DE4228710A1 - Modular implant system assembled during operation - has solid plastic between components gluing them together when activated, reduces wear and avoids need for liq. cement - Google Patents

Abstract

The modular implant system, of two or more components, can be assembled during an operation. Solid layer of plastic is provided between the components, and glues them together when activated, typically by heating. Its m.pt. can be less than that of the components, and it can be of the polyarylether ketone family. The components can be of metal alloy blasted with abrasive material. Heating can be by induction, in a stove, or in an autoclave in the operating theatre. ADVANTAGE - Reduces wear and avoids need for liq. cement.

Description

The invention relates to the attachment of modular ortho pedic implant components to each other and specifically the use of plastic materials to make this compo isolating and connecting elements.

When inserting orthopedic implants in the human body, especially the hip and knee implants, the surgeon often encounters one less optimal fit of the implant in a bone. To yourself differences of patients and surgeons to adapt to situations that lead to an unsatisfied different manufacturers have modu lare implant systems developed. Modular implant system  systems allow either pre-operative or intra-operative operational assembly of components or parts by the surgeon how to make a good one Implant seat needed for a special patient will.

Various known modular implants make Ge need a variety of mechanical fasteners tel, such as US 44 82 606, US 49 95 883, both for hip implants, US 49 50 298 and US 49 36 847, which relate to knee implants, is removable. These mechanical fasteners can be problematic as they are low relative movement between the components and the connecting elements allow ment. These movements in turn generate Material abrasion, they affect the attachment of the Implants in the bone and they stress the building component le and the connecting elements. All these results, which result from relative movement between components, lead to malfunctions when using implants.

It is just in the field of modular joint prostheses if known, polymethyl methacrylate "bone" cement to be used for fastening components. This Cement is applied in liquid form, the components and the cement hardens. In In this case, the cement only fills the space between the Components and forms a mechanical positive locking Ver binding, as far as form-fitting surfaces are provided. A Connection of the cement to the implant surface essentially does not take place. This form of ver bond is due to a low overall strength of the Connection as well as through the potential solution of the zemen tes characterized by the components, whereby Relativbe  movements and material wear take place. In addition is difficult to handle with the liquid cement, since the cement is mixed and then within a spe Partial working hours must be used, and the cement strive for it, on movement surfaces and bone upper to run flat, he must go from these flat again be removed, and the cement is also harmful Gases.

The object of the invention is a modular implant and to provide a method of assembling them, wel ches avoids the disadvantages mentioned above.

This object is achieved in that the modular implant components using a fe most heat-activated glue bonded together will. According to the present invention, components isolated from each other in order to create materi to avoid erosion between the components, and it finds a firm connection between the components Surfaces take place to allow movement and erosion between the Avoid components and the glue. In addition ver the secure connection divides the load evenly between the components. All of these benefits are real lized, in addition, the assembly of the implant clean and can be pre-operative or intra-operative carry out.

Advantageous embodiments of the invention are the Characterized the claims.

The following are exemplary embodiments of the invention explained in more detail with reference to the drawings. Show it:  

Figure 1 is an exploded view of the tibia part of a knee prosthesis.

Fig. 2 is a perspective view of a tibial shim;

Figure 3 is an exploded view of the femur part of a knee prosthesis. and

Fig. 4 is an exploded view of the femur part of a hip joint endoprosthesis.

In Fig. 1, an embodiment of a modular Im plantates is shown, which contains a tibial Grundkom component 1 , a tibial washer, and a thin plastic disc or plastic film 2 for making an adhesive bond and for preventing relative movement between components 1 and 3 . Film 2 is made of thermoplastic material with a lower melting point than components 1 and 3 . In addition, the film 2 has good connection properties between the components 1 and 3 . Experiments have shown that materials from the family of polyaryl ether ketones (PAEK) made of thermoplastic polymers solid adhesive bonds with commonly used implants, such as cobalt-chromium-molybdenum alloys (Co-Cr-Mo) and with titanium-vanadium-aluminum - Enter alloys (Ti-6Al-4V). A PAEK was specially tested, which is sold by BASF under the trade name Ultrapek® KR4177 in order to test the connection strength with Co-Cr-Mo and Ti-6Al-4V. For this purpose, two samples from cylindrical rods with an area of 3.9 cm ² were glued together with Ultrapek KR4177. The polymer was placed between the surfaces and the assembly was then heated in an oven at 410 ° C (770 ° F) for 45 minutes. The samples were then cooled to room temperature and subjected to a tensile test to determine what is necessary to separate the two sample parts. It was found that for Co-Cr-Mo samples which were cleaned, blasted with glass balls and passivated before bonding, the separation load was equal to the full tensile strength of the PAEK of 1190 Kp / cm ² (17KSI). With similarly treated Ti-6Al-4V samples, the separation load was 490 Kp / cm ² (7KSI). It has been found that the lower strength of this connection is due to the build-up of an oxide layer on the samples during heating in the oven. When the experiment was repeated with Ti-6Al-4V samples that had a titanium nitride layer, the separation load increased to 700 Kp / cm ² (10KSI). In addition, the separation load increased to 910 Kp / cm ² (13KSI) when the samples were not heated in the oven but for four minutes by induction.

A preferred embodiment of the invention contains the tibial base component 1 and the tibial underlay part 5 , cf. Fig. 2, wherein a thin layer of PAEK 4 is previously applied. After the surgeon has selected the correct components for use with a particular patient, the surgeon assembles the selected components and positions them with a bracket such as a clamp. The assembly is then heated, for example, in an oven or by induction heating. The arrangement then cools down and the prosthesis individually adapted in this way is implanted.

A preferred embodiment of the invention has been described so far, but changes in design, material, and method are possible to attach any modular implant component thereto. For example, Fig. 3 shows the femur part 6 of a knee prosthesis with different underlay parts. A front shim 7 , a distal shim 8 and a shaft extension component 9 can be attached to the femur part 6 by means of an adhesive connection with thermoplastic polymer in the manner described. Fig. 4 shows the femoral part 10 of a hip joint endoprosthesis with a lateral support part 11 , an anterior / posterior support 12 , a distal shaft attachment 13 , and a femoral head 14 , all of which can be connected to one another in accordance with the present invention, thereby ensuring a secure connection Attachment of these parts is realized, and relative movement and material removal between the components is prevented.

As already mentioned, the layer of thermoplastic material can be applied to one of the components of a connection beforehand, or the layer can be used as a separate disc, the shape of which corresponds to the components to be connected. The present invention is also useful in combination with a primary mechanical fastener such as screws, dovetail guides, snap connections, etc. For example, in Fig. 1, the thermoplastic adhesive layer 18 prevents micro movement and abrasion between the system components, such as Example the tibial base part 1 , the washer block 16 and the fastening screw 17 . In addition to metals, other materials can also be bonded to one another in the manner described, as long as the thermoplastic layer has a lower melting point than the components to be bonded and has good adhesive bonding properties with the components. The tibia part 1 can be connected to the thermoplastic adhesive layer 21 with a polymeric tibial joint surface 20 . It is also within the scope of this invention to use an operating room autoclave for heating the components, provided that the thermoplastic material has a sufficiently low melting point, which is within the range of the autoclave temperatures. In addition, various configurations of the surfaces can be used, such as, for example, groove structures, roughened surfaces or porous coatings, in order to improve the adhesive bond of the thermoplastic material to the component in question.

Claims (12)

1. Modular implant system, which can be assembled during the operation, with at least two implant components that can be joined together, characterized in that a solid plastic layer is arranged between the structural components, and that the plastic layer sticks the two components together when activated. 2. Modular implant system according to claim 1, characterized in that the plastic layer thermoplastic material, which by Erwär men is activated when it is in contact with the Baukom components. 3. Modular implant system according to claim 2, characterized in that the thermoplastic mate rial a lower melting temperature than the Implan tat components. 4. Modular implant system according to claim 2, characterized in that the thermoplastic mate rial consists of the family of polyaryl ether ketones. 5. Modular implant system according to claim 4, characterized in that the structural components from a Metal alloy consist of be with abrasives are shining. 6. Modular implant system according to claim 1, characterized in that the plastic layer before their activation on one of the implant components is applied.   7. Modular implant system according to claim 1, characterized by mechanical fasteners for Connect the building components. 8. Modular implant system according to claim 7, characterized in that the mechanical fasteners contain a screw, which by means of a screw connection on one of the components is attachable. 9. Method for connecting modular implant components during a surgical procedure, characterized by the following method steps:
the components to be connected are selected,
the structural components are positioned with a solid plastic layer in between to form an arrangement,
the arrangement is heated in order to connect the plastic layer and the structural components to one another. 10. The method according to claim 9, characterized in that the arrangement in an oven is subjected to heat. 11. The method according to claim 9, characterized in that heat by inductive heating tion of the arrangement is applied. 12. The method according to claim 9, characterized in that the heat on the arrangement is applied in an operating room autoclave.