Assessment of Neuropathic Pain in Erosive Hand Osteoarthritis

Background/Objectives: Erosive hand osteoarthritis (EHOA) is an aggressive form of hand osteoarthritis (OA) and a severely disabling condition. Patients affected by OA frequently lament symptoms suggestive of neuropathic pain (NP). The aim of our study was to ascertain the presence and severity of NP in patients with EHOA and correlate its presence with EHOA clinical characteristics. Methods: In this retrospective study, we included all consecutive EHOA patients with NP symptoms who underwent upper limb electroneurography (ENoG) and nerve ultrasound. The presence of NP was screened using the ID pain neuropathic pain-screening questionnaire (ID-Pain). In addition, the following NP questionnaires were also used: Douleur Neuropathique en 4 Questions (DN4), PainDETECT, and Neuropathic Pain Symptom Inventory (NPSI). Moreover, patients completed the Australian/Canadian Osteoarthritis Hand Index (AUSCAN) and Dreiser's algofunctional finger index questionnaires assessing EHOA disease activity. The following clinical and laboratory data were collected: age, sex, BMI, disease duration, intensity of pain (VAS 0-10), painful and swollen joints, and inflammatory indices, as well as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Results: Of the 34 patients studied, 24 (70.6%) presented NP to the ID-Pain questionnaire. According to DN4, 14 (41.2%) patients had NP, while using the PainDETECT questionnaire, 67.6% had NP. Patients with NP were statistically younger and had a higher VAS pain score compared to subjects without NP. The ENoG and median nerve ultrasound were normal in 81% of patients, while four patients had carpal tunnel syndrome. The ID-Pain questionnaire correlated with the number of painful joints (r = 0.48, p = 0.03) and with the AUSCAN questionnaire (r = 0.37, p = 0.05). The DN4 questionnaire correlated with PainDETECT (r = 0.58, p < 0.01). The PainDETECT questionnaire correlated with VAS pain (r = 0.49, p = 0.02), the DN4 questionnaire (r = 0.58, p < 0.01), and AUSCAN (r = 0.51, p = 0.02). The NPSI questionnaire correlated negatively with BMI (r = -0.53, p = 0.01) and positively with the PainDETECT questionnaire (r = 0.49, p = 0.02). Conclusions: Our study revealed that 32% to 70% of EHOA patients exhibited symptoms consistent with NP, with observed variability depending on the questionnaire utilized. Despite patients frequently exhibiting symptoms compatible with NP, only 19% of patients presented alterations on ENoG and ultrasound examinations confirming CTS. This suggests a probable nociplastic component for pain in patients with EHOA, which warrants tailored treatment. In the present study, NP correlated with clinical and functional indices of EHOA.