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Review article: Kinematic evaluation of the spine: a kinetic magnetic resonance imaging study

INTRODUCTION

Spinal degeneration is increasingly common as a result of population ageing. Degeneration typically begins in the intervertebral intervertebral /in·ter·ver·te·bral/ (-ver´te-bral) situated between two contiguous vertebrae; see under disk.

in·ter·ver·te·bral
adj.
Located between vertebrae.
 disc during the second decade of life in men and the third decade in women. It then appears posteriorly in the facet joints, causing altered mechanical function of the disc and ultimately spinal instability and clinical symptoms.1

Magnetic resonance imaging magnetic resonance imaging (MRI), noninvasive diagnostic technique that uses nuclear magnetic resonance to produce cross-sectional images of organs and other internal body structures.  (MRI 1. (application) MRI - Magnetic Resonance Imaging.
2. MRI - Measurement Requirements and Interface.
) provides the greatest range of information and accurate delineation of soft-tissue (e.g. intervertebral discs, spinal ligaments, and neural elements) and osseous osseous /os·se·ous/ (os´e-us) of the nature or quality of bone; bony.

os·se·ous
adj.
Composed of, containing, or resembling bone; bony.
 structures (e.g. facets and uncovertebral joints), enabling detection of subtle abnormalities with great sensitivity.2 However, it can obtain only non-weightbearing, static images. Spinal disorders, especially cervical and lumbar stenosis, are posture-dependent. To overcome this limitation, radiographic radiographic (rā´dēōgraf´ik),
adj relating to the process of radiography, the finished product, or its use.
 and cineradiographic studies of spinal kinematics have been reported.3-9 We evaluated spinal kinematics of patients in a weight-bearing position with dynamic motion of the spine using kinetic MRI (kMRI).

MATERIALS AND METHODS

From February 2006 to May 2007, kMRIs of 587 lumbar and 459 cervical spines of symptomatic patients in axially loaded, upright neutral (0°), flexion (40°), and extension (-20°) positions were taken, using a 0.6 Tesla kMRI scanner with a flexible surface coil. Imaging took 10 to 12 minutes to complete in each position.

The imaging protocol included sagittal sagittal /sag·it·tal/ (saj´i-t'l)
1. shaped like an arrow.

2. situated in the direction of the sagittal suture; said of an anteroposterior plane or section parallel to the median plane of the body.
 T1-weighted spin-echo sequences (repetition time [TR]/echo time [TE], 671/17 ms; slice thickness, 3.0 mm; field of view, 24 cm; matrix, 256x200; and number of excitations [NEX], 2) and T2-weighted fast spin-echo sequences (TR/TE, 3432/160 ms; slice thickness, 3.0 mm; field of view, 24 cm; and NEX, 2). All sequences were acquired without fat saturation.

T2-weighted mid-sagittal images in the 3 positions were analysed. 77 and 54 points were marked in each MRI of the cervical (C1-T1) and lumbar (L1-S1) spine, respectively. From C3 to T1 and from L1 to S1, 4 points on each vertebral body (anterosuperior, anteroinferior, posteroinferior, and posterosuperior corner) were marked, as were 2 points on the middle of the endplate, 2 points at each pedicle pedicle /ped·i·cle/ (ped´i-k'l) a footlike, stemlike, or narrow basal part or structure.

ped·i·cle
n.
1. A constricted portion or stalk.

2.
 level, and 2 points at the intervertebral disc level of the canal anteroposterior anteroposterior /an·tero·pos·te·ri·or/ (-pos-ter´e-er) directed from the front toward the back.

an·ter·o·pos·te·ri·or
adj. Abbr. AP
1. Relating to both front and back.
 (AP) diameter. In addition, at C2 one point on the tip of the odontoid process odontoid process
n.
A small, toothlike, upward projection from the second vertebra of the neck around which the first vertebra rotates.


odontoid process (ōdon´toid),
 and 6 points on the vertebral body were marked. At C1, 4 points on the anterior, superior, and inferior surfaces of the anterior tubercle tubercle (t`bərkyl') [Lat.,=little swelling], small, usually solid, nodule or prominence.  and the lower end of the spinous process were marked. At the occiput occiput /oc·ci·put/ (ok´si-put) the back part of the head.occip´ital

oc·ci·put
n. pl. oc·ci·puts or oc·cip·i·ta
The back part of the head or skull.
, 2 points on the anterior and posterior baselines were marked.

Data were calculated using the MR Analyzer Version 3. The cervical spine data included cervical lordosis lordosis /lor·do·sis/ (lor-do´sis)
1. the anterior concavity in the curvature of the lumbar and cervical spine as viewed from the side.

2. abnormal increase in this curvature.
 (Cobb's method and Harrison's posterior tangent method), atlas-odontoid distance (the distance between the posteroinferior margin of the anterior arch of the atlas The anterior arch of the atlas forms about one-fifth of the ring of the atlas: its anterior surface is convex, and presents at its center the anterior tubercle for the attachment of the Longus colli muscles; posteriorly it is concave, and marked by a smooth, oval or circular facet  and the anterior surface of the odontoid process), atlanto-occipital dislocation (the ratio BC/OA [B=basion, C=posterior arch of atlas, O=opisthion of the occipital bone, A=anterior arch of atlas]), atlas angle (the angle between the atlas plane line and true horizontal), atlas/skull angle (the angle between the plane line of C1 and the plane line of the skull at the level of the foramen magnum), vertebral height (the distance between the anterosuperior and anteroinferior corners of the vertebral body), vertebral body AP diameter (superior and inferior), spondylolithesis (the displacement of the inferior endplate of the vertebrae Vertebrae
Bones in the cervical, thoracic, and lumbar regions of the body that make up the vertebral column. Vertebrae have a central foramen (hole), and their superposition makes up the vertebral canal that encloses the spinal cord.
 above with respect to the superior endplate of the vertebrae below), disc height (the distance between the centre of adjacent vertebral endplate), disc bulge/herniation (the extension of the disc beyond the intervertebral space), spinal canal AP diameter (disc level and pedicle level), sagittal segmental translational motion (the anteroposterior motion of one vertebrae over another), and sagittal segmental angular motion (the angle between the inferior border of the 2 adjacent vertebrae).

The lumbar spine data included global lordosis (Cobb's method and posterior tangent method), segmental lordosis (Cobb's method), lumbar gravity line (vertical line drawn from the centre of L3 and its intersection with the sacral base), lumbar spine vertical height (the perpendicular distance between 2 horizontal lines drawn through the anterosuperior corners of L1 and S1), vertebral height, spondylolithesis, disc height, disc bulge/herniation, spinal canal AP diameter, sagittal segmental translational motion, and sagittal segmental angular motion.

RESULTS

A comprehensive grading system for intervertebral disc degeneration10-13 was used for analysing the spinal kinematics. We classified neutral-position T2- weighted sagittal images of all intervertebral discs into 3 to 5 grades and reported the results of kMRI of the spine.14-17

In normal cervical spines, most of the total angular mobility was attributed to C4/5 and C5/6, but mobility was significantly reduced in these segments in patients with severe disc degeneration.14 Cervical segmental mobility was significantly reduced in segments with severe cord compression, compared to those with no cord compression. It was hypothesised that the spinal cord was protected from dynamic mechanical cord compression by restricting segmental motion, and these mechanisms were closely related to the intervertebral discs.15 Changes in sagittal alignment of the cervical spine affected the kinematics and progress of cervical intervertebral disc degeneration.16

kMRI also improved the detection of lumbar disc herniations. The degree of such herniation herniation /her·ni·a·tion/ (her?ne-a´shun) abnormal protrusion of an organ or other body structure through a defect or natural opening in a covering, membrane, muscle, or bone.  increased significantly in flexion and extension images, compared to neutral images.17

DISCUSSION

The spine is subjected to great compressive forces during activities of daily living.18 Mechanical loading of the spine (due to axial compression and dynamic motion) induces mechanical stresses on the intervertebral discs, and this is an important factor in the aetiology of intervertebral disc degeneration.18 Therefore, it is important to evaluate spinal disorders under mechanical loading. For this purpose, kMRI is effective for diagnosing, evaluating, and managing degenerative disease or injury within the spine.

In our study, some patients needed pain control prior to kMRI because of severe discogenic or radicular pain in upright, weight-bearing positions. It was difficult for them to maintain their position for more than 30 minutes. Patients with severe myelopathy myelopathy /my·elop·a·thy/ (mi?e-lop´ah-the)
1. any functional disturbance and/or pathological change in the spinal cord; often used to denote nonspecific lesions, as opposed to myelitis.

2.
 should avoid dynamic motion or superfluous loading. Neurogenic neurogenic /neu·ro·gen·ic/ (-jen´ik)
1. forming nervous tissue.

2. originating in the nervous system or from a lesion in the nervous system.
 evaluation and observation prior to and during kMRI may be necessary.

© 2008 Western Pacific Orthopaedic Association Provided by ProQuest LLC. All Rights Reserved.
Copyright 2008 Journal of Orthopaedic Surgery
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright (c) Mochila, Inc.

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Author:Y Morishita and H Hymanson and M Miyazaki and H H Zhang and W He and G Wu and M H Kong and J C Wang
Publication:Journal of Orthopaedic Surgery
Date:Dec 1, 2008
Words:985
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