AT13497U1 - Intermediate piece of a multipart endoprosthesis and endoprosthesis - Google Patents

Abstract

The invention relates to an intermediate piece (2) of a modular endoprosthesis (1), in particular a modular hip endoprosthesis, which has a first connection surface (5) and a second connection surface (6), wherein the first connection surface (5) and the second connection surface (5). 6) are coated with a tantalum coating (8) with a degree of purity of at least 99%, the layer thickness (9) of the tantalum coating (8) being at least 3 μm, preferably between 3 μm and 50 μm.

Description

Austrian Patent Office AT13 497U1 2014-01-15

description

INTERMEDIATE PART OF A MULTIPLE ENDOPROTHESIS AND ENDOPROTHESIS

The invention relates to an adapter of a modular endoprosthesis, in particular a modular hip joint endoprosthesis having a first connection surface and a second connection surface. The invention further relates to a modular endoprosthesis with an intermediate piece.

Multi-part endoprostheses are known from the prior art, which have long proven tools in many embodiments to replace a damaged by an accident or wear and tear joint.

For example, a manipulation system for the visual selection and positioning of components of a multi-part joint endoprosthesis, preferably a hip joint endoprosthesis, is known from the document WO 2010/046470 A1. In this case, a navigation ball, which is provided on its surface with markings, attached during the operation of the free end of an exchangeable intermediate piece to decide based on the markers, which ideally combined of several differently shaped, interchangeable intermediate pieces with the prosthesis socket in different angular positions is. The replaceable intermediate piece is also referred to therein as a connecting neck.

Multi-part modular endoprostheses offer over one-piece endoprostheses great advantages in terms of their adaptability to different anatomical conditions, the adjustment can also be done during joint surgery. However, multi-part, modular endoprostheses have the disadvantage that at the coupling areas or at the connecting surfaces of the prosthesis parts connected to one another, micro-movements result in abrasion between the prosthesis parts, along with gap formation between the prosthesis parts and, as a consequence, crevice corrosion of the adjacent surfaces can. This is particularly the case under difficult conditions when the prosthesis is overloaded by overactivity of sport or work. As a result of the micro-movements of the parts of the prosthesis, body fluids enter the gaps between the parts of the prosthesis, which leads to a corrosion attack. Likewise, for example, a lowering of the pH due to inflammatory processes in the body of a patient can lead to a corrosion attack of the prosthesis parts. The prosthesis parts lose their repassivation layers, in particular at the connecting surfaces of the interconnected parts, and are therefore exposed to uncontrolled corrosion. Due to the corrosive attack, the prosthesis parts are weakened in their microstructure and reduced in their load stability. The corrosion effect can even lead to material fracture of a prosthetic part.

Furthermore, it can also lead to health problems for the patient when using certain alloys, such as titanium alloys or cobalt-chromium alloys for the production of prosthesis parts.

The alloys mentioned are currently used by almost all manufacturers for prosthesis parts and have prevailed in particular because of their hardness and strength in the market.

Examples of metal alloys are vitallium, which is largely composed of cobalt, chromium and molybdenum and is used in orthopedic surgery for artificial joints and other implants. Likewise, the titanium alloy Ti6AL4V, which in addition to titanium also contains 6% aluminum and 4% vanadium, has long been used for implants.

Considered in the long term, allergies can arise when using these alloys. In addition, due to the micro-movements described above, a fine attrition of the prosthesis parts at their contact surfaces, depending on the composition of the Austrian Patent Office AT 13 497 Ul 2014-01-15

Alloy also cobalt or chromium ions go into solution. Depending on the composition and concentration of the alloying metals used, metal ions can lead to allergic irritation or even to toxic phenomena in the patient's body.

It is therefore one of the objects of the present invention to provide modular endoprostheses which overcome the known disadvantages of the prior art. In particular, it is an object of the invention to provide endoprostheses that are biocompatible and corrosion resistant and low in abrasion. At the same time, such endoprostheses when worn in the body of a patient should be free of irritation or health-endangering interactions.

These objects are achieved by an intermediate piece of a modular endoprosthesis according to the preamble of claim 1 with the features of the characterizing part of claim 1.

Advantageous embodiments and developments of the invention are set forth in the subclaims Chen and the description.

The intermediate piece of a modular endoprosthesis according to the invention has a first connection surface and a second connection surface. According to the invention, the first connection surface and the second connection surface are coated with a tantalum coating having a purity of at least 99%.

The connecting surfaces of the intermediate piece are those surfaces on which the other prosthesis parts are attached and connected to the intermediate piece. For example, a shaft part for insertion into a medullary cavity of a bone with a joining surface is attached to the first connection surface of the intermediate piece and firmly joined together. By way of example, a joint ball, which forms a joint head of a ball joint, attached to a joining surface on the second connection surface of the intermediate piece and also firmly joined together with this.

Since tantalum is biocompatible and inert, that is not toxic and does not react with body tissues or fluids, elemental tantalum is used for medical implants and instruments. Furthermore, tantalum has the advantage of being particularly resistant to acids. In most acids tantalum is not soluble because of its excellent passivation properties, even aqua regia can not dissolve the metal. Due to its hardness tantalum is particularly low in abrasion, which offers a further advantage of at least partially coated with tantalum intermediate pieces. At least 99% purity of the tantalum coating ensures that the coating is ductile and has high mechanical strength. Admixtures or impurities lead to an undesirable embrittlement of tantalum, which is why it is then difficult to process.

The first and the second connecting surface of the intermediate piece according to the invention are formed in any desired shapes, wherein all conceivable cross-sectional shapes of connecting surfaces are included in the invention.

Suitably, in an intermediate piece according to the invention, the layer thickness of the tantalum coating at least 3 pm, preferably the layer thickness is between 3 pm and 50 pm.

It is advantageously ensured with a layer thickness of at least 3 pm that the tantalum coating is not abraded over a lifetime of the prosthesis. This further crevice corrosion is prevented, whereby a risk of breakage of the intermediate piece is excluded. Preferably, the layer thickness of the tantalum coating is between 3 pm and 50 pm, which represents a good compromise between a sufficient safety against crevice corrosion and a reasonable manufacturing outlay and the associated production costs.

Another advantageous feature of the invention is characterized in an intermediate piece by the Austrian Patent Office AT13 497U1 2014-01-15 that the tantalum coating is dense in relation to ion leakage from a base material of the intermediate piece.

As already mentioned, the base material usually contains metals such as cobalt, chromium, or titanium. In particular, the first two materials damage the patient's body, especially in dissolved, ionogenic form. Advantageously, in an intermediate piece, therefore, those surfaces that are particularly exposed to a corrosion attack, coated with a tantalum coating that prevents diffusion of metal ions from the underlying base material. This further increases the biocompatibility of the intermediate piece.

Advantageously, in one embodiment of the invention, the entire intermediate piece coated with the tantalum coating. In this embodiment variant, the biocompatibility of the intermediate piece or the endoprosthesis equipped therewith is further increased by the closed tantalum coating of the entire intermediate piece, and undesired ion leakage from the underlying base material is reliably avoided.

Suitably, an intermediate piece according to the invention of a cobalt-chromium alloy, a titanium alloy or a steel alloy is prepared as a base material.

The alloys mentioned have prevailed in the market because of their hardness and strength. The negative properties of these alloys, such as their tendency to crevice corrosion and unsatisfactory biocompatibility are eliminated by the tantalum coating at least at the connecting surfaces of the intermediate piece.

It is advantageous in an intermediate piece according to the invention, at least one of the two connecting surfaces is tapered, in particular conical, formed.

Under tapered connecting surfaces all conceivable cross-sectional shapes are included, which taper towards a free end or end portion of the intermediate piece and are suitable for applying or for attaching a further prosthesis part on the intermediate piece. By a conically tapered connecting surface is meant a truncated cone with a substantially circular cross-sectional area. In a conical design of the connecting surface, the intermediate piece during assembly with the prosthesis stem or with the joint ball in its position relative to the attached prosthesis parts is adjustable.

In a further embodiment according to the invention at least one of the two connecting surfaces is cylindrical in an intermediate piece. This embodiment has the advantage that even with a cylindrical formation of one or both of the connecting surfaces, the intermediate piece can be adjusted in its position when being joined to the prosthesis socket or the joint ball. Thus, when inserting the modular endoprosthesis in the body of the patient, the surgeon's work is facilitated, and the individual prosthesis parts can be adjusted to each other by adjusting their relative positions to each individual spatial situation in the reconstruction of a joint.

In one embodiment of the intermediate piece according to the invention at least one of the two connecting surfaces is formed on the outer surface of a projection or end portion of the intermediate piece.

Suitably, in a further embodiment of an intermediate piece according to the invention, at least one of the two connecting surfaces is formed on the inner surface of a recess of the intermediate piece.

In a further aspect of the invention, a modular endoprosthesis, in particular a modular hip endoprosthesis, equipped with an intermediate piece according to the invention, as well as with a joint ball having a first joining surface, at least partially complementary to the first connection surface of the intermediate piece and with her firm to-sammenfügbar, and a prosthesis stem with a second joining surface, which is at least partially complementary to the second connection surface of the intermediate piece formed and firmly together with it. Due to the tantalum coating, which is provided at least at the first and second connection surface of the intermediate piece, it is avoided that in the assembled state of the endoprosthesis between the Connecting surfaces and the corresponding joining surfaces of the prosthesis stem or the ball joint comes to a corrosion attack. This significantly increases the service life, corrosion resistance and biocompatibility of the modular endoprosthesis.

Further details, features and advantages of the invention will become apparent from the following explanation of an embodiment schematically illustrated in the drawing. In the drawings: Fig. 1 Fig. 2 Fig. 3 Fig. 4 and Fig. 5 Fig. 6 and Fig. 7 in a partial sectional view from the side a modular endoprosthesis with an intermediate piece according to the invention; in a sectional view according to the drawn in Figure 3 section plane A-A according to the invention an intermediate piece. in a partial sectional view from above of the illustrated in Figure 1 modular endoprosthesis. in each case a modular endoprosthesis according to the invention in different side views with removed joint ball; in different side views each have a prosthetic socket of a modular endoprosthesis.

1 shows an illustration of a modular endoprosthesis 1 with an intermediate piece 2 according to the invention. The intermediate piece 2 is located in its installed position between a prosthesis shaft 3 and a joint ball 4 and is firmly joined to these two prosthesis parts. This endoprosthesis 1 is used for example for the reconstruction of a human hip joint. The prosthesis shaft 3 is used for this purpose in the medullary cavity of a femur. The joint ball 4 is used for insertion into a joint socket of the hip joint to be reconstructed. The adjacent to the endoprosthesis 1 parts of the hip joint such as femur or Gelenkpan are not shown for clarity.

The intermediate piece 2 is provided at one of its free ends with a first connection surface 5, which serves for insertion of the intermediate piece 2 in a recess in the interior of the joint ball 4. At its other free end, the intermediate piece 2 is provided with a second connecting surface 6, with which it is inserted into a recess in the interior of the prosthesis shaft 3.

As a base material 7 of the intermediate piece 2 is here, for example, a metal alloy of vitallium, which is largely composed of cobalt, chromium and molybdenum used. To protect against a corrosion attack, the first connection surface 5 and the second connection surface 6 of the intermediate piece 2 are provided with a tantalum coating 8 here. For this purpose, the tantalum coating 8 is in each case applied to the base material 7 in a layer thickness 9 of, for example, 5 μm.

Between the first connecting surface 5 of the intermediate piece 2 and a first joining surface 11 in the interior of the joint ball 4, wherein the joining surface 11 is formed at least partially complementary to the first connection surface 5 of the intermediate piece 2 and firmly joined together, it may due to micro-movements a gap formation 13 come.

Thus, in the gap 13 between the first connection surface 5 and the first joining surface 11 body fluids reach, which lead in a known from the prior art adapter to crevice corrosion and to a weakening of the intermediate piece 2.

Similarly, between the second connecting surface 6 and a second joint surface 12 in the interior of the prosthesis shaft 3, wherein the second joining surface 12 at least partially complementary to the second connecting surface. 6 formed of the intermediate piece 2 and is firmly joined together, form a fine gap 13 by micro-movements of the assembled prosthesis parts. Even within this gap 13, when using a known from the prior art adapter by penetration of body fluid to crevice corrosion with the negative consequences mentioned above for the patient.

The tantalum coating 8 at the two connecting surfaces 5 and 6 of the inventive intermediate piece 2 advantageously avoids crevice corrosion in the gaps 13 between the intermediate piece 2 and the adjacent prosthesis parts 3 and 4 secured to the intermediate piece 2 and thus the biocompatibility an endoprosthesis 1 with an intermediate piece 2 according to the invention significantly increased.

Fig. 2 shows in a sectional view according to the drawn in Fig. 3 section plane AA according to the invention an intermediate piece 2. This intermediate piece 2 is at its two free ends, which form a first connection surface 5 and a second connection surface 6, each with a Tantalum coating 8 coated with a layer thickness 9. Thus, the base material 7 in the region of the first connection surface 5 and the second connection surface 6 is effectively and permanently protected against corrosion attack.

In the context of the invention, it is also possible to coat the entire spacer 2 with a tantalum coating 8. This is shown in FIGS. 4 and 5.

Fig. 3 illustrates in a partial sectional view from above the modular endoprosthesis 1 shown in Fig. 1. A view of the intermediate piece 2 according to the sectional plane A-A, Fig. 2.

The two images Fig. 4 and Fig. 5 each show the same modular endoprosthesis 1 according to the invention in different side views, the sake of clarity, the joint ball is removed in each case. The intermediate piece 2 according to the invention is here continuously coated on its entire outer surface with a tantalum coating 8. As a result, any direct contact of body tissue with the metal below the tantalum coating 8, the base material 7 forming alloy metal is avoided, thus further increasing the biocompatibility of the spacer 2 according to the invention.

In particular, in the view shown in Fig. 4 it can be clearly seen that the first connecting surface 5 of the intermediate piece 2 according to the invention is designed in the form of a cone 14 tapering outwards towards the free end of the intermediate piece 2. A cross-sectional area of the connecting surface 5 is formed by a circular cross-section 15.

It is also conceivable within the scope of the invention to form at least one of the two connec tion surfaces cylindrical. This version is not explicitly shown in the figures.

The two images Fig. 6 and Fig. 7 show in different side views each have a prosthetic socket 3 of a modular endoprosthesis 1. The second joining surface 12, which is at least partially complementary to the second connection surface of the intermediate piece, is within the recess in the prosthesis shaft. 3 to recognize. The prosthesis shaft 3 is provided with an adjustment aid 16 at the upper edge of the recess. Based on this adjustment aid 16 different settings of a Schaftantetorsion between the prosthesis shaft 3 and the attached intermediate piece 2 can be seen. 5/9 Austrian Patent Office AT 13 497 Ul 2014-01-15 LIST OF REFERENCE SIGNS: 1 modular endoprosthesis 2 spacer 3 prosthesis shaft 4 joint ball 5 first connection surface 6 second connection surface 7 base material 8 tantalum coating 9 layer thickness 11 first joint surface of the joint ball 12 second joint surface of the joint surface Prosthetic shaft 13 Gap 14 Cone 15 Circular cross-section 16 Adjustment aid 6/9

Claims (8)

Austrian Patent Office AT 13 497 Ul 2014-01-15 Claims 1. Intermediate piece (2) of a modular endoprosthesis (1), in particular a modular hip endoprosthesis, which has a first connection surface (5) and a second connection surface (6), wherein the first connection surface (5) and the second connection surface (6) are coated with a tantalum coating (8) with a purity of at least 99%, characterized in that the layer thickness (9) of the tantalum coating (8) is at least 3 pm , preferably between 3 pm and 50 pm. 2. intermediate piece (2) according to one of the preceding claims, characterized in that the entire intermediate piece (2) with the tantalum coating (8) is coated. 3. intermediate piece (2) according to any one of the preceding claims, characterized in that the intermediate piece (2) is made of a cobalt-chromium alloy, a titanium alloy or a steel alloy as the base material (7). 4. intermediate piece (2) according to one of the preceding claims, characterized in that at least one of the two connecting surfaces (5, 6) is tapered, in particular conical (14) is formed. 5. intermediate piece (2) according to one of the preceding claims, characterized in that at least one of the two connecting surfaces (5,6) is cylindrical. 6. intermediate piece (2) according to any one of the preceding claims, characterized in that at least one of the two connecting surfaces (5,6) on the outer surface of a projection or end portion of the intermediate piece (2) is formed. 7. intermediate piece (2) according to any one of the preceding claims, characterized in that at least one of the two connecting surfaces (5,6) on the inner surface of a recess of the intermediate piece (2) is formed. 8. Modular endoprosthesis (1), in particular modular hip endoprosthesis, with an intermediate piece (2) according to one of the preceding claims, a joint ball (4) with a first joining surface (11) at least partially complementary to the first connection surface (5) of the Intermediate piece (2) is formed and firmly together with it, and a prosthesis shaft (3) with a second joining surface (12) which is at least partially complementary to the second connection surface (6) of the intermediate piece (2) formed and firmly together with it. For this 2 sheets drawings 7/9