Supernumerary ribs are congenital anomalies that can occur in all areas of the vertebral column. Sacrococcygeal ribs, arising from the most caudal part of the vertebral column, are the rarest type of supernumerary ribs. They were described as early as 1960, with new reports being published every few years. Brief literature overviews were sometimes included with case reports. However, until now, no comprehensive reviews with reported search strategies have been published. The purpose of the study was to present a comprehensive review on the subject. A proposal for a clear definition of these entities is made. Where relevant, comparisons with other types of supernumerary ribs are made. An overview of supernumerary ribs in other mammals is presented. Materials and methods. A search of the Medline and Web of Science Core Collection databases was performed with several relevant keywords. The Google search engine was utilized to identify relevant literature. The references of the publications identified with the former methods were also searched. The publications were sorted according to whether they fit the definition of sacrococcygeal ribs put forward above or were called sacrococcygeal ribs but did not fit the definition. To avoid missing any relevant literature, all literature mentioning sacrococcygeal ribs regardless of the definition used were included. Additionally, literature about pelvic digits that would fit the definition was also included. Papers were excluded if they could not be sourced or did not mention sacrococcygeal ribs (any definition) or pelvic digits fitting the definition. Results and discussion. Sacrococcygeal ribs seems to occur equally often in men and women, since both accounted for half of the twelve cases identified that fit the definition. On average, they are diagnosed at 29.91 years of age, but this varied widely (from 3 to 64). This variation is to be expected, since the entities are usually discovered by accident and are present since birth. Although they are very rare, no further information about risk factors was identified. Most of the patients in the case reports did not suffer from symptoms relating to their sacrococcygeal ribs. However, some authors mention that the ribs might pose obstetrical problems during childbirth. This can be expected to be dependent on the exact size and anatomical location of the rib in question and may vary between patients. Due to the lack of symptoms that are associated with sacrococcygeal ribs, an underdetection could however be present. Therefore, further research is needed to more specifically assess the prevalence. This limited body of evidence makes it difficult to make sound conclusions about the epidemiology of these entities. Conclusion. Based on the current body of evidence, it is difficult to make sound conclusions about the condition. It is however very clear that the anomaly is very rare and that complications are relatively rare
Keywords: sacrococcygeal, sacral, coccygeal, supernumerary, ribs
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