What Causes Loss Of Hearing In A Child Post Trans Canal Tympanoplasty?

My 8.5 yr. old son injured his right eardrum with a Q-Tip when he turned 5. He had an unsuccessful patching consisting of transcanal tympanoplasty last May. The surgery resulted in a much larger hole about 80% and more significant hearing loss prompting hearing aid conversation. We do not have any infections since the operation. What should we be doing next?