# Patent

## Title
Intervertebral prosthesis placement instrument

## Abstract

The invention concerns an intervertebral prosthesis placement instrument which can be used to facilitate accurate positioning of a spinal disc prosthesis between adjacent spinal vertebrae. The instrument (10) has opposed jaws 12 formed with tips (24) that are shaped for insertion between the vertebrae. The jaws can be moved apart from one another to distract the vertebrae, allowing the prosthesis to enter between the vertebrae. The jaws also have opposed surfaces which are shaped to embrace the prosthesis between them and to guide the prosthesis into position.

## Background
CROSS-REFERENCES TO RELATED APPLICATIONS
The present application is a Divisional of U.S. patent application. Ser. No. 11/187,403 filed on Jul. 21, 2005, which application is a continuation of International Application No. PCT/IB2004/000170 filed on Jan. 26, 2004, which claimed priority from South African application 2003/0875 filed on Jan. 31, 2003; the full disclosures, all 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 & Co under the trade mark LINK SB CharitéTM and those described in EP 0 560 140, EP 0 560 141 (both Waldemar Link GmbH & 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's international patent application PCT/IB03/04051 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.

## Claims

1. A method for implanting an intervertebral prosthesis, the method comprising:
inserting a prosthesis having two vertebral contacting surfaces and at least one fin projecting from at least one of the two vertebral contacting surfaces into a placement instrument comprising opposed jaws, with the at least one fin slidably received in at least one slot in the opposed jaws and the opposed jaws being inclined toward tips of one another to define a gap in the placement instrument opposite the tips for insertion of the prosthesis;
inserting the tips of the opposed jaws between adjacent vertebrae;
moving the jaws apart from one another to cause distraction of the vertebrae; and
implanting the prosthesis by sliding the at least one fin of the prosthesis in the at least one slot of the jaws and guiding the at least one fin of the prosthesis into a vertebral slot cut into at least one of the vertebrae.

2. A method according to claim 1, wherein the step of moving the jaws apart from one another is performed by driving the prosthesis downward in the jaws to force the jaws and the vertebrae apart.

3. A method according to claim 1, wherein the at least one fin comprises a fin on each of the two vertebral contacting surfaces and wherein the at least one slot of the jaws comprises a slot on each of the opposing inner surfaces of the jaws.

4. A method according to claim 1, further comprising an initial step of cutting the vertebral slot into one of the vertebrae.

5. A method for implanting an intervertebral prosthesis, the method comprising:
providing a placement instrument comprising opposed jaws and at least one slot in the opposed jaws configured to receive at least one fin of a prosthesis, the opposed jaws being inclined toward tips of one another to define a gap in the placement instrument opposite the tips;
inserting the tips of the opposed jaws between adjacent vertebrae;
moving the jaws apart from one another to cause distraction of the vertebrae;
inserting a prosthesis having two vertebral contacting surfaces and the at least one fin projecting from at least one of the two vertebral contacting surfaces into the gap in the placement instrument with the at least one fin of the prosthesis received in the at least one slot of the jaws; and
implanting the prosthesis by sliding the at least one fin of the prosthesis in the at least one slot of the jaws and guiding the at least one fin of the prosthesis into a vertebral slot cut into one of the vertebrae.

6. A method according to claim 5, wherein the step of moving the jaws apart from one another is performed by manipulation of a pair of handles of the placement instrument.

7. A method according to claim 5, wherein the at least one fin comprises a fin on each of the two vertebral contacting surfaces and wherein the at least one slot of the jaws comprises a slot on each of the opposing inner surfaces of the jaws.

8. A method according to claim 5, further comprising an initial step of cutting the vertebral slot into one of the vertebrae.

9. A method according to claim 1, wherein the at least one slot of the jaws comprises two substantially parallel side walls, wherein the at least one fin comprises two substantially parallel side walls and the spacing of the side walls of the slot of the jaws is configured to fit and guide the at least one fin.

10. A method according to claim 5, wherein the at least one slot of the jaws comprises two substantially parallel side walls, wherein the at least one fin comprises two substantially parallel side walls and the spacing of the side walls of the slot of the jaws is configured to fit and guide the at least one fin.