Thanks for your question on Healthcare Magic. I can understand your concern. You are talking about paranasal sinuses (head sinuses). But your father is having Sinus in the chest wound. In normal wound healing, wound close from beneath in 14-20 days time. But when wound is failed to close it remain open and forms track like structure which is open on chest wall and going deep in chest cavity. Most common cause for Sinus formation is wound infection. Once wound infection is treated, Sinus will be healed and closed. Hope I have solved your query. I will be happy to help you further. Wishing good health to your father. Thanks.