Had a lumbar spinal fusionas year. now have severe pain from buttock to back of thigh going down righteg. cannot even sit for few minutes my leg cramps and to sit is so painful?

Sciatica: Even though you have had surgery in the past the solution for the sciatica would still most likely be achieved by conservative means. You should be re-evaluated and discover cause. Your prior history makes sciatica more likely, but some other etiology that what lead to your prior surgery possible. Physical therapy still the best bet for recovery.