V04 anatomy class_acetab

Berton R. Moed, MDProfessor and Chairman, Department of Orthopaedic Surgery

Saint Louis University School of Medicine

Original Authors: Kyle F. Dickson, MD & George V. Russell, Jr., MD, Created March 2004

New Author: Berton R. Moed, MD, Revised January 2007

Radiographic Evaluation, Anatomy and Classification of

Acetabular Fractures

Anatomic Considerations Osteology

• Judet and Letournel– Classification system (JBJS 1964)– Inverted “Y” two column concept (1966)

Osteology

Acetabular Columns

• Anterior (iliopubic) column – Extends from anterior iliac crest

symphysis pubis– 3 segments

• Iliac segment• Acetabular segment• Pubic segment

Acetabular Columns• Posterior (ilioischial) column

– Extends from greater sciatic notch inferior ischium

• The upper end of the posterior column attaches to the posterior aspect of the anterior column forming an angle of about 60 degrees.

• Anatomical roof of the acetabulum forms keystone of arch

Osteology

3D Anatomy of the Innominate Bone

– Originates from the internal iliac artery (70%)– Small caliber anastomoses between the obturator

and external iliac systems are common– The pubic branch of the obturator artery commonly

anastomoses behind the body of the pubis with the pubic branch of the inferior epigastric artery

Vascular Anatomy (cont.)• Obturator Artery Abnormal Anatomy

– The obturator artery originates from the inferior epigastric artery or external iliac (30%)

– In a small percentage of cases this anomalous vessel is of large caliber and can result in severe bleeding if it is unknowingly lacerated

– This is the so-called Corona Mortis

Vascular Anatomy (cont.)• Ascending branch of medial circumflex

– Main blood supply to femoral head– Deep to quadratus, obturator internus, and

piriformis, superficial to obturator externus

Vascular Anatomy (cont.)• Can be damaged with

– Dislocation of femoral head– Not leaving 1 cm tag for piriformis and obt.

internus tendons off the greater trochanter– Taking down quadratus from femur instead of

ischium

Vascular Anatomy (cont.)• Superior gluteal artery

– Greater sciatic notch– Can be damaged by aggressive superior or

lateral retraction of the abductor muscles during Kocher-Langenbeck exposure.

Important Neural Anatomy

• Sciatic nerve– Most common traumatic

& iatrogenic nerve injury

– Variable but well described anatomy

Neural Anatomy (cont.)• Superior gluteal nerve

– Greater sciatic notch– Can be damaged by aggressive superior or

lateral retraction of the abductor muscles during Kocher-Langenbeck exposure.

Neural Anatomy (cont.)• Inferior gluteal nerve

– The inferior gluteal nerve branches innervating superior third of the gluteus maximus muscle are located approximately half way between the greater trochanter and the posterior superior iliac spine.

– The nerve can be damaged by extending the Kocher-Langenbeck approach superior to this point within the substance of the gluteus maximus muscle.

Radiographic lines = bone where the x-ray beam is tangential to its surface

Radiographic Evaluation of the

Acetabulum

Radiographic Evaluation

• Anteroposterior pelvis• Judet views• CT scan

AP Radiograph

Landmarks AP View Column

1. Iliopectineal line Anterior

2. Ilioischial line Posterior

3. Radiographic U, or teardrop

Usually Ant.

4. Roof Ant. & Post.

5. Anterior rim Anterior

6. Posterior rim Posterior

AP Pelvic Radiographs • Iliopectineal line

– Anterior 3/4 corresponds to pelvic brim– Posterior 1/4 corresponds to roof of sciatic

buttress– Corresponds to quadrilateral surface

AP Radiograph

AP Pelvic Radiographs • Teardrop

– Internal limb = outer wall of obturator canal– External limb = middle 1/3 of cotyloid fossa– Inferior border = ischiopubic notch

Radiographic U orTeardrop

AP Pelvic Radiographs • Acetabular roof

– Representative of the superior weight bearing area of the acetabulum

• Anterior / posterior walls– Represent lateral extensions of articular

surfaces

AP Radiograph

AP Pelvic Radiographs

• Associated pelvic ring injuries• Bilateral acetabular fractures• Femoral head fractures• Fracture displacement• Congruency of femoral head in

acetabulum

Judet Oblique Radiographs

• Pioneered by Judet and Letournel• 45° oblique pelvic radiographs• Emphasize acetabular columns• Coccyx tip should lie above the center of

the femoral head to ensure adequate rotation

Oblique RadiographsBased on Osteology

Obturator (Internal) Oblique

• Injured side up• Coccyx centered over ipsilateral

femoral head• Obturator foramen in profile• Highlights pelvic brim, anterior column

and posterior wall• Assess congruency of femoral head in

acetabulum

Obturator (Internal) Oblique

Internal Oblique Radiograph

Obturatorforamen

Posteriorwall

Iliac (External) Oblique• Injured side down• Coccyx centered over contralateral femoral head• Iliac wing in profile• Highlights posterior column, anterior wall,

posterior border of innominate bone and quadrilateral plate

• Assess congruency of femoral head in acetabulum

Iliac (External) Oblique

External Oblique Radiograph

Posterior border of innominate bone

Iliac wing

Anteriorwall

Quadrilateralplate

Posteriorcolumn

CT ScanAdditional Information

• Assessment of soft tissue damage• Assessment of solid organ injury• Assessment of hollow organ injury• Assessment of pelvic hematomas

2-D CT Scan

• Acetabular wall fractures• Intra-articular loose fragments • Marginal impacted fragment• Degree of fracture comminution• Position of the femoral head• Femoral head lesions• Joint Congruence• SIJ and the posterior pelvic ring

3mm cuts through pelvis

2-D CT Scan

• Identification of fracture lines not visualized by radiographs

• Orientation of fracture line• Vertical portion of “T” type acetabular

fracture• Rotation of fracture fragments

2-D CT Scan

Case Example

3-D CT Scan

• Provides a good overall picture of the fracture configuration

• The averaging required to produce the image limits the detail and usefulness

• Good for teaching purposes

3-D CT Scan

• Converted from 2 dimensional CT scan data• Image quality determined by software• Allows for subtraction of femur• Allows for rotation of pelvis• All information is on the 2-D CT

Acetabular Fracture Classification

• Classified according to system developed by Judet and Letournel

• Based on the columns and walls of the acetabulum• Two types: Elementary and Associated • Adopted by OTA (Types 62-A, -B & -C) in the

attempt to standardize terminology and to allow for computerized coding

• Elementary patterns (Part or all of one column fractured)– Posterior wall fracture– Anterior wall fracture– Posterior column fracture– Anterior column fracture

(Plus “by virtue of its purity”)– Transverse

Judet & Letournel Elementary Fractures

Posterior Wall Posterior Column Anterior Wall Anterior Column

Transverse

• Associated patterns(Include at least 2 elementary forms)– Posterior column & posterior wall fractures– Transverse & posterior wall fractures– T-shaped fractures– Anterior wall or column & posterior

hemitransverse fractures– Both-column

Judet & Letournel Associated Fractures

Posterior Column & Posterior Wall

Transverse &Posterior Wall

T-shaped Both-ColumnAnterior Type withPosterior Hemitransverse

Roof Arc Measurement

• Initially described by Matta 1986• A way to determine if the

remaining intact acetabulum is sufficient to maintain a stable and congruous relationship with the femoral head

• An indicator for nonoperative versus operative treatment

• Measured on all three radiographic views– Medial roof arc > 30° on AP– Anterior roof arc > 40° on

obturator oblique– Posterior roof arc >50° on iliac

oblique• Recommendation:

All roof arcs > 45° if nonoperative treatment is to be considered

Roof Arcs Revised

• Biomechanical Study – Vrahas et al. 1999• Medial Roof Arc < 45 degrees• Anterior Roof Arc < 25 degrees• Posterior Roof Arc < 70 degrees

Roof Arc Example

45 deg

Roof Arc Example

50 deg

Roof Arc Example

50 deg

Roof Arc Example

Three weeks laterIn traction

Examplesof

Fracture Types

Posterior Wall Fractures

• Involves a separation of posterior articular surface

• Majority of the posterior column is undisturbed

• Usually associated with posterior femoral head dislocation

Posterior Wall Fractures• Subtypes

– Fracture confined below the roof– Posterosuperior fracture involving roof– Posteroinferior fracture involving subcotyloid

grove– Fractures associated with marginal impaction

• AP Radiograph– Disruption of posterior rim of acetabulum– Femoral head dislocation

• Judet Radiographs– Obturator oblique

• Highlights posterior wall fracture displacement– Iliac oblique

• Intact posterior column and anterior wall

Posterior Column Fractures• Disruption of ischium• Fracture line originates at greater sciatic

notch travels across retroacetabular surface, exits at obturator foramen

• Ischiopubic ramus fractured• Medial displacement of femoral head

Posterior Column Fractures

• AP Radiograph– Ilioischial line disrupted– Posterior column displaced medially– Iliopectineal line intact

Posterior Column Fractures

• Intact anterior column• Ischiopubic ramus fracture delineated

– Iliac oblique• Highlights posterior column fracture

Anterior Wall Fractures

• Disruption of small portion of anterior roof and acetabulum

• Much of anterior column is undisturbed• Ischiopubic ramus not fractured

• AP Radiograph– Iliopectineal line broken at 2 points – Anterior rim of acetabulum disrupted– Femoral head dislocated anteriorly and

externally rotated– Ilioischial line intact

• Fracture of anterior wall confirmed– Iliac oblique

• Integrity of posterior column confirmed

Anterior Wall Fracture Variant

• Anterior wall equivalent of the posterior wall fracture configuration

• Often shown as the anterior wall fracture rather than that originally described by Judet & Letournel

• Very rare

Anterior Column Fractures• Fracture origination variable

– Several subtypes

• Fracture terminates at ischiopubic ramus

Anterior Column Fractures• Subtypes based on fracture site at

innominate bone– Very low (anterior horn articular surface)– Low (psoas gutter)– Intermediate (anterior interspinous notch)– High (Iliac crest)

Low Intermediate

Anterior Column Fractures

• AP Radiograph– Disruption of iliopectineal line– Fracture of the ischiopubic ramus

Anterior Column Fractures• Judet Radiographs

– Obturator oblique• Better illustrates fracture• Demonstrates anterior column displacement

by femoral head– Iliac oblique

• May demonstrate an associated quadrilateral plate fracture

Transverse Fractures

• Fracture through anterior and posterior columns

• Subclassified based on level of fracture through acetabulum

• Often associated with a posterior wall

• Subtypes– Transtectal – fracture through roof of

acetabulum– Juxtatectal – fracture through highest point

of cotyloid fossa– Infratectal – through the cotyloid fossa

Trans-tectal Juxta-tectal Infra-tectal

• AP Radiograph– Iliopectineal line disrupted– Ilioischial line disrupted– Anterior rim disrupted– Posterior rim disrupted

Transverse Fractures• Judet Radiographs

– Obturator oblique• Best demonstrates fracture orientation• Confirms uninjured obturator ring

– Iliac oblique• Demonstrates fracture of quadrilateral

surface• Posterior surface usually greatest

displacement

CT Scans

• Anteroposterior fracture orientation = transverse fracture

• Follow CT proximal & distal to determine size and distinguish transverse fracture from a posterior wall (i.e. looks like a posterior wall fracture but just a transverse)

Posterior Column & Posterior Wall Fractures

• Posterior wall fracture– Same as in elementary patterns

• Posterior column fracture– Fracture begins in cavity created by posterior

wall fracture– Fracture pattern as in elementary patterns

• Central displacement or dislocation of femoral head

• Displacement of posterior wall usually greater than posterior column

• AP Radiograph– Disrupted ilioischial line– Disrupted posterior rim– Posterior dislocation of femoral head

• Intact iliopectineal line• Posterior wall fracture visualized• Direction of the line detaching the posterior column

can be seen which may split the ischium and not involve the obturator foramen.

• Judet Radiographs– Iliac oblique

• Demonstrates amount of fracture displacement• Demonstrates level of fracture through greater

sciatic notch

Transverse & Posterior Wall Fractures

• Posterior wall component variable• Transverse component extends posteriorly

to notch from the posterior wall fracture• Transverse component as in elementary

patterns

• Obturator foramen intact unless associated pelvic fracture

• Judet & Letournel considered the T-shaped fractures with a posterior wall to be a variant of this group

• Rotation similar to transverse– Around vertical symphysis axis and/or– Axis from symphysis to posterior column

fracture exit line in greater sciatic notch

• AP Radiograph– All vertical and oblique landmarks of

acetabulum are broken– Posterior hip dislocation common

• Obliquity of transverse fracture seen• Integrity of obturator ring confirmed• Size and extent of posterior wall fracture delineated

Transverse / Posterior Wall Fractures

• Integrity of iliac wing confirmed• Fracture through posterior column demonstrated

T-Type Fractures

• Includes all fractures with a transverse fracture of acetabulum with an associated vertical compartment

• Transverse component is identical to pure transverse fracture

• Judet & Letournel considered the T-shaped fractures with a posterior wall component to be a variant of the transverse and posterior wall type

T-Type Fractures

• Roof segment remains attached to iliac wing

• Orientation of the stem of fracture is variable

• Central displacement with anterior and posterior column rotating, around head “saloon door”

T-Type Fractures

• AP Radiographs– All vertical landmarks are fractured– Ischiopubic ramus fracture noted

T-Type Fractures

• Fracture orientation better defined • Fracture of ischiopubic ramus confirmed• Fracture at ischiopubic notch visualized

T-Type Fractures

• Confirms fracture of posterior column• May demonstrate fracture through quadrilateral

surface

Anterior Wall or Column Fracture with Posterior

Hemitransverse Fracture• Anterior wall or anterior column

fracture• Posterior column fractured as in a pure

transverse fracture and usually nondisplaced

• Roof fragment remains attached to iliac wing

Anterior Wall or Column / Posterior Hemitransverse

Fractures• AP Radiographs

– Anterior lesion is as elementary anterior column/anterior wall fracture

– Femoral head follows anterior component– Posterior border of acetabular fracture seen– Disrupts anterior and posterior rim

ilioischial line and iliopectineal line

Anterior Wall or Column & Posterior Hemitransverse

Fractures

• Anterior lesion better defined• Point of rupture of posterior rim

Anterior Wall or Column/ Posterior Hemitransverse

Fractures• Judet Radiographs

– Iliac oblique• Best illustrates direction of posterior fracture line• Highlights iliac wing fracture if present

Anterior Wall or Column/ Posterior Hemitransverse

Fractures• CT Scan

– Medial to lateral (coronal) anterior column fracture line

– Anterior to posterior (sagittal) posterior hemi-transverse fracture line

Both Column Fractures

• Fracture of both columns of acetabulum

• No articular surface remains attached to the axial skeleton

• Central dislocation “Saloon Door”• Spur sign obturator oblique (=

remainder of intact iliac wing)

• AP Radiographs– All 6 acetabular landmarks disrupted– Central dislocation of femoral head– Inward displacement of posterior column– Titled and displaced acetabular roof– Iliac wing fracture– Fracture of ischiopubic ramus

• Iliopectineal line disrupted• Anterior rim of acetabulum broken • Acetabular roof tilted• Posterior rim of acetabulum broken• Fracture of ischiopubic ramus• Spur sign present

Spur Sign

• Anterior rim acetabulum fractured• Iliac wing fractures defined• Displacement of posterior column delineated• Fracture line separating columns seen on

quadrilateral surface

CT Showing Spur Sign Origin

Acknowledgment

Kyle Dickson and George V. Russell, Jr. for use of many of their slides from the March 2004 version of this slideshow. Martin Bircher, Emile Letournel, Joel Matta, Tim Pohlemann and Marvin Tile for use of selected slides in both versions.

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