CT morphology and morphometry of the normal adult coccyx

Abstract

Purpose Lack of data on the in vivo morphology and morphometry of the normal adult coccyx hampers understanding of radiological abnormalities in idiopathic coccydynia. The aim of this study was to investigate normal adult sacrococcygeal morphometry. Methods Retrospective analysis of 112 adult CT scans (mean age 63 ± 14.6 years, 50 males) evaluated the following: number of coccygeal segments; joint fusion; coccygeal spicules, subluxation, sacralization, and scoliosis; sacrococcygeal straight and curved lengths and curvature indices; sacrococcygeal and intercoccygeal angles; and lateral deviation of the coccyx tip. Results Four coccygeal segments were present in 76 % of scans. Sacrococcygeal fusion was present in 57 % and intercoccygeal fusion was increasingly common more caudally; there was no significant association with age or gender. A bony spicule was present in 23 %. Subluxation was rare. Nine of 12 coccyges with a retroverted tip were female. Mean coccygeal curved length was 4.4 ± 0.8 cm in men and 4.0 ± 0.8 cm in women (P \ 0.01). Mean angle between first and last coccygeal segments was 138°± 25°in men and 147°± 25°in women (P = 0.08). There was no significant correlation between coccygeal length or curvature and stature, age or BMI. Conclusions In this first detailed study of the CT morphology and morphometry of the adult coccyx, sacrococcygeal and intercoccygeal joint fusion was common. Female coccyges were shorter, straighter, and may be more prone to retroversion, factors that may be relevant to the markedly higher prevalence of idiopathic coccydynia in women.

Authors’ reply to the letter to the editor of P.M. Foye et al. concerning “CT Morphology and Morphometry of the normal adult coccyx” by Woon JT et al. (2013); Eur Spine J 22(4):863–870

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We thank the correspondents for their kind comments about our recently published study [1]. We agree with their statement that certain bony features present in normal adults could nevertheless be a potential source of pain in some patients with coccydynia.

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Acute traumatic instability of the coccyx: results in 28 consecutive coccygectomies

“…MRI has recently shown to be indicated when radiograms fail in making diagnosis [22], while CT helped clarifying morphology and morphometry of the adult coccyx [23]. In our experience, neuroimaging can help measuring the distance between the anteriorly dislocated coccygeal tip and pre-rectal fascia and this factor may be helpful in planning surgery.…”

“…When chronic pain occurs, which happens in about 20-30 % cases [7], surgical resection should be indicated [25]. Theoretically, coccyx may be resected en-bloc or even partially without any major complications, whereas literature lacks these information [23]. In 1726, Petit, cited by Powers [24], is thought to be the first having performed coccygectomy.…”

The Michel Benoist and Robert Mulholland Yearly European Spine Journal Review: a survey of the “medical” articles in the European Spine Journal, 2013

“…There is a paucity of data on this subject. The paper by Woon et al [31] in the April issue aims to investigate normal adult sacro-coccygeal morphology. The study is based on analyzing retrospectively 112 adult CT scans of normal adult coccyx.…”