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  • Complex regional pain syndrome is defined as sustained sympathetic activity in a perpetuated reflex arc characterized by pain out of proportion to physical exam findings

  • Risk factors 

    • trauma with an exagerrated response to injury

    • surgery

    • prolonged immobilization

    • anxiety or depression

    • use of ACE inhibitors at the time of trauma

    • history of migraines or asthma

    • smoking

    • fibromyalgia

  • Pathophysiology

    • aberrant inflammatory response 

    • vasomotor dysfunction

    • maladaptive neuroplasticity

International Association for the Study of Pain Classification

  • type I 

    • CRPS without demonstrable nerve damage

    • most common

    • results from trauma, casting, or tight dressings

  • type II

    • CRPS with evidence of identifiable nerve damage

    • minimal positive response with sympathetic block

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Presentation

  • Cardinal signs 

    • exaggerated pain

    • swelling 

    • stiffness

    • skin discoloration 

  • Physical exam 

    • vasomotor disturbance

    • trophic skin changes

    • hyperhidrosis

    • "flamingo gait" if the knee is involved

    • equinovarus defomity if the ankle is involved

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Imaging

  • Radiographs

    • Osteopenia, soft tissue swelling, subperiosteal bone resorption, PRESERVATION OF JOINT SPACES

  • Three-phase bone scan 

    • indications

      • can help to rule out CRPS type I (has high negative predictive value)

    • phases

      • phase I (2 minutes) : shows an extremity arteriogram

      • phase II (5-10 minutes): shows cellulitis and synovial inflammation

      • phase III (2-3 hours): shows bone images

      • phase IV (24 hours): can differentiate osteomyelitis from adjacent cellulitis

    • findings

      • increased uptake in all phases. Phase III is most sensitive

  • EMG : if suspected nerve injury

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Treatment

Nonoperative  

  • physical therapy and pharmacologic treatment(Gabapentin, NSAIDs, steroids, biphosphonate, antidepressants…): first lign treatment

  • nerve stimulation: if symptoms present mainly in the distribution of one major peripheral nerve

  • nerve blockade: if failed initial nonoperative treatment

  • chemical sympathectomy: acts as another option when physical therapy and less aggressive nonoperative management fails

Operative

  • surgical sympathectomy: If failed nonoperative management (including chemical sympathectomy

  • surgical decompression: CRPS type II with known nerve involvement (e.g. carpal tunnel release if median nerve involved)

Prevention

  • vitamin C 500mg daily x 50 days in distal radius fractures treated conservatively    

    • 200mg daily x 50 days if impaired renal function

    • vitamin C also has been shown to decrease the incidence of CRPS (type I) following foot and ankle surgery 

  • avoid tight dressings and prolonged immobilization

Prognosis

  • typically responds poorly to conservative and surgical treatments

  • better prognosis if upper extremity, warm CRPS, children