It is not uncommon for elderly, injured, or handicapped animals to lose the use of their back or front legs. Nerve damage, DM (Degenerative Myelopathy), cancer, arthritis, injury, accident and more can result in this condition. Fortunately, this does not need to be the end of a dog's life. A dog cart or dog wheelchair can offer an animal a wholesome, healthy, quality life.
If your dog needs a cart, you can get it here: Link
http://www.eddieswheels.com
They've even fitted an alpaca with a "wheelchair."