Stainless Steel Grades - Nomenclature for Surgical Instrument Stainless Steel

[Laura Halper]

Hello all,
I have a question regarding nomenclature for stainless steel used in surgical instruments. I see lots of mention of "medical grade", as in "medical grade 316L". I know that SAE/AISI specifies the composition for various grades of stainless, including 316L.

My question is whether all "grade 316L" stainless steel is considered to be medical grade. Or does "medical grade" mean something more than just "grade" when talking about stainless steels?

Thanks.
Laura

[pkost]

Medical grade is a rather loose term as you are suggesting, it doesn't have any real definition - it is mostly used by people who don't understand what they are saying and is commonly used in conjunction with "implant grade"

I suppose when someone says that a medical grade, what they are really saying is that it
1. is biocompatible for the intended use
2. fully traceable to it's raw constituants (i.e. is not made up from reprocessed metal)
3. has a certificate of conformity saying that it is a certain grade

In reality any steel grade can be used as long as it meets that material selection criteria, i.e. it has the necessary material properties and has biocompatibility studies validating it's use. Because of the biocompatibility studies, only a few steel grades are commonly used, 316L as you suggested or 316LVM is mainly used for implants (but can be used in instruments), alternatively 420 or 17-4PH is commonly used in instrumentation as it is harder.

You may want to take a look at:
ISO 5832:Metallic materials for surgical implants
Part 1: Wrought stainless steel
Part 9: Specification for high-nitrogen stainless steel

[Laura Halper]

Thanks, Pkost, you answered my question exactly! Very helpful.