title: Single-leg-stance radiographs in the diagnosis of pelvic instability.
abstract: BACKGROUND
  In the nonacute setting, the diagnosis of pelvic instability is difficult. Patients who present with pelvic pain may have underlying instability. The purpose of the present study was to report the effectiveness of single-leg-stance radiographs in the diagnosis of pelvic instability in a consecutive series of patients presenting with pelvic pain.
  
  
  METHODS
  Thirty-eight consecutive patients (twenty-four women and fourteen men) ranging in age from eighteen to seventy-eight years who presented with pelvic pain and a history of injury (twenty-seven), childbirth (seven [four primiparous and three multiparous]), or osteopenia (four) were evaluated with a visual analog scale pain score and a standard series of radiographs in an attempt to identify pelvic instability. The average time from the onset of symptoms to the evaluation was forty-one months (range, six weeks to twenty-seven years). Each patient was evaluated with supine anteroposterior, inlet, and outlet pelvic radiographs; a standing anteroposterior pelvic radiograph; and two single-leg-standing pelvic radiographs (one with the patient standing on the left leg and one with the patient standing on the right leg). A positive finding was defined as >or=0.5 cm of vertical translation measured at the symphyseal bodies between the two single-leg-stance radiographs.
  
  
  RESULTS
  Of the thirty-eight patients, twenty-five demonstrated pelvic instability (average, 1.98 cm; range, 0.5 to 5 cm). With the numbers available, the average visual analog scale pain score for the patients with a stable pelvis was not significantly different from that for the patients with an unstable pelvis (6.4 +/- 2.9 compared with 7.3 +/- 1.9; p = 0.28).
  
  
  CONCLUSIONS
  Standing anteroposterior and single-leg-stance pelvic radiographs aid in the diagnosis of pelvic instability more effectively than do the standard three radiographs of the pelvis made in the supine position or a standing anteroposterior radiograph of the pelvis alone. Additional studies will be needed to correlate this instability with clinical symptoms.
  
  
  METHODS
  Diagnostic Level IV. See Instructions to Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedic Surgery, G2, Hennepin County Medical Center, Minneapolis, MN 55415, USA.
authors.forename: Jodi
authors.initials: J
authors.lastname: Siegel
authors.forename: David C
authors.initials: DC
authors.lastname: Templeman
authors.forename: Paul
authors.initials: P
authors.lastname: Tornetta
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D017699:Pelvic Pain / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D011187:Posture / Q000502:physiology*; D011237:Predictive Value of Tests; D011631:Pubic Symphysis / Q000000981:diagnostic imaging* / Q000293:injuries / Q000503:physiopathology; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology; D015203:Reproducibility of Results; D012737:Sex Factors