ZIRCONIUM-COATED IMPLANT COMPONENT AND USE OF SAME

Abstract

The present disclosure relates to an implant component (10, 20) having at least one connecting portion (30, 60), the connecting portion being at least partly coated with a Zr coating and the coating having a thickness of 1-20 μm, preferably 1-6 μm. The present disclosure further relates to a modular endoprosthesis comprising an implant component, to the use of a Zr coating to prevent crevice corrosion and/or fretting corrosion, and to the use of an implant component in patients suffering from a metal allergy.

Claims

1. An Implant component, comprising at least one connecting portion, the connecting portion being at least partly coated with a Zr coating and the coating having a thickness of 1-20 μm.

2. The implant component of claim 1, wherein the coating has a thickness of 3-6 μm.

3. The implant component of claim 1, wherein the connecting portion comprises a female or a male cone.

4. The implant component of claim 1, wherein the connecting portion is rotationally symmetrical.

5. The implant component of claim 1, wherein the implant component comprises a titanium-based alloy or a cobalt-based alloy.

6. The implant component of claim 5, wherein the implant component comprises a CoCr alloy.

7. The implant component of claim 1, wherein the implant component comprises a prosthesis shaft, an intermediate piece, or a joint head.

8. The implant component of claim 1, in which the Zr coating has a Zr content of at least 90 At. %.

9. The implant component of claim 1, wherein the coating is applied by a physical vapor deposition process or by an electroplating process.

10. The modular endoprosthesis comprising at least one implant component of claim 1

11. The modular endoprosthesis of claim 10, further comprising a second implant component having a connecting portion counterpart, said connecting portion counterpart engageable with said connecting portion of said first implant component, wherein said connecting portion counterpart does not have any Zr coating.

12. The modular endoprosthesis of claim 11, wherein the first implant component is a prosthesis shaft having a male cone connecting portion, and second implant component is a joint head comprising a connecting portion female cone counterpart embodied as a female cone.

13. A method of preventing corrosion of an implant comprising applying a Zr coating to a connecting portion of the implant component of claim 1, said coating applied to a thickness of 1-20 μm.

14. The method of treating a patient in need of a hip replacement joint who has a metal allergy comprising: implanting the implant component of claim 1 and the implant component is a component of a hip prosthesis.

15. The method of claim 14, wherein the implant is a modular endoprosthesis.

16. The implant component of claim 8, wherein the Zr coating has a Zr content of at least 97 At. %.

17. The implant component of claim 8, wherein the Zr coating has a Zr content of at least 99.5 At. %.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 depicts an embodiment of a modular endoprosthesis according to the present disclosure in a disassembled state;

[0042] FIG. 2 depicts the embodiment of the modular endoprosthesis from FIG. 1 in a connected state;

[0043] FIG. 3a depicts the course of the current measured during cyclic loading of an endoprosthesis having a known implant component;

[0044] FIG. 3b depicts the course of the current measured during cyclic loading of an endoprosthesis having an implant component according to the present disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0045] The preferred embodiments described below are merely examples and are not to be considered as limiting. The same reference symbols that are listed in different figures designate identical, corresponding, or functionally similar elements.

[0046] FIG. 1 depicts an embodiment of a modular endoprosthesis according to the present disclosure in an unconnected state. The modular endoprosthesis has a prosthesis shaft (10) as the first implant component and a joint head (20) as the second implant component. The prosthesis shaft (10) has a connecting portion embodied as a male cone (30). The male cone (30) has an end face (40) and an outer circumferential surface (50). The male cone (30) is coated, at least partially, with a Zr coating, the Zr coating having a layer thickness of 1-20 μm, preferably 1-6 μm.

[0047] Preferably at least the entire outer circumferential surface (50) of the male cone (30) is coated with a Zr coating. Furthermore, the end face (40) of the male cone (30) can also be coated with a Zr coating. The transition from the outer circumferential surface (50) of the male cone (30) to the end face (40) of the male cone (30) can be embodied, for example, as a chamfer or edge rounding. This transition (i.e. the chamfer or edge rounding) can also have a Zr coating according to the disclosure.

[0048] The joint head (20) has a connecting portion counterpart embodied as a female cone (60). The female cone (60) has an inner circumferential surface (70) and a bottom surface. The joint head (20) also has a joint ball (80). The joint ball is preferably embodied as a ball segment having an essentially spherical surface which acts as the joint surface of this joint component. In FIGS. 1 and 2, the female cone (60) is embodied in a connection region essentially opposing the joint ball. The connection region with the female cone (60) embodied therein projects from the side of the joint ball delimiting the ball segment. The female cone (60) can extend into the region of the ball segment. It is also possible for the connection region not to embody a projection, but rather to embody a surface that defines the ball segment and thus the joint surface. In this case the female cone (60) is formed inside the ball segment.

[0049] In the present embodiment, neither the inner circumferential surface (70) nor the bottom surface of the female cone (60) has a Zr coating. In a modification to the embodiment described above, however, the female cone (60) of the joint head (20) can also have a Zr coating, while the male cone (30) of the prosthesis shaft (10) has no Zr coating. According to a further modification, both the female cone (60) of the joint head (20) and the male cone (30) of the prosthesis shaft (10) can have a Zr coating. Preferably at least the entire outer circumferential surface (50) of the male cone (30) or the entire inner circumferential surface (70) of the female cone (60) is coated with a Zr coating.

[0050] In a variant of the embodiment described above (not shown in FIGS. 1 and 2), the female cone (60) and the male cone (30) can also be exchanged. For example, the prosthesis shaft (10) can also have a female cone, and the joint head (20) can have a male cone.

[0051] FIG. 2 depicts the above-described embodiment of the modular endoprosthesis according to the disclosure in a connected state. It can be seen from FIG. 2 that, in the connected state, the inner circumferential surface (70) of the female cone (60) is in contact with the outer circumferential surface (50) of the male cone (30). In order to avoid a double fit (which could prevent a wedging effect for the male cone (30) and the female cone (60)), it is preferred that the geometry of the male cone (30) and the geometry of the female cone (60) are matched to one another such that the end face (40) of the male cone (30) and the bottom surface of the female cone (60) are not in contact.

[0052] If the end face (40) of the male cone (30) and the bottom surface of the female cone (60) (and/or any chamfers, radii, or transition regions) are not in contact with one another, it can be assumed that no crevice corrosion and/or friction corrosion will occur on these surfaces. Thus, a Zr coating is not necessary on these surfaces. Nevertheless, a Zr coating can be provided on these surfaces. In particular, it can be advantageous for other reasons to provide a Zr coating on the end face (40) of the male cone (30), on the bottom surface of the female cone (60), and/or on any chamfers, radii, or transition regions. If a Zr coating is also provided in these regions, for example, a transition from an uncoated surface to a coated surface can be prevented there, which in turn reduces the risk of parts of the coated surface spalling (e.g. as a result of a notching effect and/or as a result of stress peaks). In addition, there is no need to mask these surfaces during the coating process (if the end face (40) of the male cone (30), the bottom surface of the female cone (60) and/or any chamfers, radii, or transition regions are also coated). This in turn results in cost advantages.

[0053] FIGS. 3a and 3b illustrate (in extracts) measured values of an experimental investigation in which a known implant component (FIG. 3a) and an implant component having a Zr coating according to the disclosure (FIG. 3b) were examined for the occurrence of crevice corrosion and/or friction corrosion. Qualitative or comparative information about the susceptibility of a connecting portion to crevice corrosion and/or friction corrosion can be obtained as an experimental investigation, for example using a measurement method according to ASTM F1875-98 (reapproved in 2014). In this method, femoral stem and head components are placed in a medium, for example a saline solution, and subjected to a cyclic load. The shaft and head components are connected by means of a connecting portion. Also placed in the medium are reference electrodes whose coating material matches the coating material of the shaft and head components to be tested. The surface area of the reference electrodes and the surface area of the (parts of the) shaft and head components added to the medium correspond to one another.

[0054] The shaft and head components as well as the reference electrodes are connected to a current measuring device that permits currents flowing (via the medium) between the shaft and head components, on the one hand, and the reference electrodes, on the other hand, to be measured. However, since the surface and the coating material of the shaft and head components and of the reference electrodes are identical, these currents are not due to a potential difference between the shaft and head components and the reference electrodes (galvanic cell/battery effect). On the contrary, the measurable current flow between the shaft and head components, on the one hand, and the reference electrodes, on the other hand, results from the fact that, as a result of the cyclical force mentioned above, parts of the passive layer (or passive layers) on the surface (or surfaces) of the connecting portion are abraded and re-form.

[0055] The average current Im over time and the average dynamic current Id can be determined from the measured values for the current flow between the shaft and head components and the reference electrodes. The average dynamic current Id is the difference between the maximum current I.sub.max measured in a specific time interval and the minimum current I.sub.min (i.e., in the time interval Δt1 the following applies: I.sub.d,Δt1=I.sub.max,Δt1−I.sub.min,Δt1).

[0056] If a lower Im value is measured for a first combination of shaft and head component than for a second combination of shaft and head component, this is considered to be indirect evidence that the first combination of shaft and head component is less susceptible to crevice corrosion and/or friction corrosion than the second combination of shaft and head component.

[0057] In particular, if a lower value Im and a lower value Id are measured for a first combination of shaft and head component than for a second combination of shaft and head component, this is considered to be indirect evidence that the first combination of shaft and head component is significantly less susceptible to crevice corrosion and/or friction corrosion than the second combination of shaft and head component.

[0058] The known implant component of FIG. 3a and the implant component having a Zr coating according to the disclosure of FIG. 3b were each connected to a further implant component having a connecting portion, in each case forming an endoprosthesis. The geometry of the endoprosthesis having the known implant component and the geometry of the endoprosthesis with the implant component with the Zr coating according to the disclosure were identical. Furthermore, identical test parameters were selected for both endoprostheses. As can be seen from FIGS. 3a and 3b, the endoprostheses were subjected to a cyclic load, the frequency of which was 1 Hz. The magnitude of the load ran periodically between 0.04 kN and 2.04 kN.

[0059] In the charts in FIG. 3a and FIG. 3b, the load (in kilonewtons) is plotted on the left-hand vertical axis, the negative sign for the load being due to its orientation (compression load). The time in seconds is entered on the respective horizontal axis of the charts. The current (in microamperes) measured between the endoprostheses and the reference electrodes during the cyclic loading of the endoprostheses is plotted on the right vertical axis in each case.

[0060] As can be seen from FIG. 3a, a current I.sub.m=4.49 μA averaged over time and a mean dynamic current I.sub.d=3.61 μmA were measured in a specific time interval for the endoprosthesis with the known implant component. As can be seen from FIG. 3b, a current I.sub.m=0.49 μA averaged over time and a mean dynamic current I.sub.d=0.68 μmA were measured in a specific time interval for the endoprosthesis with the implant component with the Zr coating according to the disclosure. Comparing the test series leads to the conclusion that the endoprosthesis having the implant component with the Zr coating according to the disclosure is less susceptible to crevice corrosion and/or friction corrosion than the endoprosthesis with the known implant component.