CA1306082C

CA1306082C - Place holder, in particular for a vertebra

Info

Publication number: CA1306082C
Application number: CA000550828A
Authority: CA
Inventors: Jurgen Harms; Lutz Biedermann
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-11-03
Filing date: 1987-11-02
Publication date: 1992-08-11
Anticipated expiration: 2009-08-11
Also published as: KR880005911A; KR950012178B1; GR3001272T3; EP0268115B1; JPS63177851A; US4820305A; DE3766939D1; JPH0442940B2; DE3637314C2; ATE59545T1; ES2019918B3; DE3637314A1; EP0268115A1

Abstract

ABSTRACT

A place holder or dummy element is provided which is in particular inserted in place of a vertebra to be removed. In order to allow a simple application the dummy element comprises a cylindrical member having at least an aperture in the wall thereof. The upper edge and the lower edge each at least partly comprise teeth for engagement with the adjacent vertebrae bodies or bone members.

Description

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PLACE HOLDER, IN PARTICULAR FOR A VERTEBRA

BACKGR_U_D__F THE_INVENTION
The invention refers to a place holder or dummy element in particular for a vertebra body,.
Whenever a vertebra body has to be removed fromthe spinal column or a bone piece from a bone, it is necessary to insert a pLace holder or dummy element between the remaining parts of the spinal column or the bone, respectively.
There is known from the German patent specification 30 23 942 a place holder, called implant, as vertebra body substitute for insertion between vertebrae bodies of the spinal column. The two opposed supporting ends of the place holder are dish-shaped and comprise cylindrical projections. The adjacent vertebrae bodies are formed such that the connection o~ the supporting ends with the adjacent ver-tebrae bodies-is possible.
There is known from the German laid open print 34 35 771 a bone matrix which comprises a plurality o~ holes for improving the stimulation of bone formation and of the bone regeneration. As a function of the piece to be substituted, the matrix is plate-shaped, semi-cylindrical or cylindrical. If such a bone matrix were placed between two vertebrae bodies, a separate connection to the adjacent vertebrae bodies would have to be provided.

OBJECTS OF THE INVENTION
________ _____ _________ It is an object of the invention to provide an improved place holder. It is a further object to design a place holder such that it can easily be inserted between two adjacent vertebrae bodies or two adjacent bone pieces.

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SUMMARY OF THE INVENTION
________________________ In order to achieve the above mentioned objects the invention provides a place holder, in particular for a vertebra, body, comprising a jacket-shaped member having at least one aperture in the wall thereof and an upper edge and a lower edge, both edges being at least partly serrated. It is thus achieved that a rotation-secured connection may be provided between the pieces to be connected. If desired, material to be introduced into the interior may be entered through the aperture. The aperture may eventually also serve for receiving a pedicle screw.
Further embodiments of the invention are characterized in the dependent claims.

BRIEF DESCRIPTION OF THE DRA~INGS
_________________________________ Further advantages, features and objects of the invention will stand out from the following description of exemplary embodiments with reference to the drawings, wherein Fig. 1 is a perspective view of an embodiment of the invention;
Fig. 2 is a top view of the apparatus of Fig. 1 in partial representation;
Fig. 3 shows a modified embodiment in a representation corresponding to that of Fig. 2;
Fig. 4 shows a modified embodiment in a representation corresponding to that of Fig. 1;
Fig. 5 is the modified embodiment in a representation corresponding to that of Fig. 2;
Fig. 6 is a bottom view of a modified embodiment;
Fig. 7 is a bottom view of a further embodiment;
Fig. 8 is a bottom view of an embodiment as shown in Figs. 4 and 5, but including a bottom plate; and Fig. 9 is a lateral view of the lower section of the embodiment shown in Fig. 8.

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DESCRIPTION OF THE PREFERRED EMBODIMENTS
As may in particular be seen from Fig. 1, the place holder or dummy element 1 i5 formed as a cylinder jacket-shaped member. In the manner shown in Fig. 1, the cylinder jacket comprises rhombus-shaped apertures 2 having their longitudinal diagonal extending parallel to the cylinder axis. Respective adjacent rows 3, 4 of such rhombuses are mutually offset by half of the rhombus height. In this manner a grid of band strips 5, 6 is formed which intersect each other wi-th an acute angle and which are inclined by respective identical angles with respect to the longitudinal diagonal of the rhombuses. It is thus achieved that a load acting onto the place holder in the direction of its longitudinal axis is taken up in uniform manner.
The upper edge 7 and the lower edge 8 are each formed such that approximately V-shaped teeth 9, 10 or 11, 12, respectively project upwards and downwards in the plane of the jacket parallel to the cylinder axis. The ends 13 of the teeth are bezelled or chamfered such that both chamfered faces inter-sect with an angle of approximately 45 such that a type of cutting edge is formed. In the embodiment shown in the Figs. 1 and 2 the jacket is formed by rolling up a correspondingly designed sheet metal strip. The two overlapping ends are inter-connected by means of a screw 14.
It is generally possible to reinforce the wall of the jacket by using two windin~s in the manner shown in Eig. 3.
In operation the place holder is inserted in axial direction between the remaining vertebrae bodiesor bone piecesin place of a removed vertebra body orbonepiece. The diameter and the axial length of the jacket are selected such that the jacket fits between the remaining pieces in that manner that these pieces keep their original distance from each other. The teeth 9, 10 and 11, 12, respectively, of the place holder engage the surfaceof the adjacent vertebrae bodiesor bones, respectively,in that manner that a torsional movement of the one adjacent part with respect to the other adjacent part is transferred to the ~3~76~2 respective other adjacent part or bralced or reduced, respectively, by means of the projecting teeth. At least the interior of the member is filled with bone cement through the apertures. If desired, that much bone cement may be introduced that the cement penetrates outwardly through the apertures and a modelling at -the outside is performed. Preferably the bone cement is filled in after insertion of the above described member. However, it is also possible to fill the interior space of the member before insertion thereof.
In the modified embodiments shown in the Figs. 4 and 5 corresponding parts are referred to by the respective identical reference sign. This embodiment differs from the above described in that cylindrical rings 15, 16 having an outer diameter which conforms to the respective inner diameter of the cylindrical jacket-shaped member are provided at the two opposed ends of the cylindrical body. The cylinder jacket is rigidly connecte~ with the close lying ring 15, 16 by means of respective screws 17. The outwardly directed side 18 of the respective ring 15, 16 has a distance d from the adjacent edge 7 or 8, respectively. This distance is preferably in the order of .5 to 2 mm. In inserting the member the ends projecting beyond the respective ring are pressed into the adjacent bone when subjected to load. The adjacent ring prevents a further penetration into the adjacent bone. The desired value of the distance d is determined by the intended way of use and -the depth of penetration desired therefor.
As may be seen from the Figs. 4 and 5, the dimensions of the rhombus-shaped apertures are selected such that the thread of a pedicle screw may be screwed into the aperture. Thus, an additional simple fixation between the place holder and the re spective adjacent vertebrae bodiesorbone pieces maybe achieved~
In the above described embodiments the cross-section is circular. Preferably the cross-section is chosen as a function of the cross-section of the parts to be connected. For ~3~6C~

connection of vertebrae bodies in the lumbal region the member preferably comprises a kidney-shaped cross-section shown in Fig. 6 or an oval cross-section shown in Fig. 7.
The embodiment shown in the Figs. 8 and 9 additionally 5 comprises a bottom plate 19 at the bottom side and a corresponding top plate 20 at the opposite side. The bottom plate and the top plate are each grid-shaped. The adjacent rings 15 and 16, respectively, serve as abutments. This embodi-ment is particularly suitable for the connection of porous 10 bones. By means of the bottom plate and top plate, respectively, it is prevented that the place holder sinks too far into e.g. the vertebrae bodies cover plate. The bottom plate and top plate, respectively, pre~2rably comprise a grid-shaped structure shown as an example in Fig. 8.
As mentioned above, the interior may be filled with bone cement. In place of the filling with bone cement, however, it is also possible to insert own or foreign bone pieces into the interior of the place holder such that the place holder has a supporting function around the inserted bone piece. Both when 20 filling with bone cement and when inserting the own bone piece a particularly fast vessel connection with the above described place holder is achieved. In addition, a safe protection of the spinal cord channel against ejected bone cement or bone pieces is achieved.
While the invention has been described in preferred form it is not limited to the precise nature shown as various modi-fications may be made without departing from the scope of the appended claims.

Claims

1. A prosthesis for insertion in a gap between vertebra wherein a damaged vertebra body has been removed and/or for insertion in a gap between parts of a bone from which a damaged part has been removed, comprising a generally cylindrical jacket disposed in the gap to be secured at its opposite ends to the opposite ends of the vertebra at opposite ends of the gap and/or the opposed ends of the parts of the bone at opposite ends of the gap, said cylindrical jacket comprising a tubular structure of a cross section corresponding to substantially the cross section of the opposed ends to be connected, said tubular structure containing a plurality of apertures disposed circumferentially and longitudinally thereof and wherein there are teeth at the opposite ends of the tubular structure, adjacent teeth extending peripherally in opposite directions and wherein the tubular structure is formed of sheet material formed into a cylinder with its ends overlapping and secured to each other by one or more screws engaged within apertures in the overlapping ends and wherein the teeth are bezelled such that the bezelled ends define acute angles forming cutting edges.

2. A prosthesis according to claim 1 wherein the jacket is formed of two layers of sheet metal disposed in concentric relation with each other and secured by said screws.

3. A prosthesis according to claim 1 wherein the jacket is of a length such that it fits between the adjacent bone ends with the teeth engaged with the surface of the adjacent bones to thus hold the bone ends at the original distance from each other.

4. A prosthesis according to claim 1 wherein the gap between the bone ends enveloped by the jacket is filled with bone cement.

5. A prosthesis according to claim 1 wherein there are annular rings of a diameter corresponding to the interior diameter of the jacket disposed within the jacket adjacent to but spaced from the ends and screws securing the rings in place, wherein the rings limit penetration of the teeth ends into the bone ends.

6. A prosthesis according to claim 5 wherein the distance between the ends of the jacket and the rings is in the order of .5 to 2 millimetres.

7. A prosthesis according to claim 1 wherein the jacket is of oval cross section.

8. A prosthesis according to claim l wherein the cross section of the jacket is kidney-shaped.

9. A prosthesis according to claim 1 wherein there are plates disposed within the jacket at the opposite ends thereof and diametrically thereof at a predetermined distance from the ends.

10. A prosthesis according to claim 9 wherein the plates are grid-shaped.

11. A prosthesis according to claim l, wherein the jacket is formed by a sheet metal comprising a plurality of approximately tetragonal apertures which are aligned such that a respective one diagonal extends substantially parallel to the cylinder axis of the jacket.

12. A prosthesis according to claim 11, wherein the apertures are substantially rhombus-shaped and the diagonal is the longitudinal diagonal thereof.

13. A prosthesis according to claim 1, wherein the jacket is formed of a biocompatible or physically tolerated material, in particular titanium.