Scapula method

Last revised by Dr Henry Knipe on 07 Sep 2021

The scapula method is used to assess posterior humeral head subluxation in patients with glenohumeral osteoarthritis as part of the work-up for shoulder arthroplasty


First, the scapular axis (medial border of the scapular body to center of the glenoid) is drawn on an axial image that is one slice below the tip of the coracoid process

Then the distance of the entire humeral head (D) is measured then the distance of the humeral head posterior to the scapular axis (A) is measured and a subluxation ratio (A/D) is calculated. Osteophytes should not be included 1


  • subluxation ratio >55% is defined as posterior subluxation

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