When it works its effective and should last if no further injury occurs.
Yes there are good pain meds from the vet to help relieve any pain. I've used some of those meds to help dogs with painful bone cancer so you can see they work well. Metacam, Rimadyl, Deramaxx and others are all examples of available meds.
You can read here about the surgery
http://www.michvet.com/library/neurology_ivds_thoracolumbar.asp
and a think to ask any vet you consider working with is what their success rate is. Vets differ in this! Sometimes this depends on the type of injury, the amount of time between injury and surgery etc.
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