Abstract:
A spinal implant include a top, wherein at least a portion of the top is configured to contact a first vertebra, a bottom, wherein at least a portion of the bottom is configured to contact a second vertebra, a side having a releasable attachment to receive an insertion device and a cam surface to engage a cam on the insertion device

Description:
[0001]    This application is a continuation of U.S. Non-Provisional Utility application Ser. No. 11/278,552, filed Apr. 4, 2006, and claims the benefit of U.S. Provisional Patent Application Ser. No. 60/669,356 filed Apr. 8, 2005, both of which applications are incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention generally relates to the field of medical devices. Some embodiments of the invention relate to spinal implants inserted in the spine of a patient during surgical procedures and to instruments used to insert the implants. Other embodiments of the invention relate to methods for positioning, rotating and advancing an implant during a surgical procedure. 
         [0003]    A spinal implant may be used to stabilize a portion of a spine. The implant may promote bone growth between adjacent vertebra that fuses the vertebra together. The implant may include a spherical protrusion, a threaded pin and an angled surface to facilitate remote adjustment of the implant position using an insertion instrument. 
         [0004]    The insertion instrument may include, but is not limited to, a threaded rod, an actuator and a lock knob. The insertion instrument can be attached and detached to the implant, rotate the implant by transferring torque from the actuator to the implant. The actuator can be used to lock the implant in relation to the instrument. The rod can be used to apply force to the implant and advance it. The implant and instruments may be supplied in an instrument kit. 
         [0005]    An intervertebral disc may degenerate. Degeneration may be caused by trauma, disease, and/or aging. An intervertebral disc that becomes degenerated may have to be partially or fully removed from a spinal column. Partial or full removal of an intervertebral disc may destabilize the spinal column. Destabilization of a spinal column may result in alteration of a natural separation distance between adjacent vertebra. Maintaining the natural separation between vertebra may prevent pressure from being applied to nerves that pass between vertebral bodies. Excessive pressure applied to the nerves may cause pain and nerve damage. 
         [0006]    During a spinal fixation procedure, a spinal implant may be inserted in a space created by the removal or partial removal of an intervertebral disc between adjacent vertebra. The spinal implant may maintain the height of the spine and restore stability to the spine. Bone growth may fuse the implant to adjacent vertebra. 
         [0007]    A spinal implant may be inserted during a spinal fixation procedure using an anterior, lateral, posterior, or transverse spinal approach. A discectomy may be performed to remove or partially remove a defective or damaged intervertebral disc. The discectomy may create a space for a spinal implant. The amount of removed disc material may correspond to the size and type of spinal implant to be inserted. 
         [0008]    Spinal implants are described in U.S. Pat. No. 5,653,763 to Errico et al.; U.S. Pat. No. 5,713,899 to Marney et al.; U.S. Pat. No. 6,143,033 to Paul et al.; U.S. Pat. No. 6,245,108 to Biscup; and U.S. Pat. No. 5,609,635 to Michelson, United States Patent Application 20050027360 to Webb. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0009]    A spinal implant is disclosed comprising: a top, wherein at least a portion of the top is configured to contact a first vertebra; a bottom, wherein at least a portion of the bottom is configured to contact a second vertebra and a side having a releasable attachment to receive an insertion device and a cam surface to engage a cam on the insertion device. The spinal implant may include a hemispherical mount and a pin mounted within the spinal implant, wherein the insertion device attaches to the pin that serves as an axis of rotation and pivots around the pin with respect to the hemispherical housing. 
         [0010]    A method is disclose comprising: inserting an implant between portions of bone, wherein the implant locked at a first angle relative to a shaft of the instrument; loosening the implant relative to the shaft; turning the shaft to pivot the implant relative to the shaft, and releasing the implant from the instrument so that the implant is in position between the bone. Turning the shaft rotates a cam fixed to the shaft across a cam surface on the implant, wherein the cam surface is slanted and the movement of the cam across the cam surface pivots the implant. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a top-side perspective view of a spinal implant attached to an insertion instrument. 
           [0012]      FIG. 2  is an exploded view showing the spinal implant separate from the insertion instrument. 
           [0013]      FIG. 3  is a perspective view of the  FIG. 3  illustrates the interaction between the Actuator  202  of the instrument and the implant  100 . 
           [0014]      FIG. 4  is a perspective view of the implant releasably attached to the insertion instrument and positioned over a vertebra. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]      FIG. 1  shows the spinal implant  100  releasably attached to an insertion instrument  200 . The implant  100  may be made by made of PEEK plastic commonly used in spinal implants. The implant includes a hemispherical mount  105  and slanted cam surface  106  from which the mount protrudes. The tip of rod  201  pivotably attaches to the mount such that the implant may pivot with respect to the axis of the instrument. The pivoting of the implant is controlled by the a knob on the instrument that rotates the cam wings  205  about the hemispherical surface. The rotation of the cam, slides the front edges of the cam wings across the and cam surface  106  and thereby forces the implant to pivot with respect to the axis of the instrument. 
         [0016]    A knob (e.g. actuator wings)  206  on the on the proximal end of the instrument enables a surgeon to rotate the cam and thereby adjust the angle between the implant and the axis of the instrument. Pivoting of the implant is caused as the actuator pushers  205  (e.g., cam) act on the slanted surface  106  of the implant  100 . As the cammed actuator  202  rotate and slide across the slanted surface  106 , the implant makes a yaw movement with respect to the axis of the instrument. Actuator  202  is equipped with the actuator wings  206  used to rotate pushers  205  (cam) from outside of the patient&#39;s body. 
         [0017]    Locking knob  207  may be tightened to bind the actuator against the implant effectively locking the implant with respect to the instrument. When locked, axial force and torque can be applied to the handle  204  to advance the implant into the spinal space and position the implant in the space. Turning the locking knob  207  that is threaded inside and engages threads on the proximal end of the rod causes the actuator  202  that is hollow to slide axially forward over the threaded rod  201  and thereby loosen or tighten the actuator against the implant. 
         [0018]      FIG. 2  shows the details of the attachment of the implant  100  to the instrument  200 . Threaded pin  102  is inserted into the channel  107  in the spherical protrusion (mount)  105  and retained there by a snap ring  103 . A threaded hollow shaft  108  in the threaded pin  102  is aligned with the slot opening  109  of the implant so that the treaded rod  201  can be threaded into the shaft  108  of the pin  102 . Slot opening allows pivoting of the implant by accommodating the pendulum motion of the rod  201 . Pin  104  is made of a material that enhances X-ray imaging. Making the pin visible assists the physician in the positioning of the implant while viewing a real-time x-ray image of the implant and vertebra. 
         [0019]    The actuator  202  may be a hollow tube that is coaxial with the rod  201 . The pushers are fixed to the distal end of the actuator. The pushers  205  include cams that engage a cam surface  106  on the implant. The proximal end of the tube has a knob (e.g. actuator wings)  206  to turn the tube and thereby move the cams against the cam surface. The angle of the implant with respect to the implant is adjusted by moving the cam against the cam surface. Adjusting the angle may allow the surgeon to properly place the implant in the spine area. 
         [0020]      FIG. 3  illustrates the interaction between the Actuator  202  of the instrument and the implant  100 . The actuator  202  is rotated around the axis of the threaded rod  201  that is engaged in the threaded pin  102 . As the cammed pushers  205  rotate, they push against the surface  106 . As a result the implant  100  turns around the axis of the pin  102 . It can be envisioned as if the implant is performing a “dog wagging its tail” motion with respect to the insert instrument  200 . 
         [0021]    If the locking knob  207  ( FIG. 1 ) is rotated, the actuator  202  is pushed against the implant  100 . Both pushers are advanced towards the surface  106  to bind the actuator against the implant so as to lock the implant with respect to the instrument. When locked, the assembly of the implant and instrument can be advanced while retaining the desired angle of the implant  100  in relation to the insertion instrument  200 . 
         [0022]      FIG. 4  shows the implant  100  with the insertion instrument  200  attached and in position on a patient vertebra  401 . Rotation of the actuator  202  in relation to the axis of the threaded rod  201  results in the rotation of the implant  100  around the axis of the pin  102 . Rotation of the knob  207  pushes the actuator  202  into the implant locking the assembly. When the assembly is locked hammer tapping can be applied to the handle  204  to advance the assembly forward. 
         [0023]    A spinal implant may be used to stabilize a portion of a spine. The implant may promote bone growth between adjacent vertebra that fuses the vertebra together. An implant may include an opening through a height of a body of the implant. The body of the implant may include curved sides. A top and/or a bottom of the implant may include protrusions that contact and/or engage vertebral surfaces to prevent backout of the implant from the disc space. 
         [0024]    A spinal implant may be used to provide stability and promote fusion of adjacent vertebra. The implant may be used in conjunction with a spinal stabilization device such as a bone plate or rod-and-fastener stabilization system. The implant may establish a desired separation distance between vertebra. The implant may promote bone growth between adjacent vertebra that fuses the vertebra together. Instrument at is necessary for insertion of an implant in a patient and alignment of the implant in the space. 
         [0025]    A discectomy may be performed to establish a disc space between vertebra. The disc space may be prepared for implant insertion by distraction of adjacent vertebra, rasping and filing of the bone to achieve the desired spacing. 
         [0026]    It is desired to perform insertion of the implant and positioning of the implant using minimum number of inserted instruments and thought the smallest possible insertion channel in the body. 
         [0027]    Implants may be constructed of biocompatible materials sufficiently strong to maintain spinal distraction. Implants may include, but are not limited to, allograft bone, xenograft bone, autograft bone, metals, ceramics, inorganic compositions, polymers such as PEEK, or combinations thereof. If the implant is not made of bone, surfaces of the implant that contact bone may be treated to promote fusion of the implant to the bone. Treatment may include, but is not limited to, applying a hydroxyapatite coating on contact surfaces, spraying a titanium plasma on contact surfaces, and/or texturing the contact surfaces by scoring, peening, implanting particles in the surfaces, or otherwise roughening the surfaces. 
         [0028]    In some embodiments, an implant may include an opening that extends through a body of the implant. The opening may have a regular shape or an irregular shape. Bone graft may be placed in the opening. The bone graft may be autogenic bone graft, allogenic bone graft, xenogenic bone graft, and/or synthetic bone graft. Some implant embodiments may be constructed from allogenic bone, such as cortical bone from a femur, tibia, or other large bone. In some embodiments, an implant may be formed from one or more pieces of allograft bone cut to a desired shape. 
         [0029]    In certain embodiments, sides of an implant may be shaped to increase contact between an implant and adjacent vertebra with notches, ribs and other similar features. Increasing contact of an implant with adjacent vertebra may inhibit movement of the implant after insertion. An increased contact area between an implant and adjacent vertebra may promote bone growth between adjacent vertebra. 
         [0030]    In some embodiments, one or more sides of an implant may be curved. One or more curved sides of an implant may allow the implant to be maneuvered in a disc space during insertion of the implant. The curvature of a side may approximate a curvature of an anterior side of a vertebra adjacent to which the implant is inserted. 
         [0031]    Instruments may be used to prepare a space for an implant between adjacent vertebra. An instrument may be used to insert an implant in a prepared space. Instruments may be supplied to a surgeon or surgical team in an instrument set. An instrument set may include one or more implants for use during an insertion procedure. An instrument set may include implants of various sizes and/or lordotic angles to allow selection of an implant to suit a patient during surgery. Instrument is attached to the implant before the insertion into the body. When the desired position of the implant is achieved, instrument is disengaged from the implant and can be extracted from the body. 
         [0032]    An instrument acts as an implant inserter. The implant inserter may be used to push the implant and to rotate the implant. After insertion of the implant, the implant may be released from the inserter without the application of significant repositioning forces to the implant. It can be imagined that the insertion instrument can be screwed into the implant using threads or use other techniques such as a tightening collet, jamming or grabbing. In the disclosed embodiment the implant turns around the axis of the implant pin as a result of the rotation of cam pushers. It can be imagined that other mechanisms can be used to rotate the implant such as ratchets or threaded push rods. The implant inserter may have a low profile that allows for visualization of the implant and surrounding area during insertion of the implant. Implant is equipped to couple and uncouple from the instrument. 
         [0033]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.