The risk of pain syndrome affecting a previously non-painful limb following trauma or surgery in patients with a history of complex regional pain syndrome.

BACKGROUND AND PURPOSE Complex regional pain syndrome (CRPS) is a challenging complication after surgery or trauma. This study sought to determine the incidence of CRPS after a second inciting event in a previously unaffected extremity in patients with a history of an ongoing CRPS diagnosis in another extremity. METHODS A retrospective review identified patients with CRPS seen in clinic over a 20-month period. The incidence of CRPS after subsequent surgery or injury in a previous unaffected extremity was determined and compared to an average incidence reported in the literature. RESULTS Ninety-three patients had a diagnosis of primary CRPS. Nineteen (20.4%) developed CRPS in one or more additional extremity compared to the incidence of 23.4 per 100,000 (0.0234%) in the literature (odds ratio 1069.6, p<0.0001, 95% CI 562.0-2035.7). Twenty patients had a documented secondary injury or surgery in a second extremity. Fifteen (75%) developed secondary CRPS compared to a CRPS incidence rate of 6.4% following distal radius fracture, as determined by literature review (odds ratio 11.7, p<0.001, 95% CI 5.9-23.2). CONCLUSIONS These result suggest that patients with a history of CRPS are more likely to develop secondary CRPS compared to the rates reported in the literature among the general population. IMPLICATIONS Patients with a history of CRPS should be counselled that they may be at risk for developing secondary CRPS if they undergo surgery or sustain trauma to another extremity.