Anterior angulation of the coccyx

Last revised by Daniel J Bell on 27 Sep 2023

Anterior angulation of the coccyx may be a normal variant but poses a diagnostic challenge for those considering coccygeal trauma.

Six 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%)

  • type V: the coccyx is retroverted or has a posterior spicule

  • type VI: the coccyx is scoliotic (lateral deviation)

The intercoccygeal angle is a useful radiological assessment to evaluate the anterior angulation of the coccyx and its deformity.

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

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Cases and figures

  • Case 1: type III coccyx
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  • Case 2: type III
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  • Case 3
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  • Case 4: type IV
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  • Case 5: type I
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  • Case 6: Type III
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