Radiographic Evaluation, Anatomy, and Classification of Pelvic Ring Injuries

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Radiographic Evaluation, Anatomy, and
Classification of Pelvic Ring Injuries

• Kyle F. Dickson, MD
• Chief of Orthopaedics, Charity Hospital
• Director of Orthopaedic Trauma
• Tulane UniversityCreated March 2004Revised
  April 2007

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Palpable Bony Landmarks

• Symphysis Pubis
• Anterior Superior Iliac Spine (ASIS)
• Iliac Wing
• Posterior Superior Iliac Spine (PSIS)

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Pelvic Ring

• 2 innominate bones
• 1 Sacrum
• Gap in symphysis lt 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 most commonly
  found)

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Neurologic Damage

• L5 S1, most common
• L2 to S4 possible
• Dependent on location of fracture and amount of
  displacement

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Denis, CORR 1988

• Sacral Fractures Neurologic Injury
• Lateral to foramen 6 injury
• Through foramen 28 injury
• Medial to foramen 57 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 Joint resist external rotation
• Post. SI and Interosseous posterior 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

• lt 6 mm of translation
• lt 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 injury displaces in sitting
  or 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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Stability ability of pelvic ring to withstand
physiologic forces without abnormal deformation
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Translational Deformities

• X axis Diastasis or impaction
• Y axis Caudad or cephalad displacement
• Z axis Anterior or posterior displacement

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Rotational Deformities

• X axis Flexion or extension
• Y axis Internal rotation or external rotation
• Z axis Abduction 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 Radiographsare 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 any plane
• Posterior fracture gap (rather than impaction)
• Avulsion of fifth lumbar transverse process,
  lateral border of sacrum (sacrotuberous
  ligament), or ischial spine (sacrospinous
  ligament)

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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

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OTA/AO Pelvic Injury Classification

• 61A Lesion sparing (or with no displacement of
  ) posterior arch
• B Incomplete disruption at posterior arch
  partially stable
• C Complete disruption of posterior arch
  unstable

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A Fractures Ring Intact

• A-1 Fracture of innominate bone avulsion
• A-2 Fracture of innominate bone direct blow
• A-3 Transverse fracture of sacrum and coccyx

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B-Ring Injury Partially stable

• B-1 Unilateral partial disruption of posterior
  arch, external rotation (open book injury)
• B-2 Unilateral, partial disruption of posterior
  arch, internal rotation (lateral compression
  injury)
• B-3 Bilateral, partial lesion of posterior arch

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C Complete Disruption Posterior Arch, Unstable
Pelvis

• C-1 Unilateral, complete disruption of
  posterior arch
• C-2 Bilateral, ipsilateral complete,
  contralateral incomplete
• C 3 Bilateral, complete disruption

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Further Classification

• A.1 Location of avulsion
• A.2 Type of fracture anteriorly
• A.3 Amount of displacement sacrum

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Further Classification (cont.)

• B Location of fracture

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Further Classification (cont.)

• C Location of fractures iliac 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-1 Ant. superior inf. rami or symphysis and
  compression of sacrum same side
• LC-2 - LC-1 anteriorly 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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Lateral Compression

• LC II Iliac wing fracture

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LC (cont.)

• LC-3 Windswept pelvis LCI 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)

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LC III Windswept pelvis
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LC III
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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

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Anteroposterior (cont.)

• APC-1 1-2 cm symphysis diastasis and minimal SI
  diastasis anteriorly (external rotation of
  hemipelvis stable pelvis).

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AP I

• Note that the ligaments are stretched, and not
  torn

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Anteroposterior (cont.)

• APC-2 Sacrotuberous, sacrospinous, and anterior
  SI joint ligaments disrupted (post SI ligaments
  intact)
• APC-3 Complete SI joint disruption (usually not
  vertically displaced)

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AP II

• Note pelvic floor ligaments are violated, as
  well as anterior SI ligaments

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Anteroposterior Compression

• APC III Complete Iliosacral Dissociation

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Vertical Shear

• Always unstable
• Ant. symphsis or vertical rami fractures-post.
  Injury variable
• Vertical displacement

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Vertical Shear
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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-up Auburn football player)

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Combined

• Combined vectors occasionally 2 separate injuries
  (ejection/landing)
• Often LC/VS, or AP/VS

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Combined Mechanical Injury
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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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Acknowledgment

Joel Matta, Phil Kregor, and Mark Vrahas for the
use of their slides
If you would like to volunteer as an author for
the Resident Slide Project or recommend updates
to any of the following slides, please send an
e-mail to ota_at_aaos.org
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