Patent Publication Number: US-10772736-B2

Title: Artificial disc

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a continuation application of U.S. patent application Ser. No. 15/260,466 filed on Sep. 9, 2016 (published as U.S. Patent Publication No. 2016-0374827), which is a continuation of U.S. patent application Ser. No. 14/070,171 filed on Nov. 1, 2013 (now issued as U.S. Pat. No. 9,463,095), which is a continuation application of U.S. patent application Ser. No. 13/421,121 filed on Mar. 15, 2012 (now issued as U.S. Pat. No. 8,597,355), both of which are incorporated in their entirety herein by reference. 
    
    
     TECHNICAL FIELD 
     This description relates to medical devices and more particularly to an artificial (or prosthetic) disc configured to be coupled to a portion of the spine. 
     BACKGROUND 
     A variety of medical devices and medical device systems may be implanted within a body of a patient to provide support to a portion or portions of the patient&#39;s body. For example, some medical devices may be implanted and coupled to backbones or portions of a spine of a patient and may be configured to provide support to the spinal bone structure of the patient. 
     When a vertebra of a patient is traumatized (e.g., damaged or diseased), a need for surgery may arise to replace and/or repair the traumatized vertebra. 
     SUMMARY 
     According to one general aspect, a medical device includes a base ring configured to be implanted within a body of a patient. The base ring provides a contact surface to a vertebra. The medical device includes multiple lower leveling plates having a non-flat bottom surface. The non-flat bottom surface of each of the multiple lower leveling plates engages an inner surface of the base ring and each of the multiple lower leveling plates is held in place within the base ring by a member extending from the base ring through a bore in the lower leveling plate. Multiple upper leveling plates have a bottom surface. The bottom surface of each of the multiple upper leveling plates engage a top surface of the multiple lower leveling plates and each of the multiple upper leveling plates is held in place within the base ring by a member extending through the upper leveling plate and engaging bores in the base ring. Multiple pads have a top surface and a bottom surface. The top surfaces of the multiple pads are arranged and configured to maintain a parallel plane and the bottom surface of each of the multiple pads engage the top surface of the upper leveling plates. A cover is configured to enclose the multiple lower leveling plates, the multiple upper leveling plates, the multiple pads and the base ring. The cover provides a contact surface to a vertebra. A compressible member is arranged through a center of the multiple lower leveling plates, the multiple upper leveling plates and the multiple pads and the compressible member has a top surface that engages the cover. 
     Implementations may include one or more of the following features. For example, the base ring may define a disc shape and the base ring may define a space between an inner wall and an outer wall. The space between the inner wall and the outer wall is configured to receive the multiple lower leveling plates and the multiple upper leveling plates. The inner wall of the base ring defines an area to receive the compressible member. A top of the outer wall of the base ring defines multiple areas to receive the multiple pads. 
     The multiple lower leveling plates and the multiple upper leveling plates are configured to equalize and distribute forces applied to the contact surface of the base ring with the vertebrae and the contact surface of the cover with the vertebrae. The multiple pads maintain the parallel plane using the multiple lower leveling plates and the multiple upper leveling plates. The non-flat bottom surface of the lower leveling plates is defined by a first flat area contouring to a sloped round area contouring to a second flat area. Each of the multiple lower leveling plates may be symmetrical about its center. The bore in each of the multiple lower leveling plates may extend through a center of the lower leveling plate from the top surface to the bottom surface. The top surface of each of the multiple pads may be flat and the bottom surface of each of the multiple pads may define a platform having a raised spherical member on a top surface of the platform. The cover may define a circumferential wall having a lip at a top of the circumferential wall. The compressible member is contained within a diameter defined by an inner wall of the base ring. The compressible member may be a biocompatible, flexible material. 
     In another general aspect, a medical device includes a base ring configured to be implanted within a body of a patient. The base ring provides a contact surface to a vertebra. Multiple layers of multiple leveling plates are configured to equalize forces applied to the contact surface of the base ring, where at least one of the layers of the leveling plates engages an inner surface of the base ring. A layer of multiple pads is included with a top surface of the pads configured to maintain a parallel plane and a bottom surface of each of the multiple pads is configured to engage a top surface of one of the layers of the leveling plates. A cover is configured to enclose the multiple layers of the leveling plates, the layer of the multiple pads and the base ring. The cover provides a contact surface to a vertebra. 
     Implementations may include one or more of the following features. For example, the medical device may include a compressible member arranged through a center of the multiple layers of the multiple leveling plates and the multiple pads. The compressible member may be contained within a diameter defined by an inner wall of the base ring and the compressible member may have a top surface that engages the cover. 
     The multiple layers of multiple leveling plates may include a layer of multiple lower leveling plates having a non-flat bottom surface that is arranged circumferentially inside the base ring. The non-flat bottom surface of each of the multiple lower leveling plates may engage the inner surface of the base ring. The multiple layers may include a layer of multiple upper leveling plates having a bottom surface that is arranged circumferentially inside the base ring. The bottom surface of each of the multiple upper leveling plates engages a top surface of the multiple lower leveling plates. The multiple pads may maintain the parallel plane using the multiple lower leveling plates and the multiple upper leveling plates. The top surface of each of the multiple pads may be flat and the bottom surface of each of the multiple pads may define a platform having a raised spherical member on a top surface of the platform. 
     In another general aspect, a method includes inserting a prosthetic disc into a portion of an anatomical structure within a body of a patient. The prosthetic disc includes a base ring, multiple layers of multiple leveling plates configured to equalize forces applied to a contact surface of the base ring and a layer of multiple pads with each of the pads having a top surface and a bottom surface. The top surface of the pads is configured to maintain a parallel plane and the bottom surface of each of the multiple pads engages a top surface of one of the layers of the leveling plates. A cover is configured to enclose the multiple layers of the leveling plates, the layer of the multiple pads and the base ring. The method includes contacting an outer surface of the base ring to a vertebrae and contacting an outer surface of the cover to a vertebrae. 
     Implementations may include one or more of the following features. For example, the prosthetic disc may include a compressible member arranged through a center of the multiple layers of the multiple leveling plates and the multiple pads. The compressible member may be contained within a diameter defined by an inner wall of the base ring and the compressible member may have a top surface engaging the cover. 
     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a medical device according to an exemplary implementation. 
         FIG. 2  is a perspective view of a base ring of the medical device of  FIG. 1 . 
         FIG. 3  is a perspective view of a lower leveling plate illustrating a bottom surface of the lower leveling plate of the medical device of  FIG. 1 . 
         FIG. 4  is a perspective view of a lower leveling plate illustrating a top surface of the lower leveling plate of the medical device of  FIG. 1 . 
         FIG. 5  is a perspective view of an upper leveling plate illustrating a top surface of the upper leveling plate of the medical device of  FIG. 1 . 
         FIG. 6  is a perspective view of an upper leveling plate illustrating a bottom surface of the upper leveling plate of the medical device of  FIG. 1 . 
         FIG. 7  is a perspective view of a pad illustrating a top surface of the pad of the medical device of  FIG. 1 . 
         FIG. 8  is a perspective view of a pad illustrating a bottom surface of the pad of the medical device of  FIG. 1 . 
         FIG. 9  is a perspective view of a cover illustrating a bottom surface of the cover of the medical device of  FIG. 1 . 
         FIG. 10  is a perspective view of a cover illustrating a top surface of the cover of the medical device of  FIG. 1 . 
         FIG. 11  is a top view shown in cross-section of the medical device of  FIG. 1 . 
         FIG. 12  is a cross-section view along the line A-A of the medical device of view of  FIG. 11 . 
         FIG. 13  is a cross-section view along the line B-B of the medical device of view of  FIG. 11 . 
         FIG. 14  is a flow chart illustrating an exemplary method including the medical device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The devices and methods described herein are generally directed to medical devices that can be used to support, stabilize and/or replace anatomical structures within a body of a patient. In some implementations, the devices and methods described herein are configured to provide support to a spine or back of a patient, including providing support between two vertebrae in the spine or back of the patient. In other implementations, other portions of the body of the patient can be supported by the devices described herein. 
     The medical devices described herein (also referred to as “apparatus” or “device”) may be used as a prosthetic or artificial disc within a body of a patient. The terms “prosthetic” and “artificial” may be used interchangeably throughout this document to mean the same thing. The medical devices described herein may be implanted within a body of a patient to assist in maintaining normal physiologic motion in the spine of the patient. 
       FIG. 1  illustrates an exploded view of a medical device  100 , according to an exemplary implementation. The medical device  100  includes a base ring  102 , a layer of multiple lower leveling plates  104   a - 104   f  and a layer of multiple upper leveling plates  106   a - 106   f . The base ring  102  may provide a contact surface  108  to a vertebra in a spine of a patient. For example, the base ring  102  may provide a contact surface  108  to mate to the superior endplate of the inferior vertebra within a patient. The multiple lower leveling plates  104   a - 104   f  and the multiple upper leveling plates  106   a - 106   f  may work together to equally distribute the forces applied to the medical device  100 . In this manner, the forces may be equalized and distributed all over an entire surface using the lower leveling plates  104   a - 104   f  and the upper leveling plates  106   a - 106   f.    
     The lower leveling plates  104   a - 104   f  include a non-flat or non-planar bottom surface  110  that engages an inner surface of the base ring  102 . Each of the lower leveling plates  104   a - 104   f  may be held in place within the base ring  102  by a corresponding support member  112   a - 112   f  In one exemplary implementation, the support members (or members)  112   a - 112   f  may be dowels. The members  112   a - 112   f  may be received into openings or bores on the inner surface of the base ring  102  and extend vertically from the base ring  102  through a bore in each of the lower leveling plates  104   a - 104   f . The non-flat bottom surface  110  on each of the lower leveling plates  104   a - 104   f  may cause the lower leveling plates  104   a - 104   f  to rock when a force is applied to the top surface  114  of the lower leveling plates  104   a - 104   f  by a bottom surface  116  of the upper leveling plates  106   a - 106   f.    
     The upper leveling plates  106   a - 106   f  may be layered to contact the top surfaces  114  of the lower leveling plates  104   a - 104   f  Each of the upper leveling plates  106   a - 106   f  may be held in place within the base ring  102  by a corresponding support member  118   a - 118   f  that extends horizontally through a bore in the upper leveling plates  106   a - 106   f  and engages bores in the base ring  102 . In one exemplary implementation, the corresponding support members  118   a - 118   f  may be dowels. The dowels allow movement of the upper leveling plates  106   a - 106   f , including movement that pivots the upper leveling plates  106   a - 106   f  about the dowel. 
     In this exemplary implementation, the medical device  100  includes six (6) lower leveling plates  104   a - 104   f  and six (6) upper leveling plates  106   a - 106   f.  In one exemplary implementation, the lower leveling plates  104   a - 104   f  are offset from the upper leveling plates  106   a - 106   f , based on the spacing and location of the bores in the base ring  102  (as illustrated in  FIG. 2  and described in more detail below). In other exemplary implementations, the bores in the base ring  102  may be located in other positions such that the each of the upper leveling plates  106   a - 106   f  lines up directly on top of one of the lower leveling plates  104   a - 104   f.    
     In other exemplary implementations, the number of lower leveling plates  104   a - 104   f  and the number of upper leveling plates  106   a - 106   f  may vary depending on a size of the base ring  102  and/or on a size of the leveling plates themselves. While the size of each of the lower leveling plates  104   a - 104   f  is illustrated in this example is uniform or the same, other exemplary implementations may include different lower leveling plates  104   a - 104   f  with non-uniform sizes or sizes that are different from each other. Similarly, while the size of each of the upper leveling plates  106   a - 106   f  is illustrated in this example as uniform or the same, other exemplary implementations may include upper leveling plates  106   a - 106   f  with non-uniform sizes or sizes that are different from each other. 
     In other exemplary implementations, the number of lower leveling plates  104   a - 104   f  and upper leveling plates  106   a - 106   f  may not be a one-to-one correspondence. For example, in one exemplary implementation, there may be more lower leveling plates  104   a - 104   f  than upper leveling plates  106   a - 106   f . Alternatively, in another exemplary implementation, there may be more upper leveling plates  106   a - 106   f  than lower leveling plates  104   a - 104   f . The variation in the number of lower leveling plates  104   a - 104   f  and upper leveling plates  106   a - 106   f  may be due, at least in part, on the size of the leveling plates and/or the size of the base ring  102 . 
     The medical device  100  includes a layer of multiple pads  120   a - 120   f . The pads  120   a - 120   f  may be arranged circumferentially around the base ring  102 . The base ring  102  may define multiple areas  124   a - 124   f  to receive the multiple pads  120   a - 120   f . Each of the pads  120   a - 120   f  may include a generally flat top surface  122  and a bottom surface that includes a platform area  124  having a raised spherical member  126 . The top surface  122  of the pads  120   a - 120   f  may be configured to maintain a parallel plane. The bottom surface having the platform area  124  and the raised spherical member  126  may engage a top surface  128  of each of the upper leveling plates  106   a - 106   f.    
     The top surfaces  122  of all of the pads  120   a - 120   f  may maintain a parallel plane across the top surfaces based on the equalizing motion of the upper leveling plates  106   a - 106   f  and the lower leveling plates  104   a - 104   f . While this exemplary implementation illustrates six (6) pads  120   a - 120   f , other exemplary implementations may use a different number of pads based on, for example, a size of the pad and/or a size of the medical device  100 , including a size of the base ring  102 . 
     The medical device  100  includes a cover  130  that is configured to enclose the lower leveling plates  104   a - 104   f , the upper leveling plates  106   a - 106   f , the pads  120   a - 120   f  and the base ring  120 . The cover  130  and the base ring  102  may be configured to hold the assembly together. The cover  130  includes a contact surface  132  configured to contact a vertebra. The contact surface  108  of the base ring  102  and the contact surface  132  of the cover  130  may include a plasma layer, for example in the form of a spray, on the surface. 
     The medical device  100  includes a compressible member  134  that is a cylindrical-shaped member that is arranged through a center of the lower leveling plates  104   a - 104   f , the upper leveling plates  106   a - 106   f  and the pads  120   a - 120   f . The compressible member  134  also may be referred to as a cushion. The compressible member  134  may be a shock dampening component that is made of or includes materials that are flexible and soft and that provide a shock dampening effect when forces are applied to the medical device  100 . 
     For example, the compressible member  134  may be a soft polycarbonate-urethane (PCU), rubber, silicone or any other flexible soft material that is biocompatible. The base ring  102  may define an area to receive the compressible member  134  and the compressible member  134  may be constrained within the area defined by the base ring  102 . 
     In one exemplary implementation, the compressible member  134  may be slightly longer than the rest of the assembly. As force is exerted between the vertebras of the spine causing compression between the base ring  102  and the cover  130 , the soft compressible member  134  would try to expand radially. Since the compressible member  134  is contained within a fixed radial area defined by the base ring  102 , the compressible member  134  would become more rigid and thus absorb shock forces well. 
     Referring also to  FIG. 2 , a perspective view of the base ring  102  of  FIG. 1  is illustrated. The base ring  102  may define a spherical or disc shape. The base ring  102  may define an inner wall  240  and an outer wall  242 . The inner wall may define an opening through which the compressible member  134  passes through. A diameter of the opening may constrain the compressible member  134 . 
     The inner wall  240  and the outer wall  242  may define an area, including an inner surface  244 , that is configured to receive the lower leveling plates  104   a - 104   f  and the upper leveling plates  106   a - 106   f  on top of the lower leveling plates  104   a - 104   f . The inner surface  244  may engage the non-flat bottom surface  110  of the lower leveling plates  104   a - 104   f . The inner surface  244  may include multiple bores  246  that are configured to receive the members  112   a - 112   f  that hold the lower leveling plates  104   a - 104   f  in position within the base ring  102 . 
     The inner wall  240  may include multiple bores  248  and the outer wall  242  may include multiple corresponding bores  250  through which the members  118   a - 118   f  may extend through to hold the upper leveling plates  106   a - 106   f  in position within the base ring  102 . 
     The top of the outer wall  242  may include multiple areas  124   a - 124   f  or cut outs of the top wall  242  that are configured to receive the pads  120   a - 120   f . The areas  124   a - 124   f  may be sized to receive the pads  120   a - 120   f  such that the sides of the pads  120   a - 120   f  abut to form a continuous top surface across all of the pads  120   a - 120   f.    
     Referring also to  FIGS. 3 and 4 , a perspective view illustrates a bottom surface  110  of a lower leveling plate  104   a  ( FIG. 3 ) and a perspective view illustrates a top surface  114  of a lower leveling plate  104   a  ( FIG. 4 ). The lower leveling plate includes a bore  360  there through. The bore  360  may extend through the center of the lower leveling plate  104   a  from the top surface  114  to the bottom surface  110 . The bore  360  is sized to receive the member  112   a  to hold the lower leveling plate  104   a  in position within the base ring  102 . The lower leveling plate  104   a  is symmetrical about its center, where the bore  360  may define the center of the plate. 
     As described above the bottom surface  110  of the lower leveling plate  104   a  is a non-flat or non-planar surface. The bottom surface  110  may engage the inner surface  244  of the base ring  102  and rock on the inner surface  244  based on the forces applied to the top surface  114  of the lower leveling plate  104   a . The bottom surface  110  may include a first generally flat area  362  that contours to a sloped area  364  and then contours to a second flat area  366 . The sloped area  364  may form a hump on the otherwise generally flat bottom surface  110 . The hump allows the lower leveling plate  104   a  to rock when forced by one or more of the upper leveling plates  106   a - 106   f.    
     The top surface  114  of the lower leveling plate  104   a  is generally flat across the top. The top surface  114  may be round at the edges and the generally flat area may round slightly downward. The top surface  114  may engage a bottom surface  116  of one or more of the upper leveling plates  106   a - 106   f.    
     Referring also to  FIGS. 5 and 6 , a perspective view illustrates a top surface  128  of an upper leveling plate  106   a  ( FIG. 5 ) and a perspective view illustrates a bottom surface  116  of an upper leveling plate  106   a  ( FIG. 6 ). The upper leveling plate  106   a  includes a horizontal bore  560  through its center. The bore  560  is configured to receive a member  118   a  that holds the upper leveling plate  106   a  in position within the base ring  102 . When the upper leveling plate  106   a  is positioned in the base ring  102 , the bore  560  is lined up with the corresponding bores  248  and  250  on the base ring  102  and the member  118   a  is received through the bores  248 ,  250  and  560  to hold the upper leveling plate  106   a  in position. The upper leveling plate  106   a  may pivot about its center on the member  118   a  as forces are applied from one or more pads  120   a - 120   f  and, in turn, may apply forces to one or more lower leveling plates  104   a - 104   f.    
     The bottom surface  116  is configured to engage a top surface  114  of one or more lower leveling plates  104   a - 104   f . The bottom surface  116  is generally flat or planar with rounded edges. The top surface  128  is generally flat and is configured to engage a bottom surface of one or more of the pads  120   a - 120   f . As can be seen from  FIGS. 3-6 , the lower leveling plate  104   a  and the upper leveling plate  106   a , are shaped and contoured to fit circumferentially around the base ring  102 . 
     Referring also to  FIGS. 7 and 8 , a perspective view illustrates a top surface  122  of a pad  120   a  ( FIG. 7 ) and a perspective view illustrates a bottom surface of the pad  120   a  ( FIG. 8 ). The pad  120   a  is shaped and contoured to fit circumferentially around the base ring  102 . As discussed above, the pad  120   a  is configured to engage the base ring in an area  124   a  defined by a cut-out of the outer wall  242 . 
     The top surface  122  of the pad  120   a  is generally flat or planar. The pad  120   a  is contoured and shaped to abut the other pads such that the top surface  122  of all of the pads may form a flat or planar surface that maintains a parallel plane using the action of the lower leveling plates  104   a - 104   f  and the upper leveling plates  106   a - 106   f.    
     The bottom surface of the pad  120   a  includes a platform area  124  and a raised spherical member  126  in the center of the platform area  124 . The platform area  124  covers at least a portion of the entire area of the pad  120   a  and does not cover the entire area under the top surface  122 . While the spherical member  126  is illustrated in this shape in this implementation, other raised shapes may be used in other exemplary implementations. 
     The spherical member  126  engages a top surface  128  of an upper leveling plate  106   a  and may exert forces on the top surface  128 . The upper leveling plate  106   a , in cooperation with the other upper leveling plates and the lower leveling plates  104   a - 104   f  act to maintain the pad  120   a  and the other pads together in a parallel plane. 
     Referring also to  FIGS. 9 and 10 , a perspective view illustrates a bottom surface of the cover  130  ( FIG. 9 ) and a perspective view illustrates a top surface  132  of the cover  130  ( FIG. 10 ). The cover  130  may be disc-shaped or spherical-shaped and may be configured to enclose other components of the medical device  100 . The cover  130  works in cooperation with the base ring  102  hold the assembly together. 
     As discussed above, the top surface  132  may function as a contact surface of a vertebrae within a body of a patient. A bottom surface  972  of the cover  130  provides a contact surface for a top of the compressible member  134  to contact. The cover  130  defines a circumferential wall  974  having a lip  976  at the top of the wall  974 . The lip  976  may bend or curve slightly inward towards the center of the cover  130  such that when assembled together with the other components of the medical device  100 , the lip  976  may hold or at least assist in holding the assembled device together. 
     Referring also to  FIGS. 11-13 , different views of the assembled medical device  100  are illustrated in cross-section.  FIG. 11  illustrates a top view of the medical device  100 .  FIG. 12  illustrates a cross-section view along the line A-A of the view in  FIG. 11 .  FIG. 13  illustrates a cross-section view along the line B-B of the view in  FIG. 11 . 
       FIGS. 12 and 13  illustrate the assembled medical device  100 . The cross-sections of the medical device  100  illustrate the base ring  102 , a lower leveling plate  104   a , an upper leveling plate  106   a , a pad  120   a  with a raised spherical member  126  providing force on the upper leveling plate  106   a , a cover  130  and a compressible member  134 .  FIG. 12  illustrates the member  118   a  extending through the upper leveling plate  106   a  to maintain the position of the upper leveling plate  106   a  within the base ring  102 .  FIG. 13  illustrates the member  112   a  extending through the lower leveling plate  104   a  to maintain the position of the lower leveling plate within the base ring  102 . 
     The lip  976  of the cover  130  extends beyond and overlaps with the base ring  102  to hold the assembly together. The cover  130  and the base ring  102  provide contacting surfaces to the vertebrae within the body of the patient. 
       FIG. 14  is a flow chart illustrating an exemplary process  1400  including the use of the medical device  100 . Process  1400  includes inserting a prosthetic disc into a portion of an anatomical structure within a body of a patient ( 1410 ). The prosthetic disc may, for example, be the medical device  100  of  FIG. 1 . 
     The prosthetic disc may include a base ring (e.g., the base ring  102 ), multiple layers of multiple leveling plates configured to equalize forces applied to the contact surface of the base ring (e.g., lower leveling plates  104   a - 104   f  and upper leveling plates  106   a - 106   f ) and a layer of multiple pads with each of the pads having a top surface and a bottom surface (e.g., pads  120   a - 120   f ). The top surface of the pads may be configured to maintain a parallel plane and the bottom surface of each of the multiple pads may be configured to engage a top surface of one of the layers of the leveling plates. The prosthetic device may include a cover configured to enclose the multiple layers of the leveling plates, the layer of the multiple pads and the base ring (e.g., cover  130  of  FIG. 1 ). 
     Process  1400  includes contacting an outer surface of the base ring to a vertebra ( 1420 ) and contacting an outer surface of the cover to a vertebra ( 1430 ). For example, the contact surface  108  of the base ring  102  may contact a vertebra ( 1420 ) and the top surface  132  of the cover  130  may contact a vertebra ( 1430 ). 
     The various components of the medical device  100  described herein can be formed with any biocompatible material used for such a medical device. For example, each of the various components can be formed with one or more biocompatible plastics and/or one or more biocompatible metals such as, for example, titanium and stainless steel. 
     While certain features of the described implementations have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the scope of the embodiments. It should be understood that they have been presented by way of example only, not limitation, and various changes in form and details may be made. Any portion of the apparatus and/or methods described herein may be combined in any combination, except mutually exclusive combinations. The embodiments described herein can include various combinations and/or sub-combinations of the functions, components and/or features of the different embodiments described.