I am going to describe a project which I believe will be exceptionally beneficial. I have been told that if the condition is not treated, the body will twist upon itself, due to improper support, leading to early and painful death.
Amputation is a frequent solution.
Along with surgery, physical therapy must be performed to make the muscles and tendons keep up. I believe PFFD could be treated by using a bone-stretching device that works more gently and slowly, in the fashion of braces on the teeth. Intelligent prosthesis would be able to hold the ankle as firmly but safely as a mother's hands. Combining stretching with slight magnetic or electric fields might be especially effective. It is known that there are some electromagnetic effects correlated with bone breakage and healing.