Question 1380
{"accessible":false,"alternatives":[{"id":6882,"text":" fixed abduction of the humeral head"},{"id":6883,"text":" fixed adduction of the humeral head"},{"id":6884,"text":" fixed external rotation of the humeral head"},{"id":6885,"text":" fixed internal rotation of the humeral head"}],"archived":false,"correctAlternativeId":6885,"explanation":"\u003cp\u003eThe\u0026nbsp;\u003cstrong\u003elightbulb sign\u003c/strong\u003e\u0026nbsp;refers to the abnormal AP radiograph appearance of the humeral head in\u0026nbsp;\u003ca href=\"https://radiopaedia.org/articles/posterior-shoulder-dislocation?lang=gb\"\u003eposterior shoulder dislocation\u003c/a\u003e. When the humerus dislocates it also\u003cstrong\u003e internally rotates\u003c/strong\u003e such that the head contour projects like a lightbulb when viewed from the front\u0026nbsp;\u003c/p\u003e","id":1380,"imageUrl":null,"imageAttribution":null,"imageAttributionCaseInfo":null,"firstQuestionPath":"/questions/1381","nextQuestionPath":null,"relatedArticles":[{"id":18811,"title":"Light bulb sign (posterior shoulder dislocation)","link":"/articles/light-bulb-sign-posterior-shoulder-dislocation?lang=us"}],"alsoUsedIn":[{"id":527,"kind":"Course","title":"X-ray Interpretation: Shoulder Injuries - page 527","link":"https://radiopaedia.org/courses/x-ray-interpretation-shoulder-injuries/pages/527"},{"id":527,"kind":"Course","title":"X-ray Interpretation: Upper Limb Injuries - page 527","link":"https://radiopaedia.org/courses/x-ray-interpretation-upper-limb-injuries/pages/527"},{"id":594,"kind":"Course","title":"Radiopaedia 2020 - Lectures Only - page 594","link":"https://radiopaedia.org/courses/radiopaedia-2020-exclusive/pages/594"},{"id":594,"kind":"Course","title":"2020 Virtual Conference Private Use - page 594","link":"https://radiopaedia.org/courses/2020-virtual-conference-private-use/pages/594"},{"id":674,"kind":"Course","title":"Trauma \u0026 Emergency Radiology Course - page 674","link":"https://radiopaedia.org/courses/medical-mums/pages/674"},{"id":674,"kind":"Course","title":"2020 Virtual Conference Private Use - page 674","link":"https://radiopaedia.org/courses/2020-virtual-conference-private-use/pages/674"}],"stem":"\u003cp\u003eThe 'light bulb sign' observed on radiographs of posterior shoulder dislocations is due to...\u003c/p\u003e","menuLinks":[{"text":"Report problem with question","url":"https://docs.google.com/forms/d/e/1FAIpQLSfO3soWYhOjJ7yErSysyCe5V4A1CqW7WK3rDA7MtAkecMGqNw/viewform?entry.1624461248\u0026entry.553583435=https://radiopaedia.org/questions/1380"}],"attemptsPercentages":[{"alternativeId":"6883","percentage":3},{"alternativeId":"6882","percentage":3},{"alternativeId":"6884","percentage":18},{"alternativeId":"6885","percentage":76}],"promptToLogin":false,"questionManager":false,"articleId":"posterior-shoulder-dislocation"}