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Prosthetic intervertebral disk

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Prosthetic intervertebral disk


An intervertebral disk prostheses for the total replacement of an intervertebral disk of the lumbar and cervical spine has an upper plate having upwardly projecting formations anchoring it to an upper vertebra on its upper face and a concavity on its inner face surrounded by an edge. A lower plate is provided with downwardly projecting formations anchoring it to a lower vertebra on its lower face and a flat inner face surrounding a groove extending front-to-back. A middle plate between the upper and lower plate has on its upper face a convexity that is identically or differently shaped to the concavity on the inner face of the upper plate and a ridge extending front-to-back surrounded by a flat lower face of the middle plate. The ridge has flanks and the groove houses the ridge of the middle plate and permits the ridge to slide front-to-back in the groove.
Related Terms: Intervertebral Disk Prostheses

USPTO Applicaton #: #20120296429 - Class: 623 1716 (USPTO) - 11/22/12 - Class 623 
Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor > Implantable Prosthesis >Bone >Spine Bone >Including Spinal Disc Spacer Between Adjacent Spine Bones

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The Patent Description & Claims data below is from USPTO Patent Application 20120296429, Prosthetic intervertebral disk.

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CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority of German patent application 10 2011 050 453 filed 18 May 2011 and is a replacement of U.S. provisional application 61/507,498 filed 13 Jul. 2011.

FIELD OF THE INVENTION

The present invention relates to an intervertebral disk prosthesis. More particularly this invention relates to a three-part intervertebral disk prosthesis for the total replacement of an intervertebral disk of the cervical and lumbar spine.

BACKGROUND OF THE INVENTION

An intervertebral disk prosthesis has at least a lower plate and an upper plate having anchor formations on their sides facing toward the adjacent vertebral bodies in case of a two-part prosthesis. A three-part-prosthesis comprises further an intermediate or middle plate. Neighboring plates articulate via their surfaces that get in contact. Thus, the parts of an intervertebral disk prosthesis are also designated as sliding partners, wherein the intermediate sliding partner arranged between upper and lower sliding partner represents an intermediate sliding plate.

The US 2009/0082867 A1 of Bueno et al discloses a prosthesis with basically 3 articulating sliding partners, in which the intermediate sliding partner has no function for keeping the central distance between the upper and lower plate. Upper and lower sliding partner have both spherical convex inner surfaces, which are identical with the exception that the upper convexity has a hole housing a pivot of the lower sliding partner, wherein the pivot ends in a sphere. An intermediate partner having a central opening is arranged between the inner surfaces of upper and lower sliding partner. The surfaces of the intermediate partner facing the inner surfaces of upper and lower sliding partner are concave-shaped. The clearance between central opening of the intermediate partner and the pivot of the lower sliding partner may be dimensioned with one value for the anterior-posterior direction of the vertebral segment and another value for the lateral direction of the vertebral segment. A prosthesis according to US 2009/0082867 A1 has no means for limiting rotation around the vertical body axis and comprises only curved articulation surfaces. Further the pivot in the hole is directly limiting the range of extension and flexion as well as the range of lateral bending to both sides.

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to is provide a functional total intervertebral disk prosthesis, providing the possibility to adjust physiological motion in anterior-posterior and both lateral directions as well as rotation around the vertical body axis in a first sliding area and front-to-back translation in a second sliding area, wherein a slip out of an intermediate sliding plate is prevented.

SUMMARY

OF THE INVENTION

The present disclosure provides an intervertebral disk prosthesis for the total replacement of an intervertebral disk of the cervical or lumbar spine, comprising an upper plate having upwardly projecting formations anchoring it to an upper vertebra on its upper surface and a concavity on its lower inner surface surrounded by an edge, a lower plate provided with downwardly projecting formations anchoring it to a lower vertebra on its lower surface and a flat upper inner surface surrounding a guide groove extending front-to-back with a first body stop on the back and/or a second body stop on the front, an intermediate sliding plate arranged between the upper and lower plate having on its upper surface a convexity, which is equally or different shaped to the concavity on the lower inner surface of the upper plate, and a guide ridge having flanks on its flat lower surface, extending front-to-back, wherein the guide groove of the lower plate houses the guide ridge of the intermediate sliding plate permitting the guide ridge to slide front-to-back within the guide groove as straight-line motion, while in the sliding area of the convexity of the intermediate sliding plate and of the concavity of the upper plate limited extension, flexion, lateral bending to right and left side, and axial rotation to both sides takes place.

It is an advantage of a total disk prosthesis according to the present disclosure that the guide ridge cannot be released from the guide groove, preventing a slip-out of the intermediate sliding plate, so-called luxation, without using an instrument. The guide ridge surface will be pressed against the flank is surfaces of the guide groove and the guide ridge is thus retained in the guide groove. The movable link between the flat upper inner surface of the lower plate and the flat lower surface of the intermediate sliding plate enables a limited straight-line movement of the intermediate sliding plate in the dorso-ventral direction limited by the first body stop and/or by the second body stop to mimic sagittal straight-line motion. In context of the description of this invention and in the claims the term ‘sagittal view’ will be used as a by-word for ‘side view’. Each of them can be used synonymic. The sagittal view is the left or the right side view of the spine, the vertebrae and the total disk prosthesis.

In order to provide a defined straight-line motion or straight-line guidance, it is useful if a dovetail guide having a V-formation or a T-section formation is provided between the guide ridge and the guide groove. The V-formation or the T-section formation are preferably built upside down within the lower plate. Basically the end of the guide ridge has a larger dimension than its stem, which is directly connected to the flat lower surface of the intermediate sliding plate, to prevent a slip out of the guide ridge out of the guide groove.

It is an advantage that a combined motion of the sliding partners is possible resulting from the limited straight-line movement of the lower surface of the intermediate sliding plate and the upper inner surface of the lower plate constituting the straight-line sliding motion in dorso-ventral direction, and the limited articulation between the convexity of the upper surface of the intermediate sliding plate and the concavity of the lower inner surface of the upper plate. Thus, the range of motion along the three body axes can be adjusted to the situation of the respective intervertebral space, including as coupled motion. In other words, consequently its motion results in a superposition of a linear translational sliding motion in the dorso-ventral direction, and of an inclination provided by the convexity in connection with the corresponding concavity resulting in flexion, in extension, in lateral bending, and in axial soft limited rotation.

It is an advantage if the guide ridge is formed integrally with the intermediate sliding plate or is connected to the intermediate sliding plate as a separate part. When the guide ridge is formed as a separate part, this provides the possibility of producing the guide ridge from the same or a different material as the intermediate sliding plate. Like the intermediate sliding plate, the guide ridge can then be made of a material that exhibits a low friction contact with the material of the lower plate. The guide ridge can be connected to the intermediate sliding plate in a conventional manner, for example by a snap closure or a screwed connection. In case, the guide ridge is formed integrally with the intermediate sliding plate, both components can be produced in a single production step and the guide ridge becomes an inherent part of the intermediate sliding plate.

It is also possible to use the upper plate as a lower plate and the corresponding lower plate as an upper plate, so that the articulating parts of the disk prosthesis are configured “upside down”. It is further intended that parts of the prosthesis are made of different material or even the same material with different properties.

A further embodiment is characterized in that the guide groove is embodied within the intermediate sliding plate and the guide ridge is assigned to the lower plate. Or the guide ridge is assigned to the upper plate, in case that the upper plate has a flat lower inner surface and the intermediate sliding plate has an upper flat surface with a guide groove, and a concavity is on the upper inner surface of the lower plate articulating with the convexity of the lower surface of the intermediate sliding plate. Here, too, the material selection of the individual components can lead to defined sliding properties of the intervertebral disk prosthesis.

It has proven to be particularly favorable if in sagittal view the intermediate sliding plate and/or the upper plate and/or the lower plate is angled. The tilt angle of the upper plate with respect to the lower plate can be restricted in a manner as elucidated hereafter. In case the upper plate is angled, it is favorable, that the concavity of the upper plate surrounds the corresponding convexity of the intermediate sliding plate in a larger range. This leads to a better stability of the prosthesis in the area of free motion between the concavity and the convexity. Further it is possible to choose predetermined angles in sagittal view for the plates to prevent a segmental kyphosis. It is also possible to provide a stop or counterstop on the surface of the intermediate sliding plate for interaction with a counterstop or stop embodied on the inner surface of the upper plate.

In order to recreate the motion of a functional intervertebral disk as precisely as possible, it has proven to be favorable for the intermediate sliding plate to have a convexity and the upper plate or the lower plate to have a corresponding concavity each with a design of sliding surfaces for having physiological range of motion in extension, flexion, lateral bending to right and left as well as in axial rotation to right and left.

It has also proven to be favorable, that the intervertebral disk prosthesis comprises a plurality of guide grooves and a corresponding plurality of guide ridges. This increases the stability of the prosthesis, which is especially needed for prostheses inserted between lumbar vertebrae. Moreover, an even stronger bond between the guide ridge and the guide groove is produced and thus an even better guided motion of the intermediate sliding plate is provided.

In order for it to be possible to adapt optimally to the conditions of the position chosen in the spine, it has proven to be useful for the convexity and the concavity to be offset in the dorsal direction, resulting in the displacement of the center of rotation in dorsal direction.

It is particularly favorable if the intermediate sliding plate is replaceable. This provides the option of revision for insertion of a different intermediate sliding plate. If the guide ridge is thereby detachably connected to the intermediate sliding plate, the replacement thereof can also be carried out after insertion of the guide ridge into the guide groove. In case the guide ridge is non-detachably connected to the intermediate sliding plate, for the removal of the intermediate sliding plate from the lower plate or the upper plate an instrument is needed. As precondition a slight elastic material of the intermediate sliding plate and/or a slit in the guide ridge is needed to connect the intermediate sliding plate with the lower plate or the upper plate. In this preferred embodiment the guide ridge can be deformed elastically, to build a secure connection between the guide ridge and the guide groove.

It is advantageous if the lower plate and/or the upper plate have at least one, preferably two tool guides. This makes it easier for a surgeon to insert the intervertebral disk prosthesis between the two vertebral bodies. Other well-known intervertebral disk prostheses, such as the M6-prosthesis, have to be destroyed before they can be removed. With these tool guides it is possible to remove, and if necessary to reinsert, the same intervertebral disk prosthesis without damaging or even destroying it.

Still other aspects, features, and advantages of the present invention are readily apparent from the following detailed description, simply by illustrating preferable embodiments and implementations. The present invention is also capable of other and different embodiments and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive. Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention.



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Previous Patent Application:
Prosthetic intervertebral disc implants
Next Patent Application:
Spine surgery device
Industry Class:
Prosthesis (i.e., artificial body members), parts thereof, or aids and accessories therefor
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stats Patent Info
Application #
US 20120296429 A1
Publish Date
11/22/2012
Document #
13365308
File Date
02/03/2012
USPTO Class
623 1716
Other USPTO Classes
International Class
61F2/44
Drawings
5


Intervertebral Disk
Prostheses


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