Abstract:
In a vertebral body replacement implant having a bottom locating part for positioning against a lower vertebral body and having a top locating part for positioning against an upper vertebral body, wherein both locating parts are telescopically displaceable relative to one another in the manner of a piston-cylinder unit, having a sealed hydraulic chamber formed by the locating parts, having a charging opening leading into the hydraulic chamber for a hydraulic medium, which upon entering the hydraulic chamber pushes the two locating parts apart from one another, and having a locking device, which may be activated by means of an instrument and upon activation fixes the two locating parts non-displaceably relative to one another, in order to facilitate the handling of the vertebral body replacement implant it is proposed that the locking device is disposed on the vertebral body replacement implant in the region of the charging opening. An instrument for handling the vertebral body replacement implant is also proposed.

Description:
[0001]    The present disclosure relates to the subject matter disclosed in German patent application 10 2008 006 491.2 of Jan. 29, 2008, which is incorporated herein by reference in its entirety and for all purposes. 
       BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a vertebral body replacement implant having a bottom locating part for positioning against a lower vertebral body and having a top locating part for positioning against an upper vertebral body, wherein both locating parts are telescopically displaceable relative to one another in the manner of a piston-cylinder unit, having a sealed hydraulic chamber formed by the two locating parts, having a charging opening leading into the hydraulic chamber for a hydraulic medium, which upon entering the hydraulic chamber pushes the two locating parts apart from one another, and having a locking device, which may be activated by means of an instrument and upon activation fixes the two locating parts non-displaceably relative to one another. 
         [0003]    Such a vertebral body replacement implant is described for example in US 2005/0060036 A1. This mode of construction makes it possible to adjust the spacing of the two locating parts in accordance with the spacing of the vertebral bodies that come into abutment on either side of the vertebral body replacement implant and then to fix the two locating parts relative to one another in the spacing adjusted by the hydraulic medium. After the fixing the hydraulic medium may be removed, the spacing of the two locating parts then being maintained exclusively by means of the locking device. 
         [0004]    In the known vertebral body replacement implant, the charging opening for the hydraulic medium is disposed in the lower part of the one locating part, the fixing device in the upper part, so that in order to introduce the hydraulic medium, on the one hand, and actuate the locking device, on the other hand, a relatively large access is required because the appropriate instruments have to brought alongside one another towards the vertebral body replacement implant. 
         [0005]    The object of the invention is to design a vertebral body replacement implant of the above general type in such a way that the handling, i.e. the filling with the hydraulic medium and the locking of the locking device, is possible through as small a body access as possible. 
       SUMMARY OF THE INVENTION 
       [0006]    In a vertebral body replacement implant of the initially described type, this object is achieved according to the invention in that the locking device is disposed on the vertebral body replacement implant in the region of the charging opening. By virtue of the spatial juxtaposition of the charging opening, on the one hand, and the locking device, on the other hand, the appropriate instruments that are needed to introduce hydraulic medium and actuate the locking device may also act substantially in the same region of the vertebral body replacement implant, thereby allowing these instruments to be brought towards the vertebral body replacement implant through a much smaller body access. 
         [0007]    It is particularly advantageous if the charging opening and. the locking device are disposed coaxially with one another. In particular, the locking device may surround the charging opening. 
         [0008]    In a preferred embodiment it is provided that the charging opening is disposed in a charging connection piece and that the locking device surrounds the charging connection piece. 
         [0009]    It is particularly advantageous if the locking device comprises a screw that is screwable into a thread of the one locating part and in the process presses directly or by means of an intermediate element against the other locating part and thereby fixes the other locating part relative to the one locating part. 
         [0010]    In particular, the screw may have a central through-channel that surrounds the charging connection piece. In this way, a particularly space-saving arrangement is obtained. 
         [0011]    The intermediate element may be a ring that surrounds the charging opening. 
         [0012]    A further underlying object of the invention is to provide an instrument for handling the vertebral body replacement implant of the previously described type that allows handling of the implant through as small a body access as possible. 
         [0013]    This object is achieved according to the invention by an instrument for handling the vertebral body replacement implant having the features of one of claims  1  to  7 , having an elongate shank, on the distal end of which holding elements for the vertebral body replacement implant are disposed, wherein the instrument is characterized in that disposed in the shank are a hydraulic tube, which may be positioned sealingly against the charging opening of the vertebral body replacement implant, and an actuating element, which passes through the shank and which upon positioning of the shank against the vertebral body replacement implant moves into working connection with the locking device. 
         [0014]    In this way, a single instrument, in which all of the active elements are surrounded by an elongate shank, may be used to handle the vertebral body replacement implant as well as both to fill the vertebral body replacement implant with the hydraulic medium and to actuate the locking device. 
         [0015]    The hydraulic tube and a charging connection piece of the vertebral body replacement implant that accommodates the charging opening may in particular be configured to be plugged in a sealed manner one into the other. 
         [0016]    In this case, it is advantageous if the hydraulic tube and the charging connection piece in the region of their plug-in connection are of a rotationally symmetrical design so that they can be twisted relative to one another about a common longitudinal axis while maintaining the sealing effect. 
         [0017]    In a particularly preferred embodiment, it is provided that the hydraulic tube additionally performs the function of the actuating element for the locking device, so that the hydraulic tube and the actuating element are one and the same component. This is advantageous particularly if the hydraulic tube is plugged together with the charging connection piece in a rotatable manner, thereby allowing the rotational movement of the hydraulic tube to be used to actuate the locking device. 
         [0018]    In this case, it may be provided that the hydraulic tube and the locking device upon positioning of the shank against the vertebral body replacement implant form a positive rotational connection, so that a rotation of the hydraulic tube about its longitudinal axis leads to a twisting of the locking device about the same axis of rotation. 
         [0019]    According to a further advantageous development, it may be provided that there is disposed in the shank a clamping apparatus, which when actuated clamps the shank in a position against the vertebral body replacement implant, in which the hydraulic tube is positioned in a sealing manner against the charging opening. In this case, it is advantageous if the clamping apparatus comprises a pull member, which is disposed between hydraulic tube and shank and on the distal end of which at least one gripping projection is disposed, which engages behind a clamping projection on the locating part accommodating the charging opening and upon displacement of the pull member in proximal direction clamps the locating part against the shank. 
         [0020]    In a preferred embodiment it is provided that gripping projections are disposed at diametrically opposite sides of the pull member, that the gripping projections are held on arms that are flexibly bendable radially apart from one another and that the radially outwardly bendable arms are movable by displacement of the shank relative to the pull member between a deployment position, in which the arms project from the shank and are therefore bendable radially apart from one another, and a clamping position, in which the shank overlaps the arms and prevents the arms from bending radially apart from one another. It is therefore easily possible to bring the gripping projections into abutment behind the clamping projections, it being sufficient for this purpose to shift the pull member into the deployment position, in which the gripping projections may be bent radially apart from one another to such an extent that the clamping projections slide through between them. By retracting the pull member, the arms that are flexibly bendable apart from one another are pushed into the shank, which then prevents the arms from bending apart from one another, so that the gripping projections have to remain in their position of engagement behind the clamping projections. 
         [0021]    The gripping projection or gripping projections may preferably have a convexly curved locating face, and it is also advantageous if the clamping projections have a concavely curved locating face. 
         [0022]    It is particularly advantageous if the pull member takes the form of a sleeve that surrounds the hydraulic tube and fills the gap between the hydraulic tube, on the one hand, and the shank, on the other hand. 
         [0023]    The shank on its distal end may carry extensions, which project in distal direction and which upon abutment of the shank with the vertebral body replacement implant engage into corresponding receiving indentations of the vertebral body replacement implant. These projections therefore position the vertebral body replacement implant relative to the shank, so that the clamping apparatus just clamps the shank and the vertebral body replacement implant against one another, while the relative alignment of the shank to the vertebral body replacement implant is guaranteed substantially by means of the extensions that engage into the receiving indentations. 
         [0024]    On the proximal end of the shank a handle may be disposed, which is preferably designed to be detachable from the shank. 
         [0025]    It is advantageous if the hydraulic tube at its proximal end projects from the shank and carries gripping faces there for twisting the hydraulic tube about its longitudinal axis. 
         [0026]    It may further be provided that the pull member on its proximal end carries an actuating device, upon the actuation of which the pull member in the shank is displaceable relative thereto in longitudinal direction. 
         [0027]    This actuating device may for example comprise a turning element, which may be screwed onto the pull member and which is supported against the shank. By twisting the turning element, the turning element is screwed to a greater or lesser extent onto the pull member and therefore displaces the pull member relative to the shank. 
         [0028]    The following description of preferred embodiments of the invention is used in connection with the drawings to provide a detailed explanation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0029]      FIG. 1 : is a perspective view of a handling apparatus for a vertebral body replacement implant with a vertebral body replacement implant tightly clamped thereon during positioning of the vertebral body replacement implant in the spinal column; 
           [0030]      FIG. 2 : is an exploded view of the handling instrument of  FIG. 1  with the various individual parts of the handling instrument and a vertebral body replacement implant; 
           [0031]      FIG. 3 : is a perspective view of a vertebral body replacement implant prior to placing on the distal end of a handling instrument; 
           [0032]      FIG. 4 : is a perspective view of the vertebral body replacement implant, onto which has been placed a hydraulic tube that is represented partially cut open; 
           [0033]      FIG. 5 : is a perspective view of the vertebral body replacement implant with hydraulic tube and pull member placed thereon, but without representation of the shank; 
           [0034]      FIG. 6 : is a perspective view of the vertebral body replacement implant with a handling instrument placed thereon; 
           [0035]      FIG. 7 : is a sectional view of the vertebral body replacement implant and the pull member along line  7 - 7  in  FIG. 5 ; 
           [0036]      FIG. 8 : is a sectional view along  8 - 8  in  FIG. 6 ;  FIG. 9 : is a sectional view along line  9 - 9  in  FIG. 6  and 
           [0037]      FIG. 10 : is a sectional view of the proximal part of the handling instrument along line  10 - 10  in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0038]    In the drawings a vertebral body replacement implant is represented, that is referred to hereinafter merely as implant  1 . This implant  1  may be handled with the aid of a handling instrument  2 , which may be detachably connected to the implant  1 . 
         [0039]    First, there now follows a detailed description of the structure of the implant  1  with reference to  FIGS. 3 to 9 . 
         [0040]    The implant comprises a bottom locating part  3  and a top locating part  4 , each of locating parts  3  and  4  carrying an annular support plate  5  and/or  6 , the mutually remote end faces of which form locating faces, by which the implant  1 , which is to replace a vertebral body, may be positioned against adjacent vertebral bodies. This is evident from the illustration of  FIG. 1 , in which however only the vertebral body  7  lying adjacent to the bottom locating part  3  is shown. The support plates  5 ,  6  carry pointed projections  8 , which are oriented in each case in the direction of the adjacent vertebral bodies and which when positioned against the adjacent vertebral bodies penetrate into these and hence secure the locating faces of the support plates  5 ,  6  against a lateral displacement relative to the vertebral bodies. 
         [0041]    The top locating part  4 . has substantially the shape of a circular cylinder that is closed at its top end  9  and open at its bottom end  10 . The bottom locating part  3  likewise has a circular-cylindrical shape and is closed at its bottom end  11  and open at its top end  12 . The bottom end  11  in this case is of a relatively thick construction, the outside diameter at the upper end of the bottom end  11  decreasing in a stepped manner, so that the upper portion  13  of the bottom locating part  3  has an outside diameter that corresponds to the inside diameter of the cylindrical top locating part  4 . The portion  13  engages into the top locating part  4  and is freely displaceable in longitudinal direction relative thereto, so that the bottom locating part  3  and the top locating part  4  are slidable telescopically apart from and towards one another. 
         [0042]    Moulded onto the top locating part  4  adjacent to its bottom end  10  is a radially projecting, internally threaded connection piece  14 , into which an attachment screw  16  having a central through-channel  15  is screwed. Outside of the internally threaded connection piece  14  this attachment screw  16  carries a widened head  17  having a non-circular cross section, the head in the illustrated embodiment carrying radially protruding projections  18  that are arc-shaped in cross section, the overall result therefore being a rosette-shaped cross section ( FIG. 4 ). 
         [0043]    Inserted in the interior of the cylindrical portion  13  of the bottom locating part  3  is a tubular piece  19 , which is closed at the bottom and open in an upward direction and which at its bottom end has a lateral opening  20 , which is aligned with the internally threaded connection piece  14  and into which is screwed a charging connection piece  21 , which passes through the channel  15  of the attachment screw  16 . The charging connection piece  21  lies against the inner wall of the channel  15 , and a flow channel  22  that passes through the charging connection piece  21  is in communication with the interior  23  of the tubular piece  19 . 
         [0044]    The charging connection piece  21  passes through the side wall of the portion  13  of the bottom locating part  3  in an elongate hole  24  that extends over a large part of the height of the portion  13 . This elongate hole  24  is surrounded by a indentation  25  in the outer wall of the portion  13 , the base  26  of which is substantially perpendicular to the longitudinal axis of the charging connection piece  21 . Engaging into this indentation  25  is a clamping ring  27 , which is mounted so as to surround the charging connection piece  21  and be longitudinally displaceable thereon and against which the attachment screw  16  is supported. When the attachment screw  16  is screwed into the internally threaded connection piece  14 , the clamping ring  27  is pressed towards the base  26  of the indentation  25  and therefore fixes the portion  13  relative to the charging connection piece  21  and hence relative to the top locating part  4  in the relative position occupied in each case. 
         [0045]    The tubular piece  19  is surrounded above the top end  12  of the portion  13  by an annular seal  28  that seals off the interior of the top locating part  4  from the tubular piece  19 . This interior is in communication with the interior of the tubular piece  19  and with the flow channel  22  of the charging connection piece  21 . When a hydraulic medium, for example a physiological saline, is introduced through the flow channel  22  into this interior and when it is introduced under pressure, the result is that the interior increases in size, i.e. the top locating part  4  and the bottom locating part  3  are pushed telescopically apart from one another, i.e. the spacing between the two support plates  5  and  6  is increased. The top locating part  4  therefore forms the cylinder and the bottom locating part  3  the piston of a structure corresponding to that of a hydraulically actuable piston-cylinder unit. 
         [0046]    The adjustment of the mutual spacing of the two support plates  5  and  6  is therefore effected by filling the interior to a greater or lesser extent with a hydraulic medium, the fixing of the spacing once achieved then being effected by tightening the attachment screw  16  and hence pressing the clamping ring  27  towards the base  26  of the indentation  25 . Once a fixing has been effected in this manner, the interior may be emptied, i.e. the hydraulic medium may be removed, the spacing of the two support plates  5  and  6  then being maintained. 
         [0047]    Given the described design of the implant  1 , it is important that the attachment screw  16  is disposed coaxially with the charging connection piece  21  so that the filling of the interior with the hydraulic medium and the actuation of the attachment screw  16  may be effected along a common axis. In order to be able to carry out these actions, the handling instruments  2  is of an appropriate design. 
         [0048]    The handling instrument  2  comprises an elongate, tubular shank  30  that is connected at its proximal end detachably to a handle  31  that projects radially from the shank  30 . For this purpose, the handle  31  by means of an annular holding eyelet  32  disposed on its upper end surrounds the shank  30 , a fastening screw  33  being screwed in radial direction into this holding eyelet  32  and fastening the holding eye  32  to the shank  30  in the screwed-in state. Immediately adjacent to the holding eyelet  32  a holding journal  34  is moulded thereon, this holding journal  34  projecting into the handle  31 , which is connected detachably to the holding journal  34  by means of a holding rod  35 , which fully passes through the handle  31  and may be screwed into the holding journal  34 . 
         [0049]    Mounted in a longitudinally displaceable manner in the interior of the holding journal  34  is a retaining pin  37 , which projects through a hole  36  in the shank  30  and engages into a circumferential groove  38  of a charging tube  39 , which is disposed in the interior of the shank  30  and fully passes through the shank  30 . Supported against the retaining pin  37  is a helical spring  40 , the other end of which rests against a step  41  in the interior of the holding journal  34 , this helical spring  40  pressing the retaining pin  37  into the circumferential groove  38 . Thus, the charging tube  39  is mounted in the shank  30  so as to be non-displaceable in longitudinal direction and at the same time freely twistable about the longitudinal axis. 
         [0050]    The holding journal  34  is surrounded by a gripping sleeve  42 , which is mounted in a longitudinally displaceable manner on the holding journal  34  and which is connected by a transverse pin  43  to the retaining pin  37 , so that the gripping sleeve  42  and the retaining pin  37  move jointly along the holding journal  34 . By means of the gripping sleeve  42  the retaining pin  37  may be displaced counter to the action of the helical spring  40 , with the result that the retaining pin  37  moves out of the circumferential groove  38  and enables a free longitudinal displacement of the charging tube  39  in the shank  30 . 
         [0051]    The charging tube  39  projects from the shank  30  at the proximal end thereof and carries a turning handle  44  there, with the aid of which the charging tube  339  may be twisted about its longitudinal axis. The interior of the charging tube  39  at its proximal end may be connected in a manner not evident from the drawing to a source for a hydraulic medium, for example to a syringe body, by means of which a physiological saline may be passed through the charging tube  39 . 
         [0052]    The charging tube  39  is directly surrounded by a clamping sleeve  45 , which fills the gap between the charging tube  39  on the one hand and the shank  30  and which in the region between the proximal end of the shank  30  and the turning handle  44  of the charging tube  39  is connected in a rotationally fixed manner to a stopper  46 , which is mounted in a longitudinally displaceable manner on the charging tube  39 . The clamping sleeve  45  is accommodated in the shank  30  so as to be non-rotatable about the longitudinal axis, so that the stopper  46  too is mounted in a non-rotatable but longitudinally displaceable manner on the charging tube  39 . The stopper  46  carries an external thread  47 , onto which is screwed a turning handle  48 , which coaxially surrounds the charging tube  39  and is supported at its distal end against the holding eyelet  32 . When the turning handle  48  is rotated, the turning handle  48  is screwed onto the external thread  47  and therefore draws the clamping sleeve  45  in proximal direction into the shank  30 . 
         [0053]    On the distal end the shank  30  carries two diametrically opposite projections  49 ,  50 , which protrude in distal direction and fit into two mutually opposite, lateral indentations  51 ,  52  in the outer wall of the top locating part  4 , these indentations  51  and  52  being situated at the level of the charging connection piece  21  and the attachment screw  16  surrounding this charging connection piece  21 . When the projections  49  and  50  are introduced into the indentations  51  and  52 , the projections  49  and  50  are applied laterally against the base of the indentations  51  and  52  and moreover against the lateral edges of the indentations  51  and  52 , thereby achieving a defined orientation of the implant  1  relative to the shank  30  when the shank  30  is pressed in distal direction towards the implant  1 . 
         [0054]    The distal end  53  of the charging tube  39  has a recess  54 , which is open towards the distal end and the cross section of which corresponds to the cross section of the head  17  of the attachment screw  16 , i.e. in the illustrated embodiment has the shape of a rosette. This recess  54  passes over via a step  55  into a proximally adjoining central sealing aperture  56 , the inside diameter of which corresponds to the outside diameter of the charging connection piece  21 . In the side wall of the sealing aperture  56  there is disposed in a circumferential groove  57  an annular seal  58 , which is applied sealingly against the outside of the charging connection piece  21  when the charging tube  39  is advanced in distal direction towards the implant  1  and at the same time the charging connection piece  21  enters the sealing aperture  56 . 
         [0055]    In this way, a sealed connection is established between the flow channel  22  of the charging connection piece  21 , on the one hand, and the interior of the charging tube  39 , on the other hand. 
         [0056]    The clamping sleeve  45  on two mutually opposite sides of its distal end carries two arms  59 ,  60 , which project in distal direction and each carry on their distal end a radially inwardly projecting gripping projection  61  and  62  respectively. These gripping projections  61  and  62  and the associated arms  59  and  60  are disposed directly alongside the distal projections  49  and  50  of the shank  30  and engage into lateral recesses  63 ,  64  on the top locating part  4  that adjoin the indentations  51  and  52  in proximal direction. The proximal ends of the recesses  63  and  64  form radially outwardly protruding clamping projections  65  and  66 . 
         [0057]    The gripping projections  61  and  62  are designed to be convexly curved in cross section, and in a corresponding manner the recesses  63  and  64  are designed to be concavely curved in cross section, so that the gripping projections  61  and  62  may engage into the recesses  63  and  64  in such a way that the recesses  63  and  64  are substantially filled by the gripping projections  61  and  62 . 
         [0058]    The arms  59  and  60  having the gripping projections  61  and  62  disposed on the distal end may be flexibly bent in a radial outward direction, thereby allowing the mutual spacing of the gripping projections  61  and  62  to be increased in such a way that the gripping projections  61  and  62  may slide past the clamping projections  65  and  66 , in the manner shown in  FIG. 7 . 
         [0059]    However, such a flexible bending-apart of the arms  59  and  60  is possible only if the shank  30  is retracted relative to the clamping sleeve to such an extent that the arms  59  and  60  are released by the shank  30 . If, on the other hand, the shank  30  is advanced in distal direction relative to the clamping sleeve  45 , the shank  30  overlaps the arms  59  and  60  and prevents them from bending flexibly apart, with the result that the spacing of the gripping projections  61  and  62  cannot be increased and the gripping projections  61  and  62  in this position are unable to slide past the clamping projections  65 ,  66 , rather they position themselves laterally against the clamping projections  65  and  66  when the clamping sleeve  45  is drawn still further into the shank  30 . This may be achieved by twisting the turning handle  48 . During this proximal movement of the clamping sleeve  45 , the gripping projections  61  and  62  position themselves against the clamping projections  65  and  66  and draw these and hence the entire implant in proximal direction, i.e. towards the shank  30 . In this case, the projections  49  and  50  are supported against the side walls of the indentations  51  and  52 . What therefore occurs is a clamping of the implant  1  to the shank  30 , i.e. to the entire handling instrument  2 . In the clamped state, the charging tube  39  engages in the region of the recess  54  over the head  17  of the attachment screw  16 , simultaneously forming a rotational positive connection, the sealing aperture  56  moreover engaging over the charging connection piece  21 , wherein a sealing effect is achieved in this region by means of the annular seal  58 . 
         [0060]    In this state, a hydraulic medium may be introduced via the charging tube  39  through a flow channel  22  into the interior  23  of the implant  1 , the charging tube  39  therefore acting as a hydraulic pipe, so that the two locating parts  3  and  4  are pushed apart from one another. Once the desired spacing has been achieved in this way, simply by twisting the charging tube about the longitudinal axis the attachment screw  16  may be screwed in the internally threaded connection piece  14  and therefore press the clamping ring  27  towards the base  26  of the indentation  25 , i.e. the two locating parts  3  and  4  are therefore fixed relative to one another in terms of their mutual spacing. 
         [0061]    As soon as this has occurred, the interior  23  may be emptied. By means of the turning handle  48  the clamping sleeve  45  is then displaced relative to the shank once more in distal direction, so that finally a flexible outward swivelling of the arms  59  and  60  and the gripping projections  61  and  62  is possible, thereby allowing the handling instrument  2  to be removed from the implant  1 . The two locating parts  3  and  4  of the handling instrument  2  then remain permanently with the adjusted spacing relative to one another. 
         [0062]    As the handling instrument  2  accommodates all of the instrument parts needed to handle the implant  1  in the cross section of the shank  30 , the access to the implant  1  for handling is possible through a very small body opening, and through this small opening it is possible to carry out both the connection to the implant and the filling of the implant  1  and hence both the adjustment of the spacing and the fixing of the two locating parts  3  and  4  relative to one another, and moreover subsequently the detachment of the handling instrument  2  from the implant  1 .