AO classification (adapted from Tscherne)
The AO classification of fracture wound severity provides a grading system for injuries of each of the skin (I), muscles and tendons (MT), and neurovascular (NV), each of which is divided into five degrees of severity.
It is designed to provide a unique, unequivocal definition of any injury and, thereby, allows accurate comparison of cases.
A full understanding of the severity of an open fracture requires consideration of each of these soft-tissue elements.
This very detailed classification is designed to be used in conjunction with the AO/OTA Fracture and Dislocation Classification.
The detailed categorisation of open fractures by the AO system is most reliably done in the operating room at the completion of primary wound care and surgical excision.
When used in a large database this multifaceted, alphanumeric classification permits very precise comparison of injury types and is most useful as a research tool. However, its complexity renders it largely impractical for everyday use in clinical practice.