BONE-ANCHORED IMPLANT, AND METHOD FOR MANUFACTURING SUCH AN IMPLANT

Abstract

An implant intended to be at least partially implanted into a bone by means of an implant part having an endosseous surface, wherein said endosseous surface comprises at least one zone having a surface topography exhibiting: an arithmetic mean peak curvature parameter (Spc) less than or equal to 1 μm.sup.1, a density of peaks parameter (Spd) greater than or equal to 0.020 μm.sup.−2.

Claims

1. An implant intended to be at least partially implanted into a bone by means of an implant part having an endosseous surface, wherein said endosseous surface comprises at least one zone having a surface topography exhibiting: an arithmetic mean peak curvature parameter (Spc) less than or equal to 1 μm.sup.1, a density of peaks parameter (Spd) greater than or equal to 0.020 μm.sup.−2.

2. The implant as claimed in claim 1, wherein the ratio of the arithmetic mean peak curvature (Spc) to the density of peaks (Spd) is comprised in the interval [5; 50].

3. The implant as claimed in claim 1, wherein the body of the implant is made of ceramic, of metal, or of metal alloy.

4. The implant as claimed in claim 1, wherein the implant comprises a porous exterior layer having a thickness comprised between 1 and 5 μm.

5. The implant as claimed in claim 1, wherein the density of peaks parameter (Spd) is less than or equal to 0.5 μm.sup.−2.

6. A method for manufacturing an implant as claimed in claim 1, comprising the following successive steps: a) supplying an implant body comprising an endosseous surface intended to be implanted into a bone, b) supplying a solution of an organic material in a solvent, said solution containing a particulate material in suspension, c) applying the solution to a zone of the endosseous surface of the implant body, d) evaporating the solvent, e) heating the implant body to a treatment temperature, the treatment temperature and duration being chosen to be high enough to eliminate the organic material and not high enough to cause the particulate material and the material constituting the implant body to melt.

7. The method as claimed in claim 6, wherein, before step e), steps c) and d) are repeated several times, preferably at least 50 times.

8. The method as claimed in claim 6, wherein the organic material is a polymer, preferably a polyethylene glycol, more preferably still, a polyethylene glycol with a molecular weight of around 4000 g/mol.

9. The method as claimed in claim 6, wherein, in order to prepare the solution of step b), use is made of a volume of organic material that is 1 to 20 times, preferably 1 to 10 times, more preferably still, 1 to 6 times, higher than the volume of particulate material.

10. The method as claimed in claim 6, wherein the particulate material is a powdered ceramic, preferably zirconia, or powdered metal, preferably titanium or a titanium alloy.

11. The method as claimed in claim 6, wherein, during step c), the solution is applied to the implant body by spraying.

12. The method as claimed in claim 6, wherein, in the solution, the particulate material represents 0.1% to 10% of the volume of the solution, preferably 0.5% to 1%.

13. The method as claimed in claim 6, wherein the particulate material has a median particle size less than or equal to 1 μm.

14. The method as claimed in claim 6, wherein: the implant body is made of ceramic, preferably of zirconia, more preferably still, of yttrium-doped or cerium-doped zirconia, the particulate material is a powdered ceramic, preferably a powdered zirconia, more preferably still, powdered yttrium-doped or cerium-doped zirconia, the organic material is polyethylene glycol.

15. The method as claimed in claim 6, wherein, during step e), the implant body is heated to a treatment temperature comprised between 600° C. and 1600° C., preferably between 1100° C. and 1600° C., and more preferably still, between 1300° C. and 1600° C.

16. The method as claimed in claim 6, wherein the implant body is made of a ceramic, of a metal, or of an alloy of metals, of which the dimensions, during step e), do not vary by more than 3 to 5%.

17. The method as claimed in claim 6, wherein the implant body is made of a ceramic, of a metal, or an alloy of metals, of which the density is at least 95% of its theoretical density.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Further objects, features and advantages of the present invention will become apparent from the following description of particular embodiments, which is given in connection with the attached figures, among which:

[0058] FIG. 1 is a diagram illustrating the various steps of one particular embodiment of a method for obtaining an implant according to the present invention;

[0059] FIG. 2 is a view on micrometric scale of an example of surface topography obtained by the method of FIG. 1 on an implant body; and

[0060] FIG. 3 is a view of various implants used during tests conducted by the applicant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] Where identical numerical references are used in a number of figures, embodiments, or variants of the invention, these numerical references refer to elements that are identical or similar in each of the figures, embodiments or variants.

[0062] Manufacturing Method

[0063] FIG. 1 schematically illustrates an example of a method of manufacture that makes it possible to obtain an implant according to the present invention.

[0064] In this example, the method of manufacture comprises the following successive steps:

a) supplying an implant body comprising an endosseous surface intended to be implanted into a bone,
b) supplying a solution of an organic material in a solvent, said solution containing a particulate material in suspension,
c) applying the solution to a zone of the endosseous surface of the implant body,
d) evaporating the solvent,
e) heating the implant body to a treatment temperature, the treatment temperature and duration being chosen to be high enough to eliminate the organic material and not high enough to cause the particulate material and the material constituting the implant body to melt.

[0065] Before step e), steps c) and d) are repeated several times, preferably at least 50 times. In other words, step e) is performed just once, after steps c) and d) have been repeated a sufficient number of times. Performing steps c) and d) 50 times has led to excellent topographies.

[0066] The organic material is a polymer, preferably a polyethylene glycol, more preferably still, a polyethylene glycol with a molecular weight of around 4000 g/mol.

[0067] In order to prepare the solution of step b), use is made of a volume of organic material that is 1 to 20 times, preferably 1 to 10 times, more preferably still, 1 to 6 times, higher than the volume of particulate material.

[0068] The particulate material is a powdered ceramic, preferably zirconia, if the implant body is made of ceramic. As an alternative, the particulate material is powdered metal, preferably titanium or a titanium alloy, if the implant body is made of metal.

[0069] During step c), the solution is applied to the implant body by spraying.

[0070] In the solution, the particulate material represents 0.1% to 10% of the volume of the solution, preferably 0.5% to 1%.

[0071] The particulate material has a median particle size less than or equal to 1 μm.

[0072] During step e), the implant body is heated to a treatment temperature comprised between 600° C. and 1600° C.

[0073] The implant body is made of a ceramic, of a metal, or of an alloy of metals, of which the dimensions, during step e), do not vary by more than 3 to 5%.

[0074] The implant body is made of a ceramic, of a metal, or an alloy of metals, of which the density is at least 95% of its theoretical density.

[0075] This method according to the invention has led to the example of surface topography illustrated in FIG. 2. In that figure, it may be seen that the surface topography obtained is in the form of a 1 to 5 μm surface layer of reduced density in which the ceramic particles are distributed almost uniformly, with a short distance between them. The ceramic particles form peaks between which there are troughs left by the organic material that has been eliminated during step e). No real pores were observed.

[0076] Shapes and Materials of the Implants Tested

[0077] FIG. 3 illustrates a number of implants S1 to S4 and P1 to P4 used during testing.

[0078] The implants S1, S2, S4 and P1 to P3 have a cylindrical shape with a length L of 12 mm and a circular cross section with a diameter D of 4.6 mm. They are provided with the same external screw thread on their lateral surface so that they can be inserted by screwing them into a hole made in a bone.

[0079] The implants P4 and S3 have a cylindrical shape with a length L′ of 12 mm and a circular cross section with a diameter D′ of 4.2 mm. They have no external screw thread on their lateral surface and are intended to be inserted by impaction into a hole made in a bone.

[0080] The implants S1 to S4 and P1 are made of ceramic, more particularly of a mixture of cerium-doped zirconia and of alumina.

[0081] The implants P2 to P4 are made of metal. The implant P2 is more particularly made of a titanium alloy Ti13Zr. The implants P3 and P4 are more particularly made of a titanium alloy Ti6Al4V ELI.

[0082] Implants with Surface Topography According to the Invention

[0083] The “S” implants (S1 to S4) are implants according to the present invention, on the exterior surface of which a surface topography has been produced using the method of the present invention illustrated in FIG. 1.

[0084] During step c), a solution of organic material (polyethylene glycol with a molecular weight of around 4000 g/mol) in a solvent has been applied by spraying to the exterior surface of the implants S1 to S4, said solution containing a particulate material in suspension (consisting of a mixture of cerium-doped zirconia and of alumina).

[0085] The particulate material was thus a ceramic powder placed in suspension. In this suspension, 10% of the suspended particles had a size less than 0.15 μm, 50% of the suspended particles had a size less than 0.4 μm and 90% of the suspended particles had a size less than 2 μm. This particle size distribution of the particulate material was measured in accordance with the ISO 13320 standard by liquid-distribution laser diffractometry on measurement equipment marketed under the tradename “MASTERSIZER 3000” by the MALVERN PANALYTICAL company.

[0086] Steps c) and d) were repeated approximately 50 times before step e) was performed at the same treatment temperature of between 1350° C. and 1450° C. for each implant.

[0087] For the implant S1, use was made of a volume of organic material that was 2 times higher than the volume of particulate material. For the implants S2 and S3, use was made of a volume of organic material that was 4 times higher than the volume of particulate material. For the implant S4, use was made of a volume of organic material that was 6 times higher than the volume of particulate material.

[0088] The parameters Spc, Spd and the Spc/Spd ratios of the surface topographies of the implants S1 to S4 are given in table 1.

[0089] The topography of the surfaces was examined quantitatively on a surface measuring 351 μm×264 μm using a 3D confocal microscope (S-Neox, Sensofar Tech S.L, Terrassa, Spain). A confocal objective lens with a magnification of ×50 giving a lateral resolution of 0.26 μm was used. The total quantity of unmeasured points was below 5%.

[0090] All of the operations were applied to the result of the measurement using the SensoMAP software (SensoMAP, version 7.4.8803, SENSOFAR TECH, Terrassa, Spain) using the Mountains Map® software (issued by Digital Surf, Besancon, France) including the Grains and Particles module and the 3D advanced surface texture module.

[0091] The Spc and Spd parameters described in the 15025178 standard were extracted from the measurements which were taken by: [0092] noise filtering (3×3 median filter), [0093] applying a form removal F− operator (5.sup.th-degree polynomial), [0094] filling in the unmeasured points using a smooth form calculated from adjacent points, [0095] applying an S-filter (0.8 μm×0.8 μm, gaussian filter), [0096] applying an L-filter (25 μm×25 μm, robust gaussian filter), [0097] thresholding in order to retain only the 95% of data centered around the median plane.

TABLE-US-00001 TABLE 0 Spc, Spd parameters and Spc/Spd ratios for the surface topographies of implants S1 to S4 Spc (μm.sup.-1) Spd (μm.sup.-2) Spc/Spd (μm) Mean over 9 Standard Mean over 9 Standard Mean over 9 Standard Implant measurements Deviation measurements Deviation measurements Deviation S1 0.521 0.147 0.040 0.006 13.251 3.940 S2 0.573 0.119 0.027 0.008 21.526 3.116 S3 0.459 0.036 0.021 0.001 22.390 2.910 S4 0.644 0.166 0.020 0.007 33.172 4.676

[0098] Implants with Surface Topography According to the Prior Art

[0099] The “P” implants (P1 to P4) are implants on the exterior surface of which a surface topography has been created according to known conventional methods. The implants P1 to P4 are thus control implants so that the effects afforded to the implants S1 to S4 by the present invention can be acknowledged.

[0100] The exterior surface of the implant P1 (made of ceramic) was blasted by particles of alumina (Al.sub.2O.sub.3) and then underwent two attacks, with hydrofluoric acid (HF) and with nitric acid (HNO.sub.3).

[0101] The exterior surface of the implant P2 (made of metal) underwent a treatment of SLA type, with blasting, followed by a double acid etching operation using hydrochloric acid (HCl) and sulfuric acid (H.sub.2SO.sub.4).

[0102] The exterior surfaces of the implants P3 and P4 (made of metal) underwent a treatment of BCP type.

[0103] The Spc, Spd parameters and the Spc/Spd ratios of the surface topographies of the implants P1 to P4 were measured, as for the implants S1 to S4, and are given in table 2.

TABLE-US-00002 TABLE 2 Spc, Spd parameters and Spc/Spd ratios for the surface topographies of the implants P1 to P4 Spc (μm.sup.-1) Spd (μm.sup.-2) Spc/Spd (μm) Mean over 9 Standard Mean over 9 Standard Mean over 9 Standard Implant measurements deviation measurements deviation measurements deviation P1 1.493 0.557 0.025 0.009 60.414 12.430 P2 3.501 0.877 0.013 0.003 275.970 84.871 P3 7.644 1.582 0.023 0.005 338.207 90.669 P4 6.056 0.558 0.015 0.001 400.514 44.251

[0104] Extraction after In Vivo Implantation

[0105] Twelve implants S3 and twelve implants S4 were inserted into the humorous of twelve separate ewes. Each ewe received one implant S3 and one implant P4, implanted in its right or left humorous respectively. At the end of a period of 4 weeks following implantation, 6 ewes were slaughtered so that the implants could be extracted axially using an INSTRON tensile test machine fitted with a load cell. At the end of a period of 8 weeks after implantation, the remaining 6 ewes were slaughtered so that the implants could be extracted axially using the same INSTRON tensile test machine fitted with a load cell.

[0106] The results are given in table 3.

TABLE-US-00003 TABLE 3 Implant extraction forces Extraction force (N) Mean over 6 implants Standard Study time Implant (N) deviation 4 weeks S3 870 160 P4 482 72 8 weeks S3 975 284 P4 552 145

[0107] It may thus be seen that the implants S3 have a markedly higher resistance to extraction than the implants P4, whether this be at 4 weeks or at 8 weeks. At 4 weeks, the resistance to extraction of the implants S3 is around 80% higher than the resistance to extraction of the implants P4. At 8 weeks, the resistance to extraction of the implants S3 is around 77% higher than the resistance to extraction of the implants P4. The proportional increase between 4 and 8 weeks is substantially identical between the implants S3 (+12%) and P4 (+14%).

[0108] These results tend to demonstrate that the implants according to the invention offer significantly earlier osteointegration and that, in the longer term, the osteointegration is significantly better.

[0109] Measurement of the Proportion of the Exterior Surface of the Implant that is in Contact with the Bone after In Vivo Implantation

[0110] Twelve of each of the implants S1, S2 and S4 (namely 36 implants) and twelve of each of the implants P1, P2 and P3 (namely 36 implants) were inserted into the femurs of twelve distinct ewes. Each ewe thus had 6 implants, namely 3 identical implants implanted in its right femur and 3 other identical implants in its left femur. At the end of a period 4 weeks after implantation, 6 ewes were slaughtered so that the BIC (bone to implant contact) parameter could be evaluated in order to determine the proportion of the exterior surface of the implant that was in contact with the bone. At the end of a period of 8 weeks after implantation, the remaining 6 ewes were slaughtered so that the BIC (bone to implant contact) parameter could be evaluated by tomography in order to determine the proportion of the exterior surface of the implant that was in contact with the bone.

[0111] The results are given in table 4.

TABLE-US-00004 TABLE 4 Proportion of the exterior surface of the implant in contact with the bone (BIC) BIC (%) Mean over Standard Study time Implant 6 implants deviation 4 weeks S1 79.6 7.1 S2 73.8 2.5 S4 70.3 9.1 P1 42.4 18.4 P2 55.8 11.3 P3 68.6 8.2 8 weeks S1 78.4 5.4 S2 88.2 5.4 S4 76 10.8 P1 79.7 7.9 P2 75.9 6.2 P3 78.8 4.2

[0112] It is thus found that, at 4 weeks, the respective BIC parameters of the implants S1, S2 and S4 are all higher (and even very markedly higher as far as the implants S1 and S2 are concerned) than the respective BIC parameters of the implants P1, P2 and P3.

[0113] It is also found that, at 8 weeks, the BIC parameters of all the implants are relatively similar. However, the S2 implants demonstrate the highest BIC parameter.

[0114] These results tend to demonstrate that the implants according to the invention offer earlier osteointegration than the implants that have undergone known conventional surface treatments. Osteointegration is significantly better for the implants S2.

[0115] Finally, the tests conducted demonstrate that the present invention affords increased and/or accelerated and/or facilitated osteointegration, particularly in the case of an implant having an implant body made of ceramic.

[0116] Some of the work relating to the present invention was carried out in the context of the LONGLIFE consortium and has received funding from the European Union's seventh framework program for research (FP7/2007-2013) under grant agreement No. 280741.

[0117] The present invention is not restricted to the embodiments explicitly described but includes the diverse variants and generalizations thereof that fall within the scope of the attached claims.