Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2000-03-31
2001-10-23
Reip, David O. (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
C606S071000
Reexamination Certificate
active
06306136
ABSTRACT:
The present invention relates generally to fixation systems for osteosynthesis of the spine, and it concerns in particular a novel plate, called a cervical plate, intended to join at least two cervical vertebrae in a particular way.
The techniques of bone fusion at the cervical level are well known and are at present practised in indications such as degenerative spine, herniated discs or, more generally, various cases of traumatology or tumours.
These techniques are based on the principle of ablation of a disc, either single or multiple, possibly combined with ablation of a vertebral body, also single or multiple.
The spaces left free by such ablations are generally filled with bone grafts which have been cut to the desired dimensions.
In this connection it is known that, in order to obtain bone fusion using a graft, it is necessary for the latter to be subjected to compressive stresses. This compression is generally obtained by a slight overdimensioning of the graft, combined with surgical distraction between the adjacent cervical bone structures.
The document U.S. Pat. No. 5,616,142 already discloses an implant having a solid plate consisting of two sliding parts, each of which has holes for anchoring screws in two adjacent vertebrae.
With this solid plate it is possible to hold in place the materials which have been introduced between the two vertebrae, such as blocks of hydroxyapatite, bone grafts or even bone substitutes.
Moreover, the ability of the two parts to slide relative to one another makes it possible to adapt easily to different spacings between vertebrae.
However, this known plate has the disadvantage that there is a risk of play between the two parts, and this play can encourage accidental loosening of the screws.
In addition, this possibility of sliding renders the implant incapable of maintaining a desired spacing between the two vertebrae in the longitudinal direction of the spine, so that the initial compression of the bone graft can be adversely affected, with, as a consequence, poor quality or speed of fusion, or even completely defective fusion.
The present invention aims to overcome these disadvantages of the prior art and to make available an implant which can be used particularly as an anterior cervical plate, which is substantially simpler to fit and in which it is possible to use a plate made up of two sliding elements in order to establish and maintain a compression of bone grafts which have been introduced between two vertebrae on which the implant is to be anchored.
Thus, the present invention proposes an implant for osteosynthesis of the spine, comprising a plate intended to be fixed to two vertebrae, such as cervical vertebrae, with the aid of bone fixation screws, in particular by an anterior approach, characterized in that the plate comprises two elements, each including at least one hole for a bone fixation screw, each of the elements being able to slide relative to the other in a direction corresponding to a closing together or distancing of the vertebrae relative to one another, and the said elements being provided with means for limiting the course of the mutual sliding between them and for blocking the said elements in a given mutual position.
Preferred, but non-limiting, features of the implant according to the invention are the following:
The two elements are arranged head to foot.
The two elements are identical.
Each element includes a first end part including the hole or holes for bone fixation screws, and a second end part having an oblong opening whose main axis defines the direction of sliding, the said opening being traversed by a projecting element integral with an intermediate part of the other element.
Each projecting element consists of a screw constituting one of the said blocking means.
The said intermediate part of each element is situated in the extension and continuation of the said first end part.
The said second end part of each element is situated offset in height relative to the said first end part and to the said intermediate part in such a way as to cover the intermediate part of the other element.
Each element additionally comprises a narrower joining part between its intermediate part and its second end part.
The said joining parts of the two elements each delimit part of a through-passage of the plate.
The said through-passage is oblong and has at its base a peripheral shoulder.
The said shoulder is bevelled.
The implant additionally comprises at least one auxiliary anchoring screw engaged in the said through-passage.
The joining part of each element defines at least one shoulder able to cooperate with the second end part or with the intermediate part of the other element, in such a way as to define a limit stop for the sliding of the two elements.
Each bone fixation screw includes an intermediate thread intended to cooperate with a corresponding thread provided in the hole for the associated screw.
Each bone fixation screw includes a head of generally frustoconical contour and provided with a plurality of branches which are separated by interstices of generally axial orientation, the conicity of the head being able to block the screw against rotation by means of the friction of the said head in the associated hole.
The said head has a groove able to cooperate with an inwardly projecting part formed in the associated hole for producing axial blocking.
At least some of the holes for bone fixation screws have an axis not perpendicular to a general plane of the plate.
The invention also proposes a set of implants, characterized in that it comprises a plurality of implants, such as have been defined above, with plate elements which have different numbers of holes for bone fixation screws and different orientations of holes for screws, and a plurality of bone fixation screws, and in that the different plate elements are visibly differentiated.
REFERENCES:
patent: 2443363 (1948-06-01), Townsend et al.
patent: 3900025 (1975-08-01), Barnes, Jr.
patent: 4289123 (1981-09-01), Dunn
patent: 5607428 (1997-03-01), Lin
patent: 5616142 (1997-04-01), Yuan et al.
patent: 5707372 (1998-01-01), Errico et al.
patent: 41 32 021 A1 (1993-04-01), None
patent: 0 599 766 A1 (1994-06-01), None
patent: 0 705 572 A2 (1996-04-01), None
patent: 2 728 454 (1996-06-01), None
DIMSO (Distribution Medicales du Sud-Ouest)
Lerner David Littenberg Krumholz & Mentlik LLP
Reip David O.
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