The balloon helps create a passage in cases where diffculty is anticiapted, usually for the frontal (forehead) sinuses.  Sometimes a combined appraoch is used whereby conventional surgery makes space but then due to narrow anatomy precluding a conventional instrument entering the frontal sinus the balloon is threaded through the created channel to confirm the right passage has been established as the sinus outflow channel.  It can also be used to open the remaining sinuses but I prefer conventional instruments due to a wider opening being created, and hence less risk of delayed contraction / scarring.

For further information please see Sinus surgery in Downloads.