Any operation, indeed, any surgical intervention inevitably causes acute pain that usually subsides over time. However, persistent, chronic postsurgical pain may be severe in 2% to 10% of patients. As reviewed by Kehlet et al, this discomfort generally lasts longer than 3 to 6 months after surgery. For example, thoracotomy has a 30% to 40% estimated incidence of chronic pain with a 10% incidence of severe, disabling pain. Several factors are in play in the development of postsurgical pain including: