Two years ago, I had an operation to remove a disc in my low back. I was completely pain free after the operation. I reinjured my back and had to have the same operation on a different disc. This time, the pain is still there. The same doctor did both operations. Why the different results?

A new study from the Stanford University School of Medicine may have the answer to your question. Almost 200 patients with sciatica (leg pain) from a bulging disc had the disc removed. One doctor did all the surgeries.

He found there are four types of disc problems. The disc is made up of two parts: the inner part called the nucleus pulposus and an outer ring of fibrous tissue called the anulus fibrosus. With a bulging or herniated disc, they may also be a bulging anulus, large defects in the anulus, pieces of disc material inside a normal anulus, or a normal anulus.

Patients with a bulging disc, but normal anulus have the best results from this operation. Patients with a bulging disc along with large anular defects (tears or cracks) have a poor result. These patients are more likely to have a second herniation and second operation.

It’s possible your second disc problem was one that doesn’t respond as well to removing the disc. Doctors are continuing to study the best way to treat all types of discs.