Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1996-11-01
2000-05-09
Yu, Mickey
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
623 16, 606 61, A61F 244
Patent
active
060598298
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to an implant, especially for insertion into a intervertebral space. Such implants are primarily intended to promote bone bridges on vertebral bodies, and they are attached between the vertebral body and the spinal column after resection of a disk or intervertebral disk.
BACKGROUND ART
It is known that a damaged intervertebral disk can be removed, and that the resulting space can be filled with cortico-spongious bone.
In this method, the vertebral bodies are first stretched apart as much as possible by means of spreaders. A special technique consists in inserting wedge-shaped elements--so-called dilators--between the two vertebral bodies, so as to spread them apart step-by-step. Dilators, each with a 1 mm larger diameter, in alternation left and right, are here attached posteriorly. After the maximum possible spread has been reached, the dilators are replaced by the above-mentioned cortico-spongious bone.
This known technique has the disadvantage that the bone is difficult to handle and to bring into the proper position, corrections being nearly impossible. Another disadvantage of this technique is that a rectangular or cylindrical recess must be punched and/or milled out of the intervertebral space, so that the bone plugs can be inserted between the originally concave sides of the adjoining vertebral bodies. This is complicated and furthermore results in damage to the vertebral body.
WO89/12431 discloses an implant for the intervertebral space. This implant has the shape of a hollow cylinder and is perforated on all sides. It can be closed from the manipulation side by means of a screw cover. Bone mass which may possibly be inserted into the cylinder cavity cannot be compressed and, in addition, the small perforations--intended only for the bone to grow in--would make pressing out the bone mass impossible.
WO90/000037 discloses a square implant, perforated on all sides, for the intervertebral space. It has a screw/wedge mechanism mounted in its interior, by means of which four claws can be run out both on the top and on the bottom. So that bone mass can be filled into this implant pre-operatively, the screw/wedge mechanism first must be unmounted and then must be remounted again, which would be very complicated. But even in such a case, the bone mass could not exit from the implant because, on the one hand, the existing, relatively large slits would be closed by the run-out claws and, on the other hand, the small perforations are unsuited for this.
PCT/CH94/00184 to BECKERS describes an implant whose specific shape and mode of insertion makes possibly an extremely stable clamping between the vertebral bodies, without thereby damaging the surface of the bony cover plate of the vertebral bodies.
The starting point of this implant is a certain shape of the cover plates which belong to the two adjoining vertebra and which bound the intervertebral space. However, in reality the geometry of the cover plate varies from patient to patient. As a result, the contact between th e bone material pt into the implant and the cover plates is not always optimal. Depending on circumstances, this can delay bone healing. The invention provides a remedy for this.
SUMMARY OF THE INVENTION
It is the object of the invention to provide an implant for the intervertebral space, such that the bone mass introduced therein--after implantation--can be compressed and can be pressed out against the treated cover plates of the adjoining vertebra, whose cartilage has been re moved. In this way, the cavity resulting from an anatomical mismatch is filled up with bone mass.
The invention achieves its set objective by means of ar implant which has the features a frame which is closed at the side but is open without restriction on the top and bottom, and which has an anterior lead-in face and a posterior manipulation face, with upper and lower boundaries of the frame being convex in shape, so that the implant has a overall lens shape. The inner cavity of the implant is open without restriction on the
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Hess Martin
Schlapfer Fridolin
Nguyen Tram A.
Synthese
Yu Mickey
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