Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1998-04-20
2000-11-07
Milano, Michael J.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
606 61, A61F 244
Patent
active
061430315
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention refers to an intervertebral implant for fusion of vertebral bodies, particularly in the region of the lumbar part of the spinal column.
BACKGROUND
From the prior art there are already different types of such intervertebral implants known though which show the following disadvantages: must be expanded by means of suitable instruments; and vertebras.
SUMMARY OF THE INVENTION
The present invention relates to an intervertebral implant which is insertable into the cleaned out intervertebral space in a controllable manner without an expanding instrument.
The implant according to the present invention comprises a flattened shaped hollow element with an outer surface having a flattened upper bone-contact face, a flattened lower bone-contact face, and two lateral faces. The upper and the lower bone-contact faces are elastically compressible towards the interior space of the hollow element such that the maximum distance between the upper and the lower bone-contact face is reducible by 0.5-5.0 mm.
The flattened hollow element can have the shape of a hollow cylinder, hollow truncated cone, hollow truncated pyramid or hollow truncated wedge.
Dimensions, geometry and material should be chosen such, that the maximum distance H between upper and lower bone-contact face is reducible by 0.5-5.0 mm preferably 1-3 mm.
In case of application of a force of pressure of 12 Newton on the upper and lower bone-contact faces the maximum distance H shall be reducible by 15% to 30% preferably 20% to 25%. The compressibility of the implant allows its insertion without having to apply an expanding instrument.
Therewith the advantage is reachable that a minimum expenditure of force is necessary for the implantation and a controllable insertion of the compressed implant is possible. A minimum invasive and open surgery technique is therewith applicable.
The large bearing area of the implant prevents its sinking in into the end plates.
A preferred embodiment of the invention consists therein, that in the interior space of the hollow element an engagement lip is provided which is engageable into an interlock means. In case of an engaged engagement lip the compressibility of the hollow element is neutralized again so that a usual rigid implant results.
Bone splinters or bone replacement material can easily be filled into the interior space of the frontally and backwardly open hollow element and the implant securely be mounted with little operating steps.
To advance a quick ingrowing of the bone the implant is suitably provided with perforations preferably in the form of longitudinal apertures. The longitudinal apertures allow a control of the ingrowing of the bone by means X-ray images in case of a material which is not permeable for X-rays.
For the improvement of the stability of position of the implant the upper and /or lower bone-contact face is provided with a three dimensional texture preferably in the form of longitudinal grooves.
Compared to the prior art the following further advantages of the implant according to the invention accrue:
The invention and further embodiments of the invention are discussed in more detail in the following by means of the partially schematic representations of an embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The figures show:
FIG. 1 a perspectival representation of the implant according to the invention in the compressible state with a loose engagement lip; and
FIG. 2 a cross-section through the implant according to FIG. 1 in the non-compressible state with engaged engagement lip.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The intervertebral implant shown in FIG. 1 and 2 consists essentially of a hollow element 1 in the shape of a hollow cylinder whose outer surface 2 consists of a flattened upper bone-contact face 3, a flattened lower bone-contact face 4 and two lateral faces 5.
The implant may be fabricated in a suitable metal (i.e. titanium), but particularly also in a synthetic material tolerated by the body like polyethylene.
The
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patent: 4863477 (1989-09-01), Monsoon
patent: 5458642 (1995-10-01), Beer et al.
patent: 5554191 (1996-09-01), Lahille et al.
patent: 5593409 (1997-01-01), Michelson
patent: 5676702 (1997-10-01), Ratron
patent: 5782919 (1998-07-01), Zdeblick et al.
Benoit Alfred
Knothe Inga
Koh Choon P.
Milano Michael J.
Synthes (U.S.A.)
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