Acromial types

Case contributed by Roberto Schubert
Annotated image

1 - flat, 2 - curved, 3 - hooked, 4 - convex.

Case Discussion

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

  1. flat inferiorly
  2. curved: parallel to the humeral head with convex undersurface - considered the commonest type 
  3. hooked: the most anterior portion of the acromion has a hooked shape, associated with increase incidence of shoulder impingement
  4. convex (upturned)
    • this is the most recent classification of acromion process
    • in this type of acromion, the undersurface is convex near the distal end
    • no convincing correlation between a type 4 acromion and impingement syndrome exists

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