A common classification of bone fracture is the AO classification (also Müller classification; AO – Arbeitsgemeinschaft für Osteosynthesefragen). The system is used to describe the location as well as the nature of fractures. For this purpose, a code is created based on the classification:
Fracture localization – body region numbering.
- Humerus [humerus]
- Radius (radius) and ulna (ulna) [forearm bones].
- Femur (thigh bone) and patella (kneecap).
- Tibia (tibia) and fibula (fibula).
- Spine
- Pelvis (pelvis)
- Hand
- Foot
- Skull and lower jaw
Fracture localization – positioning of the fracture in the bone segment.
- Proximal (Latin proximus = nearest; “closer to the center of the body” or “more closely situated”).
- Diaphyseal (pertaining to the middle piece of the long bone (diaphysis)).
- Distal (lat. distare = to move away; “located further from the center of the body” or “away”); 0.4% of all fractures and 3% of femur fractures
- Malleolar (involving the ankle).
Evaluation of the fracture – complexity
- Simple or extra-articular (outside the joint) fracture.
- Wedge fracture or partial joint involvement
- Complex fracture or complete joint fracture
More accurate assessment of the severity of the injury
- Light
- Medium
- Heavy
The AO classification also allows for the classification of associated injuries with description of skin damage (I), muscle and tendon injuries (MT), and nerve and vascular injuries (NV).
Skin injury in closed fracture:
- IC1: no skin injury
- IC2: contusion (bruising; contusion; damage to organs, tissue areas, or body parts by direct, blunt force from the outside without visible injury to the skin) without skin opening
- IC3: circumscribed decollement (separation of the skin from the subcutaneous tissue (subcutaneous fat tissue) and / or muscle fascia by external force).
- IC4: extended, closed decollement.
- IC5: necrosis (tissue damage resulting from the death of cells) due to deep contusion.
Skin injury in open fracture:
- IO1: skin puncture from the inside out.
- IO2: skin spike from the outside <5 cm with contused edges.
- IO3: skin lesion > 5 cm, circumscribed decollement with marginal contusion.
- IO4: skin loss, deep contusion, abrasion.
- IO5: extended decollement
Muscle and tendon injuries:
- MT1: No injury
- MT2: circumscribed muscle injury (limited to one muscle group).
- MT3: extensive muscle involvement (in 2 or more muscle groups).
- MT4: avulsion or loss of entire muscle groups, tendon transections.
- MT5: lodge or crush syndrome (lodge syndrome: synonym: condition in which, with the skin and soft tissue sheath closed, increased tissue pressure leads to a reduction in tissue perfusion (tissue perfusion), resulting in neuromuscular disorders or tissue and organ damage; due to the increased pressure in the muscle lodge of the forearm or lower leg (hence the name lodge syndrome here) damage to the nerves, blood vessels and muscles; crush syndrome: Muscle decay can occur as crush syndrome due to external influences as a result of injury or bruising of large muscle parts).
Neurovascular injuries (nerve-vascular injuries):
- NV1: no injury
- NV2: isolated nerve lesion (nerve injury).
- NV3: circumscribed vascular injury
- NV4: combined neurovascular injury
- NV5: subtotal, total amputation (severance of a body part, incomplete or complete, respectively).
