FR2636836A1 - Porous-structure implant, in particular for a bone prosthesis - Google Patents

Abstract

The invention relates to a surgical implant 1 for bone regrowth. The implant 1 carries at its surface a porous structure 4, itself coated with a layer 6 of hydroxyapatite. Application: acceleration of biological fixation of the implant 1 by regrowth of bone in the cavities 7.

Description

 The present invention relates to a surgical implant of a new type, intended in particular to equip bone prostheses. It relates more particularly to a porous structure, disposed on the surface of the prosthesis, to allow the bone to grow back inside the cavities thus created. The fixation of the prosthesis to the bone is thus ensured by bone proliferation, which is usually designated by the name of "biological fixation".

Such an implant can be used for example for a hip prosthesis, a knee prosthesis, etc.

 We know the advantages of "biological" fixation for bone prostheses: this dispenses with the use of a cement, the effects of which are often harmful5 for the surrounding organism.

 On the other hand, the biological fixation of a cementless prosthesis results from a process of rehabitation by bone proliferation, the development and consolidation of which are relatively slow. This results in a more or less long period of disability for the patient after the surgical operation.

The object of the present invention is to avoid these drawbacks by producing, for a bone prosthesis, a bone implant or the like, a coating whose particular porous structure facilitates and accelerates the biological fixation on the surrounding bone.

A surgical implant according to the invention, intended to be applied against a bone to be fixed therein in a biological manner, is characterized in that its zone of contact and fixation with the bone is coated with a structure comprising both - small juxtaposed spheres, fixed together and to the surface of the implant to form a porous structure in the cavities of which the bone can grow back - on the outer surface of this porous structure, a layer of hydroxyapatite, it being understood that this hydroxyapatite is the inorganic constituent of oF, which can be synthesized in the laboratory.

 We know that hydroxyapktite is a mineral compound, essentially based on calcium. Its presence acts on the rate of formation of bone cells and facilitates their proliferation in the cavities which are defined between the underlying microbeads.

 The appended drawing, given by way of nonlimiting example, will allow a better understanding of the invention and the advantages which it is likely to provide.

 The single figure is a sectional perspective illustrating the surface structure of an implant according to the invention.

There is shown in the drawing a surgical implant
cal 1, of the kind used in bone surgery
seuse. It can be a metallic part
a joint prosthesis (hip, knee, etc.). Her
surface 2 constitutes a contact zone with the surrounding bone
to which we want to fix it.

According to the invention, the surface 2 is provided with the
fixing of a structure 3, comprising both
- small spheres 5 juxtaposed, and also fixed
between them, to form a porous structure 4;
- on the outer wall of structure 4, a layer
6 of a substance promoting the proliferation of cel
the bones
Layer 6 is preferably formed by
hydroxyapatite, made, for example, in a lab
roof. Its positioning on the balls 5 of the structure in.
reuse 4 can be ensured by plasma projection
In practice, we can use technology
next
1 ~) Reference layer 5 microbeads
These are small 5 spheres, whose caliber
can vary between 100 microns and 1 mm. These spheres are fi
xed together and to support 1, and form one or more
several layers of coating, the thickness of which may vary
depending on the diameter of the microbeads that have been chosen.

This association of spherical particles 5 allows
the formation of pores 7, in the cavities of which the bone
will grow back, thus ensuring the retention of the prosthesis
to its bone support.

2 ") Hydroxyapatite of the reference layer 6
The microbeads are coated with a layer 6 of hydroxyapatite (calcium hydroxyapatite).

 This hydroxyapatite is the organic component of bone, which can be synthesized in the laboratory.

This layer which covers the surface of the microbeads 5 can have a variable thickness, and will facilitate the fixing of the prosthesis to the bone, by acting on the rate of formation of the bone cells which will penetrate inside the pores 7 formed by microbeads
The entire structure 3 (microbeads + hydroxyapatite) forms a coating which allows the biological anchoring of the prostheses. It can be replaced by any other equivalent porous structure.

 The fixation to the bone of such prostheses 1 can also be done via acrylic cement (polymethyl - surgical methacrylate). In this case, the porosity of the coating mentioned above makes it possible to improve the fixing of the cement to the prosthesis; the latter being pressurized during the impaction of the prosthesis in the bone, it will penetrate inside the cavities of the coating, and promote fixation

Claims (3)

 1 - Surgical implant intended to be applied against a bone, to be fixed therein in a biological manner, characterized in that its zone of contact and fixation with the bone, is coated with a structure comprising both  - a porous structure in the cavities (7) of  which bone can grow back  - on the exterior surface of this structure in.  reuse (4), a layer (6) of hydroxyapatite  it being understood that this hydroxyapatite is the cons  inorganic bone substitute, of which it is possi  ble to synthesize in the laboratory  2 - Surgical implant according to claim 1, characterized in that the porous structure (4) consists of small juxtaposed spheres (5) fixed together and to the surface of the implant (1).  3 - Surgical implant according to any one of the preceding claims, characterized in that the establishment of the layer (6) of hydroxyapatite on the spheres (5) of the porous structure (4) is ensured by plasma spraying.