Metal alloy for medical devices and implants

Abstract

The present invention relates to a medical device or implant made at least in part of a high strength, low modulus metal alloy comprising Niobium, Tantalum, and at least one element selected from the group consisting of Zirconium, Tungsten, and Molybdenum. The medical devices according to the present invention provide superior characteristics with regard to biocompatibility, radio-opacity and MRI compatibility.

Description

[0001] The present invention relates to an improved metal alloy for medical implants or devices for desired material properties. BACKGROUND OF THE INVENTION [0002] A medical implant or device must satisfy a number of requirements. Factors affecting the choice of the medical implant or device and the material thereof are mainly all mechanical properties and biocompatibility. The material must not cause any inflammatory reaction or allergic reaction. Commonly used materials often include nickel, like medical grade 316L stainless steel, which contains about 16% nickel. For patients with an allergic reaction the implantation of such materials is contraindicated. Another consideration in material selection is the need for the implanting physician to be able to visualize the position of the medical implant or device during procedure to the desired target site in the body, and for purposes of examination from time to time thereafter at the implant site, typically by X-ray fluoroscopy. [000...

AI Technical Summary

Benefits of technology

[0014] The alloys of the invention show excellent melting and mixing properties with excellent uniformity since Niobium and tantalum are arbitrarily miscible. Varying the amount of Tungsten, Zirconium and Molybdenum, or optionally, the amount of Cerium, Rhenium, or Hafnium, allows adjustment of the granular size of the alloy.

[0015] Surprisingly, the alloy according to the present invention is stronger than pure tantalum and in specific compositions even stronger than stainless steel. In a preferred embodiment a stent is manufactured from the alloy of the invention comprising a tailored radio-opacity while having a reduced wall thickness. Such a stent combines desired visibility under x-ray and excellent radial force with minimised delivery profile and less turbulence when employed in the vessel.

[0016] An additional advantage of the inventive alloy is the formation of a passive oxide film primarily composed of Tantalum-oxide (Ta2O5), which is generally more durable and more corrosion resistant than for example the chromium-oxide film formed during the passivation of stainless steel.

Problems solved by technology

The metal alloys commonly used for implantation (like stainless steel 316) induce a local disturbance of the magnetic field used in MRI, to the extent that imaging of surrounding tissue is impeded.

Although alloys like Nitinol behave more favourably in MRI, their MRI compatibility is not considered to be sufficiently good.

However, Niobium surfaces cannot be electropolished because of their tendency to smear (?).