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Radiographic Evaluation,

Anatomy, and Classification ofPelvic Ring Injuries

Kyle F. Dickson, MD

Chief of Orthopaedics, Charity Hospital

Director of Orthopaedic TraumaTulane University

Created March 2004

Reviewed April 2007

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Pelvic Ring

2 innominate bones

1 Sacrum

Gap in symphysis < 5 mm

SI joint 2-4 mm

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Important Stabilizing Ligaments

Posterior Iliosacral

Anterior Iliosacral

Sacrospinous

Sacrotuberous

Symphyseal

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Important Muscles

Gluteus Maximus

Iliopsoas

Rectus Abdominus

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Possible Arterial Bleeders in

Pelvic Injuries Iliolumbar artery

Superior gluteal artery

Lateral sacral artery

Internal iliac artery

Internal pudendal (active bleeding mostcommonly found)

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Neurologic Damage

L5 & S1, most common

L2 to S4 possible

Dependent on location of fracture andamount of displacement

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Denis, CORR 1988

Sacral FracturesNeurologic Injury

Lateral to foramen6% injury

Through foramen28% injuryMedial to foramen57% injury

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Pohlemann, CORR 1994

Amount of displacement move important

then location

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Potentially Damaged Visceral

Anatomy Blunt vs. impaled by bony spike

Bladder/urethra

Rectum

Vagina

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Pelvic Ring

No inherent stability

Ligaments give the pelvis stability

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Symphyseal Ligaments

Resist external rotation in double-leg stance

Rami act as struts to resist compressive and

internal rotation in single leg stance Sectioning causes little pelvic instability

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Ghanayem, J Trauma 1995

Abdominal wall contributes to pelvic

stability (laparotomy increased pelvic

displacement in cadaveric model)

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SI Joint Transfers Load from

Appendicular to Axial Skeleton

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Sacrum

Inlet View Reverse keystone where

compression forces displace sacrum

anteriorly Outlet View True keystone compression

locks sacrum into pelvic ring

Small rotating movements during gait

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Posterior Ligaments

Ant. SI Jointresist external rotation

Post. SI and Interosseousposterior

stability by tension band (strongest in body) Iliolumbar ligaments augments posterior

complex

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Sacrotuberous (sacrum behind sacro-

spinous into ischial tuberosily vertically)

Resists shear and flexion of SI joint

Sacrospinous(anterior sacral body to

ischial spine horizontally) resists external

rotation

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Normal SI Joint Motion with Gait

< 6 mm of translation

< 6 rotation Intact cadaver resist 5,837 N (1,212 lbs)

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Nachemson, Acta Orthop Scand

1966

Sitting 710 N (160 lbs) at each Si joint

Lying 196 N (44 lbs)

Lateral decubitus 686 N (154 lbs) Standing 980 N (220 lbs)

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Sitting or Double Leg Stance

Pubic rami tension and compression

posteriorly

External rotation injurydisplaces in sittingor double leg stance

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Single Leg Stance

Tension shear posteriorly and compression

of rami

Will displace internal rotation injury

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Direction of Force

Anteroposterior

Lateral compression

Vertical shear

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Stabilityability of pelvic ring

to withstand physiologic forces

without abnormal deformation

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Translational Deformities

X axisDiastasis or impaction

Y axisCaudad or cephalad displacement

Z axisAnterior or posterior displacement

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Rotational Deformities

X axisFlexion or extension

Y axisInternal rotation or external

rotation

Z axisAbduction or adduction

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Deformity of Pelvis

Defined from an anatomically positioned

pelvis in space

Deformity a combination of rotational &translational deformities

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Deformity of Pelvis (cont.)

Does not deform around a single point but

can be represented as a vector from a

normally positioned pelvis

Acute deformity difficult to measure but

direction often able to be determined

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Pelvic Instability

These injuries which will have worsening

deformity

Physical exam and radiographic evaluation

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Determining Stability

Integrity of posterior bone and ligament,

unstable = vertical plane displacement Some partial instability in rotation

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Physical Exam

Symmetrical palpable ASIS, iliac wing, and

symphysis

ASIS compression test Iliac wing compression test

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Radiographic Evaluation

Anteroposterior view (AP)

Inlet view (40 caudad)

Outlet view (40 cephalad) CT

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Good Quality Radiographs

are Essential

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Inlet (Caudad) View

Horizontal Plane

Rotation

Posterior

Displacement

Sacral ala

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Outlet (Cephalad) View

Sacrum

Cephalad

Displacement

Sacral Foramina

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Placement of Wires Show

Ant. SI joint lateral to post. SI

Radiographic brim does not always

correlate with anatomical brim

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CT Scan

Better defines posterior injury

Amount of displacement versus impaction

Rotation of fragments Amount of comminution

Assess neural foramina

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Radiographic Signs of Instability

Sacroiliac displacement of 5 mm in anyplane

Posterior fracture gap (rather thanimpaction)

Avulsion of fifth lumbar transverse process,lateral border of sacrum (sacrotuberousligament), or ischial spine (sacrospinousligament)

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Classification

Aids in predicting hemodynamic instability

Aids in predicting visceral and g.u. injuries

Aids in predicting pelvic instability Aids in understanding mechanism of injury,

force vector of injury, and surgical tactic for

reduction

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Classification Systems

Anatomical (Letournel)

Stability & Deformity (Pennal, Bucholz,

Tile) Vector force and associated injuries (Young

& Burgess)

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Anatomical Classification

(Letournel)

Where The Pelvis Breaks

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Posterior

Iliac wing fracture

Iliac wing/sacroiliac (SI) joint

(crescent fracture) SI joint

Sacrum/SI joint

Sacrum fracture

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Anterior

Rami fractures

Symphyseal disruption

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Pennal, 1961

Magnitude and direction of forces

Lateral posterior compression (LC)

Anterior posterior compression (APC)Vertical shear (VS)

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Bucholz, 1981

Tile, 1988

Added stability to the classification

OTA/AO Pelvic Injury

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OTA/AOPelvic Injury

Classification

61ALesion sparing (or with no

displacement of ) posterior arch

BIncomplete disruption at posterior arch;partially stable

CComplete disruption of posterior arch;

unstable

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A FracturesRing Intact

A-1Fracture of innominate bone; avulsion

A-2Fracture of innominate bone; direct

blow A-3Transverse fracture of sacrum and

coccyx

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B-Ring InjuryPartially stable

B-1Unilateral partial disruption ofposterior arch, external rotation (openbook injury)

B-2Unilateral, partial disruption ofposterior arch, internal rotation (lateralcompression injury)

B-3Bilateral, partial lesion of posteriorarch

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C C l t Di ti

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CComplete Disruption

Posterior Arch, Unstable Pelvis C-1Unilateral, complete disruption of

posterior arch

C-2Bilateral, ipsilateral complete,

contralateral incomplete

C3Bilateral, complete disruption

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Further Classification

A.1Location of avulsion

A.2Type of fracture anteriorly

A.3Amount of displacement sacrum

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Further Classification (cont.)

BLocation of fracture

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Further Classification (cont.)

CLocation of fracturesiliac wing,

SI joint, and sacrum

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Young and Burgess, Rad 1986

Increases clinicians diagnosis of frequently

missed lesions

Predictive index for associated injuries

Helps clinicians to select treatment based on

probable pathology and hemodynamic

status

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Lateral Compression

LC-1Ant. superior inf. rami or symphysis

and compression of sacrum same side

LC-2 - LC-1anteriorly and posteriorly

crescent fracture near anterior border at SI

joint Ileum rotated internally

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Lateral Compression

LC I: Sacral compression

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Patient WH

Progressive IR deformity that became fixed

Required anterior release & post sacral

osteotomy followed by external rotation

Pre-& postop, AP and inlet, and 2 year

follow-up

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L l C i

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Lateral Compression

LC II: Iliac wing fracture

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LC ( t )

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LC (cont.)

LC-3Windswept pelvisLCI or II on

one side of the pelvis and open book (APC)

on contralateral side (roll over mechanism

by IR on LC side and ER on contralateral

side)

LC III Wi d t l i

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LC III: Windswept pelvis

LC III

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LC III

A t t i C i

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Anteroposterior Compression

Diastasis anteriorly through symphysis

pubis or vertical Rami fractures

Posteriorly usually through SI joint

amount of displacement defines subset

A t t i ( t )

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Anteroposterior(cont.)

APC-11-2 cm symphysis diastasis and

minimal SI diastasis anteriorly (external

rotation of hemipelvisstable pelvis).

AP I

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AP I

Note that theligaments arestretched, andnot torn

A t t i ( t )

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Anteroposterior (cont.)

APC-2Sacrotuberous, sacrospinous, and

anterior SI joint ligaments disrupted (post SI

ligaments intact)

APC-3Complete SI joint disruption

(usually not vertically displaced)

AP II

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AP II

Note: pelvic floor

ligaments areviolated, as well as

anterior SI

ligaments

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A i C i

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Anteroposterior Compression

APC III: Complete Iliosacral Dissociation

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Vertical Shear

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Vertical Shear

Always unstable

Ant. symphsis or vertical rami fractures-

post. Injury variable

Vertical displacement

Vertical Shear

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Vertical Shear

Patient NJ

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Patient NJ

VS initially attempted to be treated with

anterior plate and ex-fix with hardware

failure

3 stage pelvic reconstruction ( ant.

post ant. 2 yr follow-upAuburn football

player)

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Combined

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Combined

Combined vectors occasionally 2 separate

injuries (ejection/landing)

Often LC/VS, or AP/VS

Combined Mechanical Injury

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Combined Mechanical Injury

Patient LC

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Patient LC

Combination LC and VS

Treated conservatively initially

Required 3 stage pelvic reconstruction to

restore ischial height

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See Emergent Management of

Pelvic Injuries for Application of

Classification to Treatment

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