Possible Nerve Issue
Dr. Parekh is absolutely correct.
that supplies the majority of the bottom of your foot is the tibial nerve. This nerve is in the area where the total ankle is inserted. Damage to the nerve can happen from the surgery. Also continued swelling from the surgery may be affecting the sensation you have at the bottom of your foot although the nerve itself may not be damaged.
If you have not already i would seek the care of an orthopedic foot and ankle surgeon. One in your area can be found at www.Aofas.Org.