Why Haven't There Been Nerve Regrowth Experiments In Humans?

I can't find it, but Back In The Day (late 1990s at the latest), I read some popular science articles about (and I could be getting any part of this wrong) a silicon wafer with micro-holes in it. The holes were lined with copper, IIRC. A lab animal's nerve was cut (I thought it was the spinal column, but who knows?), the wafer was placed between the two severed ends, and it regrew just fine.

This was, as I say, back in the late 90s at the latest, and I think it may have been as early as the late 80s. I can't find that exact experiment (if someone else can, I'd love a pointer; my email is at the bottom of this essay), but there's been a lot of similar research I have been able to find. In no particular order:

• Pretty much everything on the spinal cord injury blog
• Regenerating severed nerves in lab animals... in 1943: http://archsurg.ama-assn.org/cgi/content/summary/46/4/525
• 1986: http://www.jbjs.org.uk/cgi/content/abstract/68-B/5/829
• Someone talking, I think, about the thing I saw, in 1992: http://www.bio.net/bionet/mm/neur-sci/1992-October/011532.html
• 1995: http://query.nytimes.com/gst/fullpage.html?res=990CE2DD1E3CF931A1575BC0A963958260&sec=&spon=&pagewanted=all
• This may actually be the original source for the stuff I saw, not sure, from 1997: http://www.biomedexperts.com/Abstract.bme/9003901/Rat_sciatic_nerve_regeneration_through_a_micromachined_silicon_chip
• 2003: http://www.eurekalert.org/pub_releases/2003-02/dl-ppn021203.php
• 2004: http://nanotechweb.org/cws/article/tech/21048
• 2006: http://www.rxpgnews.com/research/neurosciences/regeneration/article_4875.shtml
• 2009: http://www3.interscience.wiley.com/journal/121683454/abstract

So, given all that, here's my question: why hasn't any of this been tried on humans? As someone with relatively minor spinal cord injuries, I assure you that if I was a parapelegic I'd jump at the chance to try this stuff. I mean, it's not like it can get worse then a severed spinal cord.

Seriously, I don't get why I haven't heard about miracle cures yet. The closest thing I can find is people in mexico using stem cells, which really isn't the same sort of thing.

Feel free to drop me a line if you have any insight.

-Robin

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