Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2001-03-02
2004-05-04
Shaver, Kevin (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S105000
Reexamination Certificate
active
06730087
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a distraction device for moving apart a one-piece or two-piece, possibly divided bone for lengthening or for bridging a bone gap, comprising an intra-medullary nail which can be introduced into a medullary cavity of a bone and which has at least two elements which can be moved axially relative to each other.
Such devices are known and available on the market in many different forms and designs. The aim of this distraction is endogenous reforming of bone substance. Reference may be made, for example, to EP 0 346 247 B1 which discloses an intracorporeal medullary nail which moves two parts of a bone in a mechanical manner. A disadvantage of this is that readjustment and tensioning are not readily possible.
In addition, DE 39 21 972 C2 discloses an intramedullary nail which can be lengthened likewise in a mechanical manner.
A disadvantage of the conventional distraction devices disclosed in the prior art is that they are in most cases too large and their effect is poor. They can transmit only limited distraction forces to the bone.
They are mostly of complex construction, difficult to operate, and very often have to be readjusted by surgical intervention, which is undesirable.
Moreover, such distraction devices known in the prior art are seldom suitable for very small bones, since their size is limited by complex structural parts.
The object of the present invention is to make available a distraction device of the above-mentioned type, with which high distraction forces are exerted in a controlled manner on the bone, and which can be used in any desired sizes for all extendable bones, including very small bones. It must be possible for distraction distances and distraction forces to be freely selected.
This object is achieved by the fact that at least one working device is connected to the element and to a movable holding element which is supported on the element.
SUMMARY OF THE INVENTION
In the present invention, elements are provided which are preferably inserted one within the other or guided one upon the other, and which are arranged to be displaceable. The elements are securely connected at the ends to the respective individual bone parts.
The stationary element is preferably provided with a push element on which the holding element moves axially to and fro. The holding element is supported on the outer element by means of a locking device. Here, widely differing embodiments of locking devices can be chosen. The holding element is connected at one end to the push element via a working device.
The working device, which preferably consists of wire defined in the axial direction or wound in the form of a spring, can change length considerably upon heating when so-called shape-memory alloys are used. The wire wound in the axial direction contracts by several percent of the total length and the spring becomes longer. The reciprocal support of the holding element on the two elements enforces the outward movement of one and/or the other element.
The working device is then cooled by-interrupting a supply of current, and the wire can relax. A tensioning device, which is connected to the displaceable or movable element and the holding element, moves the holding element back counter to a direction.
Also preferably used as tensioning device is a wire element to which current is applied. By this means, the wire is heated and shortens since it is-made of memory metal. The inner element is supported on the outer element via a locking device, so that the holding element can be moved in direction. The procedure is repeated.
Influence can be exerted with precision on the required distraction distance and distraction force via the number of wires fitted in working device and tensioning device, and via the corresponding distances from a receiving seat of the push element to the holding element and from the holding element to the inner element. Instead of the tensioning element, an extension spring element or compression spring element can also be used depending on configuration.
The wires which are used to heat the memory-metal wire are connected to energy transmitters which are arranged, for example, under the skin. In this way, the distraction device can be actuated over a long period of time inductively and in a contactless manner without operative outlay.
In all, the present invention makes available a distraction device which can be adapted in shape, size and technical configuration to any desired bone which is to be lengthened. Influence can be exerted with precision on the distraction behavior, for example, via the number of wires, via the length of the wires. This distraction device is also suitable for very high distraction forces in conjunction with the smallest possible insertion size.
REFERENCES:
patent: 5156605 (1992-10-01), Pursley et al.
patent: 5415660 (1995-05-01), Campbell et al.
patent: 5626581 (1997-05-01), Staehlin et al.
patent: 5704938 (1998-01-01), Staehlin et al.
patent: 5961553 (1999-10-01), Coty et al.
patent: 6033412 (2000-03-01), Losken et al.
patent: 6500177 (2002-12-01), Martinelli et al.
patent: 2726460 (1996-05-01), None
Priddy Michael B.
Shaver Kevin
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