High baseline pain is associated with treatment adherence in persons diagnosed with thumb base osteoarthritis: an observational study

Abstract Background Thumb osteoarthritis (OA) is a common and disabling condition. Adherence to prescribed conservative interventions may affect outcomes of thumb OA trials. Purpose The aim of the study was to determine whether baseline pain and hand function is associated with treatment adherence over 12 weeks in participants with thumb base OA. Study design Observational cohort study nested within a randomized-controlled trial. Methods Ninety-four participants from the intervention group were included in the analysis. Baseline pain and function were assessed using a 100 mm Visual Analogue Scale and the Functional Index for Hand Osteoarthritis questionnaire (0-30), respectively. Participants received a combination of treatments including education, orthosis, hand exercises, and topical anti–inflammatory gel. Adherence was measured using a daily self-reported diary. Participants were classified as non–adherent, partially adherent or fully adherent if they completed none, 1 and/or 2 or all 3 of the interventions as prescribed. Ordinal logistic regression modelling was performed. Results At 12-week follow-up, half of the participants were fully adherent to the treatments (n = 46, 48.9%), 30.9% of participants were partially adherent (n = 29) and 20.2% were non–adherent (n = 19, 20.2%). High baseline pain was a significantly associated with better adherence in the unadjusted model [OR = 3.15, 95% CI (1.18, 8.42)] and adjusted model [OR = 3.20, 95% CI (1.13, 8.20)]. Baseline function was not associated with adherence [OR = 1.03, 95% CI (0.47, 2.23)]. Conclusion High baseline pain was associated with better adherence in participants with thumb base OA. Higher baseline functional impairment was not associated with better adherence.