Anterior Angulation of the Coccyx

Anterior angulation of the coccyx may be a normal variant unrelated to trauma. Postacchini and Massobrio, in their study of 120 asymptomatic patients, described four types of coccyges:

• Type I (~70%): The coccyx is curved slightly forward, with its apex pointing caudally
• Type II (~15%): The coccyx is curved more markedly anteriorly, with its apex pointing straight forward. This is the case shown here, where there is anterior angulation at the first intercoccygeal joint (arrow) and with the coccygeal apex pointing straight ahead.
• Type III (~5%): The coccyx is sharply angulated forward between the first and second or the second and third segments
• Type IV (~10%): The coccyx is subluxed anteriorly at the level of the sacrococcygeal joint or at the level of the first or second intercoccygeal joints

Patient with types II-IV coccyges are more prone to develop idiopathic coccygodynia than those with a type-I configuration. Partial or total coccygectomy usually provides relief in these cases.

References

Postacchini F, Massobrio M. Idiopathic coccygodynia. Analysis of fifty-one operative cases and a radiographic study of the normal coccyx. J Bone Joint Surg Am. 1983 Oct;65(8):1116-24.