Study Design. Controlled radiological study.
Objective. Ascertain if a difference exists in the mechanical effects on the cord between the unilateral and bilateral straight leg raise (SLR) and to verify whether the effect on the spinal cord may be cumulative between the two.
Summary of Background Data. To the authors' knowledge these are the first data on noninvasive, in vivo, normative measurement of spinal cord displacement with bilateral SLR test.
Methods. Sixteen asymptomatic volunteers were scanned with 1.5-T magnetic resonance scanner (Siemens Avanto, Erlangen, Germany) using T2-weighted turbo spin-echo fat-saturation sequence.
The displacement of the medullar cone relative to the vertebral endplate of the adjacent vertebra during the passive bilateral SLR was quantified and compared with the position of the conus in the neutral (anatomic) position and with unilateral SLR. Each movement was performed twice for evaluation of reproducibility. The measurements were repeated by 2 observers. Four practitioners performed the maneuvers in a random sequence to avoid series effects.
Results. Compared with the neutral (anatomic) position, the medullar cone displaced caudally in the spinal canal by 2.33 ± 1.2 mm (μ ± SD) with unilateral (P ≤ 0.001) and 4.58 ± 1.48 mm with bilateral SLR (P ≤ 0.001). Statistical significance was also reached for bilateral versus unilateral SLR (P ≤ 0.001).
Spearman correlations proved higher than 0.99 for intra and interobserver reliability, and 0.984 for results reproducibility in bilateral SLR.
Conclusion. The caudal displacement of the medullar cone was significantly greater (almost double) with the bilateral SLR than the unilateral SLR. We hypothesize that this greater movement may be because more force was transmitted to the cord through a larger number nerve roots with the bilateral than unilateral SLR.
The high correlation values in this study show that these movements are consistent and reproducible.
This study offers baseline measurements on which further studies in diagnosis and treatment of lumbar disc protrusion and radiculopathy may be developed.
Level of Evidence: 5
The caudal displacement of the medullar cone was almost double with bilateral compared with unilateral straight leg raise (SLR), showing both difference in the mechanical effects on the cord between unilateral and bilateral SLR and linear dependence between magnitude of cord displacement and number of nerve roots involved in the movement.
*Department of Physical and Rehabilitation Medicine, Kuopio University Hospital, Kuopio, Finland
†“Prim. dr.Martin Horvat” Orthopaedic and Rehabilitation Hospital, Rovinj, Croatia
‡Department of Radiology, Kuopio University Hospital, Kuopio, Finland
§Neurodynamic Solutions, Adelaide, Australia; and
¶Department of Physical and Rehabilitation Medicine, Tampere University Hospital, Tampere, Finland.
Address correspondence and reprint requests to Marinko Rade, MSc(Orth Med), Department of Physical and Rehabilitation Medicine, Kuopio University Hospital, Box 1607, 70211 Kuopio, Finland; E-mail: firstname.lastname@example.org or email@example.com
Acknowledgment date: October 24, 2013. Revision date: January 23, 2014. Acceptance date: January 26, 2014.
The manuscript submitted does not contain information about medical device(s)/drug(s).
No funds were received in support of this work.
No relevant financial activities outside the submitted work.