NEUROPATHIC PAIN IN FIRST METATARSOPHALANGEAL JOINT OSTEOARTHRITIS: FREQUENCY AND ASSOCIATED FACTORS

Aim: To determine whether neuropathic pain is a feature of first metatarsophalangeal (MTP) joint osteoarthritis (OA). Method: Ninety-eight participants (54 women and 44 men, mean age 57.4 years, standard deviation 10.3) with symptomatic radiographic first MTP OA who were enrolled in a randomised trial assessing the effectiveness of shoe-stiffening inserts completed the painDETECT questionnaire (PDQ), which incorporates 9 questions regarding the intensity and quality of pain. The likelihood of neuropathic pain was determined using established cut-points of the PDQ (total score 38 points), where scores of ≤12 represent unlikely neuropathic pain, 13 to 18 represent possible neuropathic pain, and ≥19 represent likely neuropathic pain. Participants with unlikely neuropathic pain were then compared to those with possible/likely neuropathic pain in relation to age, sex, general health (Short Form [SF] 12), psychological wellbeing (Depression, Anxiety and Stress Scale), pain characteristics (self-efficacy, duration and severity), foot health (Foot Health Status Questionnaire [FHSQ]), first MTP dorsiflexion range of motion and radiographic severity using chi-squared or independent samples t-tests, where appropriate. Effect sizes (Cohen's d) were also calculated. Results: Thirty (31%) participants had possible/likely neuropathic pain (possible n=19, [19.4%], likely n=11 [11.2%]), as defined by the PDQ. The most common neuropathic symptoms were sensitivity to pressure (56%), sudden pain attacks/electric shocks (36%) and burning (25%). Compared to those with unlikely neuropathic pain, those with possible/likely neuropathic pain were significantly older (d=0.59, p=0.010), had worse scores on the SF12 Physical (d=1.10, p<0.001), pain self-efficacy (d=0.98, p<0.001), FHSQ Pain (d=0.98, p<0.001) and Function (d=0.82, p<0.001) questionnaires, and had higher pain severity at rest (d=1.01, p