title: Bilateral anterior dislocation of the shoulder: review of seventy cases and proposal of a new etiological-mechanical classification.
abstract: BACKGROUND
  Although anterior shoulder dislocation is common in everyday practice in Emergency Departments, bilateral presentation is a rare entity.
  
  
  OBJECTIVE
  The aim of this article is to report two additional cases of this rare injury and to introduce a new mechanism that can produce it. We made an exhaustive review of the literature and found 68 cases in printed publications. Also, we analyzed the mechanism of injury and the presence of predisposing factors, and propose a new etiological-mechanical classification.
  
  
  METHODS
  One case occurred after a trivial fall, and the other was produced by a mechanism not previously reported: the patient pushed strongly forward, expecting a resistance and finding none, his arms kept the forward movement and the shoulders dislocated.
  
  
  CONCLUSIONS
  This lesion has a bimodal distribution, affecting mainly men (70%) with a mean age of 33.5 years, whereas in women, the average age is 57 years. The most common cause is trauma (50%), followed by muscle contractions (37%) due to seizures of different causes (epileptic, hypoglycemia, toxic, or hypoxic) or electrocution. In 15.7% of the cases, the diagnosis of bilateral anterior dislocation was not acute (<3 weeks), and in virtually all of these cases it was not traumatic.
  
  
  CONCLUSIONS
  The bilateral anterior shoulder dislocation may not be as rare as previously thought and must be taken into account in emergency services. The authors propose a new etiological-mechanical classification. Also, the importance of radiologic diagnosis must be highlighted.
authors.affiliation: Orthopedic Surgery Service, Universitary Hospital Fuenlabrada, Madrid, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Ballesteros
authors.forename: Pablo
authors.initials: P
authors.lastname: Benavente
authors.forename: Nuria
authors.initials: N
authors.lastname: Bonsfills
authors.forename: Marta
authors.initials: M
authors.lastname: Chacón
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: García-Lázaro
mesh_terms: D000293:Adolescent; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D011859:Radiography; D012783:Shoulder Dislocation / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology