A Prospective Cohort Survey on Prevalence and Risk Factors for Persistent Postsurgical Pain After the Open Reduction and Internal Fixation of the Lower Limbs

Chronic pain,one of the most frequent causes for patients to seek medical care,is a recognized health problem.Chronic postsurgical pain (CPSP), commonly defined as pain that develops after a surgical procedure and persists at least 3 months, constitutes a widely underdiagnosed and often poorly treated medical problem affecting 10-50% of all postsurgical patients. According to the reports,in the United States alone,1.9 million persons abused or were dependent on prescription opioid analgesics for chronic pain in 2013,contributing to one of the worst public health crises the developed world has recently faced.Here,open reduction and internal fixation（ORIF） of lower limb fractures ,what the investigators focus, is a common surgical procedure in orthopedics and microscopic hand and foot surgery.The removal of the intramedullary nail can relieve anterior knee pain, but in a substantial number of patients, pain persists after nail removal.The most painful daily activities are kneeling and squatting.Therefore, it is increasingly important and urgent to solve the postoperative chronic pain of patients with lower extremity fractures surgery.

The underlying biology of chronic postoperative pain and genetic heritability is complex and not yet fully understood . A common feature of CPSP is that the painful sensations change from the familiar acute postoperative pain to a complex pain syndrome with nonaplastic characteristics，neuropathic characteristics, or both. Preclinical studies have revealed that neuroinflammation is one of pathological hallmarks of CPSP. The transition from acute to chronic pain starts early within the first 2 weeks after nonaplastic by peripheral and central inflammatory processes and activation of spinal glial cells.Repetitive nociception resulting from prolonged inflammatory and neuropathic responses to noxious stimuli causes a cascade of biochemical and structural changes to various pain pathways resulting in sensitization of the peripheral and central nervous system（CNS）. Cytokines and neurotrophic factors have been identified as pivotal mediators involved in neuroimmune activation pathways and cascades in various preclinical chronic pain models.

Although lower limb fracture is one of the most frequently reported triggering CPSP events, few large-scale studies have shown the occurrence of and factors associated with it.The objectives of investigators are to specify the demographic and medical factors that most likely constitute a risk of developing CPSP and to search for potential interventions to reduce the occurrence of CPSP in these limb fracture patients.