A sinus tract is a blind canal with only one opening in the skin or mucosa formed after deep tissue necrosis. The formation of sinus tracts is mainly related to infection. Wound infections due to multiple causes are not treated promptly and effectively, and the surrounding fibrous connective tissue gradually proliferates and hypertrophies under the stimulation of chronic inflammation, abscesses and foreign bodies, forming sinus tracts. If the sinus tract is incompletely removed or foreign body necrotic tissue remains, it will make the sinus tract persistent or recurrent, with localized redness and swelling of the external mouth, often accompanied by purulent discharge and obvious odor. The passages are of various shapes, mostly thin and narrow, and are often accompanied by systemic symptoms such as fever.