Fracture of pelvis - AO classification - modifed Tile AO Müller classification

The modified Tile AO Müller classification, like the original, divides pelvic fractures into three basic types according to stability based on the integrity of the posterior sacroiliac complex. It takes into consideration the direction of the force involved. In type A, the fracture does not involve the posterior arch. Type B fracture is a result of rotational forces that cause partial disruption of the posterior sacroiliac complex. Complete disruption of the posterior complex (including the sacrospinous and sacrotuberous ligaments) occurs in type C fractures, that are both rotationally and vertically unstable. Each basic type has three subtypes.

Type Description
Type A: stable - posterior arch is intact A1: fracture does not involve the pelvic ring (avulsion fracture or fracture of the iliac wing)
- A1.1: iliac spine
- A1.2: iliac crest
- A1.3: ischial tuberosity
A2: stable or minimally displaced fracture of the pelvic ring
- A2.1: iliac wing fractures
- A2.2: unilateral fracture of anterior arch
- A2.3: bifocal fracture of anterior arch
A3: transverse fracture of the sacrum
- A3.1: sacrococcygeal dislocation
- A3.2: sacrum undisplaced
- A3.3: sacrum displaced
Type B: rotationally unstable, vertically stable - incomplete disruption of the posterior arch B1: open book injury (external rotation)
- B1.1: sacroiliac joint, anterior disruption
- B1.2: sacral fracture
B2: lateral compression injury (internal rotation)
- B2.1: anterior compression fracture, sacrum
- B2.2: partial sacroiliac joint fracture, subluxation
- B2.3: incomplete posterior iliac fracture
B3: bilateral type B fracture
- B3.1: bilateral open book fracture
- B3.2: open book fracture and lateral compression
- B3.3: bilateral lateral compression
Type C: rotationally and vertically unstable - complete disruption of the posterior arch
C1: unilateral fracture
- C1.1: fracture of the iliac bone
- C1.2: sacroiliac dislocation and/or fracture dislocation
- C1.3: sacral fracture
C2: bilateral fracture with one side type B fracture (rotationally unstable) and one side type C fracture (vertically unstable)
C3: bilateral fracture with both sides type C fracture (both sides completely unstable)


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