CRPSの深部組織の痛みのメカニズム

Abstract

Complex regional pain syndrome (CRPS) is a chronic pain condition that usually follow a deep–tissue injury such as fracture or sprain. CRPS describes a broad spectrum of signs and symptoms that predominantly localize to the extremities. The cause of pain is still unknown. Using the Japanese Diagnosis Procedure Combination database, we identified 39 patients diagnosed with CRPS immediately after open reduction and internal fixation (ORIF) for limb fracture from a cohort of about 185000 inpatients treated with ORIF. The occurrence was relatively high in fractures of the distal forearm and lower limb. In terms of perioperative factors, a longer duration of anesthesia was significantly associated with a higher incidence of CRPS. Regional anesthesia could not reduce the incidence of CRPS. The incidence of CRPS was low in patients with multiple limb fractures. These patients received relatively–longer anesthesia time, but the time for one fractured limb would be comparable to that in patients with one limb fracture. Because a tourniquet procedure is widely used for ORIF of distal limb fracture in Japan, we considered that longer anesthesia time indicates longer ischemic time by tourniquet inflation. Our findings can propose that CRPS would be developed on the basis of the ischemic condition of the deep tissue. Supporting evidence comes from a previous animal model,in which the ischemic–reperfusion injury sustains chronic inflammatory condition in the deep tissue. This proposal should be confirmed in further investigations. Other proposed mechanisms focuses on the supra–spinal central nervous system. Abnormal somatotopies in the primary sensory and motor cortices were directly linked with pain intensity; Abnormal motor representation of the affected limb were observed in not only functional brain imaging studies but also psychophysical studies. Now we have not still disentangled the mechanisms of CRPS, but deep–tissues and motor control of the musculoskeletal system of the affected limb would be the potent target(s) to understand CRPS more clearly.