Allergy/hypersensitivity reactions as a predisposing factor to complex regional pain syndrome I in orthopedic patients.

Several predisposing conditions have been associated with complex regional pain syndrome I (CRPS I). The purpose of this study was to determine the relationship between a history of allergy/hypersensitivity reactions and CRPS I in orthopedic patients. Orthopedic patients with CRPS I (n=115) who experienced pain relief after a successful sympathetic nerve blockade were identified for study inclusion; a control group (n=115) matched to the CRPS I group by age, sex, and location of injury was also included. All patients in the study had an average age of 42 years. In the CRPS I group, all participants were Caucasian and the majority (80.8%) were women. The skin of patients with CRPS I was described as fair (57.7%), mottled (57.7%), or sensitive (80.8%). Of the patients with CRPS I, 78 (67.8%) reported a statistically significant history of allergies compared with the 39 (33.9%) patients in the control group (P<.0001). Patients with CRPS I who experienced complete pain relief for at least 1 month following a single sympathetic nerve block were asked to answer a questionnaire (n=35), and some then underwent immediate hypersensitivity testing using a skin puncture technique (n=26). Skin hypersensitivity testing yielded an 83.3% positive predictive value with an accuracy of 76.9%. Based on these results, a positive history for allergy/hypersensitivity reactions is a predisposing condition for CRPS I in this subset of orthopedic patients. These hypersensitivity reactions may prove important in gaining a better understanding in the pathophysiology of CRPS I as a regional pain syndrome.