Abstract: Methods and apparatus are provided for coupling a spatial frame and a brace using a coupling device having a quick-release mechanism. The spatial frame may be secured to an appendage, and the brace may support the appendage. The coupling device may include a linkage that comprises: a mounting member adapted to be detachably coupled to the brace and to a fixator post adapted to be detachably coupled the spatial frame; a position fixing member adapted to adjustably immobilize the fixator post in a coupled position when the fixator post is coupled to the mounting member; and a quick-release mechanism adapted to detachably couple the mounting member to the brace; wherein the quick-release mechanism is further adapted to be engaged and disengaged repeatedly by hand and without separate tools. Numerous other aspects are provided.