Pelvic digit, also known as a pelvic rib, pelvic finger or 11th finger, is a rare congenital abnormality where there is development of bony tissue in the soft tissue pelvis and less commonly in the abdomen. They can be associated with one or more pseudoarticulation. They are usually unilateral, though one case of bilateral pelvic digits has been reported5.
The condition was first described by Sullivan and Cornwell in 1974, where a rib was noted radiologically in a girl6. Most cases of pelvic digit variations occur to the ilium.
Pathogenesis is unknown but is thought to occur during early embryogenesis from non-fusion of the vertebral column and the superior part of the coccyx and subsequent independent development of the intervening cartilaginous segment 4.
Treatment and prognosis
It is a benign entity and if incidentally discovered no further investigation is required. In rare occasions it can provoke localized pain7.
General imaging differential considerations include:
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- 5. Hoeffel C, Hoeffel JC, Got I. Bilateral pelvic digits. A case report and review of the literature. (1993) RoFo : Fortschritte auf dem Gebiete der Rontgenstrahlen und der Nuklearmedizin. 158 (3): 275-6. doi:10.1055/s-2008-1032648 - Pubmed
- 6. Sullivan D, Cornwell WS. Pelvic rib. Report of a case. (1974) Radiology. 110 (2): 355-7. doi:10.1148/110.2.355 - Pubmed
- 7. Pelvic digit as a rare cause of chronic hip pain and functional impairment: a case report and review of the literature. (2009) Journal of Medical Case Reports. 3 (1): 139. doi:10.1186/1752-1947-3-139 - Pubmed