DE102012220808A1 - Facet joint prosthesis - Google Patents

Abstract

The invention relates to a facet joint prosthesis for vertebrae of a spine, with - a first joint body, which comprises a fastening means for non-positive and / or positive connection with a first vertebra, - a second joint body, which has a fastening means for non-positive and / or positive connection with a second vertebra adjacent to the first vertebra, and a connecting arrangement coupling the first joint body to the second joint body along a parting plane. It is provided that - the connection arrangement comprises a first connection element connected to the first joint body, - the connection arrangement comprises a second connection element connected to the second joint body, - the connection elements have corresponding sliding surfaces that can be brought into contact along a parting plane, and - the connection elements over at least an elastic element are coupled together.

Description

The invention relates to a facet joint prosthesis for vertebrae of a spinal column.

Two adjacent vertebrae of a spinal column are connected to one another via an intervertebral disc arranged between the two vertebral bodies. This articulation allows complex movement of the two vertebrae with respect to one another, which comprises a rotational movement about a longitudinal axis of the vertebrae, an inclination movement about different axes, which are arranged approximately in a transverse plane (flexion), and a sliding movement in an approximately transversal plane (extension) , In order to carry out these multifarious movements, additional facet joints are formed on the articular processes of the vertebrae which protrude from the vertebral arch. These are also called vertebral arch joints. The facet joints form a joint between a downward pointing articular process (processus articularis inferior) of the upper vertebra and an upwardly pointing articular process (processus articularis superior) of a lower vertebra. In an intact spine, two of these facet joints are always formed in pairs and approximately mirror-symmetrical to a sagittal mid-plane of the spine.

Facet joint prostheses for vertebrae of a spinal column are known.

So shows, for example DE 10 2007 038 996 A1 a facet joint prosthesis for two vertebrae of a spinal column having a first joint body having a fastener for fixed connection to an upper vertebra and a convex first articular surface and a second joint body having a fastener for fixed connection to a lower vertebra and a concave second articular surface for guiding the first joint surface. The facet joint prosthesis comprises two first joint bodies and two second joint bodies, which are each arranged in pairs, wherein the first joint body and the second joint body are each firmly connected to one another via a transverse connection. This facet joint prosthesis has a complicated structure and allows only a bilateral application, so that an implantation of this facet joint prosthesis requires a relatively complicated surgical procedure.

Other bilateral implantable facet joint prostheses are also made, for example US 8,034,078 B2 . US 2010/0312283 A1 or WO 2010/065277 A1 known.

The invention has for its object to provide a facet joint prosthesis of the generic type, which is characterized by a simple structure, easy to apply and auditable and largely simulates the behavior of the natural facet joint.

According to the invention this object is achieved by a facet joint prosthesis for vertebrae of a spinal column with the features mentioned in claim 1. Characterized in that the facet joint prosthesis comprises a first joint body, which comprises a fastening means for positive and / or positive connection with a first vertebra, a second joint body, which comprises a fastening means for non-positive and / or positive connection with a second vortex adjacent to the first vertebra, and a connection arrangement coupling the first joint body with the second joint body along a parting plane, the connection arrangement comprising a first connection element connected to the first joint body and a second connection element connected to the second joint body, the connection elements having corresponding sliding surfaces which can be brought into contact along a parting plane and the connecting elements are coupled to each other via at least one elastic element, it is advantageously possible to provide a simply constructed facet joint prosthesis, which is characterized by its modular Au fbau is variably applicable and the behavior of a natural facet joint including joint capsule largely replicates. In particular, it is possible to apply the facet joint prosthesis only unilaterally, so that only a minimal invasive intervention is required.

The facet joint prosthesis according to the invention makes it possible, as in the case of the known bilateral facet joint prostheses, in particular to limit the rotation of a vertebra of the spinal column, without substantially limiting the other directions of movement.

In a preferred embodiment of the invention, it is provided that the corresponding sliding surfaces of the connecting elements extend vertically. Due to the dividing plane defined here, the flexion and extension can take place almost unhindered. The elastic element coupling the connecting elements leads only to a small resistance to the flexion and extension. In a further preferred embodiment of the invention it is provided that the sliding surfaces are formed on overlapping portions of the connecting elements. In this way, it is advantageously possible to form the connection arrangement in a simple, in particular also easy to apply design. The overlapping portions of the connecting elements thus define the parting plane of the facet joint prosthesis. Characterized in that the sliding surfaces of the overlapping portions of the connecting elements are formed, the natural facet joint can be replicated in a particularly simple manner.

In addition, in a preferred embodiment of the invention, it is provided that the at least one elastic element is arranged in the region of the overlapping sections of the connecting elements, wherein preferably the overlapping sections have a guide groove for the at least one elastic element. This advantageously makes it possible to simulate the joint capsule of a natural facet joint in a simple manner. The overlapping portions of the connecting elements form the joint body, while the elastic element forms the joint capsule. As a result, according to the elasticity of the elastic element, a flexion and an extension possible and limited by the blocking of the connecting elements axial rotation. The guide groove for receiving the at least one elastic element ensures a safe, not during the proper use of the facet joint prosthesis changing arrangement of the elastic element.

In a further preferred embodiment of the invention, it is provided that the at least one elastic element is an elastic ring, whose inner diameter is less than idle at rest than an outer diameter of the guide groove. This advantageously ensures that a particularly secure fit of the elastic element is achieved. The positioning of the elastic element is effected by an elastic widening, wherein subsequently a self-aligning arrangement of the elastic element takes place in the guide groove.

In addition, it is provided in a further preferred embodiment of the invention that between the sliding surfaces of the connecting elements at least one damping element is arranged, which is preferably formed by an elastic intermediate layer. In this way, it is advantageously achieved that, in addition to the elastic element, a damping of the axial rotation of the joint prosthesis can be achieved, wherein the axial rotation of the facet joint prosthesis can be influenced depending on a thickness of the at least one damping element and a modulus of elasticity of the damping element. Thus, a further adaptation to the behavior of a natural facet joint is achieved.

In a further preferred embodiment of the invention it is provided that the sliding surfaces merge into a vertical movement of the connecting elements to each other limiting stop surfaces. This advantageously achieves that an extension limitation of the facet joint prosthesis can be achieved. Depending on the design of the abutment surfaces, a different, almost any extension limitation can be fixed here in a simple manner.

Furthermore, it is provided in a preferred embodiment of the invention that the sliding surfaces in the stop surfaces at an angle ≥ 90 °, in particular between 110 ° and 150 °, preferably between 130 ° and 140 °. By means of this embodiment, it is advantageously achieved that a transition between the sliding surfaces and the stop surfaces is individually adjustable, so that in addition a buffer function is created between the connecting elements, which allows a soft extension stop. This means that the extension limitation does not occur abruptly under a corresponding load but is dampened.

In addition, it is provided in a preferred embodiment of the invention that a resilience of the facet joint prosthesis is adjustable via an elasticity of the at least one elastic element. This advantageously makes it possible, by selecting different elastic elements with different modulus of elasticity, to adjust the movement limitations of the facet joint prosthesis, in particular flexion and extension, differently depending on the medical necessity. This results in extensive application possibilities of the facet joint prosthesis.

In addition, it is provided in a preferred embodiment of the invention that the fastening means are multi-axial pedicle screws. This advantageously makes it possible to securely connect the facet joint prosthesis to the vertebrae of the spine by means of per se known pedicle screws in a force-locking and / or positive-locking manner, without relaxation being expected during the intended use of the prosthesis.

Overall, it can be stated that the facet joint prosthesis according to the invention provides a modular, unilateral or bilateral, lumbar posterior, facet joint prosthesis. The modular design allows by appropriate selection of the available modules an adaptation in a simple manner to an actually required medical indication. The facet joint prosthesis is of small construction and can therefore be applied minimally invasively. Despite this small modular design, the behavior of a natural facet joint including joint capsule is largely reproducible.

The object is further achieved by a facet joint prosthesis for vertebrae of a spinal column with the features mentioned in claim 13. The fact that the facet joint prosthesis a joint body, which is a fastening means for non-positive and / or positive connection with a first vertebra of a spinal column, and having a connecting element connected to the joint body, wherein the connecting element and a second vortex adjacent second vortex along a parting plane in contact engageable sliding surfaces and the connecting element and the second vortex via at least one elastic element are coupled together , It is advantageously possible to provide a facet joint prosthesis which has only one joint body which together with a natural articular process of an adjacent vertebra forms the facet joint prosthesis. In this way, an undamaged joint extension can be obtained with only partially damaged facet joint and this can be coupled with a connected to the adjacent vertebra prosthesis. Required for this is in the undamaged joint extension on or bring a sliding surface, which is coupled to the sliding surface of the connecting element of the artificial joint body of the facet joint prosthesis.

The invention will be explained in more detail in exemplary embodiments and the accompanying drawings. Show it:

1 a schematic perspective view of vertebrae of a spine with a facet joint prosthesis;

2 a schematic exploded view of the facet joint prosthesis; and

3a - 3c different views of connecting elements of the facet joint prosthesis.

1 shows a total with 10 designated facet joint prosthesis between two adjacent vertebrae 12 and 14 a spine is implanted. The facet joint prosthesis 10 is unilateral in the area of a facet joint 16 implanted in the spine. The natural facet joint 16 includes a downwardly pointing articular appendage 18 of the upper vertebra 12 and an upwardly pointing articular process 20 of the lower vertebra 14 ,

The structure and function of the facet joint prosthesis 10 will be clarified with reference to the following figures.

So shows 2 an exploded perspective view of the facet joint prosthesis 10 , The facet joint prosthesis 10 comprises a first joint body 22 and a second joint body 24 , The joint body 22 . 24 are in each case via fastening means force and / or form-fitting with the vortex 12 respectively. 14 connected. The fasteners 26 For example, are formed by known per se multiaxial pedicle screws, which in corresponding previously created screw channels in the vertebrae 12 respectively. 14 positively and cohesively with bone cement can be introduced. The joint body 22 respectively. 24 and the fasteners 26 can also be designed together as a pedicle screw.

The facet joint prosthesis 10 comprises a connection arrangement 28 coming from a first connecting element 30 and a second connecting element 32 is formed. The connecting element 30 is with the joint body 22 and the connecting element 32 with the joint body 24 connected. This connection can be made with screw connections, clamp connections or other suitable connections not shown here in detail.

The connection arrangement 28 further comprises an elastic element 36 ,

An implantation of the facet joint prosthesis 10 takes place in the following way:
First, the joint body 22 respectively. 24 with the fastener 26 on the vertebrae 12 respectively. 14 attached. Because the fasteners 26 formed by multiaxial pedicle screws here is an alignment of the joint body 22 and 24 possible in the degrees of freedom prescribed by the pedicle screws. This makes it possible to different configurations of the vortex 12 respectively. 14 Be considered.

The orientation of the joint body 22 respectively. 24 done so that in the joint bodies 22 . 24 trained grooves 38 respectively. 40 aligned with each other.

The connecting elements 32 and 34 be with their sliding surfaces (explanations on this in the 3a to 3c ). The elastic element 36 is then via the contacted fasteners 30 and 32 striped so that the fasteners 30 and 32 are permanently coupled with each other. The assembly of the elastic element can also be done so that it is first touched from the Gleitflächenseite only via a connecting element (into the groove). As a result, it hardly needs to be stretched at all or not at all. Then push the second connecting element with the sliding surfaces in contact with the first connecting element, so that the elastic ring has to expand slightly and slips into the groove of the second connecting element. This assembly also allows for stiff rings and does not damage the rings by overstretching.

The elastic element 36 is formed by an elastic ring whose inner diameter is not equal to the unassembled state as an outer diameter of a guide groove of the connecting elements 30 and 32 , This results a firm defined seat of the elastic element 36 around the connecting element 30 respectively. 32 ,

The interconnected fasteners 30 and 32 are then in the grooves 38 respectively. 40 the joint body 22 and 24 introduced and fixed there, so that in 1 schematically shown arrangement is achieved.

Both the joint body 22 and 24 as well as the fasteners 30 and 32 and the elastic element 36 thus form individual modules of the facet joint prosthesis 10 , Depending on the actual medical indication, the facet joint prosthesis can thus be used 10 be adapted by selecting appropriate modules. This applies in particular to the elastic element 36 too, which can be provided with different moduli of elasticity. According to the selected elastic element 36 With a certain modulus of elasticity, it is thus above all the flexion, extension and, to a lesser extent, the rotation of the facet joint prosthesis 10 be set.

Based on the following 3a to 3c become the fasteners 30 and 32 explained in more detail. 3a shows a perspective view of the connecting elements 30 and 32 , The connecting elements 30 and 32 form a dividing plane 42 out, with each of the fasteners 30 and 32 in the area of the parting plane 42 a sliding surface 44 respectively. 46 has, like the side view in 3b clarified. The sliding surfaces 44 and 46 stand along an overlapping section 48 the connecting elements 30 and 32 in contact with each other.

The connecting elements 30 and 32 each have a basic body 50 respectively. 52 , In the area of the overlapping section 48 forms the basic body 50 respectively. 52 the sliding surfaces 44 respectively. 46 out. The sliding surface 44 goes over a stop surface 54 in basic body 50 and the sliding surface 46 over a stop surface 56 into the main body 52 above.

In the overlapping section 48 form the on their sliding surfaces 44 respectively. 46 adjacent fasteners 30 and 32 an annular groove 58 out. The ring groove 58 serves to accommodate the in 2 shown elastic element 36 ,

3c shows in an enlarged side view of the connecting element 30 , The connecting elements 30 and 32 are identical in their structure and mirror images of each other, in so far as the following explanations also apply to the connecting element 32 ,

It is recognizable from the main body 50 extending section 48 at which the sliding surface 44 and the ring groove 58 are formed. The sliding surface 44 goes at an angle α in the stop surface 54 above. The angle α has a size of> 90 °, in particular between 110 ° and 150 °, preferably between 130 ° and 140 °, or on the example shown by 135 °.

An end area 60 of the section 48 has a frustoconical tip 62 , wherein a conical surface 64 at an angle β to a longitudinal axis 66 of the connecting element 30 runs. The longitudinal axis 66 coincides with the dividing plane 42 ( 3a ) together. The angle β is a complementary angle to the angle α, that is, the sum of the angles α and β is 180 °.

As 3c clarifies, the sliding surface extends 44 between a starting point 68 and an endpoint 70 , In the endpoint 70 goes the sliding surface 44 in the stop area 54 above. In the starting point 68 goes the sliding surface 44 in the conical surface 64 above.

Based on 3b it becomes clear that between the starting point 68 of the connecting element 30 and the endpoint 70 of the connecting element 32 a distance a remains. This distance a thus defines the distance of the conical surface 64 from the stop surface 54 , By coupling the connecting elements 30 and 32 by means of the elastic element 36 is a relative displaceability of the connecting elements 30 and 32 along the dividing plane 42 possible. This displacement causes an approximation of the conical surface 64 of a connecting element 30 respectively. 32 to the stop surface 54 respectively. 56 of the other connecting element 30 respectively. 32 , The maximum displacement is specified by the distance a. This distance a thus limits the extension of the facet joint prosthesis 10 represents.

Because of the transition between the sliding surface 44 and the stop surface 54 is done over the angle α is not a hard stop the two fasteners 30 and 32 possible against each other. According to the elasticity of the elastic element 36 is a slight slipping of the frusto-conical tip 62 on the stop surface 54 respectively. 56 possible. It is thus possible a muted Exionsionslimitierung.

On the sliding surface 44 of the connecting element 30 and / or on the sliding surface 46 of the connecting element 32 can at least one damping element 72 be arranged. This at least one damping element 72 leads to an increase in the friction effect between the over the elastic element 36 coupled fasteners 30 and 32 , In this way, according to the choice of material of at least one damping element 72 the extension, flexion and rotation (torsion) of the facet joint prosthesis 10 to be influenced.

The at least one damping element 72 also leads to a reduction of wear of the superimposed sliding surfaces 44 and 46 the connecting elements 30 and 32 , As materials for the fasteners 30 and 32 Titanium or cobalt-chromium alloys, for example, are suitable. As material for the elastic element 36 and the at least one damping element 72 are elastic polymers, such as silicone.

In summary, it can be stated that by means of the facet joint prosthesis according to the invention 10 after a sufficient decompression of an intervertebral disc and, if appropriate, complete resection of a facet joint, an implant is provided that dynamically stabilizes the vertebrae 12 and 14 allows for simultaneous segmental mobility. Unilateral dynamic fixation is possible after unilateral facet joint resection and preservation of the contralateral facet joint.

By means of the facet joint according to the invention 10 can by selecting the dimensioning and the choice of material of the fasteners 30 and 32 and the elastic element 36 of the at least one damping element 72 Flexion, extension and lateral tilt of about 80% of normal physiological range of motion and axial rotation of 85-97% of normal rotation can be achieved.

The band stiffness of the elastic element has a major influence on this 36 , which may for example be between 20 and 50 MPa (megapascals). The facet joint prosthesis according to the invention 10 represents an implant that can be used unilaterally to obtain a facet joint, or bilaterally with an intact disc or artificial disc, resulting in nearly physiological range of motion and physiological loading of the remaining spinal structures.

LIST OF REFERENCE NUMBERS

10

 Facet joint prosthesis

12

 whirl

14

 whirl

16

 facet joint

18

 Articular process

20

 Articular process

22

 joint body

24

 joint body

26

 fastener

28

 joint assembly

30

 connecting element

32

 connecting element

34

 connecting element

36

 elastic element

38

 groove

40

 groove

42

 parting plane

44

 sliding surface

46

 sliding surface

48

 overlapping section

50

 body

52

 body

54

 stop surface

56

 stop surface

58

 ring groove

60

 end

62

 frustoconical tip

64

 Conical surface

66

 longitudinal axis

68

 starting point

70

 endpoint

72

 damping element

a

 distance

α

 angle

β

 angle

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 102007038996 A1 [0004]
• US8034078 B2 [0005]
• US 2010/0312283 A1 [0005]
• WO 2010/065277 A1 [0005]

Claims (13)

Facet joint prosthesis for vertebrae of a spinal column, comprising - a first joint body, which comprises a fastening means for frictional and / or positive connection with a first vertebra, - a second joint body, which has a fastening means for non-positive and / or positive connection with one to the first Vertebra adjacent second vertebra comprises, as well as - a first joint body with the second joint body along a parting plane to each other coupling connection arrangement, characterized in that - the connection arrangement comprises a first joint body connected to the first connecting element, - the connection arrangement connected to the second joint body second Connecting element comprises, - have the connecting elements corresponding along a parting plane engageable sliding surfaces, and - the connecting elements are coupled together via at least one elastic element. Facet joint prosthesis according to claim 1, characterized in that the sliding surfaces extend vertically. Facet joint prosthesis according to one of the preceding claims, characterized in that the sliding surfaces are formed on overlapping portions of the connecting elements. Facet joint prosthesis according to one of the preceding claims, characterized in that the at least one elastic element is arranged in the region of the overlapping portions. Facet joint prosthesis according to one of the preceding claims, characterized in that the overlapping portions have a guide groove for the at least one elastic element. Facet joint prosthesis according to one of the preceding claims, characterized in that the at least one elastic element is an elastic ring, the inner diameter of which is at rest equal to less than an outer diameter of the guide groove. Facet joint prosthesis according to one of the preceding claims, characterized in that at least one damping element is arranged between the sliding surfaces. Facet joint prosthesis according to one of the preceding claims, characterized in that the damping element is an elastic intermediate layer. Facet joint prosthesis according to one of the preceding claims, characterized in that the sliding surfaces merge in a vertical movement of the connecting elements to each other in limiting stop surfaces. Facet joint prosthesis according to one of the preceding claims, characterized in that the sliding surfaces in the stop surfaces at an angle> 90 °, in particular between 110 ° and 150 °, preferably between 130 ° and 140 °, merge. Facet joint prosthesis according to one of the preceding claims, characterized in that a resilience of the facet joint prosthesis is adjustable via an elasticity of the at least one elastic element. Facet joint prosthesis according to one of the preceding claims, characterized in that the fastening means are multi-axial pedicle screws. Facet joint prosthesis for vertebrae of a spine, with A joint body comprising a fastening means for non-positive and / or positive connection to a first vertebra, - A connected to the joint body connecting element, wherein The connecting element and a second vortex adjacent to the first vortex have contact surfaces which can be brought into contact along a dividing plane, - The connecting element and the second vortex are coupled together via at least one elastic element.

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