Hello. My name is Dr Niranjan Kavadi and I am a spine surgeon. From what is described it seems the first surgery was for decompression and fusion by anterior approach. The indication for second surgery will be more clear from the images however it is very likely the aim was again decompression and supporting the anterior construct from back. If the screw from the front was backing out it is an indication that the segments are not fusing leading to pseudoarthrosis which in simple terms means the bones are not uniting to form single solid mass of bone which ideally should happen. The risk is particularly high in smokers. I am not sure what is meant by C7 and T1 are distressed but the CT scan needs to be studied to assess if there is instability at the cervicothoracic junction. Also loosening of the screw strongly indicates nonunion. I assume you have tried analgesics and other nonoperative pain management modalities. Though there is no certainty of pain relief but treating the nonunion (if demonstarted on CT) and addressing the instability across the cervicothoracic junction to extend the fusion into thoracic spine if needed can definitely make pain a lot tolerable. It is difficult to comment upon the numbness in arms without looking at the recent MRI. Please let me know if I can be of any further help.