Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Without the ability to examine you and obtain a history, I can not tell you what the exact cause of your symptoms is. However I will try to provide you with some useful information.
One possible explanation to your continued pain is what is medically termed post-laminectomy syndrome or "failed back syndrome". This is continued pain after spine surgery. While in some cases, this is the result of incomplete removal of pressure by the disc, or continued pressure on a nerve root due to arthritis, disc, or some other process, or scar tissue, in some cases no specific anatomic cause on MRI can be found. To exclude continued pressure on a nerve, a study called EMG/NCS which tests how nerves conduct electricity and how muscles respond can be helpful. Another cause for post-laminectomy syndrome is after surgery, if physical therapy was not adequate, and the back muscles become deconditioned, this can contribute to the pain as well.
Treatment involves another surgery only if there is a clear indication, which is usually not the case. Rather, if cleared by the surgeon, appropriate physical therapy can often be the best treatment. Other treatments for the pain may include medications (non-steroidals such as advil), sometimes steroids if there is swelling (edema), temperature therapy (hot or cold packs), stretching and controlled physical therapy, muslce relaxants, and sometimes injections; these are best prescribed by an experienced physician, each has its own indications. Sometimes, referral to an experienced pain management specialist may be helpful as well.
Continued follow-up with your spine physician is recommended, with referral to a neurologist if pressure on a specific nerve is suspected (this can be suspected based on the specific distribution of arm symptoms) and/or a pain management specialist.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.