MRI's do not predict if you need surgery.
Very nice post by an MD who goes over the pros and cons of MRI's and treatment for low back pain (LBP). According to the author many of the people who have sciatica symptoms go on to have back surgery that may or may not solve the problem. Despite changes in technology and fancy titanium screws, plates and cages, the overall results of surgery have not significantly improved over the last few decades. This over-prescription of surgery is a huge problem.