Nucleus pulposus deformation in response to rotation at L1-2 and L4-5.

BACKGROUND: Spinal rotation couples with lateral flexion as a composite movement. Few data report the in vivo mechanical deformation of the nucleus pulposus following sustained rotation. MRI provides a non-invasive method of examining nucleus pulposus deformation by mapping the hydration signal distribution within the intervertebral disc. METHODS: T1 weighted coronal and sagittal lumbar images and T2 weighted axial images at L1-2 and L4-5 were obtained from 10 asymptomatic subjects (mean age 29, range: 24-34 years) in sustained flexed and extended positions plus combined positions of left rotation with flexion and extension. Nucleus pulposus deformation was tracked by mapping the change in hydration profiles from coronal and sagittal pixel measurements. FINDINGS: An average sagittal change in position of 44° (SD 14.5°) from flexion to extension was recorded between L1 and S1 (range: 18°- 60°) resulting in a mean anterior nucleus pulposus deformation of 16% of disc hydration profile (range: 3.5%-19%) in 19/20 discs. When rotation was combined with either flexion or extension, mean coronal deformation was 4.8% (SD-5.1%; range: 0.4%-15%). Lateral nucleus pulposus deformation direction varied in rotation (44% deformed left and 56% deformed right). Intersegmental lateral flexion direction more strongly predicted nucleus pulposus deformation direction with 75% deforming contralaterally. INTERPRETATION: Nucleus pulposus deformation direction in young subjects was more predictable following sagittal position change than in rotation combined with flexion or extension. Deformation magnitude was reduced in rotated positions. Intersegmental lateral flexion was a stronger predictor of nucleus pulposus deformation direction.

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

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.

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

BACKGROUND: The McKenzie management strategy of mechanical diagnosis and therapy (MDT) is commonly used for the assessment and management of spinal problems. Within this system, 'derangement syndrome' is the most common classification, for which the conceptual model is an intra-discal displacement. However, the reduction of an intra-discal displacement by MDT has never been documented. The purpose of this study was to compare, using magnetic resonance imaging (MRI), the nucleus pulposus (NP) profiles before and after the use of this approach. PATIENT CHARACTERISTICS: The patient was a 34-year-old female with a long history of right sided low back and buttock pain classified with 'derangement syndrome'. EXAMINATION: T2-weighted images of the L4-5 disc at initial assessment were compared with that at final assessment 1 month later. Initially, the MRI showed a portion of the NP displaced right and posteriorly towards the side of pain, and an overall NP position in the coronal plane shifted to the left. INTERVENTION: The patient was managed with a 1-month course of the McKenzie management strategy treatment. OUTCOMES: One month later, the displaced portion of the NP was no longer present and the left-shifted NP was centrally located. DISCUSSION: These intervertebral disc changes coincided with centralization and abolition of symptoms. This case may support the conceptual model of MDT.

An MRI investigation of intervertebral disc deformation in response to torsion.

BACKGROUND: The nucleus pulposus deforms towards an area of least compression in response to offset loading, however, there is a lack of data reporting the deformation patterns of nuclear material in rotated positions of the lumbar spine. Our purpose was to assess a novel methodology using MRI to track nuclear deformation in response to flexion and extension positions, and the combined positions of flexion with left rotation and extension with left rotation, at L1-2 and L4-5. METHODS: Three asymptomatic female subjects, mean age 27 years, underwent T2 weighted MRI sequences in flexed, extended, and left rotated positions combined with flexion and extension. A pixel profile technique was employed to determine direction and magnitude of nuclear deformation. RESULTS: In 5 of 6 discs examined, deformation of the nucleus occurred anteriorly in extension and posteriorly in flexion. Left rotation resulted in migration of nuclear material to the right in 9 of 12 discs. Of the three discs that demonstrated a right nuclear migration, two occurred at L4-5 and one at L1-2. INTERPRETATION: This methodology demonstrated that nucleus pulposus deformation can be measured reliably in various positions achieved within the confines of the MRI. The consistent migration of nuclear material following sagittal plane movement and the less consistent response to rotation positions suggest other asymmetrical loading on the intervertebral disc may accompany rotation.