Abstract:
A surgical instrument for handling an implant having two parts, each of which includes a joint surface facing the other part, wherein the joint surfaces are in contact with one another in an implanted state and permit pivoting of the two parts in relation to one another, is provided. The instrument includes holding means for detachably connecting the instrument with each of the two parts of the implant. The instrument further includes a spacer element extending between the parts of the implant when the parts are connected with the instrument and maintaining a distance between the parts, thereby preventing the joint surfaces of the two parts of the implant from contacting each other.

Description:
[0001]     This application is related to and claims the benefit of German Utility Model No. 203 10 433.1 entitled Surgical Instrument for Handling an Implant issued on Sep. 4, 2003, and German Patent Application No. 103 30 699.4-35 filed Jul. 8, 2003.  
       FIELD OF THE INVENTION  
       [0002]     The present invention pertains to an inserting instrument for an intervertebral disk prosthesis. An intervertebral disk prosthesis can be inserted with this inserting instrument such that the bearing components are protected from impact pulses that may occur during the implantation.  
       BACKGROUND OF THE INVENTION  
       [0003]     A surgical instrument for handling an implant is known, for example, from WO 01/19295 A1, and is used to pick up an intervertebral implant and then introduce it into the intervertebral space between two vertebral bodies. With the prior-art instrument, the two parts of the implant are introduced into the intervertebral space in such a way that they are closely in contact with one another and are then removed from one another to the extent that an inlay, which carries the joint surface, can be pushed in between them. The implant is consequently a three-part implant.  
         [0004]     In case of the use of two-part implants, in which the two parts have a joint surface each, which are flatly in contact with one another in the inserted state and make possible the pivotability of the two parts as a result, the two parts are introduced together into the intervertebral space. Such a connection carries a risk that the joint surfaces may be damaged. This risk is especially high if the joint surfaces are sensitive, for example, if they consist of ceramic and therefore tolerate shocks very poorly. However, it is unavoidable during the implantation of the implant that such shocks are exerted on the implant, for example, when the implant is being driven into the intervertebral space.  
         [0005]     Accordingly, there remains a need for an improved surgical instrument that reduces the risk for damage to the joint surfaces of the implant during the handling of the implant.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention pertains to a surgical instrument for handling an implant comprising two parts that have a joint surface each facing the other part, and which are in contact with one another in the implanted state and make possible the pivoting of the two parts in relation to one another as a result. The invention includes a holding device as a part of the instrument, by which the instrument can be detachably connected with each of the two parts.  
         [0007]     More specifically, a spacer element is provided on the instrument, which spacer element extends between the parts of the implant when the parts of the implant are connected with the instrument and keeps these parts at such a distance from one another that the joint surfaces of the two parts do not touch each other. The two parts are consequently removed from one another to the extent that no contact can occur between the joint surfaces during the handling and especially during the insertion into the intervertebral space, so that the risk for damage to these joint surfaces due to shocks or the like is also minimized.  
         [0008]     It is advantageous in this connection for the distance between the joint surfaces when the spacer element extends between the parts of the implant to be between 0.2 mm and 2 mm, i.e., very small, so that the overall height of the implant is increased only insignificantly for the introduction compared with the overall height that the implant has in the ready-to-function state, i.e., when the joint surfaces are in contact with one another.  
         [0009]     The spacer element may be of a substantially plate-shaped design. It is favorable if the top side facing the parts and the underside of the spacer element are flat, and the implant preferably also has corresponding, flat surfaces in this case, so that a flat contact occurs, which minimizes the development of pressure peaks.  
         [0010]     Provisions are made in an especially preferred embodiment for the top side facing the parts and the underside of the spacer element to be slightly sloped in relation to one another, i.e., the spacer element is slightly wedge-shaped, and the extraction of the spacer element after the implantation of the implant is facilitated hereby.  
         [0011]     The spacer element may have a one-piece design, but provisions are made in a preferred embodiment for the spacer element to comprise two spacer members receiving the joint surfaces between them. These spacer members are located on opposite sides of the joint surfaces, e.g., of an inlay forming the joint surfaces, which inlay is inserted into the parts of the implant, so that the parts of the implant are kept symmetrically at a distance on both sides. For example, the spacer members may extend in parallel to one another, in which case they show a similarity to the prongs of a two-pronged fork.  
         [0012]     Provisions are made in an especially preferred embodiment for the holding means and the parts of the implant to have clamping elements that can be pushed into each other for the detachable connection, which clamping elements can be braced in relation to one another at right angles to the direction in which they are pushed in. These clamping elements are not yet braced during the pushing in, and the pushing in and the extraction are possible in a simple manner as a result. However, the clamping elements are clamped due to the bracing such that it is very difficult or even impossible to pull off the parts of the implant from the holding means.  
         [0013]     The clamping elements may be, in particular, projections and setbacks that engage one another. In a preferred embodiment, the projections and setbacks are pins and holes receiving the pins.  
         [0014]     It is advantageous in this connection for the clamping elements to be able to be braced in relation to one another in a direction that extends at right angles to the displacement of the parts of the implant by the spacer element extending between them. Thus, the parts of the implant are not tensioned against the spacer element due to the tension of the clamping elements, but the pressing forces of the parts of the implant against the spacer element are independent from whether or not the clamping elements are tensioned.  
         [0015]     In a preferred embodiment of the present invention, the clamping elements may be arranged at the instrument and displaceable at right angles to the direction in which the clamping elements are pushed in.  
         [0016]     For example, provisions may be made in a preferred embodiment for the instrument to have two arms, which can be pivoted in relation to one another and which carry clamping elements for the two parts at their free ends each, and for a tensioning device, with which the arms are pivotable in relation to one another, to be arranged at the instrument. The arms may be pivoted elastically in relation to one another.  
         [0017]     In a preferred embodiment, the tensioning device is formed by a sleeve, which extends over the arms and is movable along the arms. This sleeve is preferably rotatable around its longitudinal axis for movement along the arms and is mounted at the instrument by means of a screw thread. By rotating the sleeve, the sleeve is displaced along the arm and tensions the two arms against one another in the process. Each of the two arms may carry a spacer member.  
         [0018]     Provisions are made in an especially preferred embodiment for each arm to carry at its free end a clamping jaw, at which clamping elements for both parts of the implant as well as a spacer member are arranged and which form a stop, with which the parts of the implant are in contact when the instrument and the implant are connected. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  shows a perspective view of a surgical instrument for handling an implant;  
         [0020]      FIG. 2  shows an enlarged detail of the distal end of the surgical instrument according to  FIG. 1  with a two-part intervertebral implant being held at it; and  
         [0021]      FIG. 3  shows a sectional view along line  3 - 3  in  FIG. 2 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.  
         [0023]     The surgical instrument  1  shown in the drawings comprises a handle  2  with a bar  3  held thereon, which is divided at its end located opposite the handle  2  by a longitudinal slot  4  into two parallel arms  5 ,  6 , which can be elastically pivoted against each other or apart from one another. The two arms  5 ,  6  have the same design, and only one part will therefore be described in detail below. At its end, the arm carries a clamping jaw  7 , which may be made in one piece with the arm and is broader and higher than the arm. A substantially plate-shaped spacer member  8  is arranged at each clamping jaw  7 , the spacer member  8  extending in the longitudinal direction of the bar  3  on the side facing away from the handle  2 . The two spacer members  8  of the two clamping jaws  7  extend in the direction of the bar  3  in parallel and at spaced locations from one another, so that an intermediate space  9  is left free between the plate-shaped spacer members  8 . The spacer members  8  may be designed as plates with parallel, flat top side and underside, but it is also contemplated that they have a somewhat smaller thickness toward the free end, i.e., they are slightly wedge-shaped.  
         [0024]     The thickness of the spacer member  8  is smaller than the thickness of the clamping jaw  7 , and the clamping jaws  7  form a step  10 ,  11  each on the top side and on the underside of the spacer member  8 , and pins  12  extending in parallel to the bar  3  project from the clamping jaws  7  in the area of the steps  10 ,  11 . Each clamping jaw  7  carries such a pin  12  each above and below the spacer member  8 , i.e., the instrument  1  has, as a whole, four such pins  12 , which extend in parallel to one another and are substantially shorter than the spacer members  8 .  
         [0025]     A sleeve  13  surrounding the bar  3  is mounted on the bar  3  rotatably around the longitudinal axis of the bar  3 , and the sleeve  13  is screwed onto a threaded section of the bar  3  with its end  14  facing away from the handle  2 , so that it is moved in the longitudinal direction of the bar  3  during the screwing on this threaded section. With its distal end facing away from the handle  2 , the sleeve  13  surrounds the two arms  5 ,  6  in the section  15  directly adjoining the clamping jaws  7 , and the arms  5 ,  6  are laterally widened in this section  15  such that they form obliquely extending stop faces  16  on both sides. When the sleeve  13  is fed on the threaded section in the direction of the clamping jaws  7 , it slides along at these stop faces  16  and, as a result, pivots the arms  5 ,  6  against each other, i.e., the longitudinal slot  4  becomes narrower as a result.  
         [0026]     Referring to  FIGS. 2 and 3 , the instrument  1  is used to receive an implant  20 , which comprises two parts  21 ,  22 . Both parts have a flat, plate-shaped carrier  23 , each of which carries an anchoring projection  24  on its outer side, while a ceramic inlay  26  is inserted into a depression  25  on the inner side. While the carriers  23  have essentially the same design, the ceramic inlays  26  have cooperating joint surfaces  27 ,  28 , which are substantially partial spherical surfaces; one joint surface  27  is concave and the other joint surface  28  is convex; and both joint surfaces  27  and  28  are complementary to one another and, when they are flatly in contact with one another, they make possible the pivotable supporting of the two parts  21 ,  22  in relation to one another.  
         [0027]     Both carriers  23  have two blind holes  29 , which extend in parallel to one another and are used to receive the pins  12  of the instrument  1 . The mutual distance between the blind holes  29  at one carrier  23  corresponds to the mutual distance between the pins  12  at opposite clamping jaws  7  when the arms  5 ,  6  are not pivoted, so that the pins  12  can be easily pushed into the corresponding blind holes  29  of the carriers  23  before the sleeve  13  is pushed forward. The carriers  23  are now held on the pins  12  and abut against the steps  10  of the clamping jaws  7 , thereby limiting the depth of immersion of the pins  12 .  
         [0028]     The dimensions and the arrangements of the pins  12 , of the blind holes  29 , as well as of the spacer members  8  are selected to be such that after the carriers  23  have been pushed over the pins  12 , the components are held at closely spaced locations from one another, so that the joint surfaces  27 ,  28  do not touch each other, have a short distance between them, and the gap  30  between the joint surfaces  27  and  28  is not wide, the width being, e.g., between 0.2 mm and 2 mm. This distance  30  between the joint surfaces  27  and  28  is facilitated and maintained because the spacer members  8  extend between the two carriers  23  and the carriers  23  with their inner surfaces facing each other lie on these spacer members  8 , so that a further approach of the joint surfaces  27 ,  28  is prevented from occurring with certainty even under mechanical stress on the carriers  23 . The spacer members  8  lie on opposite sides of the joint surfaces  27  and  28  and of the ceramic inlays  26 , so that the ceramic inlays  26  are protectingly received between the two spacer members  8 .  
         [0029]     The carriers  23  can be fixed in this state, in which they are pushed over the arms  5 ,  6 , by the sleeve  13  being pushed forward by screwing in the direction of the clamping jaws  7 , and the sleeve  13  then comes into contact with the stop faces  16  and pivots the arms  5 ,  6  toward each other. As a result, the pins  12  in the blind holes  29  are tensioned against each other, clamping is brought about, and the carriers  23  are held securely at the clamping jaws  7 .  
         [0030]     When the implant  20  is fixed at the instrument  1  in this manner, the implant  20  can be handled safely and reliably by means of the instrument  1 , and, in particular, the implant can be pushed in this manner into an intervertebral space between two vertebral bodies  31 ,  32 , and the pushing in can be supported by blows with a hammer, which are exerted on the rear side of the handle  2 . The instrument  1  of the present invention ensures that the forces of impact cannot cause damage to the joint surfaces  27 ,  28 .  
         [0031]     More specifically, it may be necessary during the insertion of the prosthesis  20  into the intervertebral space between vertebral bodies  31 ,  32  to strike the handle  2  of the inserting instrument  1  with a hammer in order to bring the prosthesis  20  into the desired position. Since ceramic is relatively brittle and sensitive to shocks compared with other materials, impact pulses must be prevented from being transmitted via the ceramic ball and socket joint of ceramic inlays  26 . The wedge-shaped design of the spacer members  8  is arranged at the working end of the instrument  1  for this purpose. When the intervertebral disk prosthesis  20  is mounted on the inserting instrument  1 , a small distance  30  is formed between the joint surfaces  27 ,  28  of the ceramic inlays  26 , so that these ceramic inlays  26  are just spaced apart from one another so as not to touch each other and cannot transmit any pulses during the driving-in operation.  
         [0032]     After insertion, the clamping of the carriers  23  at the clamping jaws  7  is released by screwing back the sleeve  13 , and the instrument  1  is then pulled off from the implant  20 . The wedge-shaped design of the spacer members  8  facilitates such an extraction; in addition, this wedge shape may optionally enable adaptation to the geometry of the carriers  23 , whose inner surfaces do not need to be absolutely parallel to one another, but may optionally also form a small angle with one another. During the extraction of the spacer members  8  from the intermediate space between the carriers  23 , the carriers  23  are brought closer to one another to the extent that the joint surfaces  27 ,  28  come into contact with one another and thus support the adjacent vertebral bodies  31 ,  32  in relation to one another in an articulated manner via the carriers  23 .  
         [0033]     While preferred embodiments of the invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Accordingly, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the invention.