Shoulder Elbow iSAWE 10

Question

A 45 year old man has shoulder pain after an epileptic seizure. He holds the arm internally rotated.

Shoulder Elbow iSAWE 10, ap radiograph of the shoulder
AP radiograph of the shoulder. Image by Hellerhoff, Wikimedia Commons, CC BY-SA 3.0.
  1. What is the diagnosis and what signs are seen on the radiograph?
  2. How is it confirmed?
  3. How does the size of the humeral head defect guide treatment?

Answer

Diagnosis

  • Posterior shoulder dislocation, missed in about half of cases at first presentation
  • Caused by seizures, electrocution and high energy trauma
  • Locked in internal rotation with no external rotation, posterior fullness and a prominent coracoid

Radiographic signs

  • Lightbulb sign
  • Loss of the normal half moon overlap
  • Widened glenohumeral space (rim sign)
  • Trough line from an impaction fracture

Confirmation

  • Axillary or Velpeau view
  • CT for the reverse Hill-Sachs lesion and associated fractures

Treatment by defect size

Reverse Hill-Sachs defectTreatment
Under 25 percentClosed reduction and immobilisation in external rotation
25 to 50 percentMcLaughlin procedure or allograft reconstruction
Over 50 percent or chronicArthroplasty

Related pages

Author Contributions

Orthofracs team

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.