µCT scanned calluses were processed in LR White Resin Hard Grade Acrylic (London Resin Company, Reading, UK). Sections of un-decalcified calluses, 5 µm thick, were made longitudinally at the mid-point of the callus using a Leica RM 2155 Rotary Microtome (Leica Microsystems, Nussloch, Germany). Sections (4 per callus, 4-7 calluses/group) were histochemically stained to detect tartrate-resistant acid phosphatase (TRAP; a universal cytochemical marker for osteoclasts). Sections of callus were viewed and photographed under a Leica DFC420 light microscope (Leica). To identify whether GA treatment influenced bone resorption during fracture healing, the percentage of TRAP was measured as the total area of callus stained positive for TRAP activity divided by total callus area using Leica Qwin software (Leica) as previously described[35 (link)].