Computed Tomography–Based Morphologic and Morphometric Features of the Coccyx Among Arab Adults


15 September 2014 - Volume 39 - Issue 20 - p E1210–E1219

Marwan, Yousef Abbas; Al-Saeed, Osama Mhawes; Esmaeel, Ali Abdulla; Kombar, Osama Rabie; Bendary, Abdulla Mohammad; Azeem, Mokhtar Elsayed Abdul.


Study Design.

Cross-sectional, retrospective.


To identify morphological and morphometric features of the coccyx among adult Arabs.

Summary of Background Data.

Different sacrococcygeal morphologic features were found to be associated with coccydynia.


Review of 202 computed tomographic scans of adult Arab subjects was done (mean age: 47.98 ± 16.46 yr). Sacrococcygeal morphological features including number of coccygeal segments, type of coccyx, joint fusion, joint subluxation, coccygeal spicule, coccygeal sacralization, ventral angulation of the terminal sacral segment (S5), and lateral deviation of coccygeal tip were recorded. Moreover, morphometric measurements including lengths and angles of the sacrococcygeal region were measured. Analysis of data was carried out using P value of less than 0.05 as the cutoff level of significance.


Three coccygeal segments were present in 138 (68.3%) of individuals. The majority of the subjects had coccyx type I (96; 47.5%), II (70; 34.7%), or III (31; 15.3%); type I being more common among males (P = 0.004). Bony spicule was present in 109 (54.0%) individuals. Joint fusion, joint subluxation, coccygeal sacralization, ventral angulation of S5, and lateral deviation of coccygeal tip were present in 38.6%, 31.7%, 34.2%, 38.1%, and 38.6% of the subjects, respectively. Joint subluxation and ventral angulation of S5 were more significantly present among females (P = 0.015, P = 0.014, respectively). The mean straight and curved lengths of the coccyx were 3.3 ± 0.7 cm and 3.7 ± 0.8 cm, respectively. The sacrococcygeal structures were longer in males than in females. The mean sacrococcygeal joint angle was 149.2°± 28.1°. Based on the morphometric measurements, the coccyx was more ventrally angulated among females.


The coccygeal morphology and morphometry of Arab adults share some similarities and differences with individuals of other ethnic backgrounds. Future studies should investigate the relation between these anatomic features with coccydynia among this population.

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