A cruciform anterior spinal hyperextension orthosis comprising a front portion having a rigid anterior cruciform brace assembly provided with movable upper and lower arms extending therefrom and arranged vertically, two laterally disposed movable arms extending therefrom horizontally, and body contact pads rotatably secured to the free ends of each of the upper and lower vertically disposed arms. A rear portion is provided adjustably secured to the front portion and having a paraspinal support formed in two juxtaposed segments, a pulley system comprising at least one pulley set having two pulley banks each having a plurality of pulleys, each bank disposed proximate to an adjacent edge of the juxtaposed segment, and a cable running through each pulley of each bank of pulleys in the set in alteration and in series and linking together each of the two juxtaposed segments. Adjustable mechanism for securing the front portion to the rear portion including: two straps, respectively removably attached to lateral edges of the two juxtaposed segments and adapted to be secured to two strap engaging devices, respectively, attached to each of the laterally disposed movable arms.