title: Analysis of Sacrococcygeal Morphology in Koreans Using Computed Tomography.
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.
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Cheju Halla General Hospital, Jeju, Korea.
authors.forename: Min Geun
authors.initials: MG
authors.lastname: Yoon
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Cheju Halla General Hospital, Jeju, Korea.
authors.forename: Myung-Sang
authors.initials: MS
authors.lastname: Moon
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Cheju Halla General Hospital, Jeju, Korea.
authors.forename: Bong Keun
authors.initials: BK
authors.lastname: Park
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Cheju Halla General Hospital, Jeju, Korea.
authors.forename: Hohyoung
authors.initials: H
authors.lastname: Lee
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Cheju Halla General Hospital, Jeju, Korea.
authors.forename: Dong-Hyeon
authors.initials: DH
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People / Q000706:statistics & numerical data; D003050:Coccyx / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D056910:Republic of Korea; D012189:Retrospective Studies; D012447:Sacrum / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Coccyx; Computed X-ray tomography; Koreans; Morphology; Sacrum