This is Louis the chinchilla, who broke his arm.
After a long and fiddly operation we managed to stabilise the bones in his arms using tiny metal pins usually used as cannulas! The pins go through the bone at different levels, and are then held together outside the skin by a special putty which sets rock hard and holds the pins, and therefore the bone fragments, firmly in place.
The only complication we had with Louis was that he constantly gnawed away at the putty, requiring us to repeatedly add more to the frame! Despite this, he made an excellent recovery and the pins were removed after 6 weeks.