Purpose: To describe a classification of fractures of the coccyx, according to their mechanism.
Methods: A series of 104 consecutive patients with a fracture of the coccyx was studied. The mechanism, level, characteristics of the fracture line and complications were recorded.
Results: Three mechanisms are proposed to describe these fractures: flexion, compression and extension (types 1, 2 and 3, respectively). Flexion fractures (38 cases) involved the upper coccyx in 35 cases, and in 3 cases with a perineal trauma, it was the lower coccyx; compression fractures (24 cases) involved the middle coccyx and occurred only when Co2 was square or cuneiform and Co3 was long and straight, hence a nutcracker mechanism; four patients were adolescents with a compression of the sacrum extremity and were labeled adolescent compression fracture of S5 (type 2b); extension fractures (38 cases) were obstetrical and involved the lower coccyx; their key feature was a progressive separation of the fragments with time. Flexion fractures usually healed spontaneously, but an associated intermittent luxation was possible. Nutcracker and obstetrical fractures were instable in their majority.
Conclusions: For the first time, a classification of fractures of the coccyx is presented. Each type exhibits specific features. This should help the clinician in the management of these patients. These slides can be retrieved under Electronic Supplementary Material.
Keywords: Coccydynia; Coccyx; Fracture; Pelvis; Pseudarthrosis.