Associations between positive treatment outcome expectations, illness understanding, and outcomes: a cohort study on non-operative treatment of first carpometacarpal osteoarthritis

Purpose More positive outcome expectations and illness perceptions are associated with better outcomes for patients with several osteoarthritic orthopedic conditions. However, it is unknown whether these factors also influence outcomes of non-operative treatment for first carpometacarpal osteoarthritis (CMC-1 OA). Therefore, we assess the role of pre-treatment outcome expectations and illness perceptions in reports of pain and hand function 3 months after non-operative treatment for CMC-1 OA. Materials and methods We conducted a cohort study with 219 patients treated non-operatively for CMC-1 OA between September 2017 and October 2018. Patients were included in the study if they completed measures of pain and hand function, illness perceptions (scale: 0-10), and expectations (scale: 3-27) as part of routine outcome measurements. Pain and hand function were measured before treatment and 3 months after starting treatment using the Dutch version of the Michigan Hand Outcomes Questionnaire. Multivariable linear regression analysis was used to assess the influence of outcome expectations and illness perceptions on pain and hand function. Results Both positive outcome expectations (B = 0.64; 95% CI [0.1-1.2]) and a better illness understanding (an illness perception subdomain; B = 1.53; 95% CI [0.2-2.9]) at baseline were associated with less pain at 3 months. For hand function, similar estimates were found. Conclusions We found that positive outcome expectations and a better illness understanding, were associated with a better outcome of non-operative treatment for CMC-1 OA.