Nucleus pulposus deformation in response to lumbar spine lateral flexion: an in vivo MRI investigation

Abstract

Whilst there are numerous studies examining aspects of sagittal plane motion in the lumbar spine, few consider coronal plane range of motion and there are no in vivo reports of nucleus pulposus (NP) displacement in lateral flexion. This study quantified in vivo NP deformation in response to side flexion in healthy volunteers. Concomitant lateral flexion and axial rotation range were also examined to evaluate the direction and extent of NP deformation. Axial T2-and coronal T1-weighted magnetic resonance images (MRI) were obtained from 21 subjects (mean age, 24.8 years) from L1 to S1 in the neutral and left laterally flexed position. Images were evaluated for intersegmental ranges of lateral flexion and axial rotation. A novel methodology derived linear pixel samples across the width of the disc from T2 images, from which the magnitude and direction of displacement of the NP was determined. This profiling technique represented the relative hydration pattern within the disc. The NP was displaced away from the direction of lateral flexion in 95/105 discs (p \ 0.001). The extent of NP displacement was associated strongly with lateral flexion at L2-3 (p \ 0.01). The greatest range of lateral flexion occurred at L2-3, L3-4 and L4-5. Small intersegmental ranges of axial rotation occurred at all levels, but were not associated with NP displacement. The direction of NP deformation was highly predictable in laterally flexed healthy lumbar spines; however, the magnitude of displacement was not consistent with the degree of intersegmental lateral flexion or rotation.

Comparable effect of simulated side bending and side gliding positions on the direction and magnitude of lumbar disc hydration shift:in vivoMRI mechanistic study

“…The results of the present study offer three points for consideration. First, these findings support a finding by Fazey et al 2 that there is no significant correlation between the degree of lateral flexion and the magnitude of the disc hydration shift. Second, the results indicate that the maneuver of SG produces a comparable mechanical influence to lumbar discs, Table 3 The mean (SD) segmental rotation angles (degrees) at end-range side bending (SB) and side gliding (SG) positions to the left and effect sizes (Hedges's g) of the difference between the two positions.…”

“…[1][2][3][4][5][6] Disc hydration normally shifts to the contralateral side of the movement plane. 2,4 The directional response of the disc to various loading strategies has been used as the theoretical explanation for a directional preference in the Mechanical Diagnosis and Therapy (MDT) system. In that system, side gliding (SG) is used as a repeated movement, or static loading, strategy for assessment, and treatment of patients who need lateral loading strategies.…”

“…7 Thus, SB may produce greater lateral influence to the disc throughout the lumbar spine than SG although lumbar lateral alignment does not always correlate with the magnitude of the shift of disc hydration. 2,6 Interestingly, SG is used in MDT rather than SB. It is not clear if there is any difference in the mechanical response of the disc between SB and SG.…”

Is the lateral jack-knife position responsible for cases of transient neurapraxia?

“…These findings make L-4 the vertex of the angle formed in the lumbar spine during lateral flexion. 8 These biomechanical results can be correlated to the findings of our study. Lumbar nerve roots originating above the L-4 vertebral body (L-1 to L-3) are exposed to higher levels of stretch in a laterally flexed position.…”

Nucleus pulposus deformation following application of mechanical diagnosis and therapy: a single case report with magnetic resonance imaging

“…2 It has been shown that asymmetrical loading of the disc leads to displacement of the nucleus pulposus (NP) to areas of least pressure. 3 Furthermore, it has been suggested that radial fissures bring about excessive mechanical strain on surviving annular layers, and that displaced fragments could mechanically stress surviving and innervated outer annular layers causing pain. 4 Mechanical diagnosis and therapy (MDT) proposed by McKenzie is a comprehensive management strategy for a range of spinal pain disorders using specific forms of exercise individually prescribed.…”