Pelvic radiograph (an approach)

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Systematic review

Three rings
  • trace the main pelvic ring and two obturator foramina
  • if a ring is disrupted, think fracture... then look for a second one
Joint spaces
  • the sacroiliac joints should be symmetrical, joint space range 2-4 mm
  • the symphysis pubis joint space should be ≤5 mm
  • if either joint space is widened, think main pelvic ring fracture
Acetabulum
  • trace Letournel lines: iliopectineal line, ilioischial line, acetabular roof, anterior rim, posterior rim, and teardrop
    • iliopectineal line disruption suggests a fracture involving the anterior column
    • ilioischial line disruption suggests a fracture involving the posterior column
    • teardrop displacement suggests an occult acetabular fracture
Sacral foramina
  • the arcuate lines should be smooth and symmetrical
  • If lines angulated, think sacral fracture
Proximal femur
  • the cortex of femoral head, neck, greater, and lesser trochanter should be smooth with normal trabecular pattern on AP and lateral 
    • if cortical disruption, trabecular pattern disruption or transverse sclerosis, think fractured proximal femur
  • trace the Shenton line
    • If line disruption, think fractured proximal femur

Common pathology

Proximal femoral fracture
Intracapsular
  • fracture site within the joint capsule
    • subcapital (most common), transcervical, or basicervical
  • high risk of disruption of the blood supply to the femoral head
    • displaced intracapsular fractures are associated with delayed union, non-union, or avascular necrosis
Extracapsular
  • fracture line distal to the attachment of the femoroacetabular joint capsule
    • intertrochanteric (most common) or subtrochanteric
Pubic ramus fracture
  • 40% of all pelvic fractures
  • isolated fracture of superior or inferior ramus most common stable pelvic injury
  • mechanisms:
    • fall in elderly
    • exercise-induced stress fractures
  • more: pubic ramus fracture
Complex pelvic ring fracture
  • fracture at one site often associated with a second
  • a double break represents an unstable injury
  • high energy blunt trauma
  • requires CT evaluation
  • more: complex pelvic ring fracture
Acetabular fracture
  • bimodal distribution: young (high energy) and elderly (poor bone quality)
  • impaction of femoral head, lateral compression or axial loading
  • 75% associated with femoral head subluxation/dislocation; frequently comminuted
  • more: acetabular fracture
Head of femur dislocation

Don’t miss…

Apophyseal avulsion
  • typically adolescent athletes
  • repeated or sudden muscle contraction
  • ischial tuberosity avulsion (hamstring insertion) most common
  • more: ischial tuberosity avulsion
Sacral fracture
  • common in pelvic ring fractures
  • mechanisms:
    • fall in elderly
    • high-energy blunt trauma
  • frequently missed
  • 25% associated with neurologic injury
  • more: sacral fracture
Approaches to radiographs