I am so sorry to hear about Sadie, there is nothing worse than have your loved one sick and not well...
the way I understood from the article Justicemom provided, you do not need CT or MRI, plain x ray will give you enough info to rule out tumor, trauma or disc/ bone problem.
The doggie day care I know has a water therapy pool and does good rehab for similar cases. You might want to look into acupuncture. Preventing sores and keeping a muscle tone going is a must. There are books on good massage/ stretching for dogs but paying for one session with PT and asking to teach you how to do it at home probably better.
Vitamins of group B, sp B1, B2 and B6 are responsible for muscle tone, nerve control, reflexes, numbness and tingling sensations, since they are easily destroyed during cooking process giving light supplements will help.