Демонстрація цінності низкопольного МРТ дослідження під природним навантаженням при захворюваннях хребта на сканері #GScan

1. MUSCULOSKELETAL
Positional changes in lumbar disc herniation during standing
or lumbar extension: a cross-sectional weight-bearing MRI study
Cecilie Lerche Nordberg1,2
& Mikael Boesen2
& Gilles Ludger Fournier3
& Henning Bliddal1
& Philip Hansen2
&
Bjarke Brandt Hansen1
Received: 8 January 2020 /Revised: 30 April 2020 /Accepted: 31 July 2020
# European Society of Radiology 2020
Abstract
Objectives To investigate biomechanical changes in lumbar disc herniations.
Methods Patients with lumbar disc herniation verified on a 1.5–3-T magnetic resonance imaging (MRI) scanner were imaged in
a weight-bearing 0.25-T MRI scanner in (1) standing position, (2) conventional supine position with relative lumbar flexion, and
(3) supine position with a forced lumbar extension by adding a lumbar pillow. The L2-S1 lordosis angle, the disc cross-sectional
area, the disc cross-sectional diameter, and the spinal canal cross-sectional diameter were measured for each position. Disc
degeneration and nerve root compression were graded, and the pain intensity was reported during each scan position.
Results Forty-three herniated discs in 37 patients (36.7 ± 11.9 years) were analyzed in each position. The L2-S1 lumbar angle
increased in the standing position (mean difference [MD]: 5.61°, 95% confidence interval [95% CI]: 3.44 to 7.78) and with the
lumbar pillow in the supine position (MD: 14.63°, 95% CI: 11.71 to 17.57), both compared with the conventional supine
position. The herniated disc cross-sectional area and diameter increased during standing compared with during conventional
supine position. No changes were found in the spinal canal cross-sectional diameter between positions. Higher nerve root
compression grades for paracentral herniations were found during standing compared with during conventional supine position.
This was neither found with a lumbar pillow nor for central herniations in any position compared with conventional supine.
Conclusion Disc herniations displayed dynamic behavior with morphological changes in the standing position, leading to higher
nerve root compression grades for paracentral herniated discs.
Key Points
• Lumbar herniated discs increased in size in the axial plane during standing.
• Increased nerve root compression grades for paracentral herniated discs were found during standing.
• Weight-bearing MRI may increase the diagnostic sensitivity of nerve root compression in lumbar disc herniations.
Keywords Magnetic resonance imaging . Low back pain . Spine . Intervertebral disc displacement . Weight-bearing
Abbreviations
CI Confidence interval
FOV Field-of-view
ICC Intra-class correlation coefficient
LBP Low back pain
MRI Magnetic resonance imaging
NRS Numerical rating scale
ODI Oswestry Disability Index
PDQ Pain-Detect Questionnaire
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s00330-020-07132-w) contains supplementary
material, which is available to authorized users.
* Cecilie Lerche Nordberg
cecilie.lerche.nordberg.01@regionh.dk
1
Department of Rheumatology, The Parker Institute, Copenhagen
University Hospital, Bispebjerg and Frederiksberg, Nordre Fasanvej
57, DK-2000 F Copenhagen, Denmark
2
Department of Radiology, Copenhagen University Hospital,
Bispebjerg and Frederiksberg, Copenhagen, Denmark
3
Department of Rheumatology, Copenhagen University Hospital,
Rigshospitalet, Bispebjerg and Frederiksberg,
Copenhagen, Denmark
European Radiology
https://doi.org/10.1007/s00330-020-07132-w

2. Introduction
Lumbar disc herniations are common degenerative findings in
low back pain (LBP) patients, characterized by a displacement
of disc material beyond the normal margins of the disc space
[1]. Patients with LBP caused by a herniation often experience
pain aggravation in the upright position and typically try to
reduce the pain by a light flexion of the lumbar spine [2]. This
indicates that position-dependent biomechanical changes in the
disc may be an important element in pain generation and may
explain why conventional supine magnetic resonance imaging
(MRI) scans with a pillow under the legs, which leads to relative
lumbar flexion, may not adequately assess the true nature of a
lumbar disc herniation [3, 4]. Previous MRI studies have indicated
that posterior herniations increase in the upright seated position [3]
and, more so, by adding extension during the upright position [5].
In a clinical setting, studies have found that standing weight-
bearing MRI may be feasible to detect otherwise hidden disc
herniations or nerve root compressions [3, 4, 6]. This indicates that
herniated discs are prone to biomechanical changes, and hence
may be influenced by the positioning of the patient.
In this study, we investigated biomechanical changes in
herniated discs by positional 0.25-T MRI in patients with
lumbar disc herniation, previously verified by conventional
supine 1.5–3-T MRI, in (1) standing position, (2) convention-
al supine position with light lumbar flexion using a leg sup-
portive pillow, and (3) supine position with forced lumbar
extension by adding a lumbar pillow.
Materials and methods
Design and ethics
This cross-sectional study enrolled LBP patients ≥ 18 years
with radiculopathy or sciatica, and a disc herniation (protru-
sion or extrusion) detected on a clinical conventional high-
field 1.5–3-T MRI. Patients with sequestrations were not in-
cluded, as disc material without continuity with the disc was
not expected to be affected by gravity or lumbar extension.
Exclusion criteria were spinal fractures, cancer, metastatic dis-
ease, pregnancy, or contraindications to standing MRI [7].
The study is reported in accordance with the Strengthening
the Reporting of Observational Studies in Epidemiology
(STROBE) statement [8], and all participants gave written
informed consent before enrollment. The study was approved
by the Local Ethics Committee (KF 01-045/03) and the
Danish Data Protection Agency (01758 FRH-2012-003).
Patient outcomes
All patients were initially interviewed about LBP and had a
clinical examination performed by a physician with a special
interest in spine diseases. The overall pain level was measured
on an ordinal 11-point numerical rating scale (NRS: 0 = no
LBP; 10 = worst LBP possible), and the patients had to fill in
the 13-item Pain-Detect Questionnaire (PDQ) to identify any
neuropathic component [9]. Disability was measured by the
24-item Oswestry Disability Index (ODI) questionnaire [10].
Image acquisition
All scans were performed in a low-field 0.25-T positional
MRI unit (G-Scanner, ESAOTE). The MRI protocol can be
found in the supplementary material (Supplementary Material
1). The scanning protocol entailed three scanning situations.
First, all patients were scanned in the standing position, sec-
ondly in the conventional supine position with a pillow under
the legs resulting in light flexion of the lumbar spine, and
thirdly the patients were scanned in the supine position with
extended legs and a pillow under their lumbar spine to induce
forced lumbar extension (Fig. 1). At the beginning and at the
end of each scan positioning, all patients were asked to assess
their pain intensity on the ordinal 11-point NRS.
MRI evaluations
Images from each position were separately evaluated in con-
sensus by two musculoskeletal radiology consultants blinded
from previous evaluations and without any clinical informa-
tion. The evaluation was performed in consensus, as this
method seems robust and reliable for semi-quantitative MRI
measurements [11]. According to Fardon et al [1], the disc
herniation was defined as a protrusion or an extrusion and a
central (central canal zone) or a paracentral (subarticular
zone). The degree of degeneration of the herniated discs was
assessed using Pfirrmann’s semi-quantitative grading scale,
ranging from 1 to 5, on the T2-weighted mid-sagittal image
obtained in the conventional supine position [12]. To grade
the nerve root compression due to the disc herniation in each
position, the following validated grading scale was used:
grade 0, no compromise and preserved epidural fat layer be-
tween the nerve root and the disc material; grade 1, normal
position of the nerve root and visible contact of disc material
and the nerve root; grade 2, the nerve root was displaced
dorsally by disc material; grade 3, the nerve root was com-
pressed between disc material and the wall of the spinal canal
[13].
MRI quantitative measurements
Due to the limited field-of-view (FOV) of the scanner, the
lumbar lordosis angle was measured as the L2-S1 angle on
the mid-sagittal image for each position (vertebra L1 was not
consistently included in the FOV) [14–16]. To investigate the
positional changes in the herniated disc, the following
Eur Radiol

3. dimensions were measured on the mid-axial MR images in all
three positions: (1) the disc cross-sectional diameter (anterior-
posterior midline); (2) the disc cross-sectional area; and (3) the
spinal canal cross-sectional diameter (Fig. 2; Supplementary
Material 2).
All quantitative MRI measurements were performed in
OsiriX MD (version 8.5). The sagittal images were magnified
to 1500–2500% and the axial images to 2000–3000% for
more precise measurements. Ten patients, equal to thirty
scans, were randomly selected for a second measurement after
2 months to assess the inter-reader and intra-reader agreement.
Statistical analysis
Descriptive data are reported as point estimates with a mea-
sure of dispersion (numbers, proportions, and mean ± standard
deviations [SD]). The quantitative MRI outcomes were tested
by one-way analysis of variance (ANOVA) for repeated mea-
surements and adjusted by Bonferroni post hoc correction.
Nerve root compression grades in the different positions were
compared using Wilcoxon signed-rank test, and pain
insensitivity during scans was analyzed using a paired sample
t test. Alpha level was set at 0.05. Intra-class correlation coef-
ficient (ICC) with 95% confidence intervals (95% CI) using a
two-way mixed model was used for testing the intra-reader
and inter-reader reliability for all quantitative outcomes. All
statistical analyses were performed using IBM SPSS®
Statistics, version 24.0.0.0.
Results
Patient characteristics
A total of 52 patients with a disc herniation on a conventional
supine high-field (1.5–3 T) MRI were initially included in the
study. Three patients failed to appear for the study’s additional
scan session, and one patient was not able to enter the scanner.
Five patients were excluded due to severe movement artifacts
on the standing images. Seven patients could not complete the
scans due to accentuated pain during the standing or supine
scan with a lumbar pillow. Therefore, the current study
Fig. 2 Shows the lumbar disc herniation measurements on the mid-axial T2-weighted image of a patient with a central disc herniation. a The anterior-
posterior disc cross-sectional diameter measured. b The spinal canal cross-sectional diameter. c The disc cross-sectional area
Fig. 1 Demonstrates the positioning of the patients. a The standing
position. b The conventional supine position with a pillow under the
legs. c, d The supine position with a lumbar pillow and extended legs.
An external pneumatic compression device was used to prevent fainting
in the standing position [7]
Eur Radiol

4. presents data from 43 herniated discs in 37 patients (18 fe-
male, 36.7 ± 11.9 years) (Table 1). At the clinical examina-
tion, 22 patients (59.5%) reported aggravation of their back
pain during standing, and 11 patients (29.7%) reported aggra-
vation of their back pain with lumbar extension. Six patients
(16.2%) reported aggravated back pain when lying down.
Pain assessment during scan sessions
All patients reported increased LBP intensity on the NRS from
the beginning to the end of the scanning session for all three
positions; however, this pain aggravation was most pro-
nounced during standing, and especially in the supine position
with a lumbar pillow. The most severe LBP intensity was
reported in the supine position with a lumbar pillow, and the
conventional supine position was reported the least painful
position (Table 2).
MRI evaluations
A majority of the 43 disc herniations were classified as extru-
sions (69.8%) and the remaining as protrusions (30.2%).
Based on the herniated disc’s location on the axial plane, it
was classified as a central herniation (44.2%) or paracentral
herniation (55.8%). The herniated discs were moderately to
severely degenerated with a mean of 4.0 (SD ± 0.9) on
Pfirrmann’s semi-quantitative grading scale.
Nerve root compression was graded on both sides of the 43
herniated discs resulting in 86 evaluations. In the conventional
supine position with a pillow under the legs, central hernia-
tions had few nerve root deviations (grade 2: 5.3%) or com-
pressions (grade 3: 15.8%), whereas, for paracentral hernia-
tions, nerve root deviation (grade 2: 20.8%) or compression
(grade 3: 20.8%) was more profound.
For both central and paracentral herniations, the nerve root
compression grades were almost unchanged when comparing
imaging in the supine position with a lumbar pillow with that
in the conventional supine position.
Comparing standing MRI with the conventional supine
position from the central herniations, the nerve root compres-
sion was graded higher in respect to 12 nerve roots (31.6%)
and lower in 6 nerve roots (15.8%); despite this, these changes
were not significant (Table 3).
For paracentral disc herniations, a significant change in
nerve root compression grading was reported when changing
position from conventional supine to standing position. In the
standing position, 15 nerve roots (31.2 %) were graded higher
and only three (6.3 %) were graded lower compared with the
conventional supine position.
MRI measurements of the herniated disc
The L2-S1 lordosis angle increased during standing (mean
difference [MD]: 5.61°, 95% CI: 3.44 to 7.78) and further in
the supine position with the lumbar pillow (MD: 14.63°, 95%
CI: 11.71 to 17.57) both compared with the conventional su-
pine position (Table 4; Fig. 3). There was a statistically sig-
nificant increase in the herniated disc cross-sectional area
(MD: 0.48 cm2
, 95% CI: 0.03 to 0.93) and diameter (MD:
1.10 mm, 95% CI: 0.38 to 1.82) in the standing position com-
pared with the conventional supine position. There was no
significant difference between any positions in the spinal ca-
nal cross-sectional diameter. The reliability of all quantitative
MRI measurements was tested, and a very good intra-reader
reliability (ICC: 0.98 to 1.00) and inter-reader reliability (ICC:
0.89 to 0.99) was found (Supplementary Material 3).
Table 1 Baseline characteristics
Patient characteristics (n = 37)*
Age, years, mean (SD) 36.7 (± 11.9)
Sex, females, no. (%) 18 (48.6)
BMI, kg/m2
, mean (SD) 23.6 (± 2.4)**
Positive straight legs test, no. (%) 27 (73.0)
Pain-Detect Questionnaire (PDQ), mean (SD) 9.2 (± 6.1)***
Average pain level (NRS0–10) last 4 weeks, mean (SD) 3.9 (± 1.6)***
Maximal pain level (NRS0–10) last 4 weeks, mean (SD) 5.7 (± 2.3)***
Oswestry Disability Index (ODI), mean (SD) 43.4 (± 16.0)**
MRI characteristics of the herniated discs (n = 43)
Herniation level, no. (%)
L3/L4 2 (4.7)
L4/L5 17 (39.5)
L5/S1 24 (55.8)
Herniation type, no. (%)
Protrusion 13 (30.2)
Extrusion 30 (69.8)
Herniation form, no. (%)
Central 19 (44.2)
Paracentral 24 (55.8)
Disc degeneration of the herniated level
Grade 1, no. (%) 0
Grade 2, no. (%) 3 (7.0)
Grade 3, no. (%) 7 (16.3)
Grade 4, no. (%) 18 (41.8)
Grade 5, no. (%) 15 (34.9)
Mean (SD) 4.0 (± 0.9)
Disc degeneration grades were based on Pfirrmann’s classification [12].
Herniation types and forms were based on Fardon’s criteria [1]
*Reported at the clinical examination
**Missing for 2 patients
***Missing for 3 patients
Eur Radiol

5. Table3MRIqualitativeoutcomes
Herniationnerverootcompression,no.(%)Changesinherniationnervecompressiongrading,no.(%)
StandingConventionalsupineLumbarpillowsupineConventionalsupinetostandingConventionalsupinetolumbar
pillowsupine
Standingtolumbar
pillowsupine
Centralherniation(n=19patientsequalto38nerveroots)
Grade011(28.9)14(36.8)15(39.5)No.oflevelsgradedhigher12(31.6)5(13.2)4(10.5)
Grade115(39.5)16(42.1)16(42.1)No.oflevelsgradedthesame20(52.6)26(68.4)22(57.9)
Grade25(13.2)2(5.3)1(2.6)No.oflevelsgradedlower6(15.8)7(18.4)12(31.6)
Grade37(18.4)6(15.8)6(15.8)Wilcoxonsigned-ranktestp=0.101p=0.564p=0.033
Paracentralherniation(n=24patientsequalto48nerveroots)
Grade012(25.0)17(35.5)17(35.5)No.oflevelsgradedhigher15(31.2)7(14.6)4(8.3)
Grade113(27.1)11(22.9)9(18.7)No.oflevelsgradedthesame30(62.5)39(81.2)32(66.7)
Grade28(16.7)10(20.8)9(18.7)No.oflevelsgradedlower3(6.3)2(4.2)12(25.0)
Grade315(31.2)10(20.8)13(27.1)Wilcoxonsigned-ranktestp=0.005p=0.096p=0.046
NerverootcompressionwasgradedaccordingtoPfirrmann’ssemi-quantitativegradingscaleevaluatedontheaxialT2-weightedimages.Grade0:nonerverootcontact.Grade1:contactwithoutdeviation
ofthenerveroot.Grade2:contactwiththenerverootanddeviation.Grade3:compressionofthenerveroot[13]
Thechangeinnerverootcompressiongradingbetweenpositionsisreportedasthenumberoflevelswithahigher,thesame,orlowergradingwhenchangingfromtheconventionalsupinetostanding
position(column1),changingfromtheconvectionalsupinetothesupinepositionwithalumbarpillow(column2),orchangingfromstandingtothesupinepositionwithalumbarpillow(column3)
Table2Painintensityduringscans(n=37)
Mean(±standarddeviation)Meandifference(95%confidenceinterval)
StandingConventional
supine
Lumbarpillow
supine
ConventionalsupinetostandingConventionalsupineto
lumbarpillowsupine
Standingtolumbar
pillowsupine
Start2.54(1.80)2.14(1.90)3.57(2.21)0.40(−0.01to0.82)1.43(0.92to1.95)(p<0.001)1.03(0.43to1.63)(p=0.001)
End3.76(2.14)2.41(2.02)5.32(2.47)1.35(0.77to1.93)(p<0.001)2.91(2.16to3.68)(p<0.001)1.56(0.82to2.32)(p<0.001)
ΔEnd–start*1.22(1.44)0.27(1.04)1.76(1.42)0.95(0.37to1.51)(p=0.002)1.49(0.94to2.03)(p<0.001)0.54(−0.08to1.16)
Duringthethreescans,painintensitywasassessedonthe11-pointnumericalratingscale(NRS:0=noLBP;10=worstLBPpossible).Thechangeinpainintensitygradingbetweenpositionsisreported
whenchangingfromtheconventionalsupinetostandingposition(column1),changingfromtheconvectionalsupinetothesupinepositionwithalumbarpillow(column2),orchangingfromstandingto
thesupinepositionwithalumbarpillow(column3).Theratingsarepresentedasmean±standarddeviations(SD).Differencesbetweenmeanswereanalyzedusingapairedsamplesttest
*Theaggravationinpainfromstarttillendforascanposition
Eur Radiol

6. Discussion
In the present study, 43 lumbar disc herniations in 37 patients
were evaluated for biomechanical changes by comparing MR
images in three positions: (1) the standing position, (2) the
conventional supine position with a pillow under the legs
resulting in a light lumbar flexion, and (3) the supine position
with extended legs and forced lumbar extension by adding a
lumbar pillow. All patients reported increased back pain in-
tensity during each scan. The lumbar pillow in the supine
position caused the most discomfort and the conventional su-
pine position the least discomfort. For paracentral herniations,
significant higher nerve root compression grades were found
in the standing position compared with those in the conven-
tional supine position. For central herniations, there was no
significant difference in nerve root compression grades when
comparing the standing and supine position with a lumbar
pillow with those in the conventional supine position. The
herniated disc cross-sectional area and diameter increased in
the standing position compared with those in the conventional
supine position. The herniated disc dimensions also increased
in the supine position with a lumbar pillow, although no sig-
nificant difference was found for the disc area.
Nerve root compression is only believed to be one out of
several factors (e.g., ischemia, chemical responses) associated
with LBP, radiculopathy, and sciatica in patients with disc
herniation [17]. Therefore, the biomechanical changes found
in the herniated discs, and the increased nerve root compres-
sion grades found in paracentral herniations in this study, may
only partly explain why patients reported increased pain se-
verity during standing MRI. However, the discomfort caused
by the lumbar pillow in the supine position does not seem to
be explained by an increase in nerve root compression, as no
significant difference in grading was found compared with the
conventional supine position.
Intervertebral discs, comprised of a soft central nucleus
pulposus surrounded by 10–20 concentric collagenous lamel-
lae of the annulus fibrosus, allow compressive forces of the
lumbar spine to be evenly dispersed during standing [18]. Disc
degeneration is part of an inevitable aging process in the lum-
bar spine. In a herniated disc, it is believed that radial degen-
erative fissures in the disc periphery allow the nucleus to grad-
ually migrate through the annulus, which in some cases leads
to overt herniation [19]. These radial degenerative fissures
may also weaken the disc, and consequently the degenerated
disc becomes more easily compressed like a “flat tire.” This
might explain why the disc cross-sectional area and diameter
increased in the standing position in the present study.
MRI in the upright seated position has revealed that the
posterior disc contour tends to increase in size by adding
extension, and in one study by flexion [5, 20–22]. In the
upright standing position, the lumbar spine may be affected
by an increased lordosis, gravity, and core muscle activation.
Table4PositionalMRIoutcomes
Mean(±standarddeviation)Meandifference(95%confidenceinterval)
StandingConventionalsupineLumbarpillowsupineConventionalsupinetostandingConventionalsupinetolumbar
pillowsupine
Standingtolumbarpillowsupine
Spines(n=37)
Lordosisangle(degrees)48.34(10.28)42.73(9.32)57.36(9.94)5.61(3.44to7.78)(p<0.001)14.63(11.71to17.57)(p<0.001)9.02(6.58to11.48)(p<0.001)
Alldischerniations(n=43)
Disccross-sectionalarea(cm2
)18.26(2.67)17.78(2.69)18.13(2.58)0.48(0.03to0.93)(p=0.033)0.35(−0.04to0.75)−0.13(−0.57to0.31)
Disccross-sectionaldiameter
(mm)
42.63(3.60)41.53(3.41)41.95(3.19)1.10(0.38to1.82)(p=0.001)0.42(−0.24to1.07)−0.69(−1.34to−0.03)(p=0.039)
Spinalcanalcross-sectional
diameter(mm)
15.10(3.22)15.28(2.80)15.08(3.35)−0.18(−0.63to0.28)−0.20(−0.67to0.28)−0.02(−0.61to0.57)
MRImeasurementsoftheherniateddiscarepresentedasmean±standarddeviations(SD)andthedifferencebetweenmeans(MD)andanalyzedusingone-wayanalysisofvariance(ANOVA)forrepeated
measurementsadjustedbyBonferroni
Thechangesinmeasurementsbetweenpositionsarereportedwhenchangingfromtheconventionalsupinetostandingposition(column1),changingfromtheconvectionalsupinetothesupineposition
withalumbarpillow(column2),orchangingfromstandingtothesupinepositionwithalumbarpillow(column3)
Eur Radiol

7. This study indicates that the increase in herniated disc size in
the axial plane (i.e., dynamic bulging) may be caused by grav-
ity and core muscle activation during standing rather than by
lumbar extension.
It is also believed that degeneration of the disc’s matrix
causes the annulus to bulge radially outwards, as the
dehydrated nucleus is no longer able to exert hydrostatic pres-
sure to tension the annulus [16, 18, 19]. This is further sup-
ported by the finding that moderate disc degeneration (grade:
3 to 4), assessed by Pfirrmann’s classification, can be corre-
lated to the severity of disc bulging [20]. In accordance with
this, the herniated discs in this study were found to be moder-
ately to severely degenerated.
Despite the dimensional changes in the herniated disc, we
did not find any changes in the diameter of the spinal canal
between positions. This could be explained either by a lateral
displacement of disc material or by the fact that the posterior
longitudinal ligament restrains the disc material resulting in a
cranial or caudal displacement (Fig. 3). It is possible that the
cross-sectional area of the spinal canal and dural sac area
might have further substantiated the positional changes espe-
cially in the paracentral herniation. However, studies have
investigated changes in the dimensions of the spinal canal in
the standing position and found that these changes seem to be
caused by increased thickness in the ligamenta flava and less
by changes in dimensions of the disc [14, 23, 24]. Also, one
study has found an expansion of the dual sac during standing
caused by hydrodynamic changes in the cerebrospinal fluid
[25].
Nevertheless, this study adds to the belief that weight-
bearing can detect the true nature of a disc herniation [3, 5,
20, 21, 26]. This is supported by studies in clinical settings
reporting detection of otherwise hidden disc herniation during
standing weight-bearing MRI [3, 6]. Therefore, weight-
bearing MRI may increase the diagnostic sensitivity of disc
herniations in patients suspected of nerve root compression,
i.e., patients with radiculopathy [3, 6]. However, weight-being
MRI could potentially produce false-positive findings which
do not reflect underlying pain-inducing disease mechanisms,
as disc herniations are frequent in asymptomatic individuals
Fig. 3 A 32-year-old man with LBP, radiculopathy, and a paracentral
disc herniation. Sagittal (a, b, c) and axial (d, e, f) T2-weighted images
of the patient in the standing position (a, d), the conventional supine with
a pillow under the legs (b, e), and the supine position with a lumbar pillow
and extended legs (c, f) in the 0.25-T MRI scanner (G-scanner). Notice
the change in contour of the disc on the axial images (d–f). Note the
descending herniation contained by the posterior longitudinal ligament
and, hereby, does not affect the dimensions of the spinal canal
Eur Radiol

8. [27–30]. Future studies should investigate whether weight-
bearing MR imaging findings (e.g., nerve root compression)
correlate with the clinical patient outcomes in randomized
controlled trials.
This study has several limitations. First, it is limited by its
cross-sectional design and sample size, including 43 disc her-
niations in 37 patients. However, previous studies with similar
sample sizes have provided results indicating a relationship
between positioning of the patient and dynamic changes in
the spine [5, 14, 15, 23, 25]. Second, patient characteristics,
e.g., clinical symptoms, bodyweight, and age were not
correlated to the biomechanical changes in the disc. Such
analysis would be subject to biases, as six patients contributed
with two herniated discs. Third, indirect sigs of the lumbar
pillow in supine position and an increased lordosis could
be identified on the images, resulting in the observers not
being fully blinded to the position. Fourth, seven patients
could not complete the scan sessions due to intolerable
back pain, and five patients were excluded due to move-
ment artifacts. This may be a result of the longer scan time
using a low-field strength (0.25 T) weight-bearing MRI
scanner, making it more susceptible to movement artifact
[31], or due to the underlying instability producing intol-
erable pain during the scan. Nevertheless, low-field MRI
systems have been shown to produce sufficient image
quality for the assessment of anatomical features as disc
herniations, although low-field strength compromises the
clarity and sharpness of the pathology compared with high-
field strength [32]. Low-field weight-bearing MRI scans
are today regarded as an add-on to conventional high-
field MRI, despite the advantages of low-field MRI sys-
tems such as lower purchase and running costs [32].
Comparing high-field to the low-field weight-bearing
MRI seems relevant in future studies.
In conclusion, herniated discs increased in size in the axial
plane leading to an augmentation in nerve root compression
grades for paracentral herniated discs in the standing position
compared with those in the conventional supine position.
Weight-bearing MRI may increase the diagnostic sensitivity
of disc herniations in patients suspected of nerve root com-
pression. However, MRI with a lumbar pillow may be
attempted.
Acknowledgments The authors thank the staff at the Department of
Radiology, Bispebjerg and Frederiksberg Hospital for their support
running the study. The authors thank radiologists Jacob Grindsted,
MD, and Zoreh Rasti, MD, Department of Radiology, Frederiksberg
Hospital, Denmark, for inspiration, evaluation of the MR images, and
discussions. The authors would also like to thank Sabrina Mai
Nielsen for statistical support and methodological feedback.
Funding information This study was supported by unrestricted grants
from The Oak Foundation (grant number: OCAY-13-309), the
Danish Rheumatism Association, and Frederiksberg and Bispebjerg
Hospital.
Compliance with ethical standards
Guarantor The scientific guarantor of this publication is Bjarke Brandt
Hansen, MD, PhD.
Conflict of interest Mikael Boesen has been an invited speaker regard-
ing the use of G-scanner for imaging of the lumbar spine for ESAOTE,
Genoa, Italy, the manufacturer of the G-scanner, at ESSR 2012, 2014 and
2017, Modena Meeting Nov. 2013, Imola Meeting June 2017, and ECR
2014 as well as the 1st, 2nd, and 3rd International Weight-bearing
Meeting (2016, 2018, and 2019). Philip Hansen has received a travel
grant from ESAOTE for the 1st International Weight-bearing Meeting
2016. The other authors have no conflict of interests to declare.
Statistics and biometry No complex statistical methods were necessary
for this paper.
Informed consent Written informed consent was obtained from all pa-
tients in this study.
Ethical approval Local Ethics Committee approval: KF 01–045/03.
Methodology
• prospective
• cross-sectional study
• single-center study
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