title: Vacuum phenomena in the sacroiliac joints and in association with sacral insufficiency fractures. Incidence and significance.
abstract: METHODS
  The computed tomography scans of two groups of patients of similar age and sex, with and without sacral insufficiency fractures, respectively, were assessed retrospectively.
  
  
  OBJECTIVE
  To determine the incidence of sacroiliac joint vacuum phenomena in individuals with and without sacral insufficiency fractures and to evaluate a possible association between vacuum phenomena and sacral insufficiency fractures.
  
  
  BACKGROUND
  The occurrence of vacuum phenomena is well recognized in the vertebra, but not in the sacroiliac joint. Gas foci in sacral insufficiency fractures recently has been reported. It has been suggested that the presence of vacuum phenomena may aid in the diagnosis of these fractures.
  
  
  METHODS
  The computed tomography scans of 28 female patients with sacral insufficiency fractures and of 60 age- and sex-matched control individuals were evaluated.
  
  
  RESULTS
  In the group with sacral insufficiency fractures, vacuum phenomena were detected in 69.2% of patients and in 63.5% of sacroiliac joints, with sacroiliac joint-related osteophytes found in 19.2% of patients. Very similar incidences were demonstrated in the control group. There was no correlation between sacroiliac joint osteophytes and vacuum phenomena in either group. The vacuum phenomenon was detected within the sacral insufficiency fracture in only one patient, in whom the fracture communicated with the adjacent sacroiliac joint.
  
  
  CONCLUSIONS
  Vacuum phenomena are frequently found in the sacroiliac joints of elderly women, and their presence is of no diagnostic significance when demonstrated in patients with sacral insufficiency fractures.
authors.affiliation: Department of Diagnostic Radiology, University of Hong Kong, Queen Mary Hospital, Hong Kong.
authors.forename: W C
authors.initials: WC
authors.lastname: Peh
authors.forename: G C
authors.initials: GC
authors.lastname: Ooi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D015775:Fractures, Stress / Q000000981:diagnostic imaging / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D012189:Retrospective Studies; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging*; D012447:Sacrum / Q000293:injuries*; D016103:Spinal Fractures / Q000000981:diagnostic imaging / Q000453:epidemiology*; D013128:Spinal Osteophytosis / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed