müller ao classification of fractures müller ao classification of fractures the müller ao classification of fractures is a system for classifying bone fractures initially published in 1987 by the ao foundation as a method of categorizing injuries according to therognosis of the patient's anatomical and functional outcome. "ao" is an initialism for the german "arbeitsgemeinschaft für osteosynthesefragen", the predecessor of the ao foundation. ao classification it is one of the few complete fracture classification systems to remain in use today after validation. comprehensive classification of the long bones the english language version of the system allows consistent in detail description of a fracture in defined terminology by creating a 5-element alphanumeric code: localisation morphology bone segment type group subgroup 1/2/3/4 1/2/3/(4) a/b/c 1/2/3 .1/.2/.3 localisation first, each fracture is given 2 numbers to describe which bone it affects, and where in the bone: 1 2 3 4 bone humerus radius and ulna femur tibia and fibula segment proximal segment diaphyseal segment distal segment malleolar segment (only used with tibia and fibula type each fracture is next given a letter (a, b or c) to describe the joint involvement of the fracture: segment a b c 1 extra-articular partial articular complete articular 2 simple wedge complex 3 extra-articular partial articular complete articular the exceptions to this step include: localisation a b c 11 - proximal humerus extra-articular, unifocal extra-articular, bifocal articular 31 - proximal femur extra-articular, trochanteric extra-articular, neck articular, head 44 - malleoli infrasydesmotic transyndesmotic suprasyndesmotic groups & subgroups finally, the fracture is given 2 further numbers to denote the fracture pattern and geometry. for segment 2 (diaphyseal) fractures: type group 1 2 3 a - simple spiral oblique transverse b - wedge spiral bending multifragmentory c - complex spiral segmental irregular for segment 1 and 3 (epiphyseal and metaphyseal) fractures: type group 1 2 3 a - extra-articular simple wedge complex b - partial articular split depression split-depression c - articular simple articular, simple metaphyseal simple articular, complex metaphyseal complex articular, complex metaphyseal subgroups are then used to describe the fractures in terms of displacement (versus apposition, which is the degree to which the parts are in contact with each other), rotation, angulation and shortening. ao pediatric comprehensive classification of long bone fractures a pediatric version of the long-bone classification was published in 2006 to further classify fractures of immature bone and so the effects on future growth: localisation morphology bone segment type child severity exceptions 1/2/3/4 1/2/3 e/m/d 1-9 .1/.2 i-iv ota/ao classification unifying extension the orthopaedic trauma association committee for coding and classification initially published their classification system covering the whole skeleton in 1996. in 2006 they published a revision, unifying the muller/ao and ota systems into a single alphanumeric classification, which has been further updated in 2018: localisation region/bone bone segment 1 4 scapula 5 clavicle 3 4 patella 5 1 cervical spine 2 thoracic spine 3 lumbar spine 6 1 pelvic ring 2 acetabulum 7 1 lunate 2 scaphoid 3 capitate 4 hamate 5 triquetrum and pisiform 6 trapezium and trapezoid 7 metacarpus 8 phalanges 9 multiple fractures 8 1 talus 2 calcaneus 3 navicular 4 cuboid 5 cuneiforms 7 metatarsus 8 phalanges 9 multiple fractures 9 1 craniomidface 2 mandible