As your two discs in neck are removed and got fixation by hip bone
plate in front of C 5-6 and C 6-7,due to that you had numbness
in left arm and constant pain in neck region , which may be due to some nerve
compression or fixation of the said region.
Therefore I advice you to consult your Physiotherapist or Neurosurgeon,they can solve your problem by looking into X-rays or MRI
of neck region.
Good luck and take care.