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Pilonidal Dictionary

Pilonidal – from the Latin: nesting hair. Meaning: containing hair.
Sinus or cyst (Sinus, Cyst) – a subcutaneous cavity or pocket (in the pilonidal context).
Pilonidal sinus – a subcutaneous cavity containing hair. Usually develops at the bottom of the buttocks,

Above the area of the end vertebrae of the spine (the "tailbone").
Pilonidal fistula – a fistula, a subcutaneous inflammatory canal that begins in the pilonidal space in the gluteal fossa and from there gradually extends towards the lower back, buttocks, or the rectal area, creating secondary, excretory exit wounds in these locations.
*Note: Pilonidal disease can involve a single subcutaneous pocket or multiple pockets with hair, with or without pilonidal fistulas.
*Note: The terms sinus, cyst, or pilonidal fistula are often used to describe the same pilonidal disease, regardless of the exact meaning of the term.
Pilonidal abscess – a pus-filled cavity that forms in a pilonidal sinus. This is an acute event that requires urgent treatment and drainage.
"Inverted hair", "hair that grows upside down", "ingrown hair", "hair that grows into the tailbone" – many patients

(also therapists), often use these terms, but they are not accurate. The hairs that accumulate in the subcutaneous space are usually free hairs. The hairs fall out from all parts of the body (mainly from the scalp), are trapped in the buttock recess and enter the subcutaneous pockets through openings formed in the skin after local inflammation.

"Coccyx pain", pain when sitting in the coccyx" - The pain in pilonidal disease stems from the inflammatory process in the buttock, in the skin and underneath it, and is not related to the "coccyx". There is also a phenomenon of sensitivity or pain in the coccyx area due to prolonged sitting or local pressure or after local trauma and is unrelated to pilonidal disease.

"Open" surgery - the area of skin lesion excision remains open to heal on its own (not sutured), usually due to local inflammation.

"Closed" surgery - the area of skin lesion excision is initially closed with sutures.

Flap surgery - The area of excision of a skin lesion (such as a pilonidal sinus) is covered by skin and subcutaneous tissue that is moved  from the incision border and its surroundings. The purpose of the method is to prevent tension in the area of skin suture after a wide local excision.