Histological examination of specimens at 12 weeks postoperatively. (a) Schematic diagram of the segmental defects, illustrating the location of sections taken for histological analysis. The proximal and distal segments were sectioned horizontally and the cross section of the central segment was taken (b, f, j). (b–m) Representative histomicrograms stained with H&E (40x). (b–e) Isotype-matched mAb, (f–i) rhBMP-2, and (j–m) anti-BMP-2 mAb used to functionalize ABBM-C scaffold. The blue arrows show the junction of newly formed bone and the neighboring host bone. The white arrows show the residual scaffold biomaterials, which were surrounded by connective tissue in control specimens treated with isotype-matched control mAb, while in experimental and positive control specimens the residual scaffold was not easily discernable. Abundant endothelial-lined blood vessels (green arrows) were noted in anti-BMP-2 mAb and rhBMP-2 treated sites.