Reflex Sympathetic Dystrophy (RSD or Sudecks atrophy) is a strange malady, fortunately rare, that can occur following severe trauma. To understand this, a brief simple neurology lesson is needed. There are two nervous systems in the body: 1) Central Nervous System (CNS) which controls voluntary function and is under your control, and 2) the Autonomic Nervous System or involuntary nervous system which is not under your control and is constantly working to control blood pressure, colon motility, respiration, blood vessel tone and many other functions. RSD occurs when, in that rare instance after the surgeons cut a nerve during the procedure, the CNS nerves and the ANS nerves sort of cross heal and the always active CNS nerves heal with the sensory nerves resulting in severe chronic overstimulation and resultant pain.
There was an Italian study that showed Hyperbaric Oxygen Therapy to be effective in this condition which is a Godsend, as nothing else seems to help it.