Abstract:
A height-adjustable implant for insertion between vertebrae, includes first and second sleeve parts which are rotationally fixed in coaxial alignment and interconnected in an axially displaceable manner. The first sleeve part has an internal thread. A nut is positioned coaxially in an inner space surrounded by the sleeve parts and is fixed to the second sleeve part so that it can rotate but is axially fixed. The nut has an external thread which engages in the internal thread of the first sleeve part. A toothed ring extends coaxially with the central longitudinal axis of the sleeve parts and is located on the nut. The second sleeve part has a radial access opening in the vicinity of the toothed ring. An operating instrument for activating the implant adjustment includes a handgrip and a shaft extending through the handgrip, a rotary grip carried on one end and another end carrying a toothed wheel for rotational actuation of the nut in the interior space of the implant.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This is a divisional of application Ser. No. 11/451,015, filed Jun. 12, 2006; which was a continuation application, under 35 U.S.C. §120, of International application PCT/EP2004/014060, filed Dec. 10, 2004; the application also claims the priority, under 35 U.S.C. §119, of German patent application No. DE 103 57 926.5, filed Dec. 11, 2003; the prior applications are herewith incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to a height-adjustable or length-adjustable implant for insertion between vertebral bodies. The invention also relates to an operating instrument suitable for adjusting the implant. 
         [0003]    Implants which are known, for example, from German Published, Non-Prosecuted Patent Application DE 196 22 827 A1, corresponding to U.S. Pat. No. 6,015,436, and U.S. Patent Application Publication No. US 2003/0045877 A1, have a first and a second sleeve part. The two sleeve parts are oriented coaxially and connected in a rotationally fixed and axially displaceable manner, and the first sleeve part has an external thread. In order to permit axial adjustment of the two sleeves relative to one another, a nut is provided which is secured rotatably on the second sleeve part and engages with its thread in the external thread of the first sleeve part. The two sleeve parts are moved axially relative to one another by rotating the nut. In order to rotate the nut, a rod-shaped operating instrument is inserted into a recess on the outer circumference of the nut. The nut is rotated by a distance corresponding to the pivot angle of the instrument through the use of a pivoting movement of the instrument in a plane extending transversely with respect to the longitudinal axis of the implant. Thereafter, the instrument has to be removed again from the nut and the procedure has to be repeated until the implant has a length that spans the space between two vertebral bodies. During the rotation of the nut, the second sleeve part must not be rotated along with it, so that the latter generally has to be held in place using a further instrument. The length adjustment in the known implants thus requires considerable expenditure in terms of time and equipment. In addition, a relatively large operating opening is needed to allow those manipulations to be performed without obstruction, in particular the pivoting of the operating instrument. A further disadvantage of the known implants is that surrounding tissue can be damaged both by the pivoting movement of the instrument as well as by the rotation movement of the nut. German Published, Non-Prosecuted Patent Application DE 101 27 924 A1 discloses an implant which has a similar structure to those described above. The rotation movement for height adjustment is effected by a gear unit. The gear unit includes a worm which is fitted onto the side of the implant and which can be activated with the aid of an operating instrument. 
       SUMMARY OF THE INVENTION 
       [0004]    It is accordingly an object of the invention to provide a height-adjustable spinal implant and an operating instrument for the implant, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which make available an implant with improved handling and with a larger inner space for receiving bone material. 
         [0005]    With the foregoing and other objects in view there is provided, in accordance with the invention, a height-adjustable implant for insertion between vertebral bodies. The implant comprises a first sleeve part having an internal thread and a second sleeve part having an access opening extending radially therethrough. The first and second sleeve parts are coaxially oriented about a central longitudinal axis and define an inner space therebetween, are connected to one another in a rotationally fixed and axially displaceable manner and have axially extending windows therein with mutually-facing, outwardly-open ends. Each adjacent two of the windows form a respective circumferential section therebetween in each of the sleeve parts. The circumferential sections of each one of the sleeve parts each fits axially displaceably into a respective one of the windows of the other of the sleeve parts. A nut is disposed coaxially in the inner space and secured on the second sleeve part in a rotatable but axially fixed manner. The nut has an external thread engaging in the internal thread of the first sleeve part. A toothed ring extends coaxially relative to the central longitudinal axis and is disposed on the nut in vicinity of the access opening. 
         [0006]    The first advantage of this configuration is that no pivoting movements have to be performed with an operating instrument in order to rotate the nut. Instead, it is now possible for the operating instrument to be kept in one and the same position and orientation during the entire procedure of adjusting the length of the implant, which fact greatly simplifies the operation and reduces the operating time. Moreover, only a relatively small operating opening is now needed. The driving action can be effected in a simple manner, for example using a driving toothed wheel disposed at one end of an operating instrument. Another important advantage of the proposed implant is that the nut is disposed in the inner space of the implant, with the result that, when the nut is rotated, there is no risk of damage to the surrounding tissue. This applies also to a toothed wheel of the operating instrument that meshes with the toothed ring during the length adjustment. Damage to the surrounding tissue by the two sleeve parts moving axially relative to one another can in practice be excluded by virtue of their smooth outer surface. 
         [0007]    The access opening not only ensures unobstructed access to the toothed ring, but also serves for securing an operating instrument on the implant. The corresponding end of the instrument is constructed in such a way that it can be secured in the access opening, e.g. can be inserted with an exact fit into the latter or can be screwed into it. The implant is then connected securely to the operating instrument, so that the latter can be used not only for rotating the nut but also for secure and positionally exact insertion of the implant into the spinal column. Moreover, this configuration ensures that the second sleeve part is fixed in terms of rotation during the adjustment of the implant length. Therefore, in contrast to conventional implants, only a single instrument is needed for driving the nut, for inserting the implant, and for fixing the second sleeve part in terms of rotation. 
         [0008]    The axially extending windows of the two sleeve parts are also particularly advantageous. As compared to a configuration in which two sleeve parts with different diameters engage concentrically one inside the other, this configuration first of all has the advantage of saving material and reducing weight. Moreover, a larger inner space is available that can be filled with bone material or the like. The meshed engagement of the two sleeve parts also ensures that they are mutually fixed in terms of rotation. 
         [0009]    In accordance with another feature of the invention, the toothed ring is constructed in the manner of a crown wheel. In this way, the drive pinion of the operating instrument can interact with the toothed ring in the manner of a contrate gear. This affords the advantage that the axis of rotation of the driving toothed wheel of an operating instrument runs approximately radially with respect to the central longitudinal axis of the implant and, accordingly, in the longitudinal direction of an expediently rod-shaped operating instrument. The latter can therefore be constructed in a relatively simple way, specifically by just having a centrally disposed rotation shaft with a driving toothed wheel secured on its end for rotating the nut. 
         [0010]    In accordance with a further feature of the invention, the engagement of the nut in the internal thread of the first sleeve part is preferably ensured by its being secured on the second sleeve part in such a way that its external thread, seen in the axial direction, is located outside the second sleeve part. A configuration of the nut is also conceivable in which its thread, again seen in the axial direction, is located inside the second sleeve part. In order to allow it to engage in the thread of the nut, the internal thread of the first sleeve part would then have to protrude past the inside face of the second sleeve part, for example by its having a greater wall thickness than the second sleeve part. In the preferred configuration of the nut, however, such a measure is not necessary. 
         [0011]    In accordance with an added feature of the invention, the toothed ring is preferably disposed on a surface of the nut facing away from the external thread, which is advantageous from a production point of view. Moreover, the length of the nut can be kept short. If the toothed ring were disposed on a surface facing toward the external thread, a greater axial distance would have to be present between the external thread and the toothed ring, namely at least an axial distance corresponding to the diameter of a driving toothed wheel that engages the toothed ring. 
         [0012]    In accordance with an additional feature of the invention, disposed on the inside faces of each of the circumferential sections of the first sleeve part is a radially inwardly extending projection which engages in a circumferential groove of the nut in order to fix the nut axially. In this way, it is possible to ensure that the nut is secured axially, even in the case where it is subjected to loading. In order to assemble the nut on the first sleeve part, it is placed onto the latter. It is true that the sleeve part is made of a solid material, in particular of metal. However, the circumferential sections separated from one another in the circumferential direction have such an elasticity that they are deflected inward when the nut is fitted in place and then spring back again to their original state, with the projections snapping into the circumferential groove of the nut. The positioning of the projections near the free end of the circumferential sections has the advantage of permitting the nut to be kept relatively short, without thereby reducing the maximum path of adjustment of the implant. This configuration also saves material and reduces weight and it also increases the size of the inner space of the implant. 
         [0013]    In accordance with yet another feature of the invention, in order to increase the size of the support surface of the implant, a radially widened support plate is provided which, in a preferred embodiment, is a separate part that can be secured on a sleeve part in a releasable manner. It is then possible, in each individual case, to use the appropriate support plate, for example one with a plane extending obliquely with respect to the central longitudinal axis of the implant. A support plate which is secured pivotably on a sleeve part is also conceivable. It can also advantageously be fixed in terms of rotation, for example in order to prevent a situation where an implant inserted between two vertebrae maintains its rotation position relative to the vertebral bodies or spinal column when the toothed ring is rotated. This fixing in terms of rotation is preferably achieved by several recesses, spaced apart in the circumferential direction and opening into the inside face of the sleeve part, being present in an end face of a sleeve part, and by projections of complementary shape on the support plate engaging in the recesses. 
         [0014]    With the objects of the invention in view, there is also provided an operating instrument for an implant. The operating instrument comprises a handgrip and a shaft extending through the handgrip. The shaft has one end carrying a rotary grip and another end carrying a toothed wheel for engaging the implant. An implant can be easily and safely manipulated using such an instrument. 
         [0015]    In accordance with another mode of the invention, the section of the shaft extending between the toothed wheel and the hand grip runs inside a jacket tube. This means that it cannot come into contact with tissue in the operating site, which could lead to undesired complications. 
         [0016]    In accordance with a concomitant mode of the invention, the jacket tube also serves to secure the operating instrument on the implant. For this purpose, its front end facing toward the toothed wheel is constructed in such a way that it can be secured in the access opening of the implant, for example by being inserted into the latter with an exact fit or by being screwed into it. 
         [0017]    The operating instrument for the height-adjustable implant includes a handgrip and a shaft extending through said handgrip, said shaft having one end carrying a rotary grip and another end carrying a toothed wheel for rotational actuation of the nut in the interior space of the implant; a jacket tube having a distal end affixed to said handgrip and a proximal end in proximity of said toothed wheel; a segment of said shaft extending between said toothed wheel and said handgrip extends through said jacket tube; said proximal end of said jacket tube being configured for fixation at an access opening of the implant; and said toothed wheel having teeth projecting axially out of said proximal end of said jacket tube. 
         [0018]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0019]    Although the invention is illustrated and described herein as embodied in a height-adjustable spinal implant and an operating instrument for the implant, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0020]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a diagrammatic, cross-sectional view of a first illustrative embodiment of a length-adjustable implant which includes, as its main components, a first and a second sleeve part and a nut; 
           [0022]      FIG. 2  is a perspective view of a second illustrative embodiment of an implant, likewise including the main components; 
           [0023]      FIG. 3  is a perspective view of the implant of  FIG. 2 , viewed from another angle; 
           [0024]      FIG. 4  is a perspective view of a second sleeve part of the implant of  FIG. 2 ; 
           [0025]      FIG. 5  is a cross-sectional view taken along a line V-V in  FIG. 3 ; 
           [0026]      FIG. 6  is a perspective view of a nut; 
           [0027]      FIGS. 7 and 7A  are perspective views of a support plate that can be secured on an implant; 
           [0028]      FIG. 8  is a perspective view of an operating instrument for manipulating an implant; 
           [0029]      FIG. 9  is an enlarged, fragmentary, perspective view of the operating instrument shown in  FIG. 8 ; 
           [0030]      FIG. 10  is an opened and cross-sectional side view of an illustrative embodiment of an implant with a reinforcing ring; 
           [0031]      FIG. 11  is a perspective view of an implant which is modified as compared to  FIG. 2 ; 
           [0032]      FIGS. 12 and 12A  are respective perspective and side-elevational views of a support plate that can be secured on the implant of  FIG. 2 ; and 
           [0033]      FIG. 13  is a cross-section taken through the forward portion of the operating instrument illustrated in  FIGS. 8 and 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    It is initially noted that in order to simplify matters, the implants shown in the figures, each with a first sleeve part  1 ,  101 , a second sleeve part  2 ,  102  and a nut  10 ,  110 , will be described with reference to a vertically oriented implant that rests with its first sleeve part on a support base. 
         [0035]    Referring now to the figures of the drawings in detail and first, particularly, to  FIG. 1  thereof, there is seen an illustrative embodiment in which the two sleeve parts  1 ,  2  are coaxial to one another and are fitted one inside the other in such a way that they are displaceable in a telescopic manner in the direction of their central longitudinal axis  4 . The internal diameter of the sleeve part  2  is slightly greater than the external diameter of the sleeve part  1 , such that the sleeve parts cooperate in the manner of a slide pairing in the event of a relative axial displacement. An end section of the sleeve part  1  protruding from the sleeve part  2  carries a radially outwardly directed flange  7  having an upper face  8  directed away from the sleeve part  2  which forms a support surface. The flange  7  additionally serves as an end abutment for the insertion movement of the sleeve part  1  into the sleeve part  2 . A flange  9  serving the same purpose is likewise disposed at a lower end face of the sleeve part  2  directed away from the flange  7 . 
         [0036]    The two sleeve parts  1 ,  2  are mounted one inside the other so as to be axially displaceable but fixed in terms of rotation. The fixing in terms of rotation can be obtained by ribs which extend in the direction of the central longitudinal axis  4  on the outside of the sleeve part  1  and engage in corresponding grooves in the inside face of the sleeve part  2 . A nut  10  is provided for the axial displacement of the two sleeve parts  1 ,  2 . This nut is constructed in the form of a tube section which, at its lower end, carries a radially outwardly extending flange  12  that rests on the inside face of the second sleeve part  2 . The nut  10  has an external thread  13  which engages in an internal thread  14  of the first sleeve part  1 . The internal thread  14  runs almost the entire length of the sleeve part  1 . The external thread  13  of the nut  10  has a corresponding length. It would, of course, also suffice if the sleeve part  1  were to have only a short internal thread section  14 ′ at its lower end, extending across an area  15 , for example. A short external thread section  13 ′ at the upper end of the nut  10  would also be conceivable and could extend across an area  16 , for example. The internal thread  14  of the sleeve part  1  would then be correspondingly longer, depending on the desired extent of the height adjustment of the implant. 
         [0037]    A toothed ring  17 , which is used to rotate the nut  10 , is disposed on the top face of the flange  12 . The flange  12  and the toothed ring  17  correspond to a crown wheel of a contrate gear. In the area of the toothed ring  17 , the second sleeve part  2  has an access opening  18  extending radially therethrough. An operating instrument, which cooperates with the toothed ring  17  and which will be described in more detail below, can be inserted through this access opening  18 . The sleeve part  1  is moved out of the sleeve part  2  and, if necessary, is also moved back in again, through rotation of the nut  10 . The outward movement is expediently limited by a non-illustrated abutment. Further non-illustrated radial openings can be provided in the sleeve parts  1 ,  2  and in the nut  10  in order to permit filling of the inner space of the implant with bone replacement material or the like, when placed in the spinal column. 
         [0038]    A further illustrative embodiment of a length-adjustable implant is shown in  FIGS. 2 through 6 . The two sleeve parts  101  and  102  have axially extending windows  24  opening out in their mutually facing end faces  22 ,  23  in the assembled state. Circumferential sections  25 ,  26  separating two respective adjacent windows  24  from one another fit axially displaceably into the windows  24  of the respective other sleeve part  101 ,  102 . Play is provided between the circumferential sections  25 ,  26  such that the two sleeve parts  101 ,  102  fit in one another without wobbling, but nevertheless ensure easy displaceability. 
         [0039]    The length is adjusted, or the sleeve part  101  is moved in and out, through the use of a nut  110  which is disposed coaxially inside the first sleeve part  101  and has an external thread  113  which engages in an internal thread  114  of the first sleeve part  101 . The internal thread  114  of the first sleeve part  101  extends approximately from the lower end face  22  of the sleeve part  1  to an upper end face  27  of the latter. 
         [0040]    The nut  110  has a sleeve-shaped construction, a length section  29  that carries the external thread  113  and a length section  30  that has no thread. The length section  29  or external thread  114  is disposed above the second sleeve part  102 . 
         [0041]    An end face of the length section  29  which faces downward or toward the sleeve part  102  in the assembled state, is constructed as a toothed ring  117 . The external diameter of the toothed ring  117  is smaller than the external diameter of the external thread  113  and smaller than the internal diameter of the sleeve part  102 . The external diameter of the thread  114  of the nut  110  is, by contrast, greater than the internal diameter of the sleeve part  102  and dimensioned in such a way that the thread  114  engages with the internal thread  113  of the first sleeve part  101 . 
         [0042]    An indent forming an annular groove  33  is disposed between the length section  29  and the length section  30 . In order to permit axial securing of the nut  110  on the sleeve part  102 , the latter has radially inwardly extending projections  34  which engage in the annular groove  33  of the nut  110 . The projections  34  are disposed at the free end of the circumferential sections  26  in such a way that their top face is flush with the upper end face  23  of the circumferential sections  26 . The main components of the implant, that is to say the sleeve part  101 , the sleeve part  102  and the nut  110 , are preferably made of metal. The circumferential sections  26  can, however, bend radially outward to a slight extent when the nut  110  is fitted, in such a way that the nut  110  can be inserted with its length section  30  into the sleeve part  102 , with the projections  34  snapping into the annular groove  33 . 
         [0043]    As is seen in  FIGS. 7 and 7A , in order to increase the size of the support surface of the sleeve parts  101 ,  102 , their end faces  27 ,  35  which are directed away from one another are provided with support plates  36  that protrude radially past the circumference of the sleeve parts  101 ,  102  and have a central opening  37  extending through them. The support plates  36  are preferably secured in a releasable manner. For this purpose, a skirt  38  delimiting the opening  37  is formed integrally on the underside of the support plate  36 . This skirt  38  can, for example, have an external thread with which the support plate  36  can be screwed into the first sleeve part  101 . In the embodiment according to  FIGS. 7 and 7A , however, a snap-fit connection is provided. For this purpose, the inner face of one sleeve part  101 ,  102  is provided with an annular groove  121  ( FIG. 10 ) into which it is possible to engage locking projections  54  that are formed integrally on the outer face of the skirt  38 . The skirt  38  is divided into four circumferential sections  56  by recesses  55  disposed at the end face. The ends carrying the locking projections are deflected radially inward when a support plate  36  is inserted into a sleeve part  101 ,  102 , but return to their original position, through the use of elastic restoring forces, when the locking projections  54  snap into the annular groove  121 . The face of the support plate  36  directed away from the implant carries several projections in the form of a notched ring  39  which concentrically surrounds the opening  37 . The notched ring  39  is used for fastening the implant on a vertebral body. 
         [0044]      FIGS. 11 and 12  show an illustrative embodiment in which a support plate  36   a  is secured in a rotationally fixed manner on at least one end face of a sleeve part  101 ,  102 . For this purpose, recesses  50  are provided in the end faces  27 ,  35  of the sleeve parts  101 ,  102  and are distributed uniformly about the circumference of one sleeve part  101 ,  102 . The recesses  50  extend in the axial direction and open into inside faces  51  of the sleeve parts. The recesses  55  are delimited by a curved inner wall  52  and a radial wall  53 . In the assembled state, projections  57  of complementary shape, formed on the outer face of the skirt  38  or of the circumferential sections  56 , engage in the recesses. 
         [0045]    As is seen in  FIGS. 2-5 ,  10  and  11 , two openings  40  through which bone material or bone replacement material can be introduced into the inner space of the implant, are formed in the sleeve part  102 , or its circumferential sections  26 . It is, of course, possible for a different number of openings to be provided. These openings can also be present in the sleeve part  101 . At least one of these openings forms an access opening  118  for an operating instrument, which will be described in more detail below. The toothed ring  117  protrudes into the cross section of the access opening  41 . 
         [0046]      FIGS. 8 and 9  show an operating instrument including, as its main components, an elongate hand grip  42 , a shaft  43  passing centrally through the latter in the longitudinal direction, a rotary grip  44  secured at an end of the shaft and a toothed wheel  45  secured at another end of the shaft. A section of the shaft  43  extending between the hand grip  42  and the toothed wheel  45  runs inside a jacket tube  46  having an end directed away from the toothed wheel  45  which is secured on the hand grip  42 . A free end  47  of the jacket tube  46  is widened radially. The teeth of the toothed wheel  45  are pins  48  which protrude in the longitudinal direction of the shaft  43  from a front end face of a disk  49  fixed on the latter. The operating instrument is inserted with its free end  47  into the access opening  18  or  118  in order to drive the nut  10  or  110 . The pins  48  come into engagement with the toothed ring  17  or  117 . This kind of toothed engagement is relatively robust and remains reliable and secure against blockage even when material gets into the area of the toothing. The free end  47  can be fixed in the access opening  18 ,  118  purely by frictional engagement. It is therefore conceivable for the free end  47  to be screwed with an external thread into an internal thread  122  (see  FIG. 10 ) of the access opening  18 ,  118 . 
         [0047]      FIG. 10  shows an illustrative embodiment with a reinforcing ring  119 . The latter is disposed at the upper end of the circumferential section  26  of the second sleeve part  102 . Ribs  120  protrude in the axial direction from the outer circumferential surface of the circumferential sections  26  and receive the reinforcing ring  119  between them and fix it in the axial direction. The reinforcing ring  119  makes it possible to reduce the wall thickness of the circumferential sections  26  of the second sleeve part  102  and also the circumferential sections  25  of the first sleeve part  101 , without any danger of the circumferential sections  25 ,  26  being bent radially outward when subjected to pressure. 
         [0048]    In the illustrative embodiment according to  FIG. 10 , grooves  121  are worked into corresponding inner circumferential surfaces in the upper end area and lower end area of the sleeve parts  101 ,  102 . The support plate  36  can be fixed into the grooves  121  in the manner of a snap-fit connection. Grooves  121  can also be present in the illustrative embodiments that were described in further detail above. 
         [0049]    The access opening  118  has an internal thread  122  into which an operating instrument can be screwed. The illustrative embodiment according to  FIG. 10  also shows that the access opening  118  can have a larger diameter than the other openings  40  in the circumferential sections  25 ,  26 .