...unbelievably, there have been case reports in the literature of fully-formed ribs arising from the sacrum and even the coccyx, as in this case report from 1978 (below).
This particular example belongs to a 55Y woman who had spent her whole life unaware that she had a perfectly formed rib, with a well-formed capitellum, tubercle, and body, arising from her terminal coccygeal segment and terminating in her gluteal region.
Of the few reports of sacral or coccygeal ribs, the majority are short projections, and some are even described as "digits." Below is an example of a small "digit" rib extending from the sacrum.
There has been no description of deleterious effects from sacrococcygeal ribs, and authors stress that they should not be further imaged or intervened upon in the absence of symptoms.
1. Pais M, Levine A, Pais S. "Coccygeal Ribs: Development and Appearance in Two Cases" AJR 131:164-166. July 1978
2. Rashid M, Khalid M, Malik N. "Sacral Rib: A Rare Congenital Abnormality" Acta Orthop. Belg. 74: 429-431 2008
