A segmented lumbosacral orthosis with mechanical advantage integrates two side members conjoined by cord threaded through an array of seamless tubes that are independently mounted and swivel from an axis point proximal to the end points of each tube. Each tube array is housed in a mounting bracket made from a continuous piece of material folded over to form a gap in between two sides. Each mounting bracket is attached to a side member by sliding a pin along the folded edge of the bracket through knuckles (or loops) attached to the side member—similar to a hinge. A removable posterior member is connected to each posterior end of the side members using an elastic material that expands and contracts in parity with the mechanical advantage closure system. The removable posterior panel is designed to hold a rigid or semi-rigid insert stored in three separate sections.