Chronic post-surgical pain (CPSP) is one of the most common complications after surgery. Nerve injury during surgery has been implicated in the development of CPSP. Some patients with CPSP have neuropathic pain (NP). NP is pain cause by damage or disease affecting the somatosensory nervous system. It may be associated with abnormal cutaneous sensation such as hypoesthesia (partial loss of sensitivity to sensory stimuli) or allodynia (pain from normally non-painful stimuli)