The therapeutic pads made by Ogilvie (sp?) are supposed to be excellent for helping with and/or preventing back problems. A friend that was leasing my mare used one. I believe they come in an all purpose style square pad and a half pad. Not cheap...run close to 200 I think. Last I heard, Four Feet On The Ground in Halifax was going to be carrying them, or I think you can mail order from the company.
I haven't heard much about the Lami Cell ones