The present invention relates to a polymer scaffold design and method for treating segmental long bone defects without amputation that permits permanent regrowth of bone in the area of the segmental defect, without external fixation or other problems inherent in current systems. The polymer scaffold is preferably made from a poly(ester urea) polymer and includes an outer shell, sized to fit over a segmental defect in a bone, and a collagen containing material. In some embodiments, the collagen containing material is placed in a polymer insert sized to fit within the segmental bone defect and within said outer shell. In some embodiments, the outer shell may contain struts running longitudinal struts along the inside surface of the outer shell. In some of these embodiments, the insert will have a corresponding set of grooves sized to receive the struts.