DE19545470A1 - End prosthesis or implant surface - Google Patents

Abstract

The entire implant or prosthesis surface is divided into individual surface areas or islands which are joined by leaf or spiral springs (2b) to the implant or prosthesis or by an elastic adaptor. Springs etc. should be low in E-modulus and of high elasticity and are designed to allow for relative movement between island areas and implant or prosthesis. The stiffness of the springs is modified to suit the mechanically desirable force transfer and is also modifiable in terms of bone growth depth in between the island areas. Springs are typically centrifugally etc. cast by applying e.g. wax island patterns to a positive prosthesis model so as to give a negative mould when the wax is melted out, ready for pouring with metal etc. material as required.

Description

The invention relates to the connection between an implant or a Endoprosthesis and the bone.

From a purely biological point of view, there are already various coupling solutions available on the living bones. In addition to cementing techniques cement-free solutions with differently prepared surfaces (Coatings, roughening, rough structures proven). Are common Materials such as cobalt-chrome alloys, titanium alloys or plastics.

A mechanical problem remains with all previous solutions: The different elasticity of bone and prosthesis material result from different loads on the prosthesis inevitably relative movements between Prosthesis and bone. An implant can therefore never be fully integrated will. A large part of the surface forms a connective tissue gap, which allows these relative movements.

The invention has for its object a decoupled interface between To create implant and bone, the relative movements within the Implants should take place so that the entire prosthesis surface is osseous is integrated and there is no connective tissue gap.

According to the invention, the object is achieved by integrating only individual small partial areas of the prosthesis / implant surface (silent islands, FIGS . 1a, 2a, 3a). These small areas are connected to the prosthesis or implant body via intermediate elements which can move with a defined stiffness (FIGS . 1b, 2b, 3b).

According to the invention, these connecting elements are possible on the one hand by using an intermediate element with a low E module (buffer element) ( FIG. 1b; FIG. 4a), which is fastened between the prosthesis body and the individual island. On the other hand, the principle can be implemented using a rod or leaf spring ( FIG. 2; FIG. 3) made of the material of the prosthesis body or a corresponding modification.

The actual surface of the is by machining or casting techniques Implants divided into small sectors (silent islands). The surface of the island allows osteointegration according to known methods. The single island is about that Spring element rod spring or leaf spring or buffer element with the prosthesis body connected. The size of the island and the spring stiffness of the individual islands in the 3rd Spatial axes are those at the corresponding anchoring point of the prosthesis necessary load introduction and the expected relative movements to choose accordingly.

The depth of osteointegration between the islands allows the bone to be actively modified in the sense of increasing the rigidity of the individual island ( FIGS. 4a-d). The bone can shorten the length of the spring via the waxing depth; this increases the stiffness.

The relative motion decoupled interface enables these relative movements within the implant itself; the entire implant surface can be bony are integrated. Inevitably, no connective tissue space is formed.

Description of an embodiment

The silent interface can be used for any prosthesis or implant. It can universal for dental implants, joint prostheses, support implants and all other forms of mechanical influence on the skeletal system will. The description is based on an example Hip arthroplasty.

The proven principle of a hip prosthesis is based on an im Femoral marrow anchored prosthetic stem, which is a spherical head wearing. This handle is usually made of a metallic material. But there are also described prosthesis handle made of plastic or other materials been. When the prosthesis is loaded, a different stretch of Bone and prosthesis created, relative movements in the gap between the two parts are the consequence. The stem can therefore only with the bone at a few points be connected.

The decoupled interface can be cast, milled or eroded Prosthesis body are applied.

Example 1 ( Fig. 4c, 2)

Longitudinal grooves must be made along the prosthesis socket. These are e.g. B. with 4-sided cross-section with a drill 90 degrees to the groove direction ( Fig. 2a), the bore being set a little more than the drilling radius from the surface. The removal of the holes determines the strength of the remaining spring ( Fig. 2b). The groove depth in the longitudinal direction corresponds to the distance of the center point of the holes from the surface, added to the boring radius. The grooves can also be deeper.

Example 2 ( Fig. 4b, 3)

A second possibility would be the formation of rods or leaf springs in the Centrifugal casting or with other casting techniques.

For this purpose, models of the individual silent islands (e.g. wax) are placed on the positive model applied to the prosthesis. An impression of the positive and z. B. Melting the  Wax creates the negative form with the individual silent islands, which with the metallic or other material can be cast as positive.

Example 3 ( Fig. 4a, 1)

A layer of material is added to the already completed prosthesis body low modulus of elasticity applied. On this layer they are made of material positioned with low elasticity existing silent islands. These are among themselves not in contact. They are connected to the prosthesis body via the buffer surface. So relative movements are possible.

With all three methods of manufacturing silent interfaces, the amount can be the power transmission, the amount of relative mobility and the Directions of movement via modification of material (spring constants), geometry (Feather strength, island size) and size of the individual silent element vary.

If bone now grows between the Silent Islands, the stiffness of the egg island inevitably increases. A cybernetic feedback on a purely mechanical level is conceivable here ( FIG. 5).

The production itself does not pose any technical problems.

Claims (5)

1. endoprosthesis or implant surface, characterized in that the total surface of the implant / prosthesis is divided into small individual areas and the individual surfaces are connected by an elastic element to the actual implant / endoprosthesis body. 2. Endoprostheses or implant surface according to claim 1, characterized in that the individual surface island makes a firm contact with the bone, and with a leaf or rod or coil spring or with an intermediate element lower modulus of elasticity and high elasticity with the main body of the implant connected is. 3. Endoprostheses or implant surface according to claim 1 and 2, characterized in that the connecting spring or the intermediate element relative movements between Single island and total endoprosthesis or implant body allowed. 4. Endoprostheses or implant surface according to claim 1 and 2 and 3 characterized in that the rigidity of the spring or intermediate elements of the mechanically desired Power transmission is modified in accordance with manufacturing technology. 5. Endoprostheses or implant surface according to claim 1, 2 and 3 and 4 characterized in that the bone through the waxing depth between the decoupling islands Modification of the spring stiffness is possible.