Instruments for setting acetabular cup

Abstract

A cup and a temporary insert are respectively configured to be tightly press fitted into each other along their periphery. The temporary insert includes a through hole communicating outside with a free space between the outer surface of the temporary insert and the inner surface of the cup. In the through hole can be engaged the threaded end of an impactor, for manipulating the cup when it is being set. A syringe can be engaged, enabling a liquid under pressure to be injected into the free space, thus separating the temporary insert from the cup without any risk of damaging the inner surface of the cup. Thus, the cup can be securely manipulated when it is being set without any risk of damaging the inner surface of the cup.

Claims

1. Set of acetabular cup prosthesis setting means, comprising a cup delimited by a convex proximal face, a concave distal face defining an interior surface of the cup, and a peripheral lip, and further comprising an adapter for fastening the cup to an impactor, the adapter including: fixing means for detachably fixing the adapter to the impactor, fixing means on the cup, leaving a free space between the adapter and the cup once the adapter is fixed to the cup, an access hole through which the free space between the adapter and the cup communicates with the outside, wherein: the cup comprises a cylindrical or slightly conical annular retaining surface extending the concave distal face toward the peripheral lip, wherein the concave distal face is free of holes, the adapter comprises a continuous cylindrical or slightly conical annular engagement surface permanently having a same shape as the annular retaining surface of the cup, wherein the retaining surface of the cup, and the engagement surface of the adapter, are both cylindrical or slightly conical, wherein the engagement surface of the adapter has a diameter, at room temperature, which is slightly greater than a diameter of the retaining surface of the cup, and wherein the adapter is forcibly retained in a fluid-tight manner by its annular engagement surface being gripped radially in the annular retaining surface of the cup while the free space between the adapter and the cup communicates with the outside.

2. Set according to claim 1, wherein the adapter comprises abutment means adapted to bear axially on the peripheral lip of the cup to limit the penetration of the adapter into the cup.

3. Set according to claim 1, wherein the concave distal face of the cup is substantially hemispherical, extended by a short cylindrical or slightly conical annular retaining surface.

4. Set according to claim 1, wherein the annular retaining surface of the cup comprises at least one annular groove and the annular engagement surface of the adapter comprises at least one corresponding annular rib adapted to be engaged in the annular groove.

5. Set according to claim 1, wherein the means for fixing the adapter to the impactor comprise a threaded fixing hole in the adapter for screwing in a corresponding threaded portion of the impactor.

6. Set according to claim 1, wherein the access hole to the free space between the cup and the adapter is conformed and dimensioned for the fluid-tight engagement therein of the end of a syringe.

7. Set according to claim 1, wherein the access hole of the adapter is threaded to fulfill the function of an adapter fixing hole by enabling a corresponding threaded portion of the impactor to be screwed into the adapter.

8. Set according to claim 1, wherein the impactor comprises a tubular handle with an axial passage into which may be introduced a liquid and a piston-rod that forces the liquid into the free space.

9. Set according to claim 1, wherein the adapter is a temporary trial insert comprising, on its distal face, a hemispherical cavity dimensioned to enable the engagement of the head of a femoral prosthesis.

10. Set according to claim 9, wherein the access hole of the adapter is located in the bottom of the hemispherical cavity.

11. Set according to claim 1, wherein the adapter is made of polyethylene.

12. Set according to claim 1, wherein the set further comprises an impactor having a threaded portion for screwing into a threaded fixing hole in the adapter.

13. Set according to claim 12, wherein the impactor further includes, at the base of the threaded portion, a hemispherical portion conformed and dimensioned to be accommodated in a corresponding hemispherical cavity of the adapter.

14. Set according to claim 1, wherein the adapter and cup are packaged in a sterile state in a sealed protective envelope.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other objects, features and advantages of the present invention will emerge from the following description of particular embodiments, given with reference to the appended drawings, in which:

(2) FIG. 1 is a perspective view of an assembly according to one embodiment of the invention comprising an acetabular cup prosthesis in which is forcibly engaged an impaction and temporary trial insert type adapter;

(3) FIG. 2 is a side view of the assembly from FIG. 1, inserted into a sealed protective envelope;

(4) FIG. 3 is a front view of the assembly from FIG. 1;

(5) FIG. 4 is a side view in diametral section taken along the line A-A in FIG. 3;

(6) FIG. 5 is a side view in section showing an impactor engaged in the temporary insert of the insert-cup assembly from FIG. 4; and

(7) FIG. 6 is a side view in section showing a syringe engaged in the passage of the temporary insert in an insert-cup assembly according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) In the embodiment shown in FIGS. 1 to 4, the acetabular cup prosthesis setting instruments comprise a cup 1 and an adapter 2 conformed as an impaction and temporary trial insert.

(9) The cup 1 constitutes the permanent cup intended to be fixed into an acetabular cavity in the pelvic bone.

(10) On the other hand, the adapter 2 has at least the function of an intermediate part between the cup 1 and an impactor that is used to manipulate the cup 1 when setting it in the acetabular cavity, and the adapter 2 is intended then to be replaced by a permanent insert.

(11) The cup 1 is a hemisphere with a relatively thin wall, having a convex proximal face 3, seen better in FIG. 4, of generally hemispherical shape, optionally with anchoring fins 4, and a concave distal face 5 comprising a hemispherical sliding surface 5a extended by a cylindrical or slightly conical annular retaining surface 5b extending to a peripheral lip 6.

(12) The hemispherical surface 5a of the cup 1 is perfectly smooth and regular, preferably mirror polished, in order to constitute a sliding surface in which a hemispherical permanent insert subsequently introduced into the cup 1 after it is fitted in the acetabular cavity can pivot perfectly.

(13) The adapter 2 has a generally rounded shape delimited by a convex proximal face 7 and a distal face 11 with a hemispherical cavity 8.

(14) The convex proximal face 7 of the adapter 2 has a cylindrical or slightly conical annular engagement surface 7a and a central dome 7b set back from the hemispherical shape consisting of the hemispherical sliding surface 5a of the cup 1. As a result of this, in the force-fitted position shown in FIG. 4, there remains a free space 9 between the temporary insert 2 and the cup 1.

(15) The annular engagement surface 7a has a shape that corresponds to that of the annular retaining surface 5b and a diameter such that it is forcibly retained in the annular retaining surface 5b of the cup 1, so that the adapter 2 and the cup 1 are able to constitute a subassembly able to withstand, without relative movement with respect to each other, high mechanical stresses, greater than the forces that must be applied to a cup when setting it in the acetabular cavity.

(16) In FIGS. 5 and 6, the annular engagement surface 7a and the annular retaining surface 5b are smooth.

(17) Alternatively, in the FIG. 4 embodiment, the annular retaining surface 5b of the cup 1 comprises at least one annular groove 5c and the annular engagement surface 7a of the adapter 2 comprises at least one corresponding annular rib 7c adapted to be engaged in the annular groove 5c.

(18) The hemispherical cavity 8 of the adapter 2 is dimensioned to receive a ball-joint head of a femoral joint male part. The adapter 2 can therefore constitute a temporary trial insert.

(19) At the bottom of the adapter 2 is an access hole 10 through which the free space 9 between the adapter 2 and the cup 1 communicates with the outside.

(20) The distal face 11 of the adapter 2 is flanked by a circular peripheral rib 12 that constitutes abutment means bearing on the peripheral lip 6 of the cup 1 in the force-fitted position shown in FIG. 4. As a result of this, the peripheral rib 12 opposes further penetration of the adapter 2 into the cup 1. In the embodiment shown in the figures, the access hole 10 also constitutes means for detachably fixing an impactor. For this purpose it includes an internal thread 10a.

(21) Consider now FIG. 5, which shows again the cup 1, the temporary trial insert type adapter 2, the hemispherical cavity 8 of the adapter 2, and the threaded access hole 10.

(22) This figure also shows an impactor 13 comprising a handle 13a, a stem 13b and a threaded end 13c that is screwed into the threaded access hole 10. The impactor 13 preferably includes, at the base of the threaded portion 13c, a hemispherical portion 13d conformed and dimensioned to be accommodated in the corresponding hemispherical cavity 8 of the adapter 2. Thus, the impactor 13 is used to manipulate the cup 1 during its insertion into and positioning in the acetabular cavity.

(23) FIG. 6 shows a step of separation of the adapter 2 from the cup 1. In this embodiment, a syringe 14 is provided containing an appropriate liquid, for example physiological serum, and having an end-piece 14a that is engaged in fluid-tight manner in the access hole 10 of the adapter 2. The syringe 14 is then used to inject a liquid under pressure into the free space 9, causing separation of the adapter 2 from the cup 1.

(24) Alternatively, to avoid the use of a supplementary syringe, the impactor 13 may comprise a tubular handle: thus FIG. 5 shows an impactor 13 including an axial passage 13e. During the separation step, liquid may be introduced into the axial passage 13e and then a piston-rod 13f that forces the liquid into the free space 9.

(25) In the embodiment shown in the figures, the adapter 2 includes the hemispherical cavity 8, to fulfill the temporary trial insert function. Nevertheless, without departing from the scope of the invention, the adapter 2 could have no such hemispherical cavity, serving only as an adapter for positioning the cup 1 in the acetabular cavity by means of the impactor 13.

(26) Likewise, in the embodiment shown, the access hole 10 simultaneously serves as means for fixing the impactor 13 to the adapter 2. Alternatively, a hole could be provided in the central portion of the adapter 2 for fixing the impactor 13, whereas the access hole 10 for injecting fluid could be moved. The hole for fixing the impactor must be a blind hole in this case.

(27) The use of the instruments according to the invention is explained hereinafter.

(28) In the factory, the adapter 2 may be assembled into the cup 1 by a procedure comprising the following steps:

(29) a) the adapter 2 is cooled to a sufficiently low temperature to reduce its dimensions slightly, said dimensions being initially such that the diameter of the annular engagement surface 7a of the adapter 2 is slightly greater than the diameter of the annular retaining surface 5b of the cup 1 at the same temperature; lowering the temperature of the adapter 2 reduces its outside diameter, in order to facilitate its engagement with the entry of the cup 1, which itself remains at room temperature;

(30) b) the adapter 2 is then positioned in the cup 1, so that the peripheral rib 12 abuts against the peripheral lip 6;

(31) c) once in place in the cup 1, the adapter 2 is allowed to return to room temperature to expand it, so that the adapter 2 is force-fitted into and forcibly retained in fluid-tight manner in the cup 1 by its annular engagement surface 7a.

(32) The adapter-cup assembly is then sterilized by gamma rays in a sealed protective envelope 15 (FIG. 2). From this moment onwards the adapter-cup assembly is packaged in the sterile state in the sealed protective envelope 15.

(33) At the place of use, i.e. in the operating theatre, the surgeon removes the sealed protective envelope 15 and can screw a sterile impactor 13 into the access hole 10. The surgeon can then manipulate the cup 1 by means of the impactor 13 and the force-fitted adapter 2, imparting to the cup 1 all of the mechanical forces necessary for positioning it and orienting it.

(34) The surgeon then removes the impactor 13 by unscrewing it.

(35) The surgeon can then fit into the hemispherical cavity 8 of the adapter 2 a ball-joint head of the temporary insert type, which then serves as the temporary trial insert.

(36) Once the prosthesis male part has been chosen, the surgeon can remove the temporary insert 2 from the cup 1 by introducing a liquid or other fluid under pressure, by means of a syringe 14 as shown in FIG. 6, or into the impactor 13 with the piston-rod 13f and the axial passage 13e, as shown in FIG. 5.

(37) He then fits a permanent insert into the cup 1 which is itself in place in an acetabular cavity.

(38) All the above operations are carried out with no risk of deformation of the hemispherical sliding surface 8 of the cup 1 and with no unwanted forces on the cup 1.

(39) The present invention is not limited to the embodiments that have been explicitly described, and encompasses variants and generalizations thereof within the scope of the following claims.