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 4 weeks in both groups.

Results: Mean visual analog scale pain scores decreased by 20% after 4 weeks 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 4 weeks 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.