Why Does my Medpor Ear Become Exposed? (photo)

I had medpor ear reconstruction done nearly two years ago and during this time, parts of my ear have become exposed. At the end of last year I underwent surgery which was required to cover this exposure, however I have recently realized that the ear has become exposed again at the same place, and another part of the ear is becoming slightly exposed. What is happening? Is this my fault? What should I do? Is there any point undergoing surgery again if this is going to keep happening?