Abstract:
A method to insert a spinal implant into a vertebral space, the method including the steps of: grasping the implant with a distal end of an implant insertion tool; holding a proximal end of the implant insertion tool and inserting the implant toward the vertebral space; and manipulating the proximal end to apply a yaw movement to the implant while the implant is attached to the tool and in the vertebral space.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. application Ser. No. 11/870,844 (U.S. Pat. No. 8,641,764) filed Oct. 11, 2007, and claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 60/829,065, filed on Oct. 11, 2006, the entireties of these applications are incorporated by reference. 
     
    
     BACKGROUND OF 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. 
           [0015]      FIGS. 5A ,  5 B,  5 C,  5 D and  5 E show a side view of a first alternative spinal implant tool ( FIG. 5A ), a perspective view of the actuator for the tool ( FIG. 5B ), an enlarged view of the distal end of the actuator ( FIG. 5C ), a perspective view of the spinal implant ( FIG. 5D ) and an enlarged view of the distal end with a spinal implant attached to the actuator ( FIG. 5E ). 
           [0016]      FIGS. 6A ,  6 B and  6 C show a side view of an second alternative spinal implant tool ( FIG. 6A ), a perspective view of the distal end of tool attached to a spinal implant ( FIG. 6B ), and a second perspective view of the distal end of tool attached to a spinal implant ( FIG. 6C ). 
           [0017]      FIGS. 7A and 7B  show a side view of a third alternative spinal implant tool ( FIG. 7A ), and a perspective view of the distal end of tool attached to a spinal implant ( FIG. 7B ). 
           [0018]      FIGS. 8A ,  8 B and  8 C show a perspective view ( FIG. 8A ), a top view ( FIG. 8B ) and an inner side view ( FIG. 8C ) of a spinal implant. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      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 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 cam surface  106  and thereby forces the implant to pivot with respect to the axis of the instrument. 
         [0020]    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. 
         [0021]    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. 
         [0022]      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. 
         [0023]    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 actuator 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. 
         [0024]      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 . 
         [0025]    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 . 
         [0026]      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. 
         [0027]      FIGS. 5A ,  5 B,  5 C,  5 D and  5 E show a side view of a first alternative spinal implant tool  500  to insert a spinal implant  502 . The tool has a handle  504  at a proximal end, a center rod that connects to a pin or other attachment to the spinal implant, such as rod  201  and pin  102  shown in  FIG. 2 , and a hollow rod  506  that serves as an actuator rod similar to rod  201  in  FIGS. 1 to 3 . The center rod may be turned from the handle by a turn knob  508  to rotate the spinal implant about the axis of the rod. The actuator rod  506  may be turned at the handle by a winged grip  510  to rotate the cam surface  512  at the distal end of the actuator rod. Rotating the actuator and cam surface causes the pivot yaw in a pivoting movement illustrated in  FIG. 3 . 
         [0028]    The cam surface  512  is a flat annular surface on a cylindrical metal section  514  attached to the distal end of the rod  506 . The cam surface  512  is in a plane offset from a plan perpendicular to the axis of the rod. The degrees of the offset may vary depending on the amount of yaw movement desired by the spinal implant, but is preferably in a range of  5  degrees to  25  degrees. The cam surface  512  abuts bull-nose surfaces  516  at the end of a ridge  518  at the end of the spinal implant  502 . The bull-nose surfaces  518  may be on opposite sides of a hemispherical attachment structure  519  that receives the end of the center rod and releasable pin that temporarily secures the implant to the tool. 
         [0029]    The bull-nose surfaces slide against the cam surface  512  as that surface and its rod rotate with respect to the inner rod that is attached to implant. As the bull-nose surfaces slide against the cam surface, the spinal implant moves in a yaw direction. The yaw movement of the implant is controlled by the surgeon twisting the winged grip  510  at the handle. To assist the surgeon in determining the yaw orientation of the implant, a shallow groove  520  may be machined in the cam surface. The surgeon will feel in his fingers in the winged grip the action of the bull nose surfaces sliding across the groove. Knowing when the spinal implant is in the yaw orientation corresponding to the grooves  520  gives the surgeon information helpful in positioning the spinal implant in the spine. Further, the grooves  512  may be used to lock the yaw position of the spinal implant by applying sufficient compressive force between the bull nose surfaces and cam surface. The compressive force may be adjusted by turning the rod so that its threaded end turns into or out of the pin in the hemispherical structure  519 . 
         [0030]      FIGS. 6A ,  6 B and  6 C show views of second alternative spinal implant tool  600  having many components similar to the tool  500  shown in  FIG. 5A . These similar components are labeled with the same reference numbers as used in  FIG. 5A  and the corresponding text description of the tool given for  FIG. 5A  applies to tool  600 . The distal end of the actuator rod  602  includes a gear actuator  604  that engages gear teeth on a semi-circular gear attachment  606  on the spine implant  608 . The gear actuator  604  make by half-circle gear extending partially, e.g., half-way, around the axis  610  of the rod  602 . The engagement of the teeth of the gear  604  with the teeth of the attachment  606  on the implant  608  causes the implant to pivot about pin  612  coupled to a hemispherical attachment  614  (similar to hemispherical attachment  519 ) and engaging a threaded end of the center rod  616  of the tool. The gear attachment  606  is on the end of the implant and offset from the hemispherical attachment  614 . 
         [0031]    Due to the engagement between the gear teeth of the gear attachment  606  on the implant and the gear actuator  604  on the actuator, the surgeon can turn the wing grip  510  on the actuator rod to cause the implant to yaw back and forth respect to the axis  610  of the tool  600 . Turing the actuator rod approximately  180  degrees causes the gear teeth on the gear attachment  606  to disengage and rotate away from the gear actuator  604 . Further, yaw movement of the implant can be prevent by turning locking knob  510  that the geared actuator  604  is forced into the gears of the geared to bind against the gear teeth in the gear attachment creating sufficient friction to prevent implant rotation in the yaw directions. 
         [0032]      FIGS. 7A and 7B  show a third alternative spinal implant tool  700  having many components similar to the tool  500  shown in  FIG. 5A . These similar components are labeled with the same reference numbers as used in  FIG. 5A  and the corresponding text description of the tool given for  FIG. 5A  applies to tool  600 . The center rod  702  may have a threaded end that engages a pin  704  mounted in a hemispherical attachment  708  (similar to hemispherical attachment  519 ) at the end of the spinal implant  706 . The end of the implant with the hemispherical attachment has a slanted surface  710 . The distal end of the actuator rod  712  includes a pair of legs  714  each having a bull-nose end surface  716  that slides against the slanted surface at the end of the spinal implant. The rotation of the wing grip  510  at the handle end  504  of the tool  700  turns the actuator shaft  712  and causes the bull-nose end surfaces  716  to slide against the slanted surface  708  of the implant. The sliding movement of the bull-nose end surface against the surface  708  pivots the implant in a yaw movement with respect to the axis of the tool. 
         [0033]    The spinal insertion tool may be used to prepare a space for an implant between adjacent vertebra. The tool  700  provides a steerable tool having detachable tips. These tips may include, but not limited to, interchangeable rasps, curettes, broaches, osteotomes, reamers, dissectors and implant trial sizes. The interchangeable instrument tips are steered and released by any method or combination of methods described above. 
         [0034]    The slanted surface  710  may be included in a wedge attachment  718  attached by a bracket  720  on the end of the implant  706 . The wedge attachment may be secured to the implant prior to surgery and before the implant is inserted into the spine of a patient. The wedge attachment may be interchangeable with other attachments to the spinal implant, such as wedges with slanted surfaces of varying angles to provide variable sweep of the yaw movement. In addition, the wedge attachment may be used secured to surgical rasps, curettes, spoons, picks, scrapers and other surgical tools. The wedge attachment allows a variety of surgical tools to be mounted on the end of the spinal implant tool which, with these tools, can perform surgical functions, e.g., removing bone, spinal disc and other material from a disc region of the spine, smoothing a spine surface to later receive a spinal implant and to clear away material from the disc region. Accordingly, the spinal tool may be used for surgical procedures in addition to implanting a spinal insert and steering the insert during its insertion into the spine. 
         [0035]    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. 
         [0036]    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. 
         [0037]    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. 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. 
         [0038]    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. 
         [0039]      FIGS. 8A ,  8 B and  8 C show a perspective view ( FIG. 8A ), a tope view ( FIG. 8B ) and an inner side view ( FIG. 8C ) of a spinal implant  800  formed of a polymer (PEEK) implant body and including of a metallic ball  802 . The ball may be formed of titanium and inserted in a hemispherical recess  804  of the end  806  of the implant  800 . For example, the end section  806  of the implant may be a wedge having an inner chamber to receive and hold the ball  802 . The wedge  806  is secured to an end surface  808  of the body  810  of the implant. The wedge, when secured to the body, holds the ball  802  on the implant and allows the ball to pivot with the threaded end of the spinal implant tool. The ball may be hollow and have a cylindrical aperture  812  to receive a pin. The pin (see  FIG. 2 ) has a threaded side aperture to receive a threaded end of the centre rod of a spine insertion tool. The ball  802 , and preferably the wedge  806 , are formed of a metal (such as Titanium) for strength. The body  810  of the implant may be formed of an alternate material, such as a radiolucent polymer (including, but not limited to, PEEK). 
         [0040]    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. 
         [0041]    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. 
         [0042]    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. 
         [0043]    Instruments may be used to prepare a space for an implant between adjacent vertebra.  FIG. 7  shows views of an instrument with steerable and detachable tips, including, but not limited to, interchangeable rasps, curettes, broaches, osteotomes, reamers, dissectors and implant trial sizes. The interchangeable instrument tips are steered and released by any method or combination of methods described in the paragraphs and figures above. 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. 
         [0044]    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. 
         [0045]    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.