Clin Orthop Surg.  2016 Dec;8(4):412-419. 10.4055/cios.2016.8.4.412.

Analysis of Sacrococcygeal Morphology in Koreans Using Computed Tomography

• Yoon MG
• Moon MS
• Park BK
• Lee H
• Kim DH

• KMID: 2412324
• DOI: http://doi.org/10.4055/cios.2016.8.4.412

Abstract

BACKGROUND
The sacrococcygeal morphology of Arabs and Europeans has been studied using computed tomography (CT) or magnetic resonance imaging to determine the cause of coccydynia. Studies have suggested differences in sacrococcygeal morphology among ethnic groups. However, there are no data on the sacrococcygeal anatomy of Koreans.
METHODS
We conducted a retrospective analysis of 606 pelvic CT scans that were taken at Cheju Halla General Hospital between 2008 and 2014. Fractures of the sacrum or coccyx were excluded. Differences in the sacrococcygeal morphology among age groups stratified by decade of life and between genders were analyzed using sagittal plane pelvic CT scans. The morphological parameters studied were the sacral and coccygeal curved indexes, sacrococcygeal angle, intercoccygeal angle, coccygeal type, coccygeal segmental number, and sacrococcygeal fusion.
RESULTS
The average sacral and coccygeal curved indexes were 6.15 and 7.41, respectively. The average sacrococcygeal and intercoccygeal angles were 110° and 49°, respectively. Type II coccyx was most common, and the rate of sacrococcygeal fusion was 34%. There was a moderate positive correlation between age and the sacral curved index (r = 0.493, p = 0.000) and a weak negative correlation between age and the coccyx curved index (r = −0.257, p = 0.000). There was a weak negative correlation between age and the intercoccygeal angle (r = −0.187, p = 0.000). The average intercoccygeal angle in males and females was 53.9° and 44.7°, respectively.
CONCLUSIONS
The sacrum tended to be more curved and the coccyx straighter with age. The coccyx was straighter in females than males. Knowledge of the sacrococcygeal anatomy of Koreans will promote better understanding of anatomical differences among ethnicities and future studies on coccydynia.

Keyword

Coccyx; Sacrum; Morphology; Koreans; Computed X-ray tomography

MeSH Terms

Adolescent
Adult
Aged
Aged, 80 and over
Asian Continental Ancestry Group/statistics & numerical data
Coccyx/*diagnostic imaging
Female
Humans
Male
Middle Aged
Reproducibility of Results
Republic of Korea
Retrospective Studies
Sacrum/*diagnostic imaging
*Tomography, X-Ray Computed
Young Adult

Figure

• 

  Fig. 1 Computed tomography images showing morphology of the sacrococcygeal region. (A) The coccygeal type is classified according to the angle between a line from the center of the first coccygeal segment to the tip of the last coccygeal segment and a vertical line. (B) Sacrococcygeal fusion (circle) is noted.

• 

  Fig. 2 Computed tomography images for morphometry of the sacrococcygeal region. (A) Straight (solid line) and curved (dotted line) lengths of each sacrum and coccyx. (B) Sacrococcygeal angle. (C) Intercoccygeal angle.

• 

  Fig. 3 In a 92-year-old female patient, the sacrum is curved (dotted line) and the coccyx is straight. Type I coccyx (angle) and sacrococcygeal fusion (circle) are noted.

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  Fig. 4 Differences in sacrococcygeal anatomy between a male (A) and a female (B). In the female, the sacrum is more curved and the coccyx is straighter than in the male.

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