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 vertebral body replacement element has a first member and a hollow second member, with the upper member and lower member engaging in a telescopic manner between the two members when assembled. Spacers may be inserted to adjustably define the length of the installed vertebral body placement element. The present invention further concerns a system and method for expanding and distracting a vertebral body replacement element into and within the spinal column of a patient.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional patent application No. 60/864,857, filed Nov. 8, 2006. 
    
    
     FIELD OF THE INVENTION 
     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. 
     BACKGROUND OF THE INVENTION 
     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. 
     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. 
     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. 
     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 
         FIGS. 1A-1C  are perspective illustrations of various alternative embodiments of the vertebral body replacement member according to the principles of the present invention. 
         FIG. 2  is an exploded perspective illustrating the installation of the vertebral body replacement member such as illustrated in  FIG. 1A  or  1 B within the spinal column of a patient. 
         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. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     As generally illustrated in  FIGS. 1A-1C , the disclosed apparatus is directed to a 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 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 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. 
     It is generally contemplated that the vertebral body replacement member 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 disclosed apparatus 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. 
     As illustrated in  FIGS. 1A-1C , the vertebral body replacement member generally includes a telescoping construction, including an upper section and a lower section. Turning now to  FIG. 1A , an upper section  12  and a lower section  13  of the vertebral body replacement member  11  engage or interface via a sliding joint which allows relative linear motion in the direction of an axis of linear motion  14 . Assembly, adjustment, and removal of the vertebral body replacement member  11  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 section  12  and the lower section  13  can be formed in various configurations or cross sections. Such configurations generally include a cylindrical configuration, having a substantially circular cross section as illustrated in  FIGS. 1B and 2 ; a generally cylindrical configuration with a substantially oval cross-section as illustrated in  FIG. 1A ; or in square or rectangular configurations as generally illustrated in  FIGS. 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  14  between the upper section  12  and the lower section  13 . 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 (not illustrated). In some applications, restriction of longitudinal rotation is desired and is accomplished by the non-circular alternate embodiments. The circular configuration is advantageous in that although longitudinal rotation is not required, it is possible, while providing relative linear motion of the upper section  12  and the lower section  13 . Further, as illustrated in  FIG. 1A , with a top surface  15  and a bottom surface  16  angled or contoured as discussed below, restricting longitudinal rotation of the upper section  12  and the lower section  13  is desired. Each of the upper section  12  and the lower section  13  further generally includes 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  12 , 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  13  as indicated in  FIGS. 1A-1C . It will, however, also be understood that the upper section  12  and the lower section  13  can be formed with the lower section  13  telescoping into and out of the upper section  12  as needed or desired. 
     The open ended structures of the upper section  12  and the lower section  13  further generally define a space or cavity  17  within the vertebral body replacement member  11  as the two sections  12 ,  13  are brought together. The upper section  12  generally includes a substantially flat top surface  15  that further can include channels  18  or openings formed therein, and, as illustrated in  FIGS. 1A and 1B , further can include a series of teeth or serrations  19  formed about the side edge  20  of the top surface  15  of the upper section  12  to help secure it against an adjacent upper vertebrae (not illustrated). The lower section  13  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  13  also can include series of teeth or serrations  22  formed about the side edge  16  of its lower or bottom base plate to help engage and fix the lower section  13  to the lower vertebrae (not illustrated) of the patient&#39;s spine in which it is mounted. Additionally, an upper portion of the lower section  13  may also include teeth or serrations  24 , further aiding in support of the component  11  to the vertebrae. The top surface  15  and the bottom surface of the upper section  12  and the lower section  13 , 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  12 ,  13  are mounted or engaged. 
     Openings  21 ,  25 ,  26  are formed in top  126  and bottom  27  portions of the upper section  12  and the lower section  13  of the vertebral body replacement member  11  and provide areas or points of access for bone to grow and expand into the surrounding tissue about the patient&#39;s spine to help further secure the vertebral body replacement member  11  within the patient&#39;s spine and to foster or facilitate regeneration and additional bone growth. 
     Opening  26  also provides a point of access for a tool (see  FIG. 3 , item  101 ) to install, adjust, or remove the vertebral body replacement member  11 . As illustrated in  FIG. 1C , growth openings  45  are also formed in the top and side walls thereof. The telescoping construction of the vertebral body replacement member  11  further enables the vertebral replacement member  11  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  11  as needed to fit the intervetebral space created by the excising or removal of part or the entirety of the damaged vertebral disc. 
     As further illustrated in  FIGS. 1-3 , the upper sections  12 ,  32 ,  42 ,  52 ,  62  and the lower sections  13 ,  33 ,  43 ,  53 ,  63  each generally include large slotted opening  26  openings  26 ,  36 ,  46 ,  56 ,  66  formed through the side wall or walls of the upper sections  12 ,  32 ,  42 ,  52 ,  62  and the lower sections  13 ,  33 ,  43 ,  53 ,  63  of the vertebral body replacement members  11 ,  31 ,  41 ,  51 ,  61 . Referring to  FIG. 1A , openings  21 ,  25 ,  26  enable the insertion and packing of bone material within the cavity  17  defined between the upper section  12  and the lower section  13  of the vertebral body replacement  11  member after implantation or placement of the vertebral body replacement member  11  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  25 ,  26  formed in the top, bottom, and side walls of the upper section and side walls of the lower section, as well as opening  21  in the lower section of the vertebral body replacement member  11  and into contact with the adjacent upper and lower vertebrae and the tissue surrounding the patient&#39;s spine. 
     Alternate embodiments of the vertebral body replacement member are illustrated in  FIGS. 1B and 1C .  FIG. 1B  illustrates a vertebral body replacement member  31  having an upper section  32  and a lower section  33 . The upper section  32  and the lower section  33  assemble such that the two sections  32 ,  33  fit together in a telescopic fashion. The upper section  32  and the lower section  33  as illustrated are circular in cross section but can be oval in cross section, thus preventing relative rotation between the two sections  32 ,  33 . In this embodiment, the upper section  32  has a lower portion or protrusion  34  with a reduced diameter from an upper portion  35 . A lip  36  is formed at the interface of the upper portion  35  and the lower portion  34 . When the upper section  32  and the lower section  33  are assembled, the lip  36  rests on, or comes into contact with, a rim  37  of the lower section  33  and establishes a length of the vertebral body replacement member  31 . Illustrated in  FIG. 1C , a vertebral body replacement member  41  is shown having an upper section  42  and a lower section  43  with the upper section  42  and lower section  43  being square, or rectangular, in cross section. The lower section  43  further comprises a protrusion  48 . A spacer  45  fits between the upper section  42  and the lower section  43  and is restrained by contact with the protrusion  48 , and establishes, among other things, a length of the vertebral replacement body member  41 . The spacer  45  may also increase the overall rigidity of the component  11 , help absorb shock during use, reduce component  41  wear, and reduce the amount of packing material necessary. When assembled, the spacer  45  may rest on a base  47  of the lower section  43 . 
     Still further, as best illustrated in  FIG. 3 , the upper sections  12 ,  32 ,  42 ,  52 ,  62  and the lower sections  13 ,  33 ,  43 ,  53 ,  63  of the vertebral body replacement members  11 ,  31 ,  41 ,  51 ,  61  further generally will include a distraction slot  26 ,  36 ,  46 ,  56 ,  66  or similar opening for receiving a distracter instrument  65  or tool therein. Alignment of the distraction instrument  65  or tool with the distraction slot  26 ,  36 ,  46 ,  56 ,  66  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  65  will be introduced into the distraction slots  26 ,  36 ,  46 ,  56 ,  66  formed in the upper sections  12 ,  32 ,  42 ,  52 ,  62  and the lower sections  13 ,  33 ,  43 ,  53 ,  63  for placement of the vertebral body replacement members  11 ,  31 ,  41 ,  51 ,  61  within the vertebral space or excised area between the adjacent vertebrae  103 ,  105  and thereafter expanding the sections as needed by causing the upper sections  12 ,  32 ,  42 ,  52 ,  62  and the lower sections  13 ,  33 ,  43 ,  53 ,  63  to telescope or move outwardly in a direction of travel  68  away from each other so as to expand the intervertebral body replacement members  11 ,  31 ,  41 ,  51 ,  61  as needed to fill the intervertebral space. 
     In addition, as illustrated in  FIGS. 2 and 3 , one or more spacers  54 ,  64  also can be mounted between the upper and lower sections of the vertebral body replacement member as needed. The spacers  54 ,  64  generally will be made from the same or a compatible material as the upper section  52 ,  62  and the lower section  53 ,  63  of the vertebral body replacement member  51 ,  61  and typically will be of a similar configuration and/or size as the upper section and the lower section so as to fit therebetween without substantially overlapping the side edges of the upper section  52 ,  62  and the lower section  53 ,  63  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  FIG. 2 , the upper section  52  of the vertebral body replacement member  51  can include a bottom portion  57  formed with a reduced area or diameter that is adapted to be received and telescope into the open upper end  58  of the lower section  53 . The spacers  54  can be of a similar size and configuration as the upper section  52  and the lower section  53  so as to fit over this recessed portion  57  of the upper section  52  as indicated. The spacers  54  also can be provided with teeth (not shown) as needed to help secure the spacers in place within the intervertebral space, between the adjacent vertebrae  103 ,  105 . The spacer  54  may be configured as a hollow ring, having an inner diameter that is similar to the diameter of the recessed portion  57 . The ring shaped spacer  54  may also be a split ring to facilitate assembly. As a ring, the spacer  54  is free to slide telescopically along the recessed portion  57  so when assembled, the lower surface of the ring  59  will rest against the upper rim  60  of the lower section  53  thereby establishing the minimum length of the vertebral body replacement member  51 . 
     The spacers  54  typically will be inserted as needed after implantation of the vertebral body replacement member  51  within the intervetebral space, by engagement of the upper section  52  and the lower section  53  of the vertebral body replacement  51  member by the distraction tool (see  FIG. 3 ) and expansion thereof, so as to create a gap in which the spacer  54  or spacers  54  can be inserted. Thereafter, as the distraction instrument is closed, the upper section  52  and the lower section  53  of the vertebral body replacement member  51  will be brought together, sealing into engagement with each other and with any spacers  54  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  54  are needed, the distraction tool can be engaged with the slots in an upper slot  71  and a lower slot  72  and the upper section  52  and the lower section  53  further separated to enable implantation of a additional spacers  54  as needed. 
     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. 
     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.