AO Classification of Pelvic Ring Fracture

AO Classification of Pelvic Ring FractureEducational Package 2013 (version 2)

John AuLiz AbbottDr Diana PerrimanProf. Paul Smith

Need to know

For your interest

=

=

Need to know

For your interest

Why Classify?

Accurate identification and classification of pelvic fracture guides treatment, is

potentially crucial to patient survival and is necessary for data collection.

Pelvic Fractures can be divided into:

1) Acetabular Fractures– AO Classification – Letournel & Judet Classification

2) Pelvic Ring Fractures – AO Classification– Young & Burgess Classification

3) Sacral Fractures – Denis Classification

Pelvic Fractures classification systems include:


2) Pelvic Ring Fractures – AO Classification– Young & Burgess Classification

3) Sacral Fractures – Denis Classification– Isler Classification

At Canberra Hospital and Internationally:


2) Pelvic Ring Fractures – AO Classification– Letournel & Judet Classification– Young & Burgess Classification

3) Sacral Fractures – Denis Classification

Need to know

Know how to classify acetabular # & pelvic ring # using X-rays & CT scans

AO classification

AO Classification: 5 components

Bone Segment Fracture Type

Fracture Group

Fracture Subgroup

1

2

3

1

2

3

A

B

C

AO Classification: 5 components


Fracture Group

Fracture Subgroup

1

2

3

1

2

3

A

B

C

# Localisation # Morphology

Now focusing on Pelvic Ring fractures

Pelvic Ring Fracture

1. AO classification2. Young & Burgess classification

Pelvic Ring Fracture

1. AO classification 2. Young & Burgess classification

Need to know

With respect to pelvic ring #, there are some definitions to

keep in mind.

Need to know

Pelvic ring has two arches: • (a) Posterior arch is behind

acetabular surface and includes sacrum, sacroiliac joints and their ligaments and posterior ilium, and

• (b) Anterior arch is in front of acetabular surface and includes pubic rami bone and symphyseal Joint.

Orthopaedic Trauma Association Classification, Database and Outcomes Committee (2007) Fracture and Dislocation Classification Compendium, JOT, 21(10), supplement

• Unilateral: only 1 hemipelvis involved posteriorly

• Bilateral: both hemipelvis involved posteriorly

• Contralateral: side opposite the major posterior lesion

• Ipsilateral: the side of the more severe lesion

Orthopaedic Trauma Association Classification, Database and Outcomes Committee (2007) Fracture and Dislocation Classification Compendium, JOT, 21(10), supplement


Fracture Group

Fracture Subgroup

1

2

3

1

2

3

A

B

C

AO Classification: Pelvic Ring

61 = pelvic ring


Fracture Group

Fracture Subgroup

1

2

3

1

2

3

A

B

C


B CA

Need to know

AO Classification is based on fracture stability

Need to know

B CA

Lesion sparing the posterior arch; pelvic floor intact and able to withstand normal

physiological stresses without displacement

Posterior osteoligamentousintegrity partially maintained

and pelvic floor intact

Complete loss of posterior osteoligamentous integrity;

pelvic floor disrupted

UNSTABLE

PARTIALLY STABLE

STABLE=

=

=

UNSTABLE

pelvic #are more frequently associated with

HAEMORRHAGE

Therefore, it is important NOTto miss an unstable #

“Although the anterior structures, the symphysis pubis and the pubic rami, contribute approximately 40% to the stiffness of the pelvis, clinical and biomechanical studies have shown that the posterior sacroiliac complex is more important to pelvic-ring stability.”

“Therefore, the AO classification of pelvic fractures is based on the stability of the posterior lesion.”

Anatomy Review

IliolumbarLigament

Post

erio

r Anterior

Anterior Sacroiliac Ligament

Posterior Sacroiliac Ligaments

SacrospinousLigament

SacrotuberousLigament

Ligamentous structures are major contributors to the

stability of the posterior arch


Fracture Group

Fracture Subgroup

1

2

3

1

2

3

A

B

C


BAA = no pelvic ring instability

CA

Need to know

B CAB = Rotationally unstable but Vertically stable

B

Need to know

B CAC = Grossly Unstable

C

Need to know


Fracture Group

Fracture Subgroup

1

2

3

1

2

3

A

B

C


BAA = no pelvic ring instability

CA

BA CA

For your interest

BA CA

For your interest

BA CA

For your interest

B CAB = Rotationally unstable but Vertically stable

B

B CA B

For your interest

B CA B

For your interest

B CA B

For your interest

B CAC = Grossly Unstable

C

B CA C

For your interest

B CA C

For your interest

B CA C

For your interest

For your interest

In Summary

TYPE GROUP HEMIPELVIS DISPLACEMENT STABILITY

Type A

Intact posterior arch

A1, Pelvic Ring fracture (avulsion)

None Stable A2, Pelvic Ring fracture (direct blow)

A3, Transverse Sacral fracture

Type B

Partial posterior arch disruption

B1, Open-book injury; Unilateral partial posterior arch disruption External rotation

Rotationally unstable,

vertically stable B2, Lateral Compression, Unilateral partial posterior arch disruption Internal rotation

B3, Bilateral partial posterior arch disruption Bilateral

Type C

Complete posterior arch disruption

C1, Unilateral complete posterior arch disruption Vertical (cranial) Rotationally

unstable, vertically unstable

(Grossly Unstable)

C2, Ipsilateral complete, contralateral incomplete posterior arch disruption

Ipsilateral vertical (cranial), contralateral internal or external

rotation C3, Bilateral complete posterior arch disruption Bilateral vertical (cranial)

Modified from: https://www2.aofoundation.org/wps/portal/!ut/p/c0/04_SB8K8xLLM9MSSzPy8xBz9CP0os3hng7BARydDRwN39yBTAyMvLwOLUA93I4MQE_2CbEdFAF3RnT4!/?segment=Ring&bone=Pelvis&soloState=true&popupStyle=diagnosis&contentUrl=srg/popup/decision_support/61-Emergency/Tile_classification.jsp

Need to know

Part 3: Sacral Fractures

For your interest


1. Denis classification2. Isler classification

For your interest


1. Denis classification2. Isler classification

For your interest

Denis, F., Davis, S. & Comfort, T. (1988) Sacral Fractures: An Important Problem. Retrospective Analysis of 236 Cases. CORR 227: 67-81

For your interest

# Location Frequency of neurologic injury

Zone 1 The region of the ala(Lateral to the sacral foramina)

5.9 percent, usually L5 root

Zone 2 The region of the sacral foramina 28.4 percent, predominately sciatica with rare bladder or bowel involvement

Zone 3 The central sacral canal region(Medial to the sacral foramina)

≥50 percent; most involve bowel, bladder, or sexual dysfunction

Denis, F., Davis, S. & Comfort, T. (1988) Sacral Fractures: An Important Problem. Retrospective Analysis of 236 Cases. CORR 227: 67-81

For your interest

X-rays & CTs

Inlet view (Pelvic Ring #)

Source: Up to date

Inlet Views is good for assessing: • AP shear/Translation of hemipelvis• Iliac Spines

Inlet view

Broder, J. (2011) Diagnostic Imaging for the Emergency Physician – Chapter 13 Imaging of the pelvis and hip, 706-747

Outlet view (Pelvic Ring #)

Source: Up to date

Outlet Views is good for assessing: • Vertical shear & translation • Obturator Foramina• Sacral Foramina

Outlet view

Sacral Arcuate Lines (eyebrows)

Jackson, H., Kam, J., Harris, J.H. & Harle, T.S. (1982) The sacral arcuate lines in upper sacral fractures. Radiology 145, 35-39

The arcuate lines represent the inferior surfaces of the costal elements that form the roofs of the anterior sacal canals (foramina) and neural grooves

CT reconstruction

CT reconstruction is a powerful tool for imaging difficult #’s.

How should pelvic ring # X-rays be approached?

X-ray interpretation

Be systematic• Front to back, then as a whole

i. Anterior structuresii. Posterior sturcturesiii. Pelvic Ringiv. Hemipelvis

Need to know


Anteriora) Pubic Symphysisb) Ramic) Femurd) Iliac Crests & Wingse) ASIS & AIIS

Need to know

Normal Pelvic X-ray

X-ray interpretationAnteriora) Pubic Symphysis

– widening? overlap?– Vertical alignment: is it in line with tip of coccyx in the midline?– Normal symphysis: 4 to 5mm in width & does not exceed 1cm

b) Rami– Obturator Ring: disruption?

c) Femur– Head, Neck, GT, LT & shaft– #? hip dislocation?

d) Iliac Crests & Wings– #?

e) ASIS & AIIS – Avulsion #?

Need to know


Widened pubic symphysis





d) Iliac Crests & Wings – #?


Need to know


Superior pubic ramus #

Sclerotic line representing iliac wing #

Inferior pubic ramus #





d) Iliac Crests & Wings – #?


Need to know


Avulsion ASIS fragment

Avulsion ASIS fragment


Posteriora) Sacroiliac jointb) Sacrumc) L5 TP

Need to know

Normal Pelvic X-ray

X-ray interpretationPosteriora) Sacroiliac joint (SIJ)

– Widening? Hinging? Vertical Shear? Overlap?– joints should be symmetrical – joint space less than 2 to 4mm in width

b) Sacrum– #?– Sacral arcuate lines (eyebrows) – disruptions? – Which zone? 1, 2 or 3? (implications for neurological involvement)

c) L5 TP (attachment of the iliolumbar ligament)– #?– “A fracture of the transverse process of L5 in the presence of a

pelvic fracture is associated with an increased risk of instability of the pelvic fracture” (Starks et al. 2011, JBJS Br)

Need to know


X-ray interpretationPosteriora) Sacroiliac joint (SIJ)

Need to know


Normal SIJWidened

SIJ

X-ray interpretation Need to know


Widened Pubic Symphysis

SIJ diastasis


Pelvic RingFollow ring formed by the inferior portion of the sacrum and the medial ilium and ischium, sweeping down the pubic bone to the pubic symphysis and back up the opposite side. This should follow a continuous ring.

Need to know


Normal Pelvic Ring


HemipelvisCranial displacement is consistent with a vertical shear #

Need to know

Slater, S.J. & Barron, D.A. (2010) Pelvic Fractures – a guide to classification and management, 74, 16-23.Pubic Rami #

Cranial displacement of the right hemipelvis

Vertical Shear #Vertically unstable,

Rotationally unstable

UNSTABLE

How should pelvic ring # CTs be approached?

CT interpretation

Be systematic• For axial CTs, top to bottom, 3 locations:

i. L5 vertebraeii. Iliac Wingiii. Inferior Pelvis

Need to know

CT interpretation

L5 vertebrae (axial view)

• L5 Transverse Process (attachment of the iliolumbar ligament)

– L5 TP #?– Iliolumbar ligament is the last ligament to fail in disruptions to

the posterior sacroiliac complex in pelvic ring #

Need to know

“A fracture of the transverse process of L5 in the presence of a pelvic

fracture is associated with an increased risk of instability of the

pelvic fracture” (Starks et al. 2011, JBJS Br)

Mulligan, M. & Talmi, D. (2009). Are pelvic radiographs needed in assault victims? Emerg Radiol 16(4): 299-301

UNSTABLE

CT interpretation

Iliac wing (axial view)

a) SIJb) Ilium c) Sacrum

Need to know

CT interpretation


a) SIJ– Disruptions?

e.g. Widening? Hinging?

b) Ilium – #? – Avulsion #?

c) Sacrum– #?– Vertical shear?– Which zone is it in?

Need to know

Normal left SIJ

Widened right SIJ

CT interpretation






Need to know

Widened right SIJ

UNSTABLE

Unilateral complete disruption of posterior

arch

CT interpretation






Need to know

Normal Iliac wingIliac wing #

CT interpretation






Need to know

Sacral #

UNSTABLE

Unilateral complete disruption of posterior

arch

CT interpretation

Inferior pelvis (axial view)

a) Ischial Tuberositiesb) Pubic Symphysisc) Pubic Ramid) Coccyx

Need to know

CT interpretation


a) Ischial Tuberosities– #? Symmetry?

b) Pubic Symphysis– widening? overlap?

c) Pubic Rami– #? Symmetry?

d) Coccyx

Need to know

Widened pubic Symphysis

CT interpretation





d) Coccyx

Need to know

Minimally displaced right superior pubic ramus #

CT interpretation





d) Coccyx

Need to know

Pubic rami #• Spike # could pierce bladder (suggestive of internal rotation: B2)• Transverse # (suggestive of external rotation, B1 ‘open book’)

Normal inferior pubic ramus


NOTE: Even though we have divided the educational package into pelvic ring & acetabular #s, the

two types of #s can occur together. Therefore, in clinical practice, you need to assess the

landmarks for both acetabular* & pelvic ring #s

* See acetabular # educational package

For ExampleComplete

disruption SIJComplete disruption SIJ


Femoral Head Fracture

Acetabular #


UNSTABLE

When there are more than 1 #s in the pelvis, you would classify the #s in that patient based on the individual #s (e.g. Right 61B1 & Left 61A1). However, the

main # is the more severe one.

Now, Classifying Pelvic-ring fractures using X-rays & CTs

Source: up to dateCourtesy of Jim Fiechtl, MD

Is this X-ray normal?


AP Pelvic X-rayAvulsion # of Left ASISCommon in immature skeleton

ASIS avulsion #• Sartorius (small avulsion)• TFL (bigger avulsion)• or both

AIIS avulsion #• Rectus Femoris

61 A1

Think about origin of muscles


?

X-rayAvulsion # of Right AIIS

61 A1Broder, J. (2011) Diagnostic Imaging for the Emergency Physician – Chapter 13 Imaging of the pelvis and hip, 706-747

Avulsion fragment of AIIS

61 A3

X-rayTransverse sacral #

Transverse Sacral #

Transverse Sacral #

This is an isolated transverse fracture of the sacrum, approximately at the level of the inferior margin of the left SIJ.

This runs through the neural foramen of the sacrum, so that the arcuatelines of the foramen do not form a complete circle.

Because the fracture only separates the caudad portion of the sacrum from the cephalad portion, the sacrum continues to form a complete bridge between the iliac wings, and the pelvis remains stable.

X-rayWidening of pubic symphysisTherefore, open book #Therefore, at least type B

However, difficult to classify because of incomplete information

(e.g. completeness of posterior arch disruption? involvement of

one or both sides?)

At least a Type BNB: diastasis at the pubic symphysis can cause significant haemorrhage. Emergent treatment

consists of closing the # and stabilising the pelvis by applying a pelvic binder or tying a sheet tightly

around the lower pelvis

Source: up to date

Source: up to date

X-rayWidening of pubic symphysis(Therefore not a type A, at least a type B)

CTPartial disruption of posterior arch (Therefore type B)

Unilateral(Therefore B1)

61 B1

SchematicSchematic representation of

• Pubic Symphysis disruption• Ligamentous disruption


X-ray (A)Bilateral sup. & inf. rami #Left Sacral #

Lateral compression injury with internal rotation of the hemiplevis

No vertical shear(Therefore not type C)No pubic symphysis diastasis(Therefore not B1)

61 B2

X-ray (B)Inlet view showing greater detail of the pelvic ring disruption

X-ray (C)Outlet view showing greater detail of the sacral # & the bilateral rami #


Rami #Widening of right SIJ

CTBilateral partial posterior arch disruption

• Opening of right SIJ anteriorly• Posterior right SIJ hinging• Opening of left SIJ anteriorly

61B3Source: up to dateCourtesy of Jim Fiechtl, MD

Rotationally unstable but Vertically stable

X-rayPubic symphysis intactNo vertical shear(Probably a type B)

CTComplete posterior disruption

Type B, arguably Type C

Currently vertically stable (Type B) but has the potential to become vertically

unstable (Type C) because of the complete posterior arch disruption

Tricky one!

Source: up to date

X-ray Huge pubic symphysis disruption(Therefore not a type A, at least a type B)

CT Complete disruption of posterior arch(Therefore, type C)

Unilateral(Therefore, C1)

61C1

Schematic Schematic representation of

• Pubic Symphysis disruption• Posterior arch disruption

UNSTABLE

Source: up to date

X-ray Pelvic Vertical Shear

CT reconstruction Unilateral complete disruption of posterior arch

61 C1

Schematic Schematic representation of

• Pubic Symphysis disruption• Posterior arch disruption

UNSTABLE


CTComplete posterior arch disruption (Therefore, type C)

Ipsilateral completeContralateral incomplete (arrow)(Therefore, C2)

Source: up to date

61 C2UNSTABLE


X-rayVertical Shear injuryRight Rami #Left Sacral #Left Transverse Acetabular #

Pelvic Type CVertical Shear

Acetabular Type B1

Transverse Acetabular #

Main Fracture is the Type C Pelvic Ring # because of it implications. It is associated

with a left transverse acetabular #

NB: need CT scans to provide more

information about the #s

UNSTABLENeed to know

The end

Thank you for your attention, good luck with the test.

Documents

AO Classification of Pelvic Ring Fracture