@heatherm My direct experience with spinal fusion surgery is for a fusion at C5/C6. That is an easier recovery than lumbar spine surgery because the lower end of the spine is bearing most of your body weight. It took 3 months for my bone graft to begin fusing and during that time I wore a neck brace all the time. After that, I weaned out of the brace and began physical therapy rehab. After 3 months of non use, muscles get very weak. You do need an expert surgeon with a lot of experience with the type of surgery that you need. After spine surgery, patients need to avoid twisting and bending. This is critical for lumbar surgery. If you have rods and screws placed on the spine, the angle and placement of the screws is critical to the success or failure of the hardware. The screws can pull out if placed at the wrong angles. I don't say that to worry you, but these are questions to ask your surgeon to see if you get a confident informed answer. It is best to get several opinions before you decide on surgery because it is a big decision. Learn everything you can about the procedure. Most surgeons do not promise that spine surgery will relieve pain. My surgeon didn't promise me that, and I don't think they can give you a guarantee. That is why you should get multiple opinions. Successful surgery can leave lasting pain. Physical therapy with myofascial release work to release the surgical scar tissue can help relieve some pain. I did have a lot of pain from spinal cord compression that was all over my body, and my spine surgery relieved all that pain. After surgery, you are left with the pain of the trauma from the surgical path and the healing required.

What surgery does is decompress something. For example if a disc collapses, the vertebrae get closer together and the space between them where the nerve roots exit (foramen) may get compressed if there is already arthritis there. If there is instability, vertebrae can also shift forward of back and increase pressure on the nerve roots or spinal cord. The body tries to stabilize the spine by remodeling the bone and growing bone spurs which causes a lot of nerve or spinal cord compression. I do know a patient who had lumbar spine surgery who has a lot of pain that she lives with. Find the best surgeon that you can. I tried to have my surgery locally, and came to Mayo after 5 surgeons turned me down because my case was unusual. I was very impressed with my care at Mayo and I had a great recovery. It will be a long recovery after a big spine surgery, and you will need a family member as a caregiver and to help with meals and chores. You can also find a good physical therapist who rehabs spine surgery patients and ask what the recovery is like and what kinds of difficulties arise. Make the decision in terms of regaining function or preventing further degeneration. Fusing the lumbar spine will change the body permanently and you will be stiff and move differently. Surgeons really can't guarantee to take away pain, and if they are saying that to you, please get several more opinions. The surgery can improve pain by correcting the source of it, but it is easy to mistake where the pain is coming from because there can be overlapping symptoms for different problems that cause the same pains. Sciatic pain can be caused by a pelvis out of alignment or overly tight hip flexors muscles that pull on the lumbar spine which are not spine problems, but mimic the symptoms of spine nerve root compression. A patient can have these and also a spine problem at the same time, and they all contribute something to the overall pain. These are things that a neurologist tries to separate, and this should be figured out and understood before going through spine surgery to avoid guessing about the outcome. The MRI imaging should be able to be connected to the source of the pain if it is a structural problem in the spine, and the surgeon needs to be able to explain why it causes pain in your specific case, and how their surgery can address it. Myofascial release therapy helped me have an easier surgery because my tissues were easier to move during surgery, and it helped take away pain after I was recovered enough to start PT.

Here are some links that may be of interest.
https://mskneurology.com/identify-treat-lumbar-plexus-compression-syndrome-lpcs/
https://connect.mayoclinic.org/discussion/myofascial-release-therapy-mfr-for-treating-compression-and-pain/