Implant, a method for production thereof and use thereof

Abstract

An implant, a method for production thereof, and use thereof for growing patients are disclosed, containing a Mg—Zn—Ca-based alloy. In order to meet extremely strict requirements with regard to compatibility, chemical resistance, and mechanical strength, it is proposed that the alloy contain 0.1 to 0.6 wt % zinc (Zn), 0.2 to 0.6 wt % calcium (Ca), and a remainder of magnesium (Mg), as well as impurities that are an inevitable part of the manufacturing process, which each total no more than 0.01 wt % and altogether total at most 0.1 wt %, with the quotient of the percentages by weight of Zn and Ca being less than or equal to 1.

Claims

1. An implant for growing patients containing a Mg—Zn—Ca-based alloy, the alloy consisting essentially of: 0.1 to 0.6 wt % zinc (Zn), 0.2 to 0.6 wt % calcium (Ca), and a remainder of magnesium (Mg), as well as impurities that are an inevitable part of a manufacturing process, which each total no more than 0.01 wt % and altogether total at most 0.1 wt %, with a quotient of the percentages by weight of Zn and Ca being less than or equal to 1.

2. The implant according to claim 1, wherein, with regard to intermetallic phases, the Mg matrix of the alloy contains essentially (Mg,Zn)2Ca precipitation phases.

3. The implant according to claim 2, wherein the Mg matrix of the alloy contains exclusively (Mg,Zn)2Ca precipitation phases.

4. The implant according to claim 1, wherein the implant is used for osteosynthesis.

5. A method for producing the implant for growing patients according to claim 1, comprising keeping the alloy at a temperature in a range from 200 to 400 degrees Celsius in order to produce (Mg,Zn)2Ca precipitation phases.

6. The method according to claim 5, comprising keeping the alloy at a temperature in the range from 200 to 275 degrees Celsius in order to produce (Mg,Zn)2Ca precipitation phases.

7. The method according to claim 5, wherein, before hot for the alloy is kept at a temperature in order to produce (Mg,Zn)2Ca precipitation phases.

8. The method according to claim 5, wherein, during hot forming, the alloy is kept at a temperature in order to produce (Mg,Zn)2Ca precipitation phases.

9. The method according to claim 5, wherein, during artificial aging, the alloy is kept at the temperature for the formation of (Mg,Zn)2Ca precipitation phases.

10. The method according to claim 5, further comprising producing an implant for osteosynthesis.

11. A method of using the implant according to claim 1, comprising using the alloy as a material for producing the implant for growing patients for use in osteosynthesis.

12. The method according to claim 11, comprising using the implant as a Krischner wire, a Herbert screw, a medullary nail, and/or a nail for elastically stable medullary splinting (ESIN), or the like.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(1) To document the achieved effects, medical implants in the form of nails were produced from different Mg—Zn—Ca-based alloys. The compositions of the alloys tested are specified in Table 1.

(2) TABLE-US-00001 TABLE 1 Overview of the nails Nail no. Composition 1 MgZn1, Ca0, 25Mn0, 15Y2 2 MgZn5, Ca0, 25Mn0, 15 3 MgZn0, 4Ca0, 4

(3) Nail no. 1 in Table 1 is made of a known magnesium alloy using rare earths Y as an alloying element. Nail no. 2 in Table 1, which is likewise known from the prior art, does not use rare earths as alloying elements, but requires an elevated percentage of Zn in order to achieve the desired strength, which reduces the chemical resistance (corrosion resistance) of the nail. Nail no. 3, whose composition is indicated by way of example in Table 1, contains the magnesium alloy according to the invention. With 0.4 wt % Zn, nail no. 3 lies in the claimed range of from 0.1 to 0.6 wt % Zn and with 0.4 wt % Ca, it lies in the claimed range of from 0.2 to 0.6 wt % Ca. The quotient of the weight percentages of Zn and Ca (wt % Zn divided by wt % Ca) is 1 and is therefore also less than or equal to 1, as required according to the invention. This nail no. 3 was produced from a cooled, extruded blank with subsequent material-removing machining. The extrusion was carried out within the temperature limits of 200 to 400° C.

(4) The above-mentioned nails were tested for their chemical resistances and mechanical strengths. To accomplish this, the tensile strength Rm, the yield strength Rp0,2, and the flexural strength A5 were determined in the tensile test. In addition, the degradation in SBF (simulated bodily fluid) was measured. The measurement values obtained are summarized in Table 2.

(5) TABLE-US-00002 TABLE 2 Measurement results of the tested nails Nail no. R.sub.p0,2 [MPa] R.sub.m[MPa] A.sub.5 SBF [mm/year] 1 150 250 20 0.5 2 210 295 18 4 3 200 250 22 0.25

(6) As can be inferred from Table 2, the low zinc content of nail no. 3 compared to nail no. 2 does not result in any disadvantages in the mechanical strength, but does as a result enjoy the considerable benefit of an increased chemical resistance of at most 0.25 mm/year of degradation. This is even lower than the degradation measured in nail no. 1, whose alloy disadvantageously contains rare earths.

(7) A stable, biodegradable implant is thus achieved, which is particularly well-suited for pediatrics and adolescent medicine and for growing patients in general. This is assured since no rare earths are used, the alloying components are thus biocompatible, and they can thus be used by the growing organism—but it is also nevertheless possible to provide high mechanical strength and chemical resistance.