Thumb orthosis and set of a plurality of thumb orthoses

A thumb orthosis comprising a) a spreading body designed and configured for spreading a thumb and a pointer finger, wherein the spreading body comprises a curved base leg, a first side leg and a second side leg, the first side leg and the second side leg extending from end portions of the curved base leg such that when worn by a user, the first side leg does not extend beyond a first phalanx of the thumb, and the second side leg does not extend beyond a first phalanx of the pointer finger, b) a first holding device comprising one single first holding strap held by a first end portion of the spreading body and designed and configured for holding the spreading body only at the first phalanx of the thumb, c) a second holding device comprising one single second holding strap held by a second end portion of the spreading body and designed and configured for holding the spreading body only at the first phalanx of the pointer finger, d) the thumb orthosis being exclusively held by the first holding device and by the second holding device at a hand of a user wearing the thumb orthosis, e) wherein the one single first holding strap and the one single second holding strap are flexible, elastic or form-stable, f) wherein the one single first holding strap is partially or completely looped around the first phalanx of the thumb, g) wherein the one single second holding strap is partially or completely looped around the first phalanx of the pointer finger, h) wherein the thumb orthosis consists only of the first holding device, the second holding device and the spreading body, the spreading body being an integral one-pieced component having a stable shape that can be elastically deformed, i) wherein the spreading body comprises an elasticity such that it is possible to elastically deform the spreading body by closing forces applied by the thumb and the pointer finger for reducing a distance of the first end portion and the second end portion of the spreading body, j) wherein the spreading body comprises the curved base leg, the first side leg and the second side leg which extend from end portions of the curved base leg, the first side leg and the second side leg diverging with an increasing distance from the curved base leg, and k) wherein a length of at least one of the first side leg and the second side leg of the spreading body is adjustable by removing an outer end of at least one of the first side leg and the second side leg at a predetermined separation point.