and  136  fully rotated and disposed at right angles relative to the cage  102 . The piercing members  138  may fully engage the endplates of the vertebrae. The exterior fixation blades  116  may include a radius R 1  of extension away from the shaft  118  that is greater than a radius R 2  of typical interior blades of the prior art. The larger radius R 1  provides greater encroachment and engagement within the endplates of the vertebrae. Exterior blades also provide increased volume within the hollow interior  114  of the cage  102 . 
     Including blades that are exterior to the cage may present additional concerns regarding safety of the surgeon while handling the system  100 . The system  100  may further comprise sterile packaging conducive to both transport and loading into the insertion/deployment tools. The tools themselves may include a protective sheath, sleeve, or outer members that surround the system  100  to prevent contact with the exterior blades  116 . 
     Example embodiments of the methods and systems of the present invention have been described herein. As noted elsewhere, these example embodiments have been described for illustrative purposes only, and are not limiting. Other embodiments are possible and are covered by the invention. Such embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments but should be defined only in accordance with the following claims and their equivalents. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification, and the following claims.

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