“Human tail”: Case reports of coccyx retroposition in children

Abstract

BACKGROUND: A “human tail” is a rare congenital malformation that corresponds to the protrusion on the dorsal side of the lumbar, sacrococcygeal, and paraanal regions. This study aimed to demonstrate three rare clinical cases of a tail-shaped formation caused by the protrusion of an elongated coccyx in children.

CLINICAL CASES: These patients asked for medical assistance for pain felt in the sitting position and daily discomfort because this formation barely contains any tissues other than the coccyx. The patients had no signs of neurological and lower urinary tract insufficiency. In all cases, the retroposition of the coccyx without its typical anterior angulation was determined based on radiographic and magnetic resonance imaging (MRI) signs. In one case, the coccyx was represented by four elongated vertebrae without a typical decrease in the size of the vertebrae in the caudal direction. In two cases, an angular deformity of the coccyx occurred at the level of Co_III with intercoccygeal angles of 138° and 140°.

DISCUSSION: The tail-like formations could be classified as “pseudo-tails” according to the classification by Dao and Netsky (1984) and type Ia “human tails” according to the classification by Tojima and Yamada (2020).

CONCLUSIONS: The most important feature of tail-shaped formation is the connection with occult dysraphic malformations, which requires a comprehensive preoperative examination in each case (neurological examination, radiography, computed tomography, and MRI). Careless surgery may lead to serious consequences that significantly impair patients’ quality of life.

Keywords

human tail / tail-like formation / pseudotail / protrusion of the coccyx / retroposition of the coccyx / coccygodynia / spinal dysraphism

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