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DE-102022106581-B4 - Osteosynthesis system with bone plate and bone anchor made of magnesium alloys

DE102022106581B4DE 102022106581 B4DE102022106581 B4DE 102022106581B4DE-102022106581-B4

Abstract

System for osteosynthesis comprising a bone plate (2) having at least one receiving opening (8) and a bone anchor (3) comprising an anchor head (6), wherein the anchor head (6) is configured for fixation in the receiving opening (8) by forming a positive-locking and/or friction-locking connection with the bone plate (2), wherein the bone plate (2) is made of a magnesium alloy at least in a section comprising the receiving opening (8) and the bone anchor (3) is made of a magnesium alloy at least in a section comprising the anchor head (6), wherein the magnesium alloy of the bone anchor (3) and the magnesium alloy of the bone plate (2) have different hardnesses, characterized in that • the magnesium alloy with greater hardness has a material structure achieved at least in one step by cold forming and • the bone plate (2) has a coating (12) on a base body made of the respective magnesium alloy at least in a section encompassing the receiving opening (8) and/or the bone anchor (3) has a coating (12) on a base body made of the respective magnesium alloy at least in a section encompassing the anchor head (6).

Inventors

  • Alexander Kopp
  • Kilian Reuß
  • Lennart Kölbel

Assignees

  • Medical Magnesium GmbH

Dates

Publication Date
20260513
Application Date
20220321

Claims (13)

  1. A system for osteosynthesis comprising a bone plate (2) having at least one receiving opening (8) and a bone anchor (3) comprising an anchor head (6), wherein the anchor head (6) is configured for fixation in the receiving opening (8) by forming a positive-locking and/or friction-locking connection with the bone plate (2), wherein the bone plate (2) is made of a magnesium alloy at least in a section comprising the receiving opening (8) and the bone anchor (3) is made of a magnesium alloy at least in a section comprising the anchor head (6), wherein the magnesium alloy of the bone anchor (3) and the magnesium alloy of the bone plate (2) have different hardnesses, characterized in that: • the magnesium alloy with greater hardness has a material structure achieved at least in one step by cold forming and • the bone plate (2) has a coating (12) on a base body made of the respective magnesium alloy at least in a section comprising the receiving opening (8) and/or the bone anchor (3) has a coating (12) on a base body made of the respective magnesium alloy at least in a section comprising the anchor head (6).
  2. System according to Claim 1 , characterized in that the magnesium alloy of the bone anchor (3) has a greater hardness than the magnesium alloy of the bone plate (2).
  3. System according to Claim 1 or 2 , characterized in that the magnesium alloy with the greater hardness has a material structure achieved by hammering.
  4. System according to one of the preceding claims, characterized in that the magnesium alloys of the bone plate (2) on the one hand and of the bone anchor (3) on the other hand have the same chemical composition.
  5. System according to one of the preceding claims, characterized in that the magnesium alloy of the bone plate (2) and/or the magnesium alloy of the bone anchor (3) is/are resorbable.
  6. System according to one of the preceding claims, characterized in that the receiving opening (8) in an initial state does not have a connection structure that is designed to be complementary to a connection structure of the anchor head (6) or the anchor head (6) in an initial state does not have a connection structure that is designed to be complementary to a connection structure of the receiving opening (8).
  7. System according to one of the preceding claims, characterized in that the connection structure of the anchor head (6) and/or the connection structure of the receiving opening comprises or is a thread (7).
  8. System according to Claim 6 and 7 , characterized in that the receiving opening (8) is unthreaded in the initial state or is provided with a thread (9) that is incomplementary to the thread (7) of the anchor head (6) or the anchor head (6) is unthreaded in the initial state or is provided with a thread (7) that is incomplementary to the thread (9) of the receiving opening (8).
  9. System according to one of the preceding claims, characterized in that the bone anchor (3) has an anchor shaft (4) with a shaft thread (5).
  10. System according to Claim 9 , characterized in that the thread (7) of the anchor head (6) and the shaft thread (5) have different thread parameters.
  11. System according to one of the preceding claims, characterized in that the coating (12) comprises or is an oxide layer and/or a phosphate layer.
  12. System according to one of the preceding claims, characterized in that the receiving opening (8) and/or the anchor head (6) has/have a conical basic shape.
  13. System according to Claim 12 , characterized in that the receiving opening (8) and the anchor head (6) have conical basic shapes with different taperities.

Description

The invention relates to a system for osteosynthesis with a bone plate having at least one receiving opening and with a bone anchor comprising an anchor head with a connecting structure, wherein the anchor head is arranged for fixation in the receiving opening by forming a positive and/or frictional connection with the bone plate by means of the connecting structure of the anchor head. Such a system is made from the WO 00 / 066 012 A1 This is known. Fixation can be achieved through the interaction of threads on the anchor head and the bone plate (as internal threads in the receiving opening). These threads are not complementary, so that when the threaded connection is formed, the material of one of the connecting partners is deformed. This results in a high loosening torque for the threaded connection, thus preventing unintentional loosening. To achieve targeted deformation of the material of one of the connecting partners in such an osteosynthesis system, the bone plate on the one hand and the bone anchor on the other are usually made of different materials, which differ particularly in hardness. A thread formed from a harder material can thus cut into the softer material of the other connecting partner in a defined manner (cf. US 2021 / 0 378 723 A1 and EP 3 081 180 A1 In this regard, it is known to use different titanium alloys, for example grade 4 on the one hand and grade 5 on the other, for the connecting partners. The publication “New findings on self-dissolving implants” by the Helmholtz Center Hereon describes the use of magnesium alloys for implants, whereby the resorption behavior of the implants can be influenced by the gadolinium content in the magnesium alloy. The invention is based on the objective of improving such a system for osteosynthesis. This problem is solved in a system according to claim 1. Advantageous embodiments thereof are the subject of further claims and/or will become apparent from the following description of the invention. According to the invention, in an osteosynthesis system comprising at least one bone plate having at least one receiving opening and at least one bone anchor having an anchor head, wherein the anchor head is configured for fixation in the receiving opening by forming a positive-locking and/or friction-locking connection with the bone plate, the bone plate, at least in a section encompassing the receiving opening, and the bone anchor, at least in a section encompassing the anchor head, are each made of a magnesium alloy, wherein the magnesium alloy of the bone anchor and the magnesium alloy of the bone plate have different hardnesses. Preferably, the magnesium alloy of the bone anchor has a greater hardness than the magnesium alloy of the bone plate. According to the invention, the magnesium alloy with the greater hardness is further provided that it has a microstructure achieved by cold forming. Cold forming is an advantageous method for increasing the hardness of a magnesium alloy. To achieve the hardness difference between the magnesium alloys according to the invention, it is then preferable that the magnesium alloy with the lesser hardness does not have a microstructure achieved by cold forming. However, different hardnesses can generally be achieved in magnesium alloys through different cold forming processes, so that the magnesium alloy with the lesser hardness can also have a microstructure achieved by cold forming. According to the invention, the bone plate, at least in a section comprising the receiving opening, and/or the bone anchor, at least in a section comprising the anchor head, has a coating on a base body made of the (respective) magnesium alloy. Such a coating can be used, in particular, to influence and, in particular, to slow down the corrosion and thus, if applicable, also the resorption behavior of the magnesium alloy of the associated base body. By coating the respective base body, at least in a section of the bone plate comprising the receiving opening and/or in a section of the bone anchor comprising the anchor head, the areas of the connection between the bone plate and the anchor head, through which relatively high forces and moments are typically transmitted, can be kept stable for as long as possible. A "bone plate" is understood to be a component designed to be attached to a bone. and is designed. The component can, in particular, be designed to be planar (flat or curved), such that its length and width are each greater, in particular at least two, five, or ten times greater, than its height. A "bone anchor" is understood to be a component that is designed and intended for fixation within a bone. The hardness of magnesium materials can be determined in particular as Vickers hardness (HV) according to DIN EN ISO 6507-1:2018 to -4:2018. Magnesium or magnesium alloys, in particular rare-earth magnesium alloys, magnesium-calcium-zinc alloys, and magnesium-aluminum alloys with or without the addition of yttrium, exhibit advantageo