Had to shave 10 year old pom, hair still not growing in almost 1 year later. any hope?!

by anna

I rescued a 10 year old pomeranian last winter but had to shave him because he was severely matted. Now almost a year later his hair is still not growing in, just areas around his neck and hindquarters and little "tufts" here and there. His undercoat is all that is there and is very thick so I am wondering/understand, that if they have been shaved it can grow back thicker and make it diffucult for the guard hairs to grow back? Could this be the case with him, and has anyone heard of ways to get it to grow better? He had such a beautiful full black coat before this shaving. He is cute to me either way but being a groomer myself it kills me to think of what it was before. This is the best picture of him because he is terrified of the camera!