The Intermittent and Constant Osteoarthritis (OA) Pain (ICOAP) questionnaire evaluates the constructs of 'intermittent'(tm) and 'constant'(tm) pain. Theses are conceptually different from 'pain on activity'(tm) and pain 'intensity'(tm) as measured by the WOMAC and Chronic Pain Grade (CPG), measures commonly used in OA. The purpose of this study was to evaluate the responsiveness of the ICOAP, and different pain constructs in primary total hip (THR) and total knee (TKR) replacement.
Patients completed the ICOAP, WOMAC and HOOS/KOOS pain and the CPG pre- and 6 months post surgery. Scores were standardized to 0 to 100, where higher scores indicate worse pain. Descriptive statistics were calculated for all data. The standardized response mean (SRM) was calculated for each measure as were correlations of change scores.
The THR group (n = 34) ranged in age from 37-85 years with 74% male. The TKR group (n = 44) ranged in age from 45-86 years with 75% female. Both groups had significant improvement (p < .0001) on all pain measures but the TKR group had smaller improvements. For THR, the SMR was 1.50, 2.31 and 2.29 for constant, intermittent and total scores and for TKR, was 0.84, 1.02 and 1.02 respectively. The SMR ranged from 2.05 to 2.99 for the other measures for THR and from 1.13 to 1.44 for TKR patients. Correlations of the change scores were ranged from 0.26 to 0.81.
Multi-faceted constructs of pain are effectively relieved through joint replacement and all measures including the ICOAP demonstrated responsiveness.