The effect of thumb splinting on thenar muscles atrophy, pain, and function in subjects with thumb carpometacarpal joint osteoarthritis

Background: When the first carpometacarpal joint of the wrist is immobilized using an orthosis to combat the effects of osteoarthritis, atrophy of the thenar muscles may occur. Objectives: The aim of this study was to evaluate the thenar muscle diameter and cross-sectional area, joint function, and pain, before and after being supplied with an orthosis in patients with grades 1 and 2 carpometacarpal osteoarthritis compared to a control group. Study design: Randomized clinical trial. Methods: A total of 25 volunteer patients were randomized into two groups (an orthosis group and a control group) using a randomization table. A visual analog scale, the Michigan Hand Questionnaire, and ultrasound were used to measure pain, function, and specific muscle cross-sectional areas at baseline and after 4weeks in both groups. Results: Mean visual analog scale pain scores decreased by 20% after 4weeks of splinting, while those in the control group decreased by 3%. Changes in scores were significantly different between both groups (p=0.001). There was no significant difference between the groups in either the Michigan Hand Questionnaire score or the muscle cross-sectional area. Conclusion: A large and significant effect on perceived pain in patients with first carpometacarpal joint osteoarthritis was observed after 4weeks of splint use. Differences in treatment effects were found with regard to muscle cross-sectional areas, but these were not significant. Clinical relevance Custom-made splints may be recommended for the treatment of first carpometacarpal joint osteoarthritis. Moderate to large but non-significant treatment effects were found with regard to muscle cross-sectional areas.