Why Does Scar Tissue Form 2 Years After a Successful Sinus Surgery?

My guess is either you didn't have a complete sinus surgery the first time or the scarring that occurred soon after wasn't noticed and corrected. Sometimes it takes a while for new symptoms to appear after the new scarring occurred.   Post op evaluation with frequent debridements and treatment with steroid irrigations are key to maintaining a good result  I follow my patients until they are completely healed. 

Most scar tissue is apparent in the first couple months after surgery.  It is very unusual to see late scarring.  The most frequent problem leading to recurrent infections after surgery is either incomplete ethmoidectomy or the natural openings into the maxillary sinuses were not restored at the first procedure.  Less than 5% of maxillary openings scar down assuming they were done correctly the first time.  Additional scarring with each additional procedure is,possible.