Device for coaptation of bone fragments and methods for producing such a device

Abstract

A device for coaptation of bone parts or bone fragments, comprising an integral plate obtained by moulding whereof one portion (1) is made from a first biocompatible polymer comprising at least one or, preferably, a plurality of areas or inserts (2) provided with a through hole (3), said areas or inserts being made from a second biocompatible polymer which is more malleable than the first polymer, said areas or inserts having mechanical properties allowing a self-tapping of the inner surface of the holes, by means of screws that can be used for securing said plate to bone tissue, said support portion and said areas or inserts having a partial molecular bond between them.

Claims

1. A device for coaptation of bones, comprising a single molded plate having a support portion formed from a first biocompatible polymer and at least two zones, the plate being provided with a through hole, wherein one of the zones comprises a second biocompatible polymer which is more malleable than the first biocompatible polymer, the zones having mechanical properties enabling tapping of an inside surface of the molded plate defining the hole by a screw adapted for fastening the molded plate to a bone, the support portion and the at least two zones presenting at least a partial melting.

2. The device according to claim 1 wherein the support portion comprises a zone including carbon fibers.

3. The device according to claim 1 wherein the first biocompatible polymer comprises a hardening filler in a matrix formed by the second biocompatible polymer.

4. The device for according to claim 1 wherein at least one zone is formed from Polyetheretherketone (PEEK).

5. The device according to claim 1 wherein the plate has locally increased thicknesses on the underside at a location of the at least one zone of lower hardness.

Description

(1) The above objects, features and advantages, and still others, will be better apparent from the detailed description which follows and from the accompanying drawings in which:

(2) FIG. 1 is a perspective view of a first example embodiment of a osteosynthesis plate according to the invention, for use at the location of the medial malleolus.

(3) FIG. 2 is a cross-section view on line II-II of FIG. 1.

(4) FIG. 3 is a perspective view of another, more complex example of an osteosynthesis plate according to the invention, for use at the location of the talonavicular joint.

(5) FIG. 4 is a detailed view of the osteosynthesis device according to the invention.

(6) Reference will be made to said drawings to describe an advantageous though non-limitative embodiment of the coaptation plate according to the invention and of implementation of methods of overmolding and of bi-material injection.

(7) In the present disclosure and in the claims, the expression “underside” designates the face adapted to be placed facing the bone fragments of which the coaptation is desired to be carried out.

(8) In the drawings, interfaces can be seen between the zones or inserts and their support portion; it should be clearly understood that these interfaces are only shown to enable the understanding of those drawings, whereas, since partial molecular melting together of one material with the other occurs, those interfaces are in fact not clearly constituted.

(9) Coaptation Device

(10) The coaptation device according to the invention is of an appropriate shape for the use which it is intended for. It is provided to be fastened to bone fragments, by means of screws (not shown) to ensure their coaptation. It comprises a plate 1 comprising a portion, referred to as support portion 4, is provided with at least one zone or insert 2 having a hole 3 made from a malleable biocompatible polymer presenting mechanical properties enabling self-tapping of the periphery of said holes by means of threaded screws usable for fastening said device, the remaining portion or support portion 4 of said plate 1 for coaptation of bone fragments being made from a biocompatible polymer with a Carbon filler and having, after polymerization/molding, a higher rigidity than that of the zone or insert or zones or inserts.

(11) Advantageously, the plate comprises several inserts 2.

(12) According to an advantageous feature, the zones or inserts 2 are made from natural Polyetheretherketone and the support portion 4 is made from PEEK with a with a filler of implantable Carbon fibers.

(13) Advantageously and as illustrated in FIG. 4, the coaptation plate 1 has locally increased thicknesses 5 on the underside at the location of the inserts 2. More particularly, the inserts 2 enable those locally increased thicknesses 5 to be produced such that said plate is placed on bone fragments of which it is desired to perform the coaptation, the periosteum of said bone fragments is conserved, which enables better bone reconstruction.

(14) According to a first example embodiment, the coaptation device 1 according to the invention is produced by a method of overmolding described below.

(15) According to another embodiment, the coaptation device according to the invention is produced by a method of bi-material injection described below.

(16) The Overmolding Method

(17) Such a coaptation device including one or more of the aforementioned features, is obtained by an overmolding method comprising: placing in a mold, at least one preformed part or insert made from a malleable biocompatible polymer; injecting into that mold, around said preformed part, a biocompatible polymer with a filler of Carbon fibers, and having, after polymerization/molding, a higher rigidity than that of said preformed part or insert; leaving the part to cool before ejecting it.

(18) According to an advantageous feature, the malleable biocompatible material constituting the insert is Polyetheretherketone (natural PEEK).

(19) According to another advantageous feature, the biocompatible material injected around the insert to constitute the support portion 4 of the plate 1 is PEEK with a filler of implantable Carbon fibers.

(20) As the insert of natural PEEK and the PEEK with a Carbon fiber filler constituting the remainder of the plate are compatible, there is a chemical bond between the two materials and partial melting together optimizing the strength of that bond.

(21) As the strength of that bond may be affected by different factors, such as the temperature at the interface, the cleanliness of the insert or the melting point, or the geometry of the interface, it is necessary to comply with certain conditions.

(22) Thus, according to the method of the invention, the injection is made in a mold of which the temperature is comprised between 140° C. and 220° C., and more particularly at a temperature of 175° C.

(23) According to another feature of the method of the invention, the biocompatible polymer with a Carbon filler is injected at a temperature comprised between 350° C. and 440° C. Advantageously, it is injected at a temperature of 395° C.

(24) The biocompatible polymer with a Carbon filler is injected at a speed comprised between 50 g/sec and 750 g/sec. For example, it is injected at a speed of 300 g/sec.

(25) According to the method of the invention, it is preferable to avoid extremely high holding pressures. Thus, the biocompatible polymer with a Carbon filler is injected at a pressure comprised between 500 and 2000 Bars. Advantageously, it is injected at a pressure of 1000 Bars.

(26) In order to avoid excessive shrinkage (that is to say the retraction of the material at the time of its cooling at the end of overmolding) at the final phase of production and thus avoid a possibility of functional loss, the device obtained requires a cooling time comprised between 10 seconds and 30 seconds. Preferably, the cooling time of the device obtained is 20 seconds.

(27) The Bi-Injection Method

(28) According to another example of implementation, a coaptation device according to the invention is obtained by a bi-material injection method comprising: injecting into a mold, provided with two injection points to supply each of the materials, a biocompatible polymer (PEEK) to manufacture said inserts and a biocompatible polymer with a Carbon fiber filler to manufacture the support portion 4 of the plate 1, having after polymerization/molding a higher rigidity than that of the insert; leaving the part to cool before ejecting it.

(29) According to an advantageous feature, the malleable biocompatible material constituting the insert is Polyetheretherketone (PEEK).

(30) According to another advantageous feature, the biocompatible material injected around the insert to constitute the support portion 4 of the plate 1 is PEEK with a filler of implantable Carbon fibers.

(31) As the insert of PEEK and the PEEK with a Carbon filler constituting the remaining part of the plate, i.e. the support portion, are compatible, there is a chemical bond between the two materials and partial melting together optimizing the strength of that bond.

(32) As the strength of that bond may be affected by different factors, such as the temperature at the interface, the cleanliness of the insert or the melting point, it is necessary to comply with certain conditions.

(33) Thus, according to the method of the invention, the injection is made in a mold of which the temperature is comprised between 140° C. and 220° C., and more particularly at a temperature of 175° C.

(34) According to another feature of the method of the invention, the biocompatible polymer with a Carbon filler is injected at a temperature comprised between 350° C. and 440° C. Advantageously, it is injected at a temperature of 395° C.

(35) The biocompatible polymer with a Carbon filler is injected at a speed comprised between 50 g/sec and 750 g/sec. For example, it is injected at a speed of 300 g/sec.

(36) According to the method of the invention, it is imperative to avoid extremely high holding pressures. Thus, the biocompatible polymer with a Carbon filler is injected at a pressure comprised between 500 and 2000 Bars. Advantageously, it is injected at a pressure of 1000 Bars.

(37) In order to avoid excessive shrinkage (that is to say the retraction of the material at the time of its cooling at the end of injection) at the final phase of production and thus avoid a possibility of functional loss, the device obtained requires a cooling time comprised between 10 seconds and 30 seconds. Preferably, the cooling time of the device obtained is 20 seconds.