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Need literature on biocompatibility of 316L stainless steel

+++

There is an implantable medical device on the market which has very small, passivated, 316L stainless steel parts embedded into a plastic component. Historically, 316L stainless steel has been used for permanent implants, but I am looking for a good source of literature which contains data to support the biocompatibility of the 316L stainless steel material as a permanent implant. Any suggestions?

D. P. Sin
medical device - St. Paul, Minnesota, USA


First of two simultaneous responses -- +++

ASM International is publishing a new book on this subject called Handbook of Materials for Medical Devices, edited by J. R. Davis. Unfortunately, it won't be available until +++. In the meantime, I would recommend performing a search of scientific journals, etc. Scirus, a search engine from Elsevier (largest publisher of scientific journals), is very good for this. Using "316L stainless steel biocompatiblity" as the keywords yields 242 results, of which 123 are journal articles and 119 are web pages. You can narrow or widen the search as necessary.

Toby Padfield
Automotive module supplier - Michigan

Ed. note: That search engine is a definite "keeper", Toby. Thanks!


Second of two simultaneous responses -- +++

Carpenter Technologies has information on medical alloys on their Biodur site www.biodur.com While 316LS (Carpenterýs refinement of 316L) is still used for medical devices including implants, a newer stainless alloy known as CCM (cobalt-chromium-molybdenum) has better pitting corrosion resistance vs. saline body fluids, and reduced Ni (1%) for better biocompatibility. In CCM Plus, the Ni content has been eliminated for even better biocompatibility.

316LS meets the surgical implant requirements of ASTM F138 [link is to spec at TechStreet]-03, F139-03 and F1350-02 for various physical forms of wrought 18 Chromium-14 Nickel-2.5 Molybdenum Stainless Steel (UNS S31673) for surgical implants.

The alloys CCM & CCM Plus meet ASTM F1537-00 and F799-02 for Cobalt-28-Chromium-6-Molybdenum Alloy (UNS R31537, UNS R31538, and UNS R31539) for surgical implants. These alloys are significantly more expensive than 316 due to the cobalt and higher Cr contents.

Information on titanium alloys for Surgical Implant Applications is also available. Some ASTM Specifications: ASTM 136-02a Wrought Titanium-6 Aluminum-4 Vanadium ELI (Extra Low Interstitial) Alloy (UNS R56401), F1295-01 Standard Specification for Wrought Titanium-6 Aluminum-7 Niobium (UNS R56700), and F1472-02a Wrought Titanium-6 Aluminum-4 Vanadium (UNS R56400).

You can also seek relevant literature by a citation search for ASTM F981-99 Standard Practice for Assessment of Compatibility of Biomaterials for Surgical Implants with Respect to Effect of Materials on Muscle and Bone. This document combines past Practices F361-80 and F469-78, so these would be cited by older literature.

Ken Vlach
- Goleta, California  

Ken received a special
"Contributor of the Year" award
from finishing.com for his numerous
helpful and well researched responses


+++

Additional information on international medical-quality stainless steels.

British Stainless Steel Association (http://www.bssa.org.uk) has 2 brief online articles (free registration) containing information from BS and ISO standards on medical stainless steels. Abstracts:

"Selection of stainless steels for surgical implants." The special compositions, non-metallic inclusion, ferrite and grain size requirements are outlined. Commercial 316 cannot be used for surgical implants as the composition and micro-cleanness are very unlikely to meet the ISO 5832 standards. Compared to AISI 316L, the phosphorus and sulfur limits are lower, at 0.025% P and 0.010% S, and nitrogen and copper have been added. Standards: BS 7252-1:1997, ISO 5832-1:1997 Metallic materials for surgical implants. Specification for wrought stainless steel. BS 7252-9:1993, ISO 5832-9:1992 Metallic materials for surgical implants. Specification for high-nitrogen stainless steel.

"Selection of stainless steels for surgical instruments." Compositions of 11 martensitic steels, 1 ferritic steel and 4 austenitic stainless steels of BS EN ISO 7153-1:2001 (BS 5194-1:1991) are given. Most grades match generic stainless steels, e.g., 301, 303, 304, 316 and 410. The surgical and dental applications are outlined. These include cutting and non-cutting instruments and fitting parts and assemblies. (Body implants are NOT covered by this standard.) Corrosion resistance, corrosion testing and the effects of sterilization practices are covered.

Ken Vlach
- Goleta, California

 Ed. note: Special thanks to Toby Padfield and Ken Vlach for going way beyond the call of duty with these tremendously informative responses!


+++++++

Can anyone lead me to information on the biocompatibility of stainless steel wire especially regarding chronic inflammation. My personal situation is this- 1985 broken jaw, stainless steel wire used to fix the crack, the wire is now a permanent implant. Problem, approximately 1995 I start to experience inflammation at the wired site on my jaw. I am concerned about the long-term effects of chronic inflammation and want to gather medical information regarding this as a side effect/complication of the wire and solutions thereof. I don't want to remove the wire if there is not benefit as this may cause more problems if it is not warranted.
Any help would be greatly appreciated!
Thanks!

Shawn Mark O'Hara
- Richboro, Pennsylvania, USA
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