Acromial types

The shape of the acromion had been initially divided into three types (which was known as the Bigliani classification 3), to which a fourth has been added 2.


This classification was initially proposed by Bigliani et al in 1986 on outlet view radiographs, and later modified by Kitay et al7 and Vanarthos et al in 1995, which remains the most widely accepted classification at time of writing (July 2016).

Acromion morphology (types) are based on sagittal oblique MRI:

  1. flat inferiorly (12%6)
  2. curved (56%)
    • parallel to the humeral head with concave undersurface 
    • considered most common type 3
  3. hooked (29%)
    • most anterior portion of the acromion has a hooked shape
    • associated with increased incidence of shoulder impingement
  4. convex (upturned) (3%)
    • most recent classification of acromion process shape
    • the undersurface of the acromion is convex near the distal end 4
    • no convincing correlation between a type 4 acromion and impingement syndrome exists 4, 5

See also

Upper limb anatomy
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Article Information

rID: 842
Section: Anatomy
Synonyms or Alternate Spellings:
  • Acromion types
  • Types of the acromion
  • Bigliani classification of acromion types
  • Bigliani classification of acromion morphology
  • Bigliani classification

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    Type 2
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     Type 3
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