anterior angulation of the coccyx
Anterior angulation of the coccyx may be a normal variant but poses a diagnostic challenge for those considering coccygeal trauma.
Classification
Four types of coccyx have been described:
- type I: the coccyx is curved slightly forward, with its apex pointing caudally (~70%)
- type II: the coccyx is curved more markedly anteriorly, with its apex pointing straight forward (~15%)
- type III: the coccyx is sharply angulated forward between the first and second or the second and third segments (~5%)
- type IV: the coccyx is subluxed anteriorly at the level of the sacrococcygeal joint or at the level of the first or second intercoccygeal joints (~10%)
Patients with a type II-IV coccyx are more prone to develop idiopathic coccygodynia than those with a type I configuration. Partial or total coccygectomy usually provides relief in these cases.
Radiographic features
The intercoccygeal angle is a useful radiological assessment to evaluate the anterior angulation of the coccyx and its deformity.
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