Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1999-02-08
2001-02-20
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S022460, C606S085000
Reexamination Certificate
active
06190416
ABSTRACT:
The subject of the present invention is an orthopedic surgery assembly including an ancillary tool for a hip prosthesis, a femoral raspatory and a femoral stem of the type with a removable neck. This neck has a conical bearing span designed to engage in a matching conical recess formed in the proximal end of the stem. Stems of this type are described in particular by the patents FR A 8506214 (2580926) and 9214120 (2697996) and by the European patent EP-A-0017743.
Hip prostheses with removable necks are being increasingly used because of the great possibilities they give surgeons to allow them to adapt each prosthesis to the specific needs of their patients.
Although it is possible, as in the patent document U.S. Pat. No. 4,919,679, which describes a prosthesis with a fixed neck, to use a positioning ancillary tool whose axis is situated in the extension of the stem of the prosthesis, and is connected to the latter by connection means such as a thread, because the material volume in the proximal part of the stem is sufficient to permit the drilling and then tapping of a hole, this is no longer possible with prosthesis stems which are intended to receive removable necks. This is explained particularly by the fact that the connection hole is drilled obliquely in relation to the axis of the stem and in this way prohibits any operational drilling oriented in this axis.
The invention concerns a hip prosthesis with a removable neck and relates more particularly to the connection of the stem to the neck, and to all the advantages which derive from this connection. This is because, like any other prosthesis, a prosthesis of this kind must be easy to manipulate during positioning and requires the existence of a specific ancillary tool on account of the fact that mechanical engagement via the neck is no longer possible and since it is necessary for this engagement to be solid and firm so as to constitute a compact assembly between the ancillary tool and the stem. The same also applies to the raspatories which are used to prepare the medullary channel of the femur for receiving the prosthesis stem.
It is for this reason that the invention not only relates to a solid and firm connection of the prosthesis stem to its removable neck, rendering the assembly perfectly rigid and compact, but also to a specific ancillary tool for this type of prosthesis, also making it possible to form a perfectly rigid and compact assembly both with the prosthesis stem and with raspatories, in such a way as to provide the surgeon with reliable, simple and practical operating equipment.
As regards means for indexing a prosthesis with a removable neck, there is, for example, French Patent A 2 697 996 (Medinov) which provides an indexing indentation of the removable neck consisting of a succession of identical semicircular recesses adjacent to one another on the inner periphery of the bottom of the receiving hole. These recesses are necessarily situated facing in pairs and diametrically opposite each other in order to receive a transverse connecting rod which is integral with the removable neck and whose dimensions correspond to those of the indentations. These semicircular recesses thus form a circumferential alternation of concavities and ridges which means that said ridges are very fragile not only during manipulation of the neck in the indentation, but also during diverse mechanical stresses on the connection during the functioning of the prosthesis.
The invention makes use of the hole formed on the stem, for receiving the removable neck, in order to extend it along its axis to create indexing means and means of connection to an ancillary tool.
Means for possible extraction of the removable neck can also be provided in order to permit access again to said connection means. It must in fact be anticipated that a prosthesis may one day have to be extracted, or that the removable neck alone will need to be changed in favor of a neck of different dimensions.
According to the invention, the orthopedic surgery assembly comprises common means of connection between the ancillary tool and the stem and between the ancillary tool and the raspatory, allowing both the raspatory and the femoral stem to be positioned in the intramedullary channel of a femur by means of the same ancillary tool.
According to a preferred embodiment, the connection means include, on the stem, a tapped hole extending from the bottom of a recess for receiving the removable neck, and formed in the stem, and a threaded projection constituting one end of the ancillary tool and designed to be screwed into said tapped hole.
According to a complementary feature, these connection means also include, on the raspatory, a tapped hole extending from the bottom of a recess for receiving the removable neck, and formed in the proximal end of the raspatory, this tapped hole being designed to receive the threaded projection of the ancillary tool.
Thus, the invention makes use of the fact that the neck of the stem is removable, hence that the proximal end of the stem is provided with a recess for receiving this neck, in order to form in the bottom of this recess a means for connection to the ancillary tool; correspondingly, the invention provides for arranging in the proximal end of the raspatory, which is associated with this stem, a recess and a terminal connection means identical to those of the stem.
The ancillary tool advantageously includes an end which can be detached by rotation from its handle. This is because the latter is curved in shape and could not therefore be easily screwed or unscrewed in the operating field during the surgical intervention.
According to a second embodiment of the invention, the tapped hole is extended via an axial bore passing completely through the proximal part of the stem, and this assembly includes an ancillary tool for extracting the removable neck by introduction of an end part of this ancillary tool into the bore and into the tapped hole and by impaction on the end of the removable neck, said ancillary tool consisting of a rigid rod whose end part has a diameter which is slightly smaller than that of the introduction bore.
The ancillary tool is introduced through the cortical bone of the femur after first being targeted using a specific aiming device.
Compared to the technique previously used, the invention affords an appreciable advantage in terms of cost and simplification of the equipment.
According to another characteristic of the invention, the bottom of the recess in the raspatory and in the stem has a profiled indentation whose edge is made up of alternating concave and convex curves; a corresponding end of the neck includes a male indexing part provided with complementary alternating of convex and concave curves which can fit in the female concave and convex curves of the indentation in order to index the neck in a defined angular orientation.
REFERENCES:
patent: 4705520 (1987-11-01), Ahrens
patent: 4795469 (1989-01-01), Oh
patent: 4919679 (1990-04-01), Averill et al.
patent: 4963155 (1990-10-01), Lazzeri et al.
patent: 5443471 (1995-08-01), Swaiger
patent: 3147249 (1983-06-01), None
patent: 4116507 (1992-09-01), None
patent: 0000549 (1979-02-01), None
patent: 0200672 (1986-11-01), None
patent: 2575384 (1986-07-01), None
patent: 2580926 (1986-10-01), None
patent: 2693367 (1994-01-01), None
patent: 2697996 (1994-05-01), None
patent: 1371335 (1974-10-01), None
patent: 2259859 (1993-03-01), None
Choteau Michel
Grynblat Gérard
Letendart Joël
Mathevon Henri
Stahl Philippe
Groupe Grion
Willse David H.
Wolf Greenfield & Sacks P.C.
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