Hi Thank you for your question to HCM. The type of surgery you would need depends on the nature of your complaints. It is not clear from your description what L4 and L5 discs are growing together means. Careful study of MRI images is needed to decide what type of surgery you need if at all surgery is needed.L1 and L2 discs are rarely symptomatic as compared to L4 and L5. If your complaints are of leg pain, heaviness, tingling, numbness or weakness you will need further intervention. Pain killer medications, physical therapy and bracing are the initial lines of treatment. Epidural injections and nerve specific medications will be helpful if pain is the only complaint. Decompression is the process of freeing nerves with removal of thickened ligaments, compressive part of disc and bone as necessary. Putting rods and screws and fusing the back is done for instability in the spine where the possibility is high that such instability would lead to recurrent problem. One of the examples of such instability is spondylolisthesis or slip of one vertebra on the other one. Detailed evaluation of imaging studies by a spine surgeon is advised. Hope this is helpful. I would be happy to answer any questions you may have.