Patent Publication Number: US-2021186475-A1

Title: Intervertebral prosthesis placement instrument

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 16/239,335 (Attorney Docket No. 29850-707.304), filed Jan. 3, 2019, which is a continuation of U.S. patent application Ser. No. 16/021,696 (Attorney Docket No. 29850-707.303), filed Jun. 28, 2018, which is a continuation of U.S. patent application Ser. No. 15/194,405, filed Jun. 27, 2016, now U.S. Pat. No. 10,105,131, which is a continuation of U.S. patent application Ser. No. 12/624,631, filed Nov. 24, 2009 and now U.S. Pat. No. 9,402,745, which is a divisional of U.S. patent application Ser. No. 11/187,403, filed on Jul. 21, 2005 and now U.S. Pat. No. 8,685,035, which is a continuation of International Application No. PCT/M2004/000170 filed on Jan. 26, 2004, which claimed priority from South African application ZA 2003/0875 filed on Jan. 31, 2003; the full disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to an intervertebral prosthesis placement instrument. 
     Various types of intervertebral prosthesis are known. Examples are that marketed by Waldemar Link GmbH &amp; Co under the trade mark LINK SB Charite™ and those described in EP 0 560 140, EP 0 560 141 (both Waldemar Link GmbH &amp; Co) and ZA 2002/7517. 
     It is an object of the present invention to provide an instrument which can be used to place an intervertebral prosthesis, such as one of those mentioned above, in an intervertebral space. 
     BRIEF SUMMARY OF THE INVENTION 
     According to the present invention there is provided an intervertebral prosthesis placement instrument comprising opposed jaws having tips shaped for insertion between adjacent vertebrae between which the prosthesis is to be placed, the jaws being movable apart from one another to cause distraction of the vertebrae and having opposing surfaces shaped to embrace the prosthesis between them and to guide the prosthesis into position between the distracted vertebrae. 
     In the preferred embodiment, the tips of the jaws are relatively sharp in relation to remaining portions of the jaws, thereby enabling the tips to be inserted between the vertebrae prior to distraction. The opposing surfaces of the jaws may include slots in which fins carried by the prosthesis and projecting in opposite directions are slidably receivable, the slots serving in use to guide the fins into opposing slots formed in the vertebrae. 
     The jaws may be carried by a scissors, forceps or tongs type mechanism having handles operable to move the jaws apart from one another. Preferably the jaws are inclined relative to one another and the handles are inclined relative to the slots, these features allowing the prosthesis to be inserted initially between the jaws. 
     The jaws may, for instance, inclined towards one another in a direction towards their tips with the maximum spacing between the jaws at positions remote from the tips being sufficient for the prosthesis to be inserted between the jaws. 
     Further according to the invention there is provided the combination of an instrument as summarized above and a tool which is operable to drive the prosthesis through the jaws and into position between the vertebrae: 
     Other features of the invention are set forth in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  shows a perspective view of an instrument according to this invention; 
         FIG. 2  shows a side view of a portion of the instrument seen in  FIG. 1 ; 
         FIG. 3  shows a cross-section at the line  3 - 3  in  FIG. 2 ; 
         FIG. 4  shows a view of the instrument in the direction of the arrow  4  in  FIG. 2 ; and 
         FIG. 5  shows the instrument in use. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The illustrated intervertebral prosthesis placement instrument  10  has a pair of jaws  12  carried by arms  14  which form part of a scissor-type mechanism having a single hinge point  15  and which are provided with handles  16  at their ends remote from the jaws. The jaws have opposing surfaces  18  formed with inwardly projecting ribs  20  and transverse slots  22  which extend for the height of the jaws as viewed in  FIG. 2 . At their free ends the jaws  12  are provided with relatively sharp tips or blades  24  having curved extremities  26 . 
     As will be apparent from  FIGS. 1 and 2 , the arms  14  are inclined relative to the jaws. It will be understood that by appropriate manipulation of the handles  16 , in the illustrated case by moving them apart from one another, will serve to pivot the jaws apart from one another. The invention also envisages embodiments in which a double hinge arrangement is provided whereby movement of the handles towards one another will pivot the jaws apart from one another. 
     Reference is made, by way of example only, to the specification of applicant&#39;s international patent application PCT/IB03/01529 which describes an intervertebral prosthesis having opposing plates located on opposite sides of a central core on which the plates can articulate. The plates have projecting fins which, during placement of the prosthesis, locate in slots created for the purpose in opposing surfaces of adjacent vertebra between which the prosthesis is to be installed. 
     The instrument illustrated in  FIGS. 1 to 4  is designed for use in placement of such a prosthesis. The prosthesis is indicated in  FIG. 5  by the numeral  30 . The abovementioned plates are indicated by the numeral  32 , the core by the numeral  34  and the fins by the numeral  36 . 
       FIG. 5  also shows portions of two adjacent vertebra  38  in which saw cuts have been made to form the slots  40  which will receive the fins. 
     In order to place the prosthesis  30  it is necessary to distract the vertebra, i.e separate them by a distance sufficient for entry of the prosthesis between them. To achieve this the tips  24  of the jaws  12  are inserted between the vertebra with the slots  22  in the jaws aligned with the slots  40 . The handles  14  may then be manipulated to force the jaws, and hence the vertebrae, apart from one another. The prosthesis  30  is then slipped into the gap between the jaws so as to be embraced therein with the fins  36  in the slots  22 . The prosthesis is then slipped downwardly through the inter-jaw gap. Throughout this movement the prosthesis is guided by the guidance of the fins  36  in the slots  22 . The prosthesis is moved right through the inter-jaw gap and eventually past the tips  24  so as to locate between the vertebrae with the fins in the slots  40 . 
     It will accordingly be understood that the slots  22  serve to guide the fins into the slots  40 . 
     Referring to  FIG. 4  it will be noted that the jaws are inclined towards one another in a direction towards their tips  24 . The gap  42  between them at the top, i.e. at their extremities remote from the tips  24 , is sufficient for initial insertion of the prosthesis between them at this location. Thus in an alternative placement procedure it is possible to locate the prosthesis initially in the gap  42  and then drive it downwardly so as to force the jaws, and hence the vertebrae, apart from one another instead of manipulating the handles to force the jaws apart. The numeral  44  in  FIG. 5  indicates a tool which is used to hold and position the prosthesis during the placement procedure. It will be possible to tap on the upper end of this instrument to drive the prosthesis downwardly as required. 
     It will also be understood that the procedures described above may be combined, so that initial distraction of the vertebra is achieved by manipulation of the handles  14  and subsequent distraction to the distance necessary to accommodate the prosthesis between them is achieved by tapping or otherwise urging the prosthesis downwardly. 
     The instrument  10  serves both to facilitate insertion of the prosthesis between the vertebrae and to ensure that the prosthesis is accurately guided into position so that its fins  36  locate properly in the slots  40 .