Bit late to this, but there are a few stories I know that would seem to fit this fetish/genre:
(Quick shameless plug to my own ebook, Psych Ward Nightmare by Tabitha Kohls:
https://www.amazon.com/dp/B00JI5KZL2It isn't exactly the sort of story you're asking for, more body-modification themed, but it has some of the same trapped in an asylum elements. Actually, all three of my Nightmare books probably fall into this theme.)
Otherwise, there are several free stories on the late C. Lakewood's Stripsearch4 Yahoo group (
https://groups.yahoo.com/neo/groups/StripSearch4/info), particularly his "Asylum" and Joe Doe's "Powerless" story about a de-powered Supergirl trapped in an asylum.
Many other stories on the site touch on people trapped in prisons and boarding schools, a very similar concept to the asylum stories. Imreadonly also has several good stories there, though I think he's mostly found on The Spanking Library site.
Likewise, many of Katie Smith's 'Tracey' stories should fall into this theme as well. I think her current site is another Yahoo Group called Traceystories (
https://groups.yahoo.com/neo/groups/Traceystories/info)