Why is Milwaukee brace must be worn 23 hours a day?

The Milwaukee brace, also known as a cervico-thoraco-lumbo-sacral orthosis or CTLSO, is a back brace used in the treatment of spinal curvatures (such as scoliOSis or kyphosis) in children. It is a full-torso brace that extends from the pelvis to the base of the skull. This brace is normally used with growing adolescents to hold a 25° to 40° advancing curve. It is often prescribed to be worn 23 hours a day for several years, or in some cases, permanently to offset worsening of the spinal curve deformity.