Abstract:
An intervertebral implant includes a first surface configured to engage a first vertebral body, a second surface configured to engage a second vertebral body, a side wall connecting the first surface and the second surface to define a hollow space of the implant, and a rotatable insert configured to be positioned in the space, wherein an elongate opening extends through the side wall into the space, and wherein the insert comprises a spring portion configured to hold the insert in the space by frictional engagement with the side wall and an engagement portion configured to engage with a tool through the opening when the insert is positioned in the space.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 61/496,801, filed Jun. 14, 2011, the contents of which are hereby incorporated by reference in their entirety, and claims priority from European Patent Application EP 11 169 884.1, filed Jun. 14, 2011, the contents of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     Field of the Invention 
     The invention relates to an intervertebral implant that has a top surface configured to engage a first vertebral body, a bottom surface configured to engage a second vertebral body, and a side wall connecting the top surface and the bottom surface, a hollow space defined by the side wall and an elongate opening extending through the side wall into the space. The implant further includes a rotatable insert that is held within the space by a spring force. The insert has an engagement portion configured to engage with a tool through the opening. 
     Description of Related Art 
     An intervertebral implant configured to engage with an insertion device for inserting between first and second vertebral members is known from U.S. Pat. No. 7,935,148. The intervertebral implant has an opening including an elongated shape that extends through the side wall. A connection member including a receptacle is contained within the side wall. The insertion device has a first end configured to connect with the connection member of the implant body. The first end is selectively positionable between orientations to provide for the connection. 
     Another intervertebral implant is known from US 2010/0094422 A1. The implant has a support body and a rotatable insert therein. An installation instrument is also disclosed for removable attachment to the implant and engagement with the rotatable insert to selectively permit rotation between the insert and the support body. 
     SUMMARY 
     It is an object of the invention to provide an intervertebral implant that is simplified in terms of design and use, in view of the possibilities that are available for final positioning of the implant between vertebral bodies. 
     The intervertebral implant according to embodiments of the invention has a compact design. An insertion procedure of the implant is simple and safe, since a connection between the implant and an insertion tool can be easily fixed/tightened and loosened. When the connection between the tool and the implant is loosened, the implant can be moved into a desired position by rotating it relative to the tool. To this effect, the implant may include an insert that remains fixed relative to the tool, and the other portions of the implant may rotate relative to the insert. During rotation, the intervertebral implant is safely held by the insertion device and is prevented from inadvertent disconnecting from the tool. 
     The design of the intervertebral implant allows for a large portion of the hollow interior space of the implant to be available for fusion. 
     In some embodiments, existing intervertebral implants could be modified and upgraded with the insert. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention will become apparent from the description of the accompanying drawings. In the drawings: 
         FIG. 1  shows a perspective view of an embodiment of an intervertebral implant and a tool for inserting the intervertebral implant; 
         FIG. 2  shows an enlarged view of a portion of  FIG. 1 ; 
         FIG. 3  shows an exploded perspective view of the enlarged portion in  FIG. 2 ; 
         FIG. 4  shows a perspective view of an insert provided for an intervertebral implant according to an embodiment of the invention; 
         FIG. 5  shows another perspective view of the insert of  FIG. 4 ; 
         FIG. 6  shows a perspective view of the intervertebral implant of  FIG. 1  before inserting the insert; 
         FIG. 7  shows a perspective view of the intervertebral implant of  FIG. 6  with the insert mounted; 
         FIG. 8 a    shows a cross-sectional view of the intervertebral implant with the insert in a first position limited by a first stop; 
         FIG. 8 b    shows a cross-sectional view of the intervertebral implant with the insert in a second position limited by a second stop; 
         FIGS. 9 a  to 9 d    show schematic cross-sectional views of steps of engaging a tool with the intervertebral implant and rotating the implant according to an embodiment of the invention; 
         FIGS. 10 a  to 10 f    schematically show steps of inserting and positioning the intervertebral implant between two vertebral bodies according to an embodiment of the invention; 
         FIG. 11  shows a perspective top view of an insert according to a second embodiment of the intervertebral implant; 
         FIG. 12  shows a top view of the intervertebral implant according to the second embodiment with a tool connected to the intervertebral implant in a first position; 
         FIG. 13  shows a top view of the intervertebral implant according to the second embodiment with the tool connected thereto in a second position; 
         FIG. 14  shows a perspective top view of an intervertebral implant according to a third embodiment, where an insert is not yet mounted; 
         FIG. 15  shows a top view of the intervertebral implant of  FIG. 14  according to the third embodiment, with an insert mounted and a tool connected to the intervertebral implant in a first position; 
         FIG. 16  shows the intervertebral implant with the tool according to the third embodiment in a second position; 
         FIG. 17  shows a perspective top view of an insert of an intervertebral implant according to a fourth embodiment; 
         FIG. 18  shows a perspective bottom view of the insert of the intervertebral implant according to the fourth embodiment; 
         FIG. 19  shows a top view of the intervertebral implant with insert according to the fourth embodiment and a tool connected thereto in a first position; 
         FIG. 20  shows a top view of the intervertebral implant with the tool according to the fourth embodiment in a second position; 
         FIG. 21  shows a perspective view from a top of an intervertebral implant with insert according to a fifth embodiment, and the tool connected thereto in a first position; 
         FIG. 22  shows a perspective view of an insert corresponding to the intervertebral implant according to the fifth embodiment; 
         FIG. 23  shows another perspective view of the insert corresponding to the intervertebral implant according to the fifth embodiment; 
         FIG. 24  shows a perspective view of the intervertebral implant without the insert according to the fifth embodiment; and 
         FIG. 25  shows another perspective view of the intervertebral implant without the insert according to the fifth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a perspective view of a first embodiment of an intervertebral implant  1  and a tool  50  for inserting the intervertebral implant  1 . As shown in particular in  FIGS. 1 to 3 , the intervertebral implant  1  includes a top face  2 , a bottom face  3 , and a side wall  4  connecting the top face  2  and the bottom face  3 . The side wall  4  defines an interior hollow section  5 . The top face  2  and the bottom face  3  have openings so that the hollow interior section  5  extends into the top face  2  and the bottom face  3 . Hence, the top face  2  and the bottom face  3  are formed by upper and lower rims of the side wall  4 , respectively. Furthermore, a center wall  6  may be provided that separates the hollow interior section  5  in two parts. The height of the side wall  4  is such that the implant can be inserted between a first and a second vertebral body. The height of the implant  1  may be largest around the center wall  6  and may decrease towards outer ends of the implant  1 . Teeth  7  or other engagement portions project from the top face  2  and the bottom face  3  for engaging end plates of the vertebral bodies. 
     The implant  1  has two opposite long sides  4   a  and two opposite short sides  4   b  connecting the long sides  4   a . The short sides  4   b  are rounded. The contour of the side wall  4  may be arcuate, for example, it may have a kidney-shape or a banana-shape. 
     As can be seen in particular in  FIGS. 2 and 3 , an opening  8  is provided in the side wall  4  that extends completely through the side wall  4  into the interior hollow section  5 . The opening  8  has an elongate shape and extends preferably over a length in a circumferential direction along a short side  4   b . The opening  8  may have a substantially rectangular contour and may be located substantially in a center of the side wall  4  along a vertical direction between the top face  2  and the bottom face  3 . 
     As shown in  FIG. 6 , a guide groove  9  is provided at the inner wall of the side wall  4  around the elongate opening  8 . The guide groove  9  extends from both ends of the elongate opening into each of the long sides  4   a  of the side wall. The height of the guide groove  9  in a vertical direction (i.e., in a direction from the bottom face  3  to the top face  2 ) is the same or greater than the height of the elongate opening  8  in the vertical direction. The length of the guide groove  9  in a circumferential direction is dimensioned such that an insert  10 , shown in  FIGS. 1 to 7 , can be accommodated and guided in the groove. When the insert  10  is inserted into the hollow interior section  5  and placed into the groove  9 , the groove  9  prevents the insert  10  from falling out. 
     The insert  10  of the implant  1  according to the first embodiment is a substantially hollow cylindrical member. A cylinder axis C defines an axis of rotation. A slot  11  extends parallel to the cylinder axis C through the wall of the hollow cylinder to provide first and second flexible substantially semi-spherical arms  10   a ,  10   b  that can be compressed slightly towards each other, thereby narrowing the slot  11 . At a position opposite to the slot  11 , the insert  10  includes a solid portion  12 , for example, a cuboid-like portion extending between the flexible arms  10   a ,  10   b . The size of the solid portion  12  is such that it does not restrict the flexibility of the arms  10   a ,  10   b . The solid portion  12  has a recess  13  for engagement with a tool  50 . The recess  13  can be, for example, a threaded bore. 
     The first flexible arm  10   a  has at its outer wall, adjacent to its free end, a first stop in the form of a first protrusion  14   a . The second flexible arm  101 ) has at its outer wall, adjacent to its free end, a second stop in the form of a second protrusion  14   b . As shown in  FIGS. 8 a  and 8 b   , the insert  10  provides, with its cylinder axis C, an axis of rotation for the implant. Hence, when the insert  10  is inserted, it can be rotated relative to the rest of the implant between a first position defined by or limited by an abutment of the first protrusion  14   a  at the inner wall ( FIG. 8 a   ), and a second position defined by or limited by an abutment of the second protrusion  14   b  at the inner wall ( FIG. 8 b   ). The first protrusion  14   a  provides an abutment surface at a position away from the slot  11 , such that when the insert  10  is within the guide groove  9  and the first protrusion  14   a  abuts against the inner wall of the side wall  4  of the implant, recess  13  is located at or opens near an end of the opening  8  opposite to where the first protrusion  14   a  is positioned. The second protrusion  14   b  is at a position at the free end of the second flexible arm  101 ), such that the recess  13  is at the other end of the elongate opening  8  when the protrusion  14   b  abuts against the inner wall of the side wall  4  of the implant  1 . 
     The tool  50  will now be explained with reference to  FIGS. 1 to 9 . The tool  50  includes a handle  51  that is connected to a drive shaft  52  (See, e.g.,  FIG. 9 a   ) with an end portion  53  for engagement with the recess  13  of the insert  10 . In the embodiment shown, the end portion  53  is a threaded end portion that engages a threaded bore of recess  13 . The drive shaft  52  is rotatable within a sleeve  54  that is connected to a counter holding portion  55 . An end portion  56  of the sleeve is concavely curved with a curvature that may be adapted to a curvature of the outer wall of the short side  4   b  of the side wall  4 . The tool  50  is, however, not limited to the specific example shown, and may have various different constructions. 
     The connection between the tool and the implant will now be explained with reference to  FIGS. 9 a  to 9 d   . When the insert  10  is inserted into the implant as shown in  FIG. 9 a   , the recess  13  faces the opening  8 . The recess  13  may then be engaged with the end portion  53  of the drive shaft  52 . In the case of a threaded bore of recess  13  and a threaded end portion  53 , screwing the end portion  53  into the bore results in clamping the short side  4   b  of the implant between the insert  10  and the end portion  56  of the sleeve  54  of the tool  50 . The connection between the implant  1  and the tool  50  may be fixed in this configuration. A slight loosening of the threaded connection may allow for rotation of the insert  10  with tool  50  relative to the rest of the implant  1 . The rotation is limited in both directions by the abutment surfaces of the protrusions  14   a ,  14   b , respectively, at or against the side wall  4 . 
     The implant  1 , including the insert  10 , is made of a biocompatible material. For example, the implant can be made of stainless steel or titanium, or of a biocompatible metal alloy, such as a nickel titanium alloy, for example Nitinol, or can be made of a biocompatible plastic material, for example, PEEK (polyetheretherketone). 
     Use of the implant  1  during surgery will now be described with reference to  FIGS. 10 a  to 10 f   .  FIGS. 10 a  to 10 f    schematically show steps for inserting and positioning the intervertebral implant  1  into a space between two vertebral bodies of adjacent vertebrae  200 . First, the tool  50  is connected to the implant  1 . The insert  10  is in a position such that the recess  13  is positioned at approximately a center of the elongate opening  8  along a lengthwise direction of the opening  8 . By tightening the connection between the insert  10  and the tool  50 , the implant  1  is fixed to the tool  50 . Then, as shown in  FIG. 10 a   , the implant  1  is introduced into the intervertebral space between two neighboring vertebrae, where one of the vertebrae is shown as vertebra  200  in the drawings. The narrow side  4   b  of the implant  1  that is on a side of the implant  1  opposite to the tool  50  acts as a leading side. In the method shown, the intervertebral implant  1  is introduced into the space between the vertebral bodies using a posterior and lateral approach to access the space between the vertebral bodies. 
     When the implant  1  and the tool  50  experience resistance and cannot be pushed or advanced further, as shown in  FIG. 10 b   , the fixation between the implant  1  and the tool  50  is loosened slightly by screwing back the drive shaft  52  (e.g., by rotation). This loosens the clamping between the implant  1  and the tool  50  so that the implant  1  is rotatable about the cylinder axis C of the insert  10 . As shown in  FIGS. 10 c  and 10 d   , the implant  1  rotates around the cylinder axis C of the insert  10  so that the recess  13  of the insert  10  is shifted along the elongate opening  8 . Then, as shown in  FIG. 10 e   , the implant  1  is shifted to its final position. As depicted in  FIG. 10 f   , thereafter, the tool  50  is disconnected by unscrewing the drive shaft  52  from the threaded recess  13  and is removed. 
     Since the tool  50  can be easily connected to and separated from the implant  1 , the handling of the implant  1  is simplified. Meanwhile, during implantation, the implant  1  is safely connected to the tool  50  and cannot escape. 
     Furthermore, the design of the insert  10  is such that most of the hollow interior space remains available for fusion. The insert  10  remains with the implant  1  after implantation, and occupies very little space therein. As shown, for example in  FIGS. 2 and 8   a  to  9   d , when the insert  10  is positioned inside the hollow interior section  5  in position to be removably connected with the tool  50 , there is more hollow space outside an outer surface of the insert  10  facing away from a center of the insert  10  than there is hollow space between the flexible arms  10   a ,  10   b  of the insert  10 . 
       FIGS. 11 to 13  illustrate a second embodiment of the implant. The implant  1 ′ differs from the implant  1  of the first embodiment in the designs of the inserts. The insert  10 ′ of the second embodiment differs from the insert  10  of the first embodiment in the construction of the stops. All other parts of the implant  1 ′ and the insert  10 ′ are the same as in the first embodiment. The description thereof will not be repeated. The insert  10 ′ has, instead of two separate stops provided at the flexible arms  10   a ,  10   b , respectively, only one single protrusion  14  that is formed by a thickened end portion of the first flexible arm  10   a . The thickened end portion  14  extends along the axial length of the insert  10 ′ and is provided adjacent to the slot  11 . By the thickened end portion  14 , an outer diameter at the end of the flexible arm  10   a  is greater than an outer diameter at the flexible arm  10   b . The size of the thickened end portion  14  is such that it can limit the rotation of the implant  10 ′ between two positions, as shown in  FIGS. 12 and 13 . When the insert  10 ′ is in a first position, the recess  13  of the insert  10 ′ is positioned approximately at a center of the elongate opening  8  along a lengthwise direction of the opening  8 . The thickened portion  14  abuts against one of the long sides  4   a  of the side wall  4 . Here, the connection between the tool  50  and the implant  1 ′ is substantially straight as shown in  FIG. 12 . When the insert  10 ′ is rotated relative to the implant  1 ′ by approximately 90′, the thickened end portion  14  abuts against the opposite long side  4   a  of the side wall  4 , and the recess  13  of the insert  10 ′ is positioned at an end of the elongate opening  8  opposite to where the thickened portion  14  is positioned. The connection between the tool  50  and the implant  1 ′ is substantially perpendicular, as shown in  FIG. 13 . 
     A third embodiment of the implant is illustrated in  FIGS. 14 to 16 . The implant  1 ″ differs from the implant  1  according to the first embodiment by the positions of the guide grooves. The guide groove  90  includes two groove parts located opposite to each other at the inner wall of the side wall  4 , in the areas of the long sides  4   a . The groove parts of the guide groove  90  are located at a distance from the elongate opening  8 . When the insert  10  is inserted into the hollow interior section  5 , a portion of each of the flexible arms  10   a ,  10   b  is received in the guide groove  90 , respectively. As can be seen in  FIG. 15 , in some embodiments, the position of the guide groove  90  is such that when the insert  10  is inserted, there is a distance between the recess  13  and the opening  8 . 
       FIG. 15  shows the engagement of the end portion  53  of the drive shaft  52  of the tool  50  with the recess  13  of the insert  10 . Since there is a distance between the insert  10  and the opening  8 , the connection is not fixed and the rest of the implant  1 ″ can be rotated around the insert  10 . By further engagement of the tool  50  and the insert  10 , the insert is drawn against the opening  8  by slightly compressing the flexible arms  10   a ,  10   b , so that the connection between the implant  1 ″ and the tool can be fixed. 
     The implant  1 ″ can also be equipped with the insert  10 ′ according to  FIGS. 11 to 13 . 
     A fourth embodiment of the implant is shown in  FIGS. 17 to 20 . The implant according to the fourth embodiment includes an insert  100  that is different from the inserts  10  and  10 ′ of the previous embodiments in that the insert  100  can be mounted such that the flexible portions  110   a ,  110   b  of the insert  100  are facing towards the elongate opening  8 . The insert  100  is a substantially hollow cylindrical part, similarly as seen in the previous embodiments, and has a slot  111  forming two flexible arms  110   a ,  110   b . Opposite to the slot  111 , a solid portion  112  extends into the space between the flexible arms  110   a ,  110   b . The solid portion  112  has an engagement portion  113  for the tool  50 , which can be a threaded through hole. At an outer side of the insert  100  that faces away from the slot  111 , the insert  100  includes a protrusion  114  that, in some embodiments, extends from the threaded through hole  113  asymmetrically toward a side of the first flexible arm  110   a . The protrusion  114  acts as a stop to limit rotation of the insert  100  relative to the rest of the implant  1 ′″ in two directions. The insert  100  further has a circular recess  115  that is provided at the position of the slot  111  to allow the end portion  53  of the tool  50  to be guided therethrough. 
       FIGS. 19 and 20  show a top view of the implant  1 ′″ with the insert  100  mounted therein. The insert  100  is mounted such that the flexible arms  110   a ,  110   b  are oriented towards the opening  8 . Hence, the threaded through hole  113  is positioned at a distance from the opening  8 . The end portion  53  of the drive shaft  52  of the tool  50  is guided through the elongate opening  8  and engages the threaded through hole  113 . A size of the circular recess  115  is such that the end portion  53  can pass therethrough. When a threaded connection between the end portion  53  and the through hole  113  is tightened, the flexible arms  110   a ,  110   b  are slightly compressed and drawn against the opening  8  and/or the inner wall of the side wall  4 . Thereby, the connection between the implant  1 ′″ and the tool  50  can be fixed. Loosening the connection allows a rotation of the implant  1 ′″ relative to the tool  50 . As shown in  FIG. 19 , the movement of the implant  1 ′″ relative to the tool  50  is limited in a first direction when the protrusion  114  abuts against one of the long sides  4   a  of the side wall  4 . In this position, the threaded through hole  113  points to approximately a center of the elongate opening  8 . When the implant  1 ′″ is rotated with respect to the tool  50 , the other or opposite portion of the protrusion  114  abuts against the other or opposite one of the long sides  4   a  of the side wall  4 , to limit the rotational motion in the second direction. The range of motion is around 90°. 
     A fifth embodiment of the implant is shown in  FIGS. 21 to 25 . Parts and portions that are identical or similar to the previous embodiments are indicated with the same reference numerals, and the descriptions thereof are therefore not repeated. In this embodiment, a protrusion  1413 ′ on insert  1000  is positioned on arm  10   b  at a position away from slot  11  in a circumferential direction. A position of the protrusion  14   b ′ is selected such that when the insert  1000  is rotated relative to the implant into an end position similar to that shown in  FIG. 8 b   , the protrusion  14   b ′ snaps into groove  9 . This may give feedback to a surgeon or other practitioner that such an end position has been reached. 
     Furthermore, side walls of solid portion  12 ′ that face inner walls of flexible arms  10   a ,  10   b  each have a curved recess  12   a  to facilitate insertion of the insert  1000  between inner walls of implant  1 ″″. 
     The implant  1 ″″ may further have elongate openings  80  in sidewall  4  and additional grooves  90   a ,  90   b . In particular, on a long side  4   a , there may be additional elongate openings  80 , for example, to allow ingrowth of bone material and vessels. Meanwhile, the grooves  90   a ,  90   b  at the long sides  4   a  may serve for easier insertion of the insert  1000  into interior hollow section  5 . In such embodiments, once the insert  1000  has been inserted into the interior hollow section  5  at the position of the grooves  90   a ,  90   b , the insert  1000  may then be displaced relative to the rest of the implant  1 ″″ into the groove  9 . 
     Various modifications of the embodiments are also possible. The contour and the shape of the implant may be different from the examples shown. For example, the contour may have any other shape, such as circular, rectangular, oval, etc. A height of the side wall  4  may be constant throughout the implant. The center wall  6  can be omitted. It is also possible to adapt existing intervertebral implants that may not include such an opening, by providing the implants with an elongate opening, a guide groove, and an insert piece as described above. 
     The insert also does not have to include stops. When the tool  50  is connected to the implant, an abutment of the end portion  53  of the tool  50  at the ends of the elongate opening  8  may also provide for limiting the relative movement between the pieces. However, the stops may be useful to limit the motion of the insert once it is inserted into the implant when the tool is not yet connected. The constructions of the various embodiments may also be interchangeable. For example, it is possible to have a design with the two groove portions  90  in any of the embodiments shown. The positions and shapes of the protrusions that act as stops can also vary. In particular, the shapes can be different. The elongate opening  8  can be provided at another position and/or several openings can be provided. 
     In addition, the connection between the insert and the tool need not be a threaded connection. Any other connection that can be easily fixed and loosened, for example, a snap-in connection, may also be utilized. 
     While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is instead intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.