Normal multiplanar movement of the spinal cord during unilateral and bilateral straight leg raise: Quantification, mechanisms, and overview

Abstract

The purpose of this investigation was to provide a full set of normal data describing neural biomechanics within the vertebral canal in all three planes with unilateral and bilateral SLR tests to allow for clinical comparison with clinical cases. This is done following the notion that, due to neural continuum, tensile forces are transmitted through the lumbosacral nerve roots and dura to the conus medullaris (linear dependency principle). In this controlled radiologic study 10 asymptomatic volunteers were scanned with 1.5T magnetic resonance scanner (Siemens Magnetom Aera, Erlangen, Germany) using different scanning sequences for planning and for measurement purposes. Conus displacement in both antero-posterior direction (sagittal slices) and lateral direction (axial slices) was quantified during unilateral passive left, right SLR, and bilateral SLR and compared with the position of the conus in the neutral (anatomic) position. It is shown that the conus medullaris displaced laterally and anteroposteriorly in response to unilateral and bilateral SLRs. Pearson's correlations were higher than 0.95 for both intra- and inter-observer reliability. The observed power was higher than 0.99 for all the variables tested. Following this, the authors conclude that lateral and antero-posterior displacement of conus medullaris into the vertebral canal occurs consistently with unilateral and bilateral SLRs following directions predicted by tension vectors. Summative information collected in this line of research in neuroradiology is here presented. We believe we have presented the first conclusive and complete full set of normal data on non-invasive, in vivo, normative measurement of spinal cord displacement with the SLR ever presented. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1335-1342, 2017.

Extending the straight leg raise test for improved clinical evaluation of sciatica: reliability of hip internal rotation or ankle dorsiflexion

“…The SLR moves the sciatic nerve up to the nerve roots and a positive test may arise from problems anywhere along this coursethigh, buttock, and spine [18,19]. Published data on neural movement during the SLR (with or without pathology) [16,[20][21][22][23][24] and the knowledge on all the possible causes of sciatic symptoms imply that SLR may not be at its best when utilized to distinguish solely the presence of LIDH, or other mechanical compression to the nervous structures, but as a test to assess neural mechanosensitivity -without determining a cause. Hence, we modified the SLR to address these known issues.…”

Reduced Spinal Cord Movement With the Straight Leg Raise Test in Patients With Lumbar Intervertebral Disc Herniation

“…Using magnetic resonance imaging (MRI), Rade et al (14) established normal multiplanarspinal cord movement with the SLR (11)(12)(13)15,16).It is apparent thatthe conus medullaris consistently moves in a caudal direction (11,13), primarily due to direct transmission of forces through the lumbosacral nerve roots (16), and that conus movement prevails over bony movement (16). The conus displacement is double with a bilateral compared with the unilateral SLR, possibly being a reflection of the number of nerve roots transmitting the force (i.e.…”

Extending the Straight Leg Raise Test for Improved Clinical Evaluation of Sciatica: Reliability of Hip Internal Rotation and Ankle Dorsiflexion

“…We extended the SLR by adding differentiation movements to it based on the meticulous scienti c data on the effects of different components of the SLR to the nervous system [9,[13][14][15][16][17]21]. Moreover, as the SLR is employed more than other tests in clinical practice worldwide with LBP, implementing on the execution and interpretation of this test may create a more relevant impact in the scienti c and clinical community.…”

“…The SLR moves the sciatic nerve up to the nerve roots and a positive test may arise from problems anywhere along this course -thigh, buttock, and spine [11,12]. With published data on neural movement during the SLR (with or without pathology) [9,[13][14][15][16][17], and the fact that sciatic symptoms can be caused variously, we modi ed the SLR to address these issues.…”