Evaluation of coccygeal bone variability, intercoccygeal and lumbo-sacral angles in asymptomatic patients in multislice computed tomography

The coccyx is a highly variable structure in the human caudal spine. Previous studies have revealed a significant correlation between coccyx shape and the pain syndrome coccygodynia. The aim of this study was to carry out a complex morphological evaluation of the coccyx in a group of asymptomatic patients of different sex and age examined by multislice computed tomography (MSCT) of the pelvis for different clinical reasons. MSCT pelvis examinations from various nontraumatic clinical conditions from consecutive adult patients (250 males and 250 females of comparable age, mean 54.9 ± 14.8 years) were used. Based on middle sagittal plane reconstructions: coccyx configuration (types I–IV according to Postacchini and Massobrio classification, each successive type characterized by a more pronounced anterior position of coccyx), number of segments, length and angles (intercoccygeal and lumbo-sacral) were measured. The results obtained were analyzed statistically. The following types of coccyx were observed in the study group: type I in 16.2 %, type II 40.0 %, type III 32.4 %, and type IV 11.4 % cases. In most cases (50.8 %), three segments were noted. Lumbo-sacral angle varied from 15.6° to 66.4° (average 41.6° ± 7.7°), and intercoccygeal angle from 0° to 107° (average 51° ± 23.3°). A significant negative correlation between age and number of segments as well as age and intercoccygeal angle was observed. In males, the coccyx was significantly longer, while in females the intercoccygeal angle was significantly wider. Type I was significantly more frequent in males, while type IV was found more often in females. The results obtained differ from other results in the literature. Our research could be useful to determine population standards, and help (together with clinical history) future studies of associations between idiopathic coccygodynia and coccyx morphology.