atrophy in pad of thumb

I had disk surgery to replace disk in base of thumb with tendon in arm about 7 years ago.  The past several months (10 or so) atrophy has been worsening in my thumb and the thumb is moving further inward toward palm.  There is quite a noticeable difference in the size of my left thumb and my right thumb, the left thumb being about 1/3 smaller than the right.  

Could the surgery have caused this to happen?  Is there anything that can be done to correct it (implant into thumb pad?)