Surgery – Instruments – Orthopedic instrumentation
Patent
1997-07-29
2000-05-02
Buiz, Michael
Surgery
Instruments
Orthopedic instrumentation
606 77, 606232, A61B 1758
Patent
active
060567503
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an osteosynthetical fixing element for the fixing of a bone implant which bone bore-hole and an expanding body which can be driven into an opening of the accommodating body and where the accommodating body is radially expandable by a wedge effect.
EP-B1 409 364 discloses a connecting element for osteosynthesis which is designed as an expandable, elastically deformable sleeve. The sleeve has a diameter which, reduces from an end side and is provided with a slot extending in the longitudinal direction. The expansion of the sleeve is effected by a pin which is designed so as to be axially symmetrical and preferably tapers in conical fashion in the direction of insertion and whose outer diameter is greater than the smallest outer diameter of the sleeve and smaller than the greatest outer diameter thereon. At the periphery of the sleeve different kinds of toothing elements are provided consisting for example of sawtooth-shaped barbs, helical or concentric projections.
Upon the driving-in of the pin, the outer wall of the sleeve, inserted into a corresponding bore in the bone fragments to be connected, is pressed against the surrounding bone material and wedged accordingly.
A disadvantage of the known implant for the osteosynthetic connection of reset bone fragments consists, in particular, in that--independently of the quality of its stabilising effect--primarily the attainable stability of the connection is unpredictable and highly variable in the longitudinal direction.
Furthermore, upon the fixing of this element torsion stresses arise which are unpredictable in terms of their effects and which reduce the stability of the connection.
SUMMARY OF THE INVENTION
Commencing from the shortcomings of the prior art, the object of the invention is to provide a fixing element of the type referred to in the introduction with which an improved osteosynthetic stabilisation, approximating the fixing properties of a metallic fixing element, is attainable.
This object is fulfilled by the instant invention where the accommodating body is subdivided in the longitudinal direction and includes at least two sub-elements which are separate from one another or are connected to one another so as to be movable in such a manner so that the driving-in of the expanding body into the accommodating body results in the accommodating body being expandable, substantially over its entire length, as a result of the mutual wedge effect of the accommodating body and the expanding body.
The invention includes the recognition that, in the case of an osteosynthetic fixing element insertable in an accommodating opening (bore or other longitudinal channel), as uniform as possible an introduction of force should take place for the attainment of a stable connection to the bone. This relates both to the fixing of bone fragments and to the fixing of ligaments to the bone. The corresponding also applies to the fixing of plates. In order to replace the conventionally used screw, an element is required which, solely by virtue of its expansion, facilitates the introduction of force over the entire bone area which is passed through, without the stability of said element being subjected to excess stress. Therefore for example insertion under torsion stress, as in the case of conventional metal screws, is not to be employed.
In contrast to the known conical expanding element, it is provided that the relative expansion takes place over the entire length of the outer surface, which latter is in engagement with the bone material, and by as constant as possible a longitudinal amount sufficient to establish a reliable interlocking connection of the outer profiling. The cross-sectional enlargement relates to that part of the individual sub-elements which is in the leading position during the insertion of the expanding body and thus forms the movement front. Here double triple or also multiple subdivision in the longitudinal direction is possible. Due to the fact that the sub-elements are freely displaceable re
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Buiz Michael
Kinberg Robert
Reip David O.
Voorhes Catherine M.
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