Strengthening of the First Dorsal Interosseous for Thumb Carpometacarpal Osteoarthritis

Thumb CMC osteoarthritis is a normal part of aging. Most patients are able to adapt to symptoms of pain and disability, other patients might benefit from non-operative interventions; e.g. splinting, corticosteroid injections, pain medication, and multiple hand exercises.

The dorsal ligament complex is one of the components for stability of the thumb CMC joint. These ligaments specifically create stability for pinch and grip during the final phase of opposition. Both, the opponens pollicis (OP) and the first dorsal interosseous (FDI) play a key role in centralizing the metacarpal on the trapezium. A retrospective study showed that a dynamic stability modeled approach, including targeting the FDI, reduced pain and improved function in patients with thumb CMC osteoarthritis. Recently, another study demonstrated that reduction of radial subluxation - the thumb metacarpal versus the trapezium CMC joint - was achieved by contraction of the dynamic stabilizers of the healthy hand, specifically with the focus on the FDI.

More clinical research is needed to determine if there are efficacious (effective and low-cost) evidence-based exercise programs for pain reduction and functional improvement in patients with thumb CMC osteoarthritis. The investigators are interested in the effect of FDI strengthening in patients with thumb CMC osteoarthritis. Therefore, the investigators hypothesized that there is no difference in the change of lateral pinch strength at 12 weeks between patients treated with a splint versus patients treated with a splint and FDI strengthening for thumb CMC osteoarthritis. We also tested the same hypothesis for 3-point chuck strength, VAS for pain, and PROMIS Upper Extremity CAT.