What happens when an ankle fracture fails to heal after 12 weeks?

Ankle fracture. Good question...The important issue is what bone is failing to heal..And at what level. There are multiple classifications of ankle fractures. And, each one is drastically different. See a specialist, and get it checked out. So, you will get the best answer and results.
Options... There are a few options for delayed bone healing. If the fracture is in good alignment and apposition, one may consider a bone stimulator, more time, improve stability of the fracture site and limiting activities. These are just some of the options.
Ankle. There are a few things. If treated nonoperatively, i would probably see if there are any endocrine-related reasons for the delayed union first and correct that if necessary. If that is normal, you could try a bone stimulator to see if that helps. Your last option would be surgery if you are still having pain from the non-healing bone.
Ankle fracture. Ankle fractures that don't heal after 12 weeks usually require surgical intervention. This is where some screws and plates would be placed in the bone to stabilize the bone and put it in anatomical alignment. If the patient can not undergo surgery often times a bone stimulator can be ordered to help the bone heal. Using a bone stimulator may take some time so be patient.