Intervertebral prosthesis placement instrument

<u>BACKGROUND TO THE INVENTION</u>

0001THIS invention relates to an intervertebral prosthesis placement instrument.

0002Various types of intervertebral prosthesis are know. Examples are that marketed by Waldemar Link GmbH &amp; Co under the trade mark LINK ® SB Charité and those described in <patcit id="pcit0001" dnum="EP0560140A"><text>EP 0 560 140</text></patcit>, <patcit id="pcit0002" dnum="EP0560141A"><text>EP 0 560 141</text></patcit> (both Waldemar Link GmbH &amp; Co) and <patcit id="pcit0003" dnum="ZA20027517"><text>ZA 2002/7517</text></patcit>.

0003Publication <patcit id="pcit0004" dnum="EP1153582A"><text>EP 1 153 582</text></patcit> discloses a tool for installing an artificial disk prosthesis between adjacent vertebrae, including a pair of opposed levers separated by a fulcrum. Blade tips push the vertebrae apart upon progressing of the disk, so the disk can be inserted between them.

0004Publication <patcit id="pcit0005" dnum="US20020045904A"><text>US 2002/0045904</text></patcit> discloses an instrument for introducing intervertebral implants between adjacent vertebral. The instrument forms a guideway along which the intervertebral implant is inserted laterally into the intervertebral space.

0005It 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.

<u>SUMMARY OF THE INVENTION</u>

0006According to the present invention there is provided an intervertebral prosthesis placement instrument, according to claim 1.

0007In 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.

0008The 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.

0009The 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.

0010Further 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.

0011Other features of the invention are set forth in the appended claims.

<u>BRIEF DESCRIPTION OF THE DRAWINGS</u>

0012The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: <dl id="dl0001"><dt><b>Figure 1</b></dt><dd>shows a perspective view of an instrument according to this invention;</dd><dt><b>Figure 2</b></dt><dd>shows a side view of a portion of the instrument seen in <figref idref="f0001">Figure 1</figref>;</dd><dt><b>Figure 3</b></dt><dd>shows a cross-section at the line 3-3 in <figref idref="f0001">Figure 2</figref>;</dd><dt><b>Figure 4</b></dt><dd>shows a view of the instrument in the direction of the arrow 4 in <figref idref="f0001">Figure 2</figref>; and</dd><dt><b>Figure 5</b></dt><dd>shows the instrument in use.</dd></dl>

<u>DESCRIPTION OF A PREFERRED EMBODIMENT</u>

0013The 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 <figref idref="f0001">Figure 2</figref>. At their free ends the jaws 12 are provided with relatively sharp tips or blades 24 having curved extremities 26.

0014As will be apparent from <figref idref="f0001">Figures 1 and 2</figref>, the handles 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.

0015Reference 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.

0016The instrument illustrated in <figref idref="f0001">Figures 1 to 4</figref> is designed for use in placement of such a prosthesis. The prosthesis is indicated in <figref idref="f0001">Figure 5</figref> 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.

0017<figref idref="f0001">Figure 5</figref> 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.

0018In 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.

0019It will accordingly be understood that the slots 22 serve to guide the fins into the slots 40.

0020Referring to <figref idref="f0001">Figure 4</figref> 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 <figref idref="f0001">Figure 5</figref> 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.

0021It 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.

0022The 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.