Zebris versus Myrin: a comparative study between a three-dimensional ultrasound movement analysis and an inclinometer/compass method: intradevice reliability, concurrent validity, intertester comparison, intratester reliability, and intraindividual variability

Spine (Phila Pa 1976). 2003 Nov 1;28(21):E433-40. doi: 10.1097/01.BRS.0000090840.45802.D4.


Study design: Experimental study.

Objectives: To compare two devices for measuring cervical range of motion, a three-dimensional ultrasound motion device (Zebris) and a gravity-reference goniometer (Myrin).

Summary of background data: Assessment of cervical range of motion is used to evaluate the effect of different treatments, determine impairment, and ascertain the relationship between neck disorders and cervical spine mobility.

Methods: Sixty "neck-healthy" volunteers (25 men, 35 women; mean age 38 years, range 22-58 years) performed active maximal movements in flexion-extension, rotation, and lateral flexion. Maximal cervical range of motion was recorded simultaneously with the Zebris and Myrin devices. Intradevice reliability, concurrent validity, intertester comparison, intratester reliability, and intraindividual variability were computed.

Results: Our study showed good agreement of full-cycle cervical range of motion measurement between devices, testers, and the test and retest (intraclass correlation [ICC] was >0.90 for intradevice reliability, >0.93 for concurrent validity, and >0.92 for intratester reliability). Method error, assessed with the within-subject coefficient of variation for 95% of the measurements, was 5.4% to 11.1% for intradevice reliability, 4.4% to 7.6% for concurrent validity, 3.6% to 7.6% for intratester reliability, and 5.3% to 9.9% for individual variability. Individual variability did not increase with an increased cervical range of motion.

Conclusion: Both devices are reliable and showed good agreement. We conclude that the two techniques can be used interchangeably. Our study supports the continued use of the Myrin-a gravity-reference goniometer in routine clinical orthopedic work. The more sophisticated three-dimensional method adds information and allows evaluation of combined motion in two and three dimensions and is suitable for research.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Cervical Vertebrae / diagnostic imaging*
  • Cervical Vertebrae / physiology*
  • Female
  • Humans
  • Imaging, Three-Dimensional / instrumentation
  • Imaging, Three-Dimensional / methods
  • Male
  • Middle Aged
  • Movement
  • Observer Variation
  • Orthopedic Equipment*
  • Reproducibility of Results
  • Ultrasonography / instrumentation*
  • Ultrasonography / methods