Abstract:
This invention concerns a vertebral body replacement element to be inserted into an intervertebral space, thus supporting the spinal column of a patient. The present invention further concerns a system and method for expanding and distracting a vertebral body replacement into and within the spinal column of a patient.

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
       [0001]    Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. This application is a continuation application of U.S. application Ser. No. 11/937,242, filed Nov. 8, 2007, which claims the benefit of U.S. Provisional Application No. 60/864,857, filed Nov. 8, 2006, each of which is hereby incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The present invention generally relates to a vertebral body replacement to be inserted into an intervertebral space, thereby supporting the spinal column of a patient. The present invention further relates to a system and method for expanding and distracting a vertebral body replacement element into and within the spinal column of a patient. 
         [0004]    2. Description of the Related Art 
         [0005]    Back pain is one of the most significant problems facing the workforce in the United States today, is a leading cause of sickness-related absenteeism, and the main cause of disability for people between the ages of 19 and 45. Back pain can occur from pinching or irritating a spinal nerve, compression of the spine, vertebral shifting relative to the spinal cord axis, and formation of bone spurs. The most common cause of disabling back pain, however, generally stems from trauma to a vertebral disc, such as from mechanical shock, stress, tumors, or degenerative diseases. In many cases, the disc can become permanently damaged or degenerated, such that the preferred treatment necessitates partial or total excision and replacement of the damaged disc. 
         [0006]    Traumatic injury to a vertebral disc that is not removed frequently can promote scar tissue formation. Such scar tissue typically is thicker than the healthy tissue, such that the disc continues to progressively degenerate, lose water content, and can stiffen and become significantly less effective as a shock absorber. Eventually, the disc can deform, herniate, or collapse, eliminating the flexibility of the spinal column, and potentially leading to further degeneration or damage to other vertebral discs of the spinal column. At such a point, the only option is for the damaged disc to be partially or completely removed. 
         [0007]    When the disc is partially or completely removed, generally it is necessary to replace the excised material to prevent direct contact between the boney surfaces of the adjacent vertebrate on either side of the removed disc. For example, U.S. Pat. No. 6,824,565 of Muhanna discloses a vertebral spacer that is inserted between adjacent vertebrate to provide restorative force and function as a shock absorber between the adjacent vertebrate. Another alternative approach has been to insert a “cage” that can maintain a space occupied by the removed disc to prevent the vertebrate from collapsing and impinging upon the nerve roots of the spine. Still further, spinal fusion has been used to restrict motion and stabilize patients&#39; spines by fusing adjacent vertebrate together. This generally can reduce mechanical back pain by preventing the now immobile vertebrate from impinging on a spinal nerve; however, such stability and pain reduction generally is created at the expense of spinal flexibility and motion. In addition, many conventional techniques for disc repair and replacement can be limited in terms of their size or configuration and thus generally are not designed to accommodate variations in size of the gap resulting from the excising of the vertebral disc material. Further, conventional techniques often cannot accommodate expansion or growth of the spine, frequently requiring replacement of the vertebral spacers with other, different size spacers. 
         [0008]    Accordingly, it can be seen that a need exists for a vertebral body replacement and system and method of implanting such a vertebral body replacement that addresses the forgoing related and unrelated problems in the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIGS. 1A-1C  are perspective illustrations of various alternative embodiments of the vertebral body replacement member according to the principles of the present invention. 
           [0010]      FIG. 2  is an exploded perspective illustrating the installation of the vertebral body replacement member such as illustrated in  FIGS. 1A  or  1 B within the spinal column of a patient. 
           [0011]      FIG. 3  is a perspective illustration, illustrating the distraction of the intervetebral body replacement member according to the principles of the present invention positioned between adjacent vertebrate of the patient&#39;s spine to enable insertion of a spacer therebetween. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    As generally illustrated in  FIGS. 1A-1C , the present invention is directed to an vertebral body replacement member or elements for insertion into an intervertebral space or gap between vertebrae of a patient&#39;s spine to replace substantially all of a vertebral disc or vertebrae that has been excised or removed due to damage or degeneration of the disc. The vertebral body replacement member of the present invention generally is useful to replace a vertebral disc that has degenerated due to traumatic injury, vertebral displacement, disease (i.e., autoimmune disease, rheumatoid arthritis, etc.), or any other pathological condition of the spinal column that may injure or shift the intervetebral discs. The vertebral body replacement member of the present invention provides support to the adjacent vertebrae of the patient&#39;s spine to help maintain the separation between the vertebrae, while also preserving the natural curvature of the spine and further enabling regenerative bone growth and adjustment of the intervertebral spacing between the adjacent vertebrae to accommodate growth or expansion therebetween. 
         [0013]    It is generally contemplated that the vertebral body replacement member of the present invention can be made from any bio-compatible or physically inert material or combination of such materials having the mechanical strength capable of maintaining the intervetebral space between adjacent vertebrae, as indicated in  FIGS. 2 and 3 , without impinging upon nerves and/or restricting movement and further bone growth or regeneration of the spinal column discs adjacent the intervetebral space in which the present invention is mounted. Examples of such materials can include bone, such as bone sections from a femur or other bones of the patient or from donors, metal materials such as titanium, titanium alloys, stainless steel, chrome, cobalt, and other, similar materials, as well as various polymeric materials such as methyl methacrylate (MMA), urethane, polyacetal material, reinforced polymers such as carbon fiber or polyether keytone, polycarbonates, polypropylene, polyamides, and silicone based polymers as generally understood in the art. 
         [0014]    As illustrated in  FIGS. 1A-3 , the vertebral body replacement member of the present invention generally includes a telescoping construction, including an upper section and a lower section. The upper section and lower section of the component engage or interface via a sliding joint which allows relative linear motion. Assembly, adjustment, and removal of the vertebral body replacement member is enhanced with the sliding joint because the sections advantageously move more freely than with other attachment or interfacing means. While alternate attachment or interfacing means may be available, an acceptable alternate does not include a threaded means. The upper and lower sections can be formed in various configurations including generally cylindrical having a substantially circular cross section as illustrated in  FIGS. 1A and 2 ; cylindrical with a substantially oval cross-section as illustrated in  FIG. 1B ; or can be formed in square or rectangular configurations as generally illustrated in  FIG. 1C and 3 . Among other functions, the non-circular embodiments have the added benefit of restricting longitudinal rotation relative to the axis of linear motion between the upper and lower sections. An alternate means of restricting longitudinal rotation between the upper and lower sections from those disclosed in  FIGS. 1B and 1C  would be a key and keyway interface. In some applications, restriction of longitudinal rotation is desired and is accomplished by the non-circular embodiments. The circular configuration is advantageous in that although longitudinal rotation is not required, is possible, while providing relative linear motion of the upper and lower sections. Further, with the top and bottom surfaces angled or contoured as discussed below, restricting longitudinal rotation of the upper and lower sections is desired. Each of the upper and lower sections further generally will include an open-ended body formed from a bio-compatible or physically inert material as discussed above, and one of the sections, for example the upper section, will be formed with at least a portion of its body having a slightly smaller diameter or cross-sectional area than the lower section so as to telescope into and out of the open upper end of the lower section as indicated in  FIGS. 1A-1C . It will, however, also be understood that the upper and lower sections can be formed with the lower section telescoping into and out of the upper section as needed or desired. 
         [0015]    The open ended structures of the upper and lower sections further generally will define a space or cavity within the vertebral body replacement member as the two sections are brought together. The upper section generally will include a substantially flat top that further can include channels or openings formed therein, and, as illustrated in  FIGS. 1A and 1B , further can include a series of teeth or serrations formed about the side edges of the upper or top portion of the upper section to help secure it against an adjacent upper vertebrae. The lower section typically has a similar construction, with an open upper end, a closed, substantially flat bottom surface, and further generally includes slots or openings formed in its bottom or base plate. The lower section also can include series of teeth or serrations formed about the side edges of its lower or bottom base plate to help engage and fix the lower section to the lower vertebrae of the patient&#39;s spine in which it is mounted. The top and bottom surfaces of the upper and lower sections, respectively, additionally can be angled or contoured as needed to substantially match the contour of the adjacent upper and lower vertebrae on which the sections are mounted or engaged. 
         [0016]    The openings formed in the top and bottom portions of the upper and lower sections, respectively, of the vertebral body replacement member, as well as growth openings formed in the side walls thereof, such as indicated in  FIG. 1C , provide areas or points of access for bone to grow and expand into the surrounding tissue about the patient&#39;s spine to further help secure the vertebral body replacement member within the patient&#39;s spine and to foster or facilitate regeneration and additional bone growth. The telescoping construction of the vertebral body replacement member further enables the vertebral replacement member to expand or extend as needed to accommodate such additional or regenerative bone growth and to enable further adjustment of the spacing provided by the vertebral body replacement member as needed to fit the intervetebral space created by the excising or removal of part or the entirety of the damaged vertebral disc. 
         [0017]    As further illustrated in  FIGS. 1-3 , the upper and lower sections each generally include a large slotted opening formed through the side wall or walls of the upper and lower sections of the vertebral body replacement member. This opening enables the insertion and packing of bone material within the cavity defined between the upper and lower sections of the vertebral body replacement member after implantation or placement of the vertebral body replacement member within the patient&#39;s spine. Such implanted bone material can then fuse to and grow with the existing remaining vertebrae of the patient, expanding out through the openings formed in the top, bottom, and side walls of the upper and lower sections, respectively, of the vertebral body replacement member and into contact with the adjacent upper and lower vertebrae and the tissue surrounding the patient&#39;s spine. 
         [0018]    Still further, as illustrated in  FIG. 3 , the upper and lower sections of the vertebral body replacement member further generally will include a distraction slot or similar opening for receiving a distracter instrument or tool therein. Alignment of the distraction instrument or tool with the distraction slot is preserved because of the restriction of relative longitudinal rotation between the upper section and lower section in the non-circular embodiments (and the circular embodiment with keyways or other restrictive rotational restraints). The ends of the distracter instrument will be introduced into the distraction slots formed in the upper and lower sections for placement of the vertebral body replacement member within the vertebral space or excised area between the adjacent vertebrae and thereafter expanding the sections as needed by causing the upper and lower sections to telescope or move outwardly away from each other so as to expand the intervertebral body replacement member at needed to fill the intervertebral space. 
         [0019]    In addition, as illustrated in  FIGS. 1C-3 , one or more spacers also can be mounted between the upper and lower sections of the vertebral body replacement member as needed. The spacers generally will be made from the same or a compatible material as the upper and lower sections of the vertebral body replacement member and typically will be of a similar configuration and/or size as the upper and lower sections so as to fit therebetween without substantially overlapping the side edges of the upper and lower sections and, provide a more mechanically robust and rugged structure due to the superior load carrying abilities of a nested structure in compression having a large load bearing surface. For example, as illustrated in  FIGS. 1B ,  2  and  3 , the upper section of the vertebral body replacement member can include a bottom portion formed with a reduced area or diameter that is adapted to be received and telescope into the open upper end of the lower section. The spacers can be of a similar size and configuration as the upper and lower sections so as to fit over this recessed portion of the upper section as indicated in  FIGS. 2 and 3 . The spacers also can be provided with teeth as needed to help secure the spacers in place within the intervertebral space. 
         [0020]    The spacers typically will be inserted as needed after implantation of the vertebral body replacement member within the intervetebral space, by engagement of the upper and lower sections of the vertebral body replacement member by the distraction tool and expansion thereof, so as to create a gap in which the spacer or spacers can be inserted. Thereafter, as the distraction instrument is closed, the upper and lower sections of the vertebral body replacement member will be brought together, sealing into engagement with each other and with any spacers contained therebetween. Thereafter, the distraction tool or instrument can be removed and the surgical opening in the patient&#39;s back closed. Still further, if additional spacers are needed, the distraction tool can be engaged with the slots in the upper and lower slots and the upper and lower sections further separated to enable implantation of a additional spacers as needed. 
         [0021]    The present invention thus provides a simple device, typically made from a single, biocompatible material with minimal parts and generally utilizing only a minimal presences of screws, if at all, or similar fasteners to attach the upper and lower sections of the vertebral body replacement member to the adjacent vertebrate of the patient. The vertebral body replacement member further is radiolucent and expandable, and any distraction required is done by distracting the device internally through the engagement of the distraction instrument with the slotted openings in the upper and lower sections thereof, such that there is no distraction or engagement of screws that could damage bone. The growth openings formed in the top, bottom and side walls of the upper and lower sections, respectively, further enable bone growth out of the vertebral body replacement member and into the surrounding bone and tissue to help promote healing and more natural freedom of movement, while maintaining the intervetebral space and preventing collapse of the patient&#39;s spine. 
         [0022]    It will be understood by those skilled in the art that while the foregoing has been described with reference to preferred embodiments and features, various modifications, variations, changes and additions can be made thereto without departing from the spirit and scope of the invention.