I'm so sorry.
Another broken femur: my Cora. Broken March '09. No sign of OS on the x-rays. Leg pieced back together with plate, screws, and wires. Rocky "recovery". OS finally showed up in October. Too late at that point to do anything but say goodbye.
On a happier note, nygreys's Lass broke her femur, was put back together, and is still with us. It's been about a year, if I recall correctly. I believe that they did a biopsy while repairing the leg.