Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1997-07-28
2001-01-09
Millin, V. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
Reexamination Certificate
active
06171341
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a type of humeral prosthesis that is provided with a rod to be anchored in the humeral canal of a patient, a metaphyseal element that extends upwards from said rod and towards the inside, this metaphyseal element being fitted, at an area of connection, to a flange against which rests an approximately hemispheric calotte or cap suitable to interact with the shoulder socket. The mentioned area of connection is arranged approximately along a median line of the flange.
2. History of the Related Art
When the upper extremity of the humerus is fractured, the humerus generally breaks into several pieces, in particular the shaft, the humeral tuberosities and, lastly, the head of the humerus that interacts with the shoulder socket.
When such a fracture is set, only the head of the humerus must be replaced by an approximately hemispheric cap, while the other fractured pieces may be set around a prosthesis.
Well known in the art are prosthesis of this type which, as a rule, comprise a rod, or shaft portion, that is inserted in the humeral canal of the shaft of the bone. This rod is extended by a metaphyseal element that is bent upwards and towards the inside of a prosthesis worn by a standing patient, around which prosthesis are brought together the tuberosities constituting the metaphysis of the bone with the intention of setting them. The metaphyseal element of the prothesis is joined to a flange of the seat of a cap replacing the head of the humerus.
This type of protheses, such as, for example, those of NEER, present however certain disadvantages. In fact, they are made out of one only block which renders it necessary to have a large number of implants to meet the anatomic requirements of the different patients. Furthermore, these prosthesis have only one size of rod and of cap, and the latter cannot be offset as proven necessary in some cases. Moreover, the space of the upper portion of the prosthesis does not allow, in the case of serious fractures of the upper portion of the humerus, a satisfactory setting between the osseous fragments.
Furthermore, from French Patent A-2 689 758 is known a humeral prosthesis that comprises in its metaphyseal element a reinsertion flange. This flange is provided with perforations through which pass threads that ensure the anchoring of the bone to the prosthesis. However, the perforations of very slight diameter do not allow for the osseous fragments to come closer together. Thus, the mutual uniting of these fragments proves to be insufficient which, of course, is detrimental to the physical integrity of the patient.
SUMMARY OF THE INVENTION
Thus, the aim of the present invention is to produce a humeral prosthesis of aforementioned type that would overcome the above-mentioned disadvantages of the hitherto known prosthesis.
With this in mind, the invention relates to a humeral prosthesis of the mentioned type, characterized by the fact that the area of connection extends only over a portion of the median line in order to establish outside of the area of connection, or outside of a portion of the area of connection, a clearance zone for the joining and fusing of the osseous fragments of the metaphysis.
The invention allows the attaining of the above-mentioned objectives. In fact, the presence of a clearance zone allows the formation of a cluster of fragments or even the placing of a graft in order to facilitate the osteosynthesis subsequent to the surgical intervention. In comparison with the hitherto known prosthesis in which the osseous fragments of the metaphysis were attached only to the prosthesis, the prosthesis in accordance with the invention thus has the advantage that these osseous fragments could be brought together and be approximately attached to each other according to their crowding and their original configuration. This would allow a clearly better osseous uniting.
The joining and fusing clearance zone for the osseous fragments is located at the outside portion of the overall clearance zone of the metaphyseal element. As a matter of fact, it is this external proximal portion that seems to be the most difficult one to set because of the stress transfers to which this osseous portion is subjected during the normal shoulder action.
According to an advantageous aspect of the present invention, the median line of the flange is a diameter that is roughly co-planar with the rod's axis.
According to another aspect of the present invention, the metaphyseal element is provided with one branch extending the humeral rod and connecting it to the flange at the area of connection in order to constitute, outside the area of connection, the clearance zone for the joining and fusing of the fragments of the metaphysis.
This branch may be provided with a concavity oriented towards the inside. It can be provided with at least one fin thinner than this branch, oriented towards the inside and/or the outside, and provided with perforations. These perforations are intended for the passing of suture threads which would allow the anchoring of the osseous fragments to the prosthesis to obtain a better reconstruction. The fact that the fin is thinner than the only branch ensures a better positioning of the various osseous fragments with respect to each other, thus ensuring a close contact between them.
According to another aspect of the present invention, the metaphyseal element comprises two inside and outside branches that extend from the rod and are attached to the flange at the area of connection in order to constitute between these areas of connection a cavity that forms the mentioned clearance zone for the joining and fusing of the osseous fragments of the metaphysis. This outside branch constitutes a bearing surface for the spongy bones and avoids that they collapse.
In this case, the outside branch may be provided with a fin thinner than such branch that is oriented towards the outside and provided with perforations for the passing of suture threads.
According to an advantageous aspect of the present invention, the metaphyseal element is provided with one branch that extends from the humeral rod and is attached to the flange at an area of connection, as well as with a lug that protrudes from the flange in an opposite direction of the cap and, outside of the branch, the clearance for the joining and fusing of the fragments of the metaphysis is established between the area of connection of the branch and the area of connection of the lug. The presence of the lug avoids the collapsing of the spongy bone because of the bearing surface constituted by this lug. Furthermore, because this lug extends only to the humeral rod, the clearance zone for the joining and fusing of the osseous fragments of the metaphysis, established between the outside branch, the lug and the flange, opens at the rod. This clearance zone is thus of major dimensions allowing a satisfactory consolidation of the osseous fragments to each other.
The lug may be provided with a fin thinner than the lug, oriented towards the outside and provided with perforations intended for the passing of the suture threads.
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patent: 5489309 (1996-02-01), Lackey et al.
patent: 5658340 (1997-08-01), Muller et al.
patent: 5725161 (1998-03-01), Camino et al.
patent: 2689758 (1992-04-01), None
patent: 2689758 (1993-10-01), None
patent: 1340451 (1972-01-01), None
patent: 0555629A1 (1993-08-01), None
Zimmer Catalog, Warsaw, Ind., Feb. 1973.*
Boileau Pascal
Walch Gilles
Dowell & Dowell , P.C.
Millin V.
Stewart Alvin
Tornier SA
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