Observer Performance Studies

Ultrasound Evaluation of Sacroiliac Motion 
in Normal Volunteers

The goal of this study [6] was to demonstrate quantitatively, using ultrasound imaging, the passive range of motion of the normal sacroiliac (SI) joint.  Generally the SI is thought of as a joint with very little if any motion capability.  Manual medicine practitioners, however, contend that there is substantial SI motion.  This study tried to demonstrate and record SI motion.

Methods

Imaging Procedure

  • 22 volunteers without SI joint problems served as volunteers
  • Each subject had an initial rating of SI motion made using a manual medicine spring testing technique; 1 = mild mobilty; 2 = moderate mobility; 3 = sustantial mobility; 4 = very mobile
  • Manual medicine spring testing of each SI joint was performed while simultaneous ultrasound recordings were made
  • Recordings were made at the PSIS & approximately 2 cm caudal to the PSIS (inferior) levels for right & left SI joints

Image interpretation

  • The ultrasound video recordings were shown to 6 radiologists
  • On the left side of the screen was a static view of the SI level at rest
  • On the right were the real time recordings of the SI during spring testing
  • Readers were asked to judge maximum displacement (mm) of the SI during spring testing using the scale provided on the monitor
  • Readers were also asked to rate overall movement as : 0 = no motion; 1 = mild motion; 2 = moderate motion; 3 = marked motion

Results

Percentage of cases judged to move 2 mm or more on spring testing

Joint % of Cases
Left  
PSIS AP 70.45
PSIS ML 59.85
INF AP 47.73
INF ML 51.52
Right  
PSIS AP 68.18
PSIS ML 49.24
INF AP 35.61
INF AAP 36.36

Overall Movement

  • Overall 82% of the subjects were judged to to have > 2 mm of SI movement in at least 1 joint
  • There was more movement at the AP projection than the ML projection
  • There were no male-female differences in SI movement

Conclusions

  • The range of passive SI joint motion is more than 2 mm and may be up to 10 mm in some subjects
  • Ultrasound is a valid technique for evaluating passive SI joint movement
  • Radiologists had little trouble identifying the relevant anatomic features necessary to make the movement judgments
  • All 6 radiologists were well correlated with each other in the judgments of motion

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