Anterior luxations are a rare lesion (less than 5% of the cases of coccydynia). They have nothing to see with posterior luxations, but should be considered as a more marked form of hyper mobility. The difference lies in the axis of displacement of the luxated vertebra (usually the most distal one): there is no sagittal rotation (flexion) as in hyper mobility but a slip in the sitting position. As in hyper mobility, anterior luxations ocures in curved coccyges, with a low incidence and a high sagittal pelvic rotation.

Case #1: The anterior luxation typically involve the last vertebra. Is is rarely a complete luxation.

Case #2: The diagnosis may be difficult. Here, the last but one joint (X) is involved.

Case #3: This case is a combination of anterior luxation and hyper mobility. This latter seems predominant.

Case #4: Another typical case.

Case #5: The need for excellent radiographs. Left : standard film. Center : dynamic film, which appears normal... but the distal vertebra is not seen. It is annoying, because it was the one which was luxated (right, X)