Prospective examination of pain-related and psychological predictors of CRPS-like phenomena following total knee arthroplasty: a preliminary study.

We hypothesized that preoperative emotional distress and pain intensity would predict the occurrence of signs and symptoms of complex regional pain syndrome (CRPS) following total knee arthroplasty (TKA). Depression (Beck Depression Inventory, BDI), anxiety (State Trait Anxiety Inventory, STAI), pain (McGill Pain Questionnaire-Short Form, MPQ), and signs/symptoms meeting IASP criteria for CRPS were assessed preoperatively, and at 1-, 3-, and 6-months postoperatively in 77 patients undergoing TKA. The prevalence of subjects fulfilling CRPS criteria was 21.0% at 1 month, 13.0% at 3 months, and 12.7% at 6 months postoperative. Higher preoperative scores on the STAI predicted positive CRPS status at 1-month follow-up (P<0.05), with a similar non-significant trend for preoperative BDI scores (P<0.10). Diagnostic sensitivity for the STAI was good (0.73), with moderate specificity (0.56). Neither measure predicted CRPS at later follow-up (P>0.10). Greater preoperative pain intensity predicted positive CRPS status at 3-month (MPQ-Sensory and MPQ-Affective; P<0.01) and 6-month (MPQ-Sensory) follow-up (P<0.01), but not at 1-month (P>0.10). Diagnostic sensitivity was high (0.83-1.00), with moderate specificity (0.53-0.60). Post-TKA patients with CRPS were more depressed at 1-month follow-up (P<0.05) and more anxious at 6-month follow-up (P<0.05) than patients with ongoing non-CRPS pain (all other comparisons non-significant, P>0.10). Overall, results indicate that CRPS-like phenomena occur in a significant number of patients early post-TKA; however, it is not associated with significantly greater complaints of postoperative pain. There appears to be a modest utility for preoperative distress and pain in predicting CRPS signs and symptoms following TKA, although false positive rates are relatively high.