title: John Thomas sign--a memorable but misleading sign in hip fractures.
abstract: OBJECTIVE
  The John Thomas sign is a favourite of medical students and theorizes that in femoral neck fractures, the male member will lie to the side of the fracture on the plain radiograph. The aim of this study was to evaluate the accuracy, and examine the phenomenon of eponymous signs. We sought to answer the following questions: (1) How accurate is the sign in the context of a consecutive series of male patients with hip fractures? (2) Is there a relationship between side and size of penile lie and the side of fracture?
  
  
  OBJECTIVE
  That the accuracy of the John Thomas sign is, like many eponymous signs, spurious.
  
  
  METHODS
  Two hundred male AP pelvis radiographs were examined, of which 100 had a hip fracture and compared these against 100 control films that did not. Age at presentation, and the side, length and angle of penile lie were measured.
  
  
  RESULTS
  The results show two findings: that the accuracy of the supposed "sign" is less accurate than the toss of a coin; and that left lie and left-sided fractures are more common. We fail to show a relationship between side of fracture, John Thomas size or degree of angulation.
  
  
  CONCLUSIONS
  John Thomas sign is no better than the toss of a coin in relation to hip fractures, and is not related to side of fracture, or penile attitude. We propose that the side of lie observed in male fractures may be as a result of handedness or natural underlying body asymmetry rather than as a result of the fracture.
  
  
  METHODS
  Level III Case control study.
authors.affiliation: Department of Radiology, Saint Vincent's University Hospital, Elm park, Dublin 4, Ireland. Electronic address: iangmurphy@gmail.com.
authors.forename: I G
authors.initials: IG
authors.lastname: Murphy
authors.affiliation: Department of Trauma & Orthopaedic Surgery, Saint Vincent's University Hospital, Elm park, Dublin 4, Ireland.
authors.forename: C G
authors.initials: CG
authors.lastname: Murphy
authors.affiliation: Department of Radiology, Saint Vincent's University Hospital, Elm park, Dublin 4, Ireland.
authors.forename: E J
authors.initials: EJ
authors.lastname: Heffernan
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D004850:Eponyms; D005265:Femoral Neck Fractures / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D010413:Penis / Q000000981:diagnostic imaging*; D011859:Radiography
keywords: Eponymous signs; Hip fracture; Medical education; Medical heuristics; Radiology; Trauma