Acromion index

The acromion index (AI) is a parameter that can be measured on the AP radiograph (or sometimes on coronal CT or MR images) to assess predisposition to rotator cuff pathology.

It is taken as the ratio between

GA: distance from the plane of the glenoid cavity to the lateral edge of the acromion and

GU: distance from the plane of the glenoid cavity to the lateral edge of the humeral head.

Acromion index (AI) = GA / GU

A high AI has been suggested as one of the associated factors for progression to large-to-massive rotator cuff tears in rotator cuff disease but only in some populations 3.

Research by some authors suggest that an acromion index over 0.7 being symptomatic in some populations 4.

See also

Article information

rID: 90426
Synonyms or Alternate Spellings:
  • Acromion index (AI)

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Cases and figures

  • Fig 1: as measured on AP radiograph
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