Maigne JY, et al. - A series of 104 consecutive individuals with a fracture of the coccyx was investigated in order to define a classification of fractures of the coccyx, according to their mechanism. Three mechanisms were purposed to explain these fractures ie, flexion, compression, and extension (types 1, 2 and 3, respectively). Flexion fractures (n = 38) included the upper coccyx in 35 patients, and in three with a perineal trauma, it was the lower coccyx; compression fractures (n = 24) included the middle coccyx and occurred only when Co2 and Co3 were square or cuneiform and long and straight, therefore, a nutcracker mechanism; four were adolescents with a compression of the sacrum extremity and were marked adolescent compression fracture of S5 (type 2b); extension fractures (n = 38) were obstetrical in nature and included the lower coccyx; a gradual separation of the fragments with time was their chief peculiarity. Flexion fractures normally improved spontaneously, but a correlated intermittent luxation was possible. Moreover, in their majority, nutcracker and obstetrical fractures were unstable in nature. Hence, a classification of fractures of the coccyx was exhibited for the first time. Furthermore, each type displays distinct characteristics. This should aid the clinician in the management of these cases.