Intercoccygeal angle and type of coccyx in asymptomatic patients

PURPOSE: To assess the intercoccygeal angle of asymptomatic patients (without coccydynia), to study if there is a difference of angle between types of coccyx and between genders with the same type of coccyx. MATERIALS AND METHODS: Ninety-two patients (42 females, 50 males, range of ages 8-86, mean 50) who underwent computed tomography (CT) angiography and colonoscopy were included in the study. CT images with slice thickness of 1 or 1.5 mm were evaluated with 3D sagittal reformats and intercoccygeal angle, type of coccyx were examined. RESULTS: Twenty-one females and 18 males had type 1 coccyx with mean intercoccygeal angle 36.4 degrees +/- 10.56 (33.29 degrees for females and 40.05 degrees for males) and the difference of the angles between genders is statistically significant (P = 0.044). Among 36 patients (14 were females and 22 were males) with type 2 coccyx demonstrated mean intercoccygeal angle of 56.36 degrees +/- 10.8. 15 patients were shown to have type 3 coccyx and the mean intercoccygeal angle was 72.1 degrees +/- 31.86. No significant difference of angles was seen between genders. Type 4 coccyx was not seen and two coccyx could not be classified. There was a significant difference of intercoccygeal angle between the groups overall. CONCLUSION: Type 1 is the most common coccyx type in asymptomatic patients. Significant difference of intercoccygeal angle was defined between the types of coccyx. These values may be reference for the patients underwent surgery for the coccydynia and a new classification may be needed since exceptional shape of coccyx exists that could not be defined according to the known classification.