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) |
References:
1. Kellam JF, Mayo K. Pelvic ring disruptions. In: Browner BD, Jupiter JB, Levine AM, et al., eds. Skeletal Trauma, 3rd ed. Philadelphia, PA: WB Saunders, 2003:1052–1062.
2. Pohlemann T. Pelvic ring injuries: assessment and concepts of surgical management. In: Rüedi TP, Murphy WM, eds. AO principles of fracture management. Stuttgart-New York: Thieme;200:391-412.
3. Pennal GF, Tile M, Waddell J P, Garside H. Pelvic disruption: assessment and classification. Clinical orthopaedics and related research. 1980;151:12-21.
4. Tile M. Acute pelvic fractures: I. Causation and classification. Journal of the American Academy of Orthopaedic Surgeons, 1996, 4.3: 143-151
5. Müller E, ed. Comprehensive Classification of Pelvis and Acetabulum Fractures. Bern, Switzerland, Maurice E. Müller Foundation, 1995.