Abstract
The manual skill required to use scissors is related to the grip strength and stability of the thumb. Patients with thumb metacarpophalangeal (MP) joint hyperextension laxity may not exert sufficient grip strength, and the thumb may become unstable. In the medical field, severe congenital cases have been reported; therefore, we investigated mild congenital thumb MP joint hyperextension laxity in nursery schools and found 3 cases among 13 infants. We then, to derive assistance and guidance for these infants, analyzed the condition of hyperextension in terms of the direction of movement, joint movement, and point of emphasis. As a result, we found that the finger hole on the thumb side of a pair of scissors should be sized such that it does not reach the base of the proximal phalanx to stabilize the thumb, and that it was instructed to bend the interphalangeal joint when using scissors.
