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Revision as of 06:41, 22 December 2024 editNetha Hussain (talk | contribs)Autopatrolled, Extended confirmed users11,902 edits added Category:Radiologic signs using HotCat← Previous edit Revision as of 06:41, 22 December 2024 edit undoNetha Hussain (talk | contribs)Autopatrolled, Extended confirmed users11,902 edits Adding short description: "Radiologic sign in posterior shoulder dislocation"Tag: Shortdesc helperNext edit →
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{{Short description|Radiologic sign in posterior shoulder dislocation}}
The '''light bulb sign''' is a radiological finding observed on plain radiographs in the context of posterior ].<ref>{{cite web |title=Light bulb sign (X-ray) |url=https://article.scholarena.com/Light-bulb-Sign.pdf |publisher=Scholarena |access-date=22 December 2024}}</ref> It refers to the abnormal, rounded appearance of the humeral head, which resembles a "light bulb," due to internal rotation of the arm following dislocation.<ref>{{cite web |title='Light Bulb Sign' in Posterior Shoulder Dislocation |url=https://www.medscape.com/viewarticle/828763 |website=Medscape |access-date=22 December 2024 |language=en}}</ref> The '''light bulb sign''' is a radiological finding observed on plain radiographs in the context of posterior ].<ref>{{cite web |title=Light bulb sign (X-ray) |url=https://article.scholarena.com/Light-bulb-Sign.pdf |publisher=Scholarena |access-date=22 December 2024}}</ref> It refers to the abnormal, rounded appearance of the humeral head, which resembles a "light bulb," due to internal rotation of the arm following dislocation.<ref>{{cite web |title='Light Bulb Sign' in Posterior Shoulder Dislocation |url=https://www.medscape.com/viewarticle/828763 |website=Medscape |access-date=22 December 2024 |language=en}}</ref>
==Pathophysiology== ==Pathophysiology==

Revision as of 06:41, 22 December 2024

Radiologic sign in posterior shoulder dislocation

The light bulb sign is a radiological finding observed on plain radiographs in the context of posterior shoulder dislocation. It refers to the abnormal, rounded appearance of the humeral head, which resembles a "light bulb," due to internal rotation of the arm following dislocation.

Pathophysiology

In posterior shoulder dislocation, the humeral head is displaced posteriorly out of the glenoid cavity. This injury is frequently associated with internal rotation where the humeral head rotates internally, altering its usual elliptical contour to a more rounded shape, creating the "light bulb" appearance. On anteroposterior (AP) radiographs, the humeral head no longer overlaps the glenoid, further emphasizing its abnormal shape.

Causes

Posterior shoulder dislocations typically result from trauma such as seizures or electric shocks, which cause forceful contraction of the internal rotator muscles of the shoulder.

Imaging Features

Plain Radiography

The light bulb sign is best observed on an AP radiograph of the shoulder. Key features include:

  • Rounded humeral head: The humeral head appears symmetrically rounded, resembling a light bulb due to internal rotation.
  • Loss of normal glenohumeral overlap: The humeral head is posteriorly displaced, disrupting the alignment with the glenoid cavity.
  • Rim sign: Widening of the joint space (>6 mm) between the medial edge of the humeral head and the glenoid. This sign is not specific to posterior dislocation, and can occur also in hemarthrosis.

References

  1. "Light bulb sign (X-ray)" (PDF). Scholarena. Retrieved 22 December 2024.
  2. "'Light Bulb Sign' in Posterior Shoulder Dislocation". Medscape. Retrieved 22 December 2024.
  3. Abrams, Rachel; Akbarnia, Halleh (2024). "Shoulder Dislocations Overview". StatPearls. StatPearls Publishing. Retrieved 22 December 2024.
  4. Ketenci, IE; Duymus, TM; Ulusoy, A; Yanik, HS; Mutlu, S; Durakbasa, MO (December 2015). "Bilateral posterior shoulder dislocation after electrical shock: A case report". Annals of medicine and surgery (2012). 4 (4): 417–21. doi:10.1016/j.amsu.2015.10.010. PMID 26904192. {{cite journal}}: |access-date= requires |url= (help)
  5. Koutserimpas, Christos; Piagkou, Maria; Karaiskos, Ilias; Chronopoulos, Efstathios; Arkoudis, Nikolaos-Achilleas; Koutserimpas, Christos; Piagkou, Maria; Karaiskos, Ilias; Chronopoulos, Efstathios; Arkoudis, Nikolaos-Achilleas (27 October 2023). "Posterior Dislocation of the Shoulder: The Light-Bulb Sign". Cureus. 15 (10). doi:10.7759/cureus.47800. ISSN 2168-8184. Retrieved 22 December 2024.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  6. "Eurorad.org". Eurorad - Brought to you by the ESR. Retrieved 22 December 2024.
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