It may not have been possible to repair the fracture. More likely it wasn’t possible to put a dog this small under anesthesia. There might have been an infection. We don’t have the details of the measures taken; I’m sure they did what they could. Ok, now that I followed a link, the story from the .nz site states: “His tiny leg was put in a cast but the medication he was given for it caused stomach ulcers and he did not survive.” I wonder if it was Rimadyl.