Morphologic evaluation of the coccyx in the pediatric population.

Purpose: This computed tomography study aimed to display the alteration in the coccyx morphology (its ossification process, dimension and angulation) in children with advancing age.

Methods: Pelvic radiologic scans of 180 children aged 1-18 years were retrospectively evaluated to observe changes in the coccyx morphology with age, and to measure the linear length (LL), curvilinear length (CLL), sacrococcygeal angle (SCA), and intercoccygeal angle (ICA).

Results: The present study divides the postnatal evolution of the coccyx into three phases as follows: (a) in the first stage when the coccyx is of the shortest, it is completely cartilage until the age of 2 (infancy period) and its first segment begins to ossify by the age of 3 (early childhood period), (b) in the second stage when the coccyx is of medium size, its first segment is completely ossified by the age of 6 (late childhood period) and the ossification of its all segments is completed from the age of 11 (prepubescent period), and (c) in the third stage when the coccyx is of the longest, it reaches to adult size (postpubescent period). Linear functions were calculated as y = 15.647 + 1.145 × age (p < 0.001, R² = 0.561) for LL, and as y = 16.829 + 1.243 × age (p < 0.001, R² = 0.559) for CLL.

Conclusion: Considering that morphological features of the coccyx, such as ICA, can be used in the diagnosis of coccydynia, our dataset may facilitate the identification of children with suspected coccydynia.