Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1997-12-05
1999-11-16
Yu, Mickey
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
623 18, A61F 242, A61F 230
Patent
active
059849711
DESCRIPTION:
BRIEF SUMMARY
FIELD OF APPLICATION
This invention relates to a metacarpal-phalangeal or interphalangeal prosthesis, especially for joints in the hands and feet.
Where a finger or toe is lost or its functional performance is compromised as a result of injury, impact, rheumatoid arthritis, osteoarthritis, post-traumatic or post-infective osteoarthritis, modern surgical techniques make it possible to replace the natural joint with an artificial joint which is located between the metacarpal bone and the phalanges or between adjacent phalanges.
STATE OF THE ART
Some types of phalangeal prosthesis which generally comprise a joint connecting two pins which can each be implanted in the metacarpal bone and/or phalanges have been in use for many years.
The pins may be constructed of rigid materials, for example steel, titanium, carbon, or using soft materials, such as resins or silicone rubbers.
In the latter case, first introduced in the 70s by Swanson, the pins are joined together by a unitary connecting member with a transverse depression which encourages elastic flexion of the joint and rotation of the pins. Although this type of joint is aesthetically very satisfactory and provides an appreciable range of movement, it has some short term disadvantages, such as complete flipping of the joint and excessive movement in a lateral plane, and in the long term progressive disintegration of the bone and stiffening of the joint.
In metal prostheses the pins may be bare or coated with biocompatible material, such as hydroxyapatite. A disadvantage of these prostheses is their tendency to release metals which enter into the blood circulation and can cause metal intoxication. A further disadvantage arises from the high cost of the basic material, which may be extremely rare, such as titanium.
In rigid prostheses the joints are hinge or ball joints, and may be provided with elastic members, and have the disadvantage that they can stiffen in the course of time and cause infections, as they are in contact with bone and connective tissues.
U.S. Pat. No. 4,204,284 discloses a finger joint prosthesis comprising two pins and a flexible joint with the pins being made of biocompatible material (see column 4 lines 45-column 6 line 15; FIGS 1 and 2).
EP-A-280424 discloses a finger joint endoprostheses and it mentions as being advantageous to employ compatible materials and in the detailed examples reference is made to one and the same material being used for all the components such as protective caps etc. (see column 3, line 53-column 4-line 4).
This invention is intended to eliminate or at least reduce the above mentioned disadvantages by providing a rigid pin endoprothesis which permits easy implantation without any risks of incompatibility or infection, such as to guarantee mobility in the joint over a period of time.
The invention accomplishes these objects by the provision of a metacarpal-phalangeal or interphalangeal prosthesis, particularly for joints in the hand or foot, comprising two pins (2, 3) which can be inserted into bone adjacent to a joint to be restored, and a flexible joint (4) or coupling designed to join the said pins to each other, said pins (2, 3) being constructed of a material which is biocompatible with the surrounding tissue, said joint (4) being encapsulated in a protective enclosure, characterized in that said enclosure is formed of the same basic material as the pins (2, 3) and comprises a pair of opposing half shells (5, 6) integral with the corresponding pins (2, 3).
Because of the fact that the pins and the enclosure for the pins are formed of the same basic material as the pins and the layer covering the joint, the endoprosthesis according to the invention guarantees absolutely stable and durable anchoring in the bone, with minimum risk of infection or rejection.
Preferably the biocompatible material is a hardening plastic resin with high compatibility.
Preferably, the material forming the said pins and the said enclosure is a bone cement mixture, for example comprising a solid phase of polymethyl methacrylate
REFERENCES:
patent: 3466669 (1969-09-01), Flatt
patent: 3992726 (1976-11-01), Freeman et al.
patent: 4204284 (1980-05-01), Koeneman
Abbiati Gianrico
Delaria Giorgio
Faccioli Giovanni
Petrolati Maurizio
Soffiatti Renzo
Nguyen Dinh X.
Tecres S.p.A.
Yu Mickey
LandOfFree
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