Determining Isolated Thumb Forces in Osteoarthritic and Healthy Persons

Carpometacarpal (CMC) osteoarthritis (OA) can dramatically impair thumb function resulting in the inability to complete basic tasks. Development of a method to detect thumb forces changes is essential to understand of the progression of carpometacarpal osteoarthritis and the effects of treatment. The goals of this study were to (1) develop a method to measure thumb forces in multiple directions, (2) perform an initial demonstration of this method on three populations, young healthy (YH), older healthy (OH), and older participants with carpometacarpal osteoarthritis, and (3) determine the effects of short-term exercises on thumb force production in these pilot groups. A multi-axis load cell with a custom-built apparatus and a hand grip dynamometer were used to measure thumb and grip forces. Forces were collected in four directions: radial abduction and adduction, and palmar abduction and adduction. All participants completed thumb and grip testing prior to (week 0), during (week 2), and following (week 6), a hand exercise regimen. Group differences and the effects of exercise on force production were determined. Hand exercises improved thumb forces in young healthy female participants during radial (p = 0.017) and palmar abduction (p = 0.031) and female participants with osteoarthritis during palmar abduction (p = 0.010). Exercise improved grip strength in young healthy males (p = 0.028), young healthy females (p = 0.041), and females with osteoarthritis (p = 0.027). This research demonstrates the successful use of a new device to determine isolated thumb forces, and its clinical utility to identify changes after a short exercise regimen.