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.

Abdominal and pelvic anatomy
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Article information

rID: 18563
Section: Anatomy
Synonyms or Alternate Spellings:
  • Anterior angulation of coccyx
  • Forward angulation of the coccyx
  • Anterior deformity of the coccyx

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Cases and figures

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    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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