DE102011000377A1 - Vertebral cage implant has through-hole or recess that is formed along height direction, and is provided with inhomogeneous cross-section along longitudinal direction - Google Patents

Abstract

The vertebral cage implant (1) has through-hole or recess (4) that is formed along height direction. The through-hole or recess is provided with inhomogeneous cross-section along longitudinal direction. The contact surfaces (6,8) spaced along height direction support connection of vertebrae of spinal column. The cross section of through-hole or recess in the plane of contact surfaces is greater than that in the longitudinal section plane of implant. The implant is made of titanium, titanium alloy, or plastic material.

Description

The present invention relates to a vertebral cage, for example for use as a fracture implant, preferably in the case of an incomplete vertebral body fracture for monosized vertebral body fusion or as an intervertebral implant in the case of degenerated or damaged intervertebral discs.

Background of the invention

Basically, modern medicine and spine surgery in particular endeavors to obtain as much as possible of natural material during necessary surgical procedures for implanting prostheses and thus to ensure the original function of the damaged or diseased body part / organ as far as possible.

Degenerative conditions (caused, for example, by age-related remodeling processes) but also spinal injuries such as vertebral body fractures due to falls or traffic accidents are those common spinal injuries that cause spondylodesis, i. H. may require the surgical stiffening of one or more segments of the spine. In the case of spinal fractures, different types of injury are distinguished depending on the pattern and severity. The most common types of injury are the so-called compression injuries (type A injury according to Magerl / A0 classification), which are dominated by the subgroup of burst fractures (A3 fractures). Bursting fractures show complete or partial disintegration of the vertebral body while the dorsal ligaments are still intact. These so-called A3 fractures are often unstable and are therefore - as opposed to stable fractures - usually treated surgically.

For this purpose, the stabilization of the fractured spine u. a. often a ventral spondylodesis is applied for fusion of adjacent vertebrae / vertebral bodies, d. h., it is an operative stiffening of one or more segments brought about. The aim of this operation is to re-stabilize the spine via implants and to immobilize the affected segments until a bony fusion has taken place. For this purpose, after the removal of the fractured bone material as well as the damaged intervertebral disc tissue usually a bone chip is used. However, in order to avoid the disadvantages associated with the use of bone chips (eg removal morbidity, correction loss, etc.), a cage-like implant may alternatively be used.

In the case of degenerative changes, for example, of the intervertebral disk, such cages are also used for fusion operations, which are then inserted into the intervertebral space (also referred to as intervertebral disc space) between two adjacent vertebral bodies. For this purpose, initially arranged in the intervertebral space and two adjacent vertebrae movably connecting disc is completely or partially removed. Then the cage is implanted as a kind of spacer in the intervertebral space. This receives on the one hand the height of the segment, so the distance between the adjacent vertebral bodies and on the other hand it allows by the immobilization of the motion segment, the bony fusion of the vertebral bodies.

In addition to solid implants (so-called support bodies) are vortex cages or cages with in the vertical (along the spine) direction extending openings, for example in the form of through holes or one / two-sided blind holes known which each form an interior of the cage. To promote and / or accelerate the fusion of adjacent vertebrae vertebral bodies (in the case of a monosegmental fracture treatment) or vertebral bodies in the case of a bi-segmental fracture treatment) these openings - depending on the embodiment before or after implantation in the intervertebral space - with autologous bone or bone substitute material filled in a condensed way. This creates a sort of pathway for bony growth between the vertebral endplates and the bone / bone replacement material within the implant that facilitates and accelerates healing.

Depending on the type of cage (eg ALiF, PLiF, TLiF, ACiF implant) and type of access (in the patient's abdominal, lateral or supine position), the spine is implanted into a cage of the type described above exposed at the site to be treated and removed the disc tissue using appropriate instruments, such as Rongeurs and curettes. The two now directly opposite vertebral body surfaces should be as clean as possible of cartilage material and bloodily sanded (refreshed).

Once the cage is selected to be the right size and height, it is filled with bone substitute material by stuffing it tightly into the said space. The cage filled in this way is then pushed / knocked between the two vertebrae to be supported against one another by means of a corresponding forceps, by means of which it can be gripped on engagement holes formed on the cage or similar points of engagement / recesses. The vertebrae are slightly pushed apart and the precisely inserted cage is held securely between the two vertebrae (vertebrae) thanks to its ribbed top and bottom. The The grip can finally be removed and removed.

Such an implanted cage usually ensures stability of the spine in the treated area immediately after implantation. Only in the case of insufficient cages or insufficient support is a revision necessary to replace the potentially unstable cage with another, as the insufficiently penetrated, unstable Cage due to changes in position (dislocation) a danger to the dura and the Represents esophagus. Such instability also results in micromovements between the implant and the adjacent bone or bone material, which can locally lead to bone resorption.

State of the art

The DE 10 2005 027 283 A1 discloses a cage of this genus in the form of a kidney-shaped interim implant having at least one aperture for anterior vertebral fusion. As a further embodiment, two through a central web separate openings are described.

The EP 1 504 732 A1 and the US 2005 019 26 69 A1 describe a hollow Schraubcage for filling with bone or osteogenic bone replacement material, which in addition to vertical openings for bony Durchbauung also has lateral openings for the vascular supply.

Furthermore, the EP 880 950 A1 an angularly expandable cage for the cervical spine with a substantially rectangular recess for the bony Durchbauung.

In the US 2004 0 024 464 A1 is a porous metal spacer described with conical, angularly arranged through holes, which extend from an implant side to the contact surfaces and each form a receptacle for bone screws for implant securing. Ie. the through holes are adapted in shape, dimension and positioning to the bone screws to be used.

Finally, the reveals WO 2005 102 226 A1 a cage with an opening in the spine longitudinal direction. On the side of the cage windows are formed which have an inhomogeneous cross-section and are provided for controlling the cement distribution / of the cement jacket around the implant.

The breakthroughs of known cages usually have a large diameter and therefore require large amounts of bone / bone substitute material. In addition, this reduces the remaining contact surface of the cage, which makes the cage too weak. On the other hand, in the case of small apertures, the autologous bone does not experience the stress necessary to achieve a rapid and complete fusion. The bone within the cage can then reabsorb and transform into simple connective tissue, which in the worst case can be a pseudarthrosis. Furthermore, it has been shown that the cross section of the opening uniform from the kernal to the caudal causes only a moderate compression of the bone / bone substitute material. Moreover, the comparatively large amount of bone within the cage on the contact surface to the adjacent vertebral endplate must be supplied / maintained vital, which should therefore be as large as possible, so that here a constructive contradiction to the necessary stability of the cage itself occurs. Finally, it is in principle advantageous to coat the surfaces of the cage in order to accelerate the ingrowth of the cage into the bone material. However, the formation of such a coating within the aperture is difficult and often incomplete.

General description of the invention

In view of the above-described problems, the basic object of the present invention is to provide an implant or a generic swivel cage (hereinafter referred to as Cage), by means of which a fusion of two vertebrae / vertebral body is achieved even safer, faster and more effective. An object of the invention is to achieve the structure of the interior of such cage with bone as quickly and safely.

This object is achieved by a swivel cage of the relevant type with the features of patent claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

The inventive vertebrate cage or cage according to one aspect therefore has at least one fillable bone or bone substitute material or at least one bone or bone substitute fillable cage height direction recess whose respective cross section is inhomogeneous longitudinally from at least one cage abutment surface , As a result, in contrast to a uniform, ie constant cross-section, an improved blood flow of the stuffed bone / bone replacement material can be achieved, which accelerates the healing of the implant. The internal stability of the cage is essentially preserved or compared to a cage with uniform Breakthrough cross section improved. In addition, this construction provides a more favorable geometric prerequisite for coating the insides of the at least one opening or the at least one recess with a material which promotes the growth of the bone in the at least one cage interior created thereby.

Another aspect of the invention provides for the formation of two abutment surfaces arranged in implant height direction for a support engagement with two vertebrae of a spinal column, wherein the cross section of the at least one aperture or of the at least one recess in the plane of at least one of the abutment surfaces increases is than in another longitudinal section plane of the respective aperture or the respective return. This achieves a larger contact area between the cage filler material and the adjacent vortex. At the same time, the compression force on the cage filler increases during natural sintering processes.

In this case, it is advantageous if the cross-section of the at least one opening / recess of at least one of the abutment surfaces of the implant or of its two abutment surfaces decreases toward an implant center section seen in the height direction (hourglass shape). This decrease in cross-section can be achieved continuously, in steps or by one or more (differently) inclined, adjoining surfaces.

It is also advantageous if the inclination of the areas determining the cross-section decrease is between 15 ° and 60 ° with respect to the central axis of the opening / recess. In this case, a preferably continuous / complete inner coating of the at least one opening or at least one return from the outside can take place.

Another aspect of the invention provides that the implant according to the invention consists of a metallic material, in particular titanium or a titanium alloy or a resorbable or non-resorbable plastic, preferably PEEK.

According to another aspect of the invention, the two height-spaced abutment or bearing surfaces of the implant, which are supported on two vertebrae of a spine, have different surface sizes. Preferably, one of the support surfaces is widened in the direction toward particularly viable vortex regions in relation to the other support surface. This has the advantage of avoiding a collapse of the cage in one of the vertebral bodies to be merged and thus to accelerate the fusion process.

It has proven to be advantageous if the widening bearing surface extends beyond the vertebral body at least partially into the region of the vertebral arch, since a vortex in this section is particularly resilient.

To constructively implement these properties, the implant according to a further aspect of the invention may have a base body which forms the smaller of the two bearing surfaces on one side and merges on an opposite side in a connection part, which by forming a projecting nose in one side bearing surface direction of the main body or bar forms the larger of the two bearing surfaces. Due to the formation of this nose-shaped projection, the implant can slide at the appropriate sections between the vertebrae in order to transmit particularly high axial forces there.

Finally, it should be noted that the above aspects individually and in any combination with each other can solve the task and should therefore be claimed individually or in any combination within the scope of this application.

figure description

The invention will be explained below with reference to preferred embodiments with reference to the accompanying figures.

1a to 1c show different variants of a cage according to a first preferred embodiment of the invention in the form of an intervertebral implant with differently shaped recesses and

2a to 2 B show two variants of a cage according to a second preferred embodiment of the invention in the form of an intervertebral implant with differently shaped openings.

In the 1 and 2 is a cage or an intervertebral implant 1 illustrated according to the invention with at least one opening 2 or at least one (preferably two) return 4 the / at at least one (preferably two) contact surface or bearing 6 . 8th opens to the outside, and which is filled with a cage filler material such as bone or bone substitute material (not shown). The cross section of the at least one opening 2 or the at least one return 4 is inhomogeneous, preferably in the way that it differs from the at least one Contact surface or from the two contact surfaces 6 . 8th decreased from the implant center.

In concrete shows the 1a a first variant of a cage according to the invention 1 , the present case with a return 4 starting from a support surface 6 is formed, which can be brought into supporting engagement with a vertebra / vertebral body. Alternatively, it is of course possible from both in the height direction of the Cage 1 spaced bearing surfaces 6 . 8th starting one (or more) recesses 4 form, which are aligned either axially longitudinal or off-axis to each other in the longitudinal direction.

The cage 1 is in the 1a symbolically represented as a substantially cuboid smooth body, which, however, can take on a different shape in real design, for example, with different sized bearing surfaces and the bearing surfaces 6 . 8th self-structured, for example grooved or corrugated. The in 1a showed a return 4 has a dull pyramid shape with the largest diameter or the largest pyramid surface in the plane of the one bearing surface shown 6 and the smallest diameter or smallest pyramid area in a height-wise central area of the cage 1 , The the return 4 defining inner walls of the cage 1 are presently smooth, but may also have a surface structure. In addition, at least the bearing surfaces 6 . 8th Preferably, in addition, the cage interior walls and more preferably all exterior cage surfaces are coated with a material (eg, a microporous pure titanium layer) that promotes rapid growth of the cage 1 effected in the bone tissue.

As further in the 1a is shown, the inner edges of the at least one pyramidal recess 4 sharp-edged. But they can also be rounded or chamfered. Furthermore, from the cage side surfaces of recesses or holes 10 attached, which either serve as Einriffsmöglichkeit for a not shown implantation instrument and / or but form additional openings for vascular supply.

The 1b shows a Cage variant with a to 1a different form of return, with all other features remaining the same. In this case, the at least one return 4 not pyramiden- but partially circular (preferably a concave semicircle) is formed. This trough thus has the same advantages as the Rücksprungsvariante according to the 1a , but is even easier to manufacture and thus more cost effective. At the cage 1 according to the 1b are the lateral recesses 10 However, executed exclusively as blind holes and thus have only the task of coming into operative engagement with the implantation instrument.

Finally, the shows 1c a cone shape as a third variant for the at least one return 4 , where all other features identical to the variant according to the 1a are. In this case, the cone shape has a peak in a center portion of the cage 1 , But it is also possible, a truncated cone comparable to the truncated pyramid according to the 1a train. Furthermore, here are the lateral recesses 10 as blind holes according to the 1b executed - so have only the function to serve as an attack option for the implantation instrument.

As already discussed, the cage according to the invention can 1 also with at least one opening 2 be formed, which are the two bearing surfaces 6 . 8th connects, thus creating a continuous cage interior.

In the 2a this is at least one opening 2 represented as two pointed truncated pyramidal stumps in a central portion of the cage 1 the narrowest point of the opening 2 define. In this case, the pyramidal surfaces are in the planes of the bearing surfaces 6 . 8th the biggest. Such a breakthrough shape causes the cage filler material filled therein to support the cage 1 compressed at a vortex. At the same time, the contact surface with the vortex (based on the volume of the filling material) is as large as possible and thus ensures the perfusion of the filling material. This circulation can still through the lateral recesses 10 be improved, at least some of them into the opening 2 pass.

Alternatively to the in 2a illustrated pyramid shape, the opening 2 also consist of two tapered cones or funnels, as in the 2 B is shown. Again, it is possible the lateral recesses 10 into the at least one opening 2 to lengthen and thereby improve the circulation / supply of the stuffed material.

It should be noted at this point that the inclination of the aperture inner walls can be basically arbitrary. In principle, even at a low inclination, a positive effect on the perfusion of the cage filling material is achieved without the cage 1 even excessively weakened. However, it has been shown that an angle of inclination of the aperture inner walls of 15 ° to 60 ° with respect to the aperture central axis is particularly favorable, since in this case the inner walls can be coated comparatively easily (continuously) from the outside. In addition, the compromise between Cage weakening and healing rate proves to be favorable in this dimensioning.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102005027283 A1 [0010]
• EP 1504732 A1 [0011]
• US 20050192669 A1 [0011]
• EP 880950 A1 [0012]
• US 20040024464 A1 [0013]
• WO 2005102226 A1 [0014]

Claims (14)

Vertebral cage type implant having at least one aperture ( 2 ) or at least one return ( 4 ) in each implant height direction, characterized in that the / at least one opening / recess ( 2 . 4 ) has a longitudinally inhomogeneous cross-section. Implant according to claim 1, characterized by two contact surfaces spaced apart in the implant height direction ( 6 . 8th ) for a support engagement with two vertebrae of a spinal column, wherein the cross-section of the at least one perforation / recess ( 2 . 4 ) in the plane of the contact surfaces ( 6 . 8th ) is larger than in another longitudinal section plane of the implant ( 1 ). Implant according to claim 2, characterized in that the cross-section of the / the at least one opening / recess ( 2 . 4 ) of at least one of the contact surfaces ( 6 . 8th ) of the implant ( 1 ) decreases from an implant center section seen in the height direction. Implant according to claim 3, characterized in that the decrease of the cross section is achieved continuously linearly or exponentially, stepwise or by one / more inclined adjoining surfaces. Implant according to one of claims 2 to 4, characterized in that the inclination of the cross-sectional decrease determining surfaces between 15 and 60 ° relative to the central axis of the / of the opening / return ( 2 . 4 ) is. Implant according to one of the preceding claims, characterized in that the opening (s) ( 2 . 4 ) in the transverse section appears circular, rectangular, triangular or oval. Implant according to one of the preceding claims, characterized in that it consists of a metallic material, in particular titanium or a titanium alloy or a resorbable or non-resorbable plastic preferably PEEK. Implant according to one of the preceding claims 2 to 7, characterized in that the inner surfaces of the / at least one opening / recess ( 2 . 4 ) and / or the contact surfaces ( 6 . 8th ) of the implant are completely or partially coated. Implant according to one of the preceding claims 2 to 8, characterized in that the two contact surfaces ( 6 . 8th ) has a surface structure, preferably in the form of grooves, grooves or thorns, and / or is curved convexly or canted like a saddle roof. Implant according to one of the preceding claims 2 to 9, characterized in that the two bearing surfaces ( 6 . 8th ) have different surface sizes. Implant according to claim 10, characterized in that one of the contact surfaces ( 6 ) in the direction of particularly viable vortex regions in relation to the other bearing surface ( 8th ) is extended. Implant according to claim 11, characterized in that the widening support surface ( 6 ) extends beyond the vertebral body at least partially into the region of the vertebral arch. Implant according to one of the preceding claims 2 to 12, characterized by a base body which on one side the smaller of the two bearing surfaces ( 8th ) forms and on an opposite side merges into a connecting part, which by forming a one-sided in bearing surface direction of the main body projecting nose or bar the larger of the two bearing surfaces ( 6 ) trains. Implant according to one of the preceding claims, characterized in that on some or all sides of the implant recesses ( 10 ) are provided, which preferably at least partially into the / the opening ( 2 . 4 ).

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