Keywords:
Outcomes, Equipment, Diagnostic procedure, MR-Functional imaging, MR, Musculoskeletal spine
Authors:
H.-S. Kim, G. Choi, W. H. Kim, H. J. Ma; POHANG/KR
DOI:
10.1594/essr2018/P-0027
Purpose
Introduction and Background:
- Degenerative spinal disorder such as spinal stenosis or disc herniation (with neck and back pain,
cervical and lumbar radicular pain etc.) is one of the most common medical and surgical problems with a prevalence ranging from 60 to 90%.(1,2,3).
- Stenosis of the lumbar spinal canal may cause low back pain,
sciatica,
and neurogenic claudication.
- Pressure on the spinal cord and nerve roots associated with spinal degeneration may be caused by disc displacement or herniation; spinal stenosis,
a narrowing of the spinal canal; or osteoarthritis,
cartilage breakdown at spinal joints.
★ Imaging diagnosis
- Diagnosis often begins with a spinal x-ray,
which does not show the discs but can show other bony changes in the spine.
- Magnetic resonance imaging (MRI) scans are the primary means of diagnosis because they can show the disc in detail and allow physicians to see the nerves and spinal canal space and how they are affected by the disease.
- Computed tomography (CT) scans also may be used.
- However,
the diagnosis,
even with MRI,
can be difficult with the presence of findings that do not correlate well with a patient’s symptoms.
★ Weight-Bearing (W-B) studies
- It is common knowledge that in many patients the symptoms are induced by walking or standing,
and often worsen with long period of standing/sitting or activity.
- On the other hand,
symptoms are relieved with bed rest and lying down position (4,5,6).
- The most important aspect in the dynamic pathology is the relationship between symptoms and both posture and function.
- Another component to consider is the gravity.
- During erect posture,
the gravity of the upper body and the tonus of postural musculature of the trunk create an axial load compressing the lumbar intervertebral discs.
(7)
- Compressive load can increase the load in the lumbar spine by 80% compared with that in the supine position.
- In addition,
the intra-discal pressure also changes with the position of spine where it increases in standing,
sitting,
and a forward flexed position.
- Prolonged standing can diminish the size of the neural foramens and central spinal canal because the discs lose water content and height whenever the load on the spine is increased.
- Scanning patients in a recumbent position may potentially miss the occult pathology,
which may be revealed in a weight-bearing or more positional mode such as flexion or extension.
- Radiologists failed to report certain pathologic findings,
which had to be handled during the surgery (8).
★ W-B MRI
-
Conventional high-field MRI is the Gold standard image modality to evaluate the degenerative spinal disorders.
However,
images are acquired with patients in the supine position.
So,
it fails to address the real posture of human body (9).
- W-B MRI is introduced to address aforementioned clinical consideration depending on body posture.
- Recently,
W-B MRI equipment has been developed which allows spinal imaging in both supine and upright position.
- With use of this W-B MRI system,
it is possible to carry out examinations in supine and true weight-bearing positions.
- Furthermore the technological advancement of open equipment resulted in significant improvement in image quality.
- Capable of obtaining images of the spine in orthostatic (standing) position,
which should better evidence pathological conditions that are sometimes “invisible” in the supine position(10).
- In addition,
forced flexion and extension of the lumbar spine during the weight-bearing scan,
known as kinematic MRI (kMRI),
has also been shown to cause significant changes in the morphology (11).
- The intra- and inter-examiner reliability of measurement of anatomic areas with this MR-Scanner was excellent (12).
- Basic studies (change the measurement of the spinal parameters,
canal/dural sac,
foraminal/central/lateral recess stenosis) of the W-B MR have been published already.
※ A Study with 35 normal athletes,
with G-Scan examinations showed :
- Increased lumbar lordosis (6.3˚ ± 5.6˚)
- Eventual reduction of SDSD (sagittal dural sac diameter) : L3-4,
L4-5
- The neural foramens : level 1 narrowing at L4-5,
L5-S1
- No significant differences of
- SCCA (spinal canal cross-sectional area)
- DSCA (dural sac cross-sectional area)
- The lateral recesses
(2) Mauch at al.
2010
※ Under physiological conditions (in the transition from supine to upright position),
57 patients with G-Scan showed:
- Increased lumbar lordosis angle(35.5̊˚ → 41.6˚ )
- Increased maximum A-P diameter of the dural sac (13.1mm →14.5mm)
- Decreased lumbosacral angle (136.7˚ → 131.7˚)
- Decreased L3-4 disc height (12.9mm → 1.2mm)
- Decreased L3-4 interspinous distance (14.6mm → 12.8mm)
- Pathological changes were found in all patients.
- Moreover,
upright MRI demonstrated disc protrusions in 11 patients ,
pseudocyst of the facet joint in 1 patient with negative findings in supine position → visualization of occult spine and disc pathologies !
(10) Tarantino,
et al,
2013
※About 26 % ( 61/230) stenotic levels were detected which were visualized exclusively in scans obtained under W-B conditions ( with G-Scan).
In all of these cases,
disc disease was associated with facet pathology.
These patients showed a worsening of symptoms,
while maintaining the erect posture,
which correlates well with dynamic stenosis.
(3) Splendiani,
et al,
2014
Purposes;
So far,
there are only a limited number of investigations in clinical practice pertaining to the proper protocol in performing a W-B MRI for the management of patients with spinal disorders,
and correlation with the treatment results.
The objective of this study is to determine the effectiveness of the weight-bearing (W-B) Magnetic Resonance (MR) imaging for enhancing the detection of the spinal pathology,
which would affect formulating the final surgical plan for symptomatic patients.