FR2684544A1 - Acetabular implant - Google Patents

Abstract

The acetabular implant comprises a metal ring (1) and a polyethylene core. The ring (1) has, radially in its periphery, anchoring regions (1a) (1b) (1c) with a capacity for elastic deformation, the said regions being to be stressed by bearing parts (3a) on an element (3) intended to be fixed into the said ring (1) in order to concomitantly cause extension of the anchoring regions into determined parts of the acetabulum, ensuring stiffening of the ring.

Description

 Cotyloid implant.

 It is well known to use acetabular implants comprising a metal ring and a polyethylene core, intended to cooperate with a spherical femoral head.

 The invention relates more particularly to implants intended to be fixed in the acetabular cavity of the cementless iliac bone. Generally, the ring is hemispherical to follow the internal movements of the acetabulum.

 Many solutions have been proposed to ensure the primary fixing of the ring.

 For example, the external surface of the ring can be coated with a structure having various asperities, such as spikes, ribs, fins, capable of ensuring immediate fixing after impaction. However, this results in difficulties in positioning the ring in the acetabulum, making it difficult for the surgeon to work, in order to correctly orient said ring.

 Macroscopic coatings have also been proposed to ensure a primary fixation, making it possible to immobilize the ring intraoperatively, thus allowing the surgeon to put in place more easily, the fixing screws, for example. On the other hand, these macroscopic coatings catch and destroy the surface of the acetabular cavity, thus being likely to harm the stability of the implant in the more or less long term.

 There are also known rings having radial slots delimiting elastically deformable parts. Generally, all or only part of these elastically deformable zones have, as indicated above, arrangements capable of ensuring the fixing of the whole of the ring in the acetabulum, in combination with the polyethylene core. Such arrangements cause mechanical stresses at the level of the polyethylene core which risks aging very badly, causing micromovements and wear.

 The object of the invention is to remedy these drawbacks in a simple, safe, efficient and rational manner.

 The problem which the invention proposes to solve is to ensure a primary fixing of the ring by elasticity, in order to be able to orient it, while having, on the other hand, the objective, on the one hand, of avoiding excessive stress on the polyethylene core in charge and, on the other hand, stiffen the entire ring.

 Another problem which the invention proposes to solve is to ensure the fixing of the ring, at the level of the acetabular periphery constituting a very resistant zone.

 To solve these different problems, the ring has radially in its periphery, anchoring zones with elastic deformation capacity, said zones being able to be stressed with bearing parts which has an element intended to be fixed in said ring. , to cause, concomitantly, the overflow of the anchoring zones in specific parts of the acetabulum, while ensuring the stiffening of the ring.

 To solve the problem of subjecting the anchoring zones to a certain elasticity, the latter are formed from the opening of the ring and extend in the direction of its polar part, constituting elastic blades equipped with retainer arrangements, cooperating with the acetabular cavity.

 To solve the problem posed of ensuring the expansion of the anchoring zones, under the effect of the impaction of the element, the bearing parts of said element act as ramps.

 To solve the problem of stiffening all of the elastic anchoring zones, the element is a crown, the support parts of which act as ramps, are suitably distributed around its circumference, in a manner corresponding to the number and the distribution of the elastic blades.

 The crown is put in place after finding the correct orientation of the ring in the acetabular cavity. This crown has the effect of ensuring the expansion of the elastic blades, to cause, concomitantly, the uniform sinking of their arrangements in Itos subchondral of the acetabular periphery, thus ensuring the immobilization of the ring, in the acetabular cavity .

 To resolve the problem posed of ensuring the impaction and fixing of the crown in the ring, the latter has tabs cooperating with a peripheral groove formed in the hemispherical cavity of the ring, at its opening.

 To solve the problem of ensuring a secure and effective fixing of the ring, the number and location of the blades are determined to cooperate with the pubis, the ischium and the roof of the acetabulum.

 Advantageously, the blades at rest are in the extended position.

 To solve the problem posed of ensuring the primary fixing of the ring at the bottom of the acetabular cavity, the ring is hemispherical and has, between the blades, housings for the engagement and the positioning of heads of anchoring screws .

 Another problem which the invention proposes to solve is to obtain the rotation blocking of the polyethylene core.

 Such a problem is solved in that the crown has arrangements cooperating with arrangements complementary to the core, capable of ensuring the locking in rotation of said core.

 To solve the problem posed of avoiding micromovements from front to back of the core, the crown notably has, at the level of its hooking lugs, prominences cooperating with a circular groove of the core, to ensure its retention.

The invention is set out below in more detail with the aid of the appended drawings, in which:
Figure 1 is a perspective view before mounting of the crown and the metal ring.

 Figure 2 is a plan view of the ring before the crown is put in place.

 Figure 3 is a plan view of the crown alone.

 FIG. 4 is a cross-sectional view along line 44 of FIG. 2.

 Figure 5 is a cross-sectional view along line 55 of Figure 2.

 Figure 6 is an exterior view of the crown.

 Figure 7 is a cross-sectional view of the ring, after fixing the crown and impaction of the core.

 Figure 8 is a sectional view taken along line 8-8 of Figure 7.

 Figure 9 is, on a very large scale, a partial sectional view of the coursonne.

 FIG. 10 shows the fixation of the acetabular implant according to the invention in the acetabulum.

 In known manner, the acetabular implant comprises a metal ring (1) and a polyethylene core (2). The shape of the ring is hemispherical and completely covers the core (2), even in the case of a two-edged core. Such provisions avoid all significant stresses on polyethylene and limit the risks of creep.

 According to the invention, the ring (1) has radially in its periphery, anchoring zones (la) (lob) (1c), with elastic deformation capacity.

 As shown in particular in FIGS. 1 and 2, these anchoring zones (la) (lob) (Ic) are formed from the opening (Id) of the ring and extend in the direction of its polar part ( 1e). These anchoring zones (la) (lob) (Ic) constitute elastic blades obtained by two parallel cutting lines (if) and (1g). These elastic blades have external retaining arrangements (lai) (obi) (here) in the form, for example, of profiled prominences, such as projections.

 As indicated, the elastic blades (la) (lob) (Ic) converge in the direction of the polar opening (read) of the ring (1). The number and distribution of the blades (la) (lob) (tic) are determined so that the projections (lai) (obi) (here) cooperate after impaction of the nucleus, in the acetabular cavity of the iliac bone, with the pubis , The ischium and the roof of the acetabulum.

 As an indication, the ring has three blades (la) (1b) (1 c) offset angularly and successively by 105, 1500 and 105.

The ring (1) may also have four elastic blades distributed angularly around the circumference of said ring, so that two of them cooperate with the roof of the acetabulum, while the other two cooperate respectively with the pubis and the ischium.

 According to another characteristic underlying the invention, the blades (la) (lob) (lc) are subjected to the action of support parts (3a) which has an element (3) intended to be fixed in said ring to cause concomitantly, the overflow of said blades (la) (lob) (lc) in the aforementioned parts of the acetabular cavity. This element (3) is constituted by a crown, the bearing parts (3a) of which are suitably distributed around its circumference, in a manner corresponding to the number and the distribution of the elastic blades (1a) (lob) (in).

 The support parts (3a) are formed by profiled prominences acting as ramps (Figure 9). Note that these ramps (3a) can have different profiles, depending on the porous state of the acetabulum.

 The crown (3) has projecting legs (3b) cooperating with a peripheral groove (1h) formed in the hemispherical cavity of the ring (1) at its opening (nest).

The end of the legs (3b) has lugs (3b1) capable of being engaged in the circular groove (1h). We also plan to practice in the hemispherical cavity of the ring (1), a second groove (1k) (dashed lines in Figures 4 and 5) parallel to the groove (1h), for the engagement of the lugs (3b1) giving thus a second position at the crown (3), so as to increase the ramp effect, to cause concomitantly, a greater expansion of the elastic blades (la) (lob) (in).

 The upper part of the hemispherical cavity of the ring (1) has an internal recess (li) for housing the crown (3) and its legs (3b). The profile and the depth of this recess are determined to allow the integration of the crown, in continuity with the whole of the hemispherical cavity of the ring.

 The blades (la) (lob) (in), at rest, are in the extended position, to extend beyond the outer periphery of the ring. When the crown (3) is placed in the ring, the ramps (3a) come to rest on the blades (la) (lob) (lc) causing, as the impaction progresses of said crown, their expansion and, concomitantly, Impaction of the projections (lai) (obi) (here) in the corresponding parts of the acetabular cavity. At this level, the primary fixing of the ring is ensured. Note that prior to the positioning of the crown (3) in the ring (1), the latter can be oriented, as desired, in the acetabular cavity.

 The ring is fixed by means of screws (4) engaged in holes (il). These holes are, in a known manner, profiled to allow the angular orientation of the screw heads (4), which have a hemispherical profile. These holes (1j) are drilled between the elastic blades (la) (lob) (il), being suitably positioned, so that the screws penetrate in particular at the level of the roof of the acetabular cavity. The fixing of the ring can also be carried out by means of pins.

 Note that the ring, as produced according to the characteristics of the invention, may have a surface treatment giving it a rough and porous appearance, to ensure, in a known manner1 a secondary fixation.

 The polyethylene core (2) can be either with a flat edge, or with an anti-dislocation upper overhang, or with a flat edge with a retentive anti-dislocation stop.

 According to the invention, the anti-rotation behavior of the core (2) is ensured by peripheral notches (2a), cooperating with tenons (3c) formed peripherally in the bore of the crown (3).

 The retention of the core (2) in the ring (1) is effected by means, for example, of a groove (2b), able to cooperate with projections (3b2) formed in particular at the end of the legs (3b) . These projections (3b2) are formed opposite the projections (3b1) cooperating with the circular groove (1h) of the ring (1).

The advantages clearly emerge from the description, in particular it is emphasized and recalled:
- The possibility of orienting the ring before its primary fixation.

 - The use of a crown which stiffens the ring and ensures the expansion of the elastic blades for the primary fixing of the ring.

 - Automatic retraction of the elastic blades, in cup impaction.

 - The anti-rotation and front to back fixing of the core is made by the blades in the rest position of the crown.

Claims (10)

-1- Cotyloid implant comprising a metal ring (1) and a polyethylene core (2), characterized in that the ring (1) has radially in its periphery, anchoring zones (la) (lob) (lc ) with capacity for elastic deformation, said zones being to be covered by bearing parts (3a) which has an element (3) intended to be fixed in said ring (1), to cause, concomitantly, the overflow of the anchoring zones in specific parts of the acetabular cavity, while ensuring the stiffening of the ring. -2- cotyloid implant according to claim 1, characterized in that the anchoring zones (la) (lob) (lc) are formed from the opening (nest) of the ring and extend in the direction of its polar part (1 e), constituting elastic blades equipped with retaining arrangements (lai) (obi) (here), cooperating with the acetabular cavity. -3- Cotyloid implant according to claim I, characterized in that the support parts (lai) (lbl) (here) of the element (3) act as ramps. -4- Cotyloid implant according to any one of claims 1, 2 and 3, characterized in that the element (3) is a crown, whose bearing parts (3a) which act as ramps, are suitably distributed on its circumference, in a corresponding manner, to the number and distribution of the elastic blades (lai) (obi) (here). -5- Cotyloid implant according to claim 4, characterized in that the crown (3) has tabs (3b) cooperating with a peripheral groove (1h) formed in the hemispherical cavity of the ring, at its opening. -6- Cotyloid implant according to claim 2, characterized in that the number and location of the blades (la) (lob) (tic) are determined to cooperate with the pubis, ischium and the roof of the acetabulum. -7- Cotyloid implant according to claim 2, characterized in that the blades (la) (lob) (lc) at rest, are in the extended position. -8- Cotyloid implant according to any one of claims I and 2, characterized in that the ring (1) is hemispherical and has, between the blades (la) (lob) (it), housings (1j) for engaging and positioning heads of anchoring means (4). -9- Cotyloid implant according to claim 2, characterized in that the crown (3) has arrangements (3c) cooperating with complementary arrangements (2a) of the core (2), capable of ensuring the locking in rotation of said core. -10- Cotyloid implant according to claim 1, characterized in that the crown (3) has in particular, at its hooking lugs (3b), prominences (3b2) cooperating with a circular groove (2b) of the core ( 2), to ensure its retention.