Hi neil2
On what grounds did your Doctors take the precaution of an MRI plus 8 months in a plaster cast? presumably because they suspected a Charcot foot ? If preventative measures are taken early enough in the process, they can prevent a mid foot collapse and so I suppose your foot could retain its shape. If your Doctors do not think it was a Charcot have they given you any other diagnosis? I do have a Charcot foot and ankle collapse and have spent at least 10 out of the last 15 years in plaster and having surgery, unfortunately I was sent away from A and E having been told it was a sprain so I continued to walk on it in agony. Often X rays for Charcot do not show bone damage until it is too late by which time the bones have fragmented and collapsed.
As long as your foot has recovered and has maintained its bone structure and your Doctors are aware of the problems you have had, why do you feel it is up to you to prove you have had a Charcot? You are obviously well aware of the condition and acted promptly the last time something went wrong, I wish you good luck with it.