Spinal Cord Movement During SLR Part 1

Rade M. et al. In Vivo Magnetic Resonance Imaging Measurement of Spinal Cord Displacement in the Thoracolumbar Region of Asymptomatic Subjects. Part 1: The Straight Leg Raise. Spine: 2014

  • The SLR is one of the most widely used and accepted tests for diagnosing IVD herniation and radiculopathy. However, although the direction of nerve root displacement is consistent, the published evidence is far from conclusive in terms of magnitude of nerve root or spinal cord displacement 
  • In this article, the authors are investigating the neural biomechanics during the execution of an SLR maneuver in in vivo asymptomatic subjects with the aid of magnetic resonance imaging. The authors hypothesize that if any caudal movement of the medullar cone would show itself in the SLR, it may occur via sliding of, and direct transmission of forces through, the lumbosacral neural roots and dura to the spinal cord. 
  • Sixteen asymptomatic volunteers who were in the age range from 23 to 56 years (mean age, 33 ± 10.7 yr), with were included in the study. Asymptomatic volunteers were chosen to make use of the normal situation providing normative measurements and avoid potentially confounding variables such as local impairments or neural dysfunctions that may occur in a symptomatic population. 
  • Measurements were taken twice by the main author, (M.R.), with 2 months between each measurement, and once by coauthor (J.M.) to allow for evaluation of intra- and interobserver reproducibility. The subjects were scanned randomly in the following positions: supine, Right SLR, Left SLR. Because of the restrictions from the MR, only a mean of 50 degrees of hip flexion was able to be achieved. 
  • The spinal cord displacement was a mean of 2.33 mm during the applied SLR test. The presented results suggest that there may indeed be a proportional relationship between the behavior of the medullar cone and the mobility of the lumbar nerve roots with the SLR 
  • In the published literature, the greatest amount of nerve root displacement during the SLR was shown to occur between 60 ° and 90 ° of hip flexion. It is therefore possible that a slightly greater amount of caudal displacement of the medullar cone may be recorded if the MR device architecture allowed for more than 50 ° of hip flexion. 
  • These sliding movement in response to a unilateral SLR may also be predictable both in terms of magnitude and direction. This is a key feature that may allow for improvements in assessment measures, diagnosis, and treatment design

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