Surgical removal of the ankle bone.
Because there is only one rating level, the evidence needed is straightforward: records confirming the removal of the talus bone took place. Operative reports or surgical notes that document the astragalectomy are the most direct form of evidence. Post-operative records, imaging such as X-rays showing the absent bone, and treatment notes from follow-up care can all support that the procedure occurred. If the surgery happened during or because of your military service, service treatment records showing the injury or condition that led to the surgery are also relevant. Statements from you or people who know you describing how the ankle affects your daily life or work may help establish the overall picture of your disability.
Conditions that are often caused or made worse by this one. If you have any of these, they may be claimable as secondary service connection.