Sarah, they don't have to be sterile for theatre... however, I'd never let a patient wear a gown they have brought from home into an operating theatre (and I admit theatre patients on a very regular basis). I have no way of knowing where it's been or what bugs are on it (ie - how much of an infection risk is it?). Even if it were a hospital type gown that gave us easy access to your chest should we need it. I would, however, be more than willing to assist a patient into one when they were back on the ward.

As a human being, I think it is a cool idea! And would also be interested in knowing where you saw them!