The only immediate contraindications I can think of when giving reflexology are:
contagious skin conditions, such as athletes foot, fungal nails, verrucas, etc (although, if you cover a verruca with a plaster, I consider you can carry on with treatment and going lightly in the effected area so not to cause any discomfort/pain)acute or severe attacks of arthritic pain or flare ups, only offering treatment to the effected areas in times when the arthritis is in remission. gout would also fall into this category.open wounds or broken skin still healing.
And even then, you can also offer reflexology on the hands, if the feet are contraindicated.
There are others that I can't think of off the top of my head, but generally common sense is what prevails when considering what a contraindication is in a reflexology context in my opinion. As well as what you feel comfortable to treat; if you're unhappy treating something, then don't - though I advise that you can explain your reasons to your client.
In the case of metal plates/pins - ask yourself what possible problems could occur from you giving someone reflexology who has them? What could reflexology do anatomically, physiologically or emotionally/mentally do to a body holding a metal plate/pin? If you can see a valid reason not to give a treatment, then obviously listen to that reasoning. Otherwise, do as mentioned before in this thread; note everything down when taking a full medical history from your client and go gently in the presenting area, etc.
Also, if in doubt, always ask the client to fill in a disclaimer or ask them to seek advice/permission from their doctor - as then you have covered your bases. Your tutor should have mentioned this to you, as well as showing you example documentation.
The fact that your tutor doesn't know, or certainly can't advise you any better does strike me as odd and concerning... Who is the awarding body for your reflexology qualification? Why not give them a call or pop them an email - after all, they're accrediting you and your case studies. If they believe metal plates/pins contraindicate, then ask them their reasons - as you need to know, so you explain to your client why it is not possible to treat them.
I'd be intrigued to know what the Insurance bodies think about this? And whether or not they have protocol or documentation as to what they deem a 'contraindication' as with regards to each discipline...? If they do, so far they certainly haven't offered it...