What Causes Flat Feet Despite Having Stents Placed In Ankles?

Sister had stents put in her ankles about 4 years ago and has had trouble with them ever since. It didn t correct her issue and we are wondering if there is a corrective surgery to remove these and replace with another device or treatment. She is 46 years old and stents were inserted due to flat feet and the physician trying to produce an arch in her feet.