Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1994-08-22
1999-11-09
Yu, Mickey
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
623 18, A61F 236
Patent
active
059805757
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a hip joint prosthesis for permanent anchoring in the human hip joint. More particularly, the present invention relates to such a prosthesis including an attachment part for a ball unit designed to be anchored in the neck of a human femur (collum femoris). Furthermore, this attachment part, which is intended to be inserted into a channel extending through the femoral collum, is provided with parts for carrying a ball or caput intended to be attached to the collum after removal of the head of the femur.
BACKGROUND OF THE INVENTION
The present invention relates to the development of a hip joint prosthesis of the kind disclosed in WO 89/11837. This document inter alia discloses a hip joint prosthesis comprising a primary fixture in the shape of a sleeve which is intended to be inserted into a central hole bored longitudinally through the collum femoris from the outer side of the femur and a secondary fixture in the shape of a cap having a spherical shape intended to be attached to and cover the end of the collum femoris when the head of the collum has been partially or entirely removed and the outside of the remaining end has been cut to a cylindrical shape. The primary and secondary fixtures are interconnected by means of a bolt which at one end has an internal thread. The bolt is to be inserted into the sleeve and its internal thread is to be made to engage a central, threaded stud projecting from the spherical cap. When the bolt is tightened, the cap is pressed over the cylindrically cut caput or end of the collum.
The prior art device thus is relatively complicated, both in terms of its construction and use.
In some applications, however, it may not be suitable to use this type of prior art device. One reason for this is that the shape of the collum may make it difficult to retain enough cortical bone to give the secondary fixture of cap a firm support, since the shape of the collum may vary to a great extent.
This prior device is also designed to be inserted in a two-step procedure; i.e., some parts of the prosthesis are to be inserted in a first operation, and the remaining parts are subsequently in a second operation after a healing period of a few months.
Other similar prior art is disclosed for instance in DE-A1-28 45 231, DE-A1-27 24 040, United U.S. Pat. No. 4,795,473 and U.S. Pat. No. 4,005,495.
The object of the present invention is to provide a hip joint prosthesis which is simple in construction and use and which is particularly suited for insertion in a one-step operation, and which can also be adapted to fit different conditions.
SUMMARY OF THE INVENTION
According to the present invention, this and other objects have been obtained by the discovery of an attachment part in a hip joint prosthesis of the type described above which also comprises a fixture comprising two main parts; namely, a first part which is to extend through a bore hole from the collum femoris towards the outer side of the femur and a second part which is intended to fit into a cylindrical cavity cut into the cancellus bone of the collum.
The fixture can be made in one piece but, in one preferred embodiment, comprises two separate parts which are firmly attached to each other before the fitting of the fixture into the femur.
This invention thus results in the cortical bone remaining intact to a larger degree, and the load conditions being such that a physiologically appropriate load on the upper part of the collum can be achieved. Forces can thus be transferred from the fixture to the femur without any noticeable movements by means of the direct or indirect contact with the inside of the cortical bone in the collum.
Further in accordance with the present invention, a hip joint prosthesis for permanent anchoring in the human hip bone has been provided which comprises attachment means for attaching a ball unit to be anchored in the neck of a human femur, the attachment means including a first cylindrical fixture portion for extending from the collum femoris toward
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Albrektsson Bjorn
Carlsson Lars
Jacobsson Magnus
Rostlund Tord
Wennberg Stig
Astra Aktiebolag
Snow Bruce E.
Yu Mickey
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