United States Patent
`
`[19]
`
`[11] Patent Number:
`
`4,917,704
`
`[45] Date of Patent:
`Apr. 17, 1990
`Frey et a1.
`
`[54]
`
`[75]
`
`INTERVERTEBRAL PROSTHESIS
`
`Inventors:
`
`Otto Frey, Winterthur; Rudolf Koch,
`Berlingen, both of Switzerland
`
`[73] Assignee:
`
`Sulzer Brothers Limited, Winterthur,
`Switzerland
`
`[21] Appl. No.: 204,020
`
`[22] Filed:
`
`Jun. 8, 1988
`
`[30]
`
`Foreign Application Priority Data
`
`Jul. 9, 1987 [CH]
`
`Switzerland ...................... 2606/87-1
`
`Int. Cl.4 ........................... A61F 2/44
`[51]
`[52] US. Cl. ........................................ 623/17; 128/69;
`606/61
`[58] Field of Search ....................... 623/ 16, 18, 17, 20;
`305/35 EB, 13; 152/209 R; 360/32 R; 128/69,
`92 YM, 92 YP
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`5/1954 Knowles ........................... 623/ 16 X
`2,677,369
`2/1975 Stubstad .
`'
`3,867,728
`4,034,418 7/1977 Jackson et a1.
`....................... 623/20
`4,064,567 12/1977 Burstein et a1.
`.................. 623/20 X
`
`4,108,229
`8/1978 Herman ............................ 305/13 X
`4,568,294 2/1986 Owsen .....
`305/35 EB
`
`7/1986 Doty .................. 623/ 17
`4,599,086
`
`4,611,581
`9/1986 Steffee .
`...... 128/69
`4,714,469 12/1987 Kenna .................................,.. 623/17
`
`FOREIGN PATENT DOCUMENTS
`
`.............. 623/ 17
`0042271 12/ 1981 European Pat. Off.
`.
`0179695
`4/1986 European Pat. Off.
`2263842 7/ 1974 Fed. Rep. of Germany .
`2365873 8/ 1976 Fed. Rep. of Germany .
`2372622 6/ 1978 France .
`1107854
`8/1984 U.S.S.R. ................................ 623/17
`
`Primary Examiner—V. Millin
`Assistant Examiner—David J. Bender
`Attorney, Agent, or Firm—Kenyon & Kenyon
`
`ABSTRACT
`[57]
`The intervertebral prosthesis provides a replacement
`for a damaged disk. The prosthesis is formed as a solid
`body of kidney-shape and is provided with a metal mesh
`covering for the ingrowth of tissue. Raised parts are
`formed on the opposite surfaces of the kidney-shaped
`body impart lateral stability when in situ.
`
`14 Claims, 1 Drawing Sheet
`
`
`
`NUVASIVE 1007
`
`1
`
`

`

`US. Patent
`
`4,917,704 '
`
`
`
`2
`
`

`

`1
`
`INTERVERTEBRAL PROSTHESIS
`
`4,917,704
`
`This invention relates to an intervertebral prosthesis.
`More particularly, this invention relates to an interver-
`tebral prosthesis for an arthrodesis.
`.
`As is known, for an arthrodesis of two lumbar verte-
`brae relative to each other, two different approaches ,
`have been customary. In one approach, bone splinters
`have been removed from another part of the body, for
`example, from the pelvis or the shin, and placed as a
`partial replacement of the damaged intervertebral disk
`between the two vertebrae from the ventral direction
`and secured with bone screws. However, it has been
`shown that securement of the two adjacent vertebrae is
`insufficient and does not have the requisite stability,
`especially shortly after implantation when the bone
`tissue of the Vertebrae has not yet become intergrown
`with the bone splinters.
`In the other approach, two adjacent vertebrae have
`been secured relative to each other by cross plates
`which are firmly connected with the two vertebrae
`from the dorsal direction, for example by means of
`screws. However, experience has shown that the cross
`plates which are arranged relatively far from the inter-
`vertebral disks effect only an insufficient securement of
`the vertebrae in the dorsal region of the vertebrae, par-
`ticularly in the case of a greater intervertebral disk
`damage or in the case of a complete replacement of an
`intervertebral disk. Also, the plates tend toward insta-
`bilities in the reciprocable stiffening of the vertebrae.
`French Patent 2372622 describes an intervertebral
`prosthesis which is formed of a disk and which is pro-
`vided with weld-like raised parts in the form of spheri-
`cal segments on opposite sides. Such a disk is to be
`placed between a pair of vertebrae with the spherical
`segments placed in hollow spherical-shaped depressions
`of the Vertebrae. In this case, the disk is stiff and non-
`deformable while the raised parts are elastic. However,
`an arthrodesis of the two vertebrae is not possible with
`such a construction.
`
`Various types of intervertebral prosthesis have also
`been known for implantation within a spinal column.
`For example, German OS 2365873 describes a skeletal
`type prosthesis which can be implanted in place of a
`vertebrae and secured in situ by means of screws to
`adjacent vertebrae. German US 263842 describes a com-
`posite disk like structure which is to be implanted be-
`tween a pair of vertebrae to replace a damaged disk.
`HoWeVer, the stability of such a prosthesis cannot be
`ensured since no means is provided for a primary fixa-
`tion of the prosthesis in place. Published European
`Patent Application 179695 describes a prosthesis which
`is intended to replace a damaged disk and which is
`constructed of a peripheral ring with a multi-apertured
`insert. However, such a prosthesis is relatively cumber-
`some to use and does not provide for a primary fixation
`of the prosthesis in situ. U.S. Pat. No. 3,867,728 de-
`scribes a prosthesis for spinal repair Which is made of a
`core element of elastic polymer and an outer covering
`of porelike material to provide for tissue ingrowth.
`However, the securement of such a prosthesis in place
`cannot be readily obtained and the prosthesis does not
`have the required stability for primary fixation.
`Accordingly, it is an object of the invention to pro-
`vide an intervertebrae prosthesis which can be im-
`planted and secured at relative low operative expense.
`
`10
`
`15
`
`20
`
`25
`
`30
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`35
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`45
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`50
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`55
`
`65
`
`2
`It is another object of the invention to ensure a firm
`and stable stiffening of two vertebrae when using an
`intervertebral disk replacement.
`Briefly, the invention provides an intervertebral pros-
`thesis comprised of a disk-like body which can be slid
`between two vertebrae from the ventral direction to
`function as a disk replacement. In addition, the disk-like
`body is provided with weld-like raised parts on opposite
`surfaces to enhance lateral stability of the body in situ.
`The prosthesis is distinguished by great simplicity
`since the prosthesis is formed solely of a disk-like body
`for fitting between a pair Of vertebrae. The weld-like
`raised parts which are preferably of a cross section
`having a cylindrical segment shape form an acute angle
`with each other and are placed from the ventral direc-
`tion into surgically prepared bores of the vertebral bod—
`ies which are adapted to the raised parts. These raised
`parts thus ensure lateral stabilitY of the arthrodesis as
`well as primary securement. Furthermore, it is advanta-
`geous if the angle formed by the raised parts on a given
`surface is 90°.
`In Order to adapt the prosthesis to the anatomical
`conditions, the prosthesis body may be kidney-shaped
`and/or may have a thickness which tapers conically
`from ventral to dorsal.
`The prosthesis body may be of a synthetic material,
`for example, polyethylene having the specifications
`customary for implants. In addition, the surfaces of such
`a synthetic material body may be covered with a metal
`mesh, for example, a multi-layered wire mesh of tita-
`nium or a titanium alloy in order to support tissue in-
`growth and thereby ensure a long term securement.
`Alternatively,
`the prosthesis body may consist of
`titanium or a titanium alloy. In this case also, the sur-
`faces of the body may be provided with a structure
`which supports tissue ingrowth and which may also be
`formed of a wire mesh secured to the disk body by spot
`welding.
`These and other objects and advantages of the inven-
`tion will become more apparent from the following
`detailed description taken in conjunction with the ac-
`companying drawings wherein:
`FIG. 1 illustrates a plan view of a prosthesis con-
`structed in accordance with the invention;
`FIG. 2 illustrates a cross-sectional view taken on line
`11—11 of FIG. 1;
`FIG. 3 illustrates a plan view of a modified prosthesis
`in accordance with the invention;
`'
`FIG. 4 illustrates a view of the prosthesis of FIG. 3
`from dorsal to ventral:
`
`FIG. 5 illustrates a view of a prosthesis in situ be-
`tween two vertebrae; and
`FIG. 6 illustrates a ventral view of a modified pros-
`thesis in accordance with the invention.
`
`Referring to FIG. 1, the intervertebral prosthesis is
`comprised of a disk-like body 1 for fitting between a
`pair of vertebrae and is provided with a pair of weld-
`like raised parts 2 on each of two opposite surfaces to
`enhance lateral stability of the body 1 in situ. As indi-
`cated, the raised parts 2 define a chevron rib and are
`disposed on axes which define an angle of 90". As seen
`in FIG. 1, the rib defined by the raised parts 2 is directed
`from ventral to dorsal.
`
`The disk 1 is of kidney or bean-shape which is curved
`convex ventrally and concave dorsally. In addition, the
`body 1 has a thickness which decreases from ventral to
`dorsal as indicated in FIG. 2.
`
`3
`
`

`

`4,917,704
`
`5
`
`10
`
`15
`
`4
`2. An intervertebral prosthesis as set forth in claim 1
`wherein said angle is equal to 90°.
`3. An intervertebral prosthesis as set forth in claim 1
`wherein said raised parts on each surface of said body
`define a chevron shaped rib directed from ventral to
`dorsal.
`
`4. An intervertebral prosthesis as set forth in claim 1
`wherein said body is kidney-shaped.
`5. An intervertebral prosthesis as set forth in claim 1
`wherein said body tapers comically from ventral to dor-
`sal.
`6. An intervertebral prosthesis as set forth in claim 1
`wherein said body is made of synthetic material and
`which further comprises a metal wire mesh on said
`opposite surfaces for an ingrowth of tissue.
`7. An intervertebral prosthesis as set forth in claim 1
`wherein said body is made of a metal selected from the
`group consisting of titanium and titanium alloy.
`8. An intervertebral prosthesis for an arthrodesis
`comprising a kidney-shaped disk-like body for fitting
`between a pair of vertebrae, said body having a raised
`chevron-shaped rib disposed on opposite surfaces
`thereof to enhance lateral stability of said body in situ,
`each said rib projecting from a respective surface along
`the length thereof.
`9. An intervertebral prosthesis as set forth in claim 8
`wherein each rib has a cross-section of cylindrical seg-
`ment shape.
`10. An intervertebral prosthesis as set forth in claim 8
`wherein each chevron shaped rib is directed from ven—
`tral to dorsal.
`
`11. An intervertebral prosthesis as set forth in claim 8
`wherein said body is made of synthetic material and
`which further comprises a metal wire mesh on said
`opposite surfaces for an ingrowth of tissue.
`12. An intervertebral prosthesis for an arthrodesis
`comprising a kidney-shaped disk-like body for fitting
`between a pair of vertebrae, said body having raised
`parts disposed on opposite surfaces with each part pro-
`jecting from a respective surface along the length
`thereof, each part extending from a ventral edge
`towards a dorsal edge along an axis intersecting with a
`ventral-to-dorsal plane of said body and with an axis of
`another of said parts to enhance lateral stability of said
`body in situ.
`13. An intervertebral prosthesis as set forth in claim
`12 wherein said parts on each surface define a chevron-
`shaped rib.
`14. An intervertebral prosthesis as set forth in claim
`12 wherein said parts on each surface terminate in a
`region where said axes thereof intersect and a bridge-
`like web on each surface connects said parts thereat.
`5|!
`*
`5k
`*
`I!
`
`3
`The raised parts 2 each extend from the ventral edge
`5 to the dorsal edge. However, as indicated in FIG. 3,
`the parts 2 may terminate in the region where the axes
`of the parts 2 intersect. In this case, the parts 2 are
`connected by a bridge-like web 3 (see FIG. 4).
`The entire prosthesis including the body 1 and the
`parts 2 are covered with a multi-layered wire mesh 4,
`for example of titanium. Where the body 1 is made of a
`synthetic material such as polyethylene, at least one
`layer of the mesh 4 may be embedded in the body 1. In
`known manner, the mesh 4 serves to support tissue in
`growing onto and into the mesh.
`Referring to FIG. 5, in order to improve a primary
`securement of the prosthesis prior to ingrowth of bone
`tissue, the ventral edge 5 of the body 1 is covered by a
`pair of fishplates 6. As indicated, the fishplates 6 only
`partially cover the ventral edge. In addition, each plate
`6 is provided with a pair of openings 8 for the passage of
`bone screws into the adjacent vertebrae 9. These open- 20
`ings 8 are formed as part of a spherical bowl in order to
`facilitate alignment of the screws (not shown) in any
`direction.
`
`Referring to FIG. 6, the prosthesis may also be pro-
`vided with an integral fishplate arrangement 7 which
`covers the ventral edge 5, for example, as described in
`copending patent application Ser. No. 07/203,950, filed
`June 8, 1988. In this case, the fishplate arrangement 7
`has pairs of openings 8 as above.
`During implantation of the prosthesis body, for exam-
`ple, from ventral to dorsal, the body is slightly com-
`pressed by the vertebrae 9. Thereafter, the fishplates 6
`or fishplate arrangement 7 can be secured to the Verte-
`brae 9 by means of bone screws to effect primary fixa-
`tion.
`
`25
`
`30
`
`35
`
`The invention thus provides a prosthesis which can
`be used as an intervertebral disk replacement which
`ensures a stable stiffening (arthrodesis) of two vertebrae
`relative to each other. In addition, the raised parts of the
`prosthesis body which are placed into surgically pre-
`pared bores in the vertebrae ensure a primary secure-
`ment and an increased lateral stability of the prosthesis.
`What is claimed is:
`1. An intervertebral prosthesis for an arthrodesis
`comprising a disk-like body for fitting between a pair of
`vertebrae, said body having weld-like raised parts dis-
`posed on opposite surfaces thereof dimensioned to en-
`hance lateral stability of said body in situ, each said 50
`raised part on said body having a cross-section of cylin-
`drical segment shape and forming an acute angle with a
`second raised part on a respective surface of said body.
`
`45
`
`55
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`60
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`65
`
`4
`
`

`

`UNITED STATES PATENT AND TRADEMARK OFFICE
`CERTIFICATE OF CORRECTION
`41,917,704
`
`:
`
`PATENTNO.
`
`DATED
`
`; April 17, 1990
`
`INVENTOR(S):
`
`OTTO FREY, et al
`
`It is certified that error appears in the above-identified patent and that said Letters Patent is hereby
`corrected as shown below:
`
`olumn 1,
`olumn 1,
`olumn 1,
`olumn 1,
`olumn 2,
`
`line 18 "Vertebrae" should be —vertebrae-
`line 48 "263842" should be —2263842-
`line 51 "Ho We Ver" should —However—
`line 60 "Which" should be -which—
`line 12 "Of" should be —of—
`
`
`
`Signed and Sealed this
`
`Seventeenth Day of September, 1991
`
`Arrest:
`
`Arresting Ofi‘icer
`
`Commissioner of Parent: and Trademarks
`
`HARRY F. MANBECK. JR.
`
`
`
`5
`
`