Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1998-08-26
2001-02-27
Snow, Bruce (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
Reexamination Certificate
active
06193756
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a tubular support body for bridging two vertebrae having two cages which are placed one within the other and are provided with cut-outs and which each has a support flange at the outer front surface.
Support bodies of this kind are implanted in the region of the intervertebral discs when the intervertebral discs themselves no longer withstand the stresses which the adjacent intervertebral discs exert on them and a support body is required as a fill-in.
Support bodies of this kind are often designed as cages which are filled with autologous bone chips prior to the implantation. The cut-outs in the cages are herein chosen in such a manner that the bone tissue is captive, but that a supply of the bone tissue takes place through the cutouts after the implantation at the same time.
The patent specification DE 195 04 867 shows support bodies which can be pushed together to their insertion length prior to implantation. This has the disadvantage that the required construction length must be very precisely determined in advance. The orthopaedist must therefore have an entire arsenal of components in the operating room in order to assemble one of a suitable size.
A different design is shown in EP-A-0 693 274 with adjustable threads which determine the length of a support body at a suitable height and are subsequently secured by screws which penetrate radially into the thread. An embodiment of this kind has the disadvantage that it can actually be fixed only once due to the damage which arises at the thread. Achieving a certain bias force on the securing screws is possible only via a plastic deformation of the threaded passages at the support body.
SUMMARY OF THE INVENTION
It is an object of the present invention is to provide a multiply adjustable support body with few parts. This object is satisfied in that a first cage has at least three radially projecting lugs or protrusions at its jacket which can be introduced into three axially extending lead-in channels or a multiple thereof in the jacket of the other cage in order to be able to reach latch-in positions at different depths.
An advantage of the invention consists in that support bodies of different lengths can already be manufactured with two parts simply by pushing together and in that there is no danger that the push connection is released as long as a pressing force is present in the main load direction through the ligamenture or the weight. A further advantage consists in that the cut-outs at both cages can be matched to one another through definite latch-in positions in such a manner that the cut-outs align with one another in the region of covering and thus a supply of the bone chips lying within the cage and a growing-in can take place independently of the latch-in position. A further advantage consists in that no loose small parts such as securing screws or fastening screws are present in the field of operation.
Thus it is advantageous to provide the latch-in positions at the end of the respective lead-in channel with a clamping for the protrusions. This clamping can be done in the radial direction onto the protrusions, with the two cages being under a bias force with respect to one another in the radial direction and the spring action of the cages in itself producing a bias force. It is however also possible to clamp the protrusions in the latch-in position at their periphery through a reduction in the width of the lead-in channels. An elastic clamping is achieved here in that the lead-in channels have only a small wall thickness in the peripheral direction in the latch-in region and border on cut-outs which permit an elastic back resilience of the wall in the clamping region. The tolerances for a protrusions diameter “D” and for the clamping diameter “d” of the lead-in channel should be chosen in such a manner that 0.01 mm < D − d < 0.2 mm is satisfied. The clamping has the advantage that, in a setting prior to the insertion of the implant, it can be handled as a single-piece body for the insertion.
The support bodies can be provided at their outer ends with connection pieces which have an outer securing plane disposed at an inclination and which can be latched into the support body at different angles of rotation to compensate for deviations from parallelism between two adjacent vertebrae.
REFERENCES:
patent: 3102536 (1963-09-01), Rose
patent: 5290312 (1994-03-01), Kojimoto
patent: 5531792 (1996-07-01), Huene
patent: 5571192 (1996-11-01), Schonhoffer
patent: 5702455 (1997-12-01), Saggar
patent: 5776197 (1998-07-01), Rabbe et al.
patent: 36 05 630 A1 (1987-09-01), None
patent: 44 09 392 A1 (1995-09-01), None
patent: 195 04 867 C1 (1996-02-01), None
patent: 2 730 158 (1996-08-01), None
patent: WO 94/18913 (1994-09-01), None
Donno Cosimo
Studer Armin
Snow Bruce
Sulzer Orthopaedie AG
Townsend and Townsend / and Crew LLP
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