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PEM Ortho X-ray Curriculum

Common Presentations

Anterior fat pad

  • usually visualized as a thin radiolucent line on lateral view
  • seen just anterior to the coranoid fossa (anterior border of the distal humerus)
  • forms "sail sign' when displacement anteriorly and superiorly
  • may not always imply elbow joint capsular distension
  • this is usually from an effusion

   Posterior fat pad

  • lines over the olecranon fossa, which is deeper and more concave than the coranoid fossa
  • visualization of the posterior fat pad on the lateral view implies joint capsular distension, usually due to hemarthrosis
  • when visualized, this is always pathologic, indicating intraarticular hermarthrosis or effusion



Shows displacement of anterior and posterior fat pads
FIGURE 3: Posterior supracondylar buckle fracture


  • FIGURE 3 shows displacement of anterior and posterior fat pads (both shown)
  • the anterior humeral line (shown) along the posterior aspect of the supracondylar region

Anterior humeral line (FIGURE 3)

  • along anterior surface of the distal humerus on lateral view
  • should normally intersect the middle to anterior third of the capitellum
  • posterior displacement of the distal segment (e.g. from a supracondylar or physeal fracture) causes:
  • anterior humeral line to intersect more anteriorly or pass completely anterior to the capitellum

Radiocapitellar line (FIGURE 3)  

  • drawn along the central axis of the proximal radius on lateral view
  • if it doesn't intersect third of capitellum:
    • consider either radial head dislocation and/or fracture through the radial neck
    • radial head should point to the capitellum in all views

Radial head contour

  • The slope from diaphysis to metaphysis towards the radial head should be gradual and smooth without any sharp angles