1105
Flexion and Traction Effect on G-C6 Foraminal Space
S. Craig Humphreys,
LaurieLomasney,T~D,
MD, Jt$Lrey Chase, MD, Avinash Patwardhan,
Scott%. Hodges, DO
ABSTRACT. Humphreys SC, Chase J, Patwardhan A, Shuster
J, Lomasney L, Hodges SD. Flexion and traction effect on
C5-C6 foraminal space. Arch Phys Med Rehabil 1998;79:
1105-9.
Objective: To determine the effects of cervical flexion and
traction on foraminal volume and isthmus area at the C5-C6
foraminal space in cadavers.
Design: This study evaluated the foraminal space at C5-C6
in cadaver specimens during flexion and traction of the cervical
spine.
Setting: An orthopedic biomechanics laboratory and department of radiology of a university medical center.
Patients or Other Participants: Nine cadaver cervical
spines, Cl through T3, were used in the study. Superficial
tissueswere dissected, preserving the ligaments.
Interventions: Proximal and distal portions of the cadaver
spines were potted using bone cement. Spines were mounted
and imaged with computed tomography in neutral position, 15”
of flexion, and maximum flexion with and without 251bs of
axial traction.
Main Outcome Measures: The areas and volumes of the
foramen were measured and calculated.
Results: Flexion alone significantly increased the foraminal
volume and isthmus area at C5-C6. Traction resulted in little
additional change.
Conclusions: For cervical spines with mild to moderate
degenerative changes at C5-C6, cervical flexion with or without
traction produces significant increasesin foraminal volume and
area at the foraminal isthmus.
0 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and
Rehabilitation
T
HE COMPLEX REGIONAL anatomy of the cervical spine
has been well studied.’ The cervical spine gives off dorsal
and ventral roots that coalesce at each spinal level to form
cervical nerve roots. Compression of the root or ganglion may
produce radicular pain. Kikuchi and associates2showed in their
cadaveric study that three factors are responsible for radicular
symptoms: abnormalities of the nerve and nerve roots, changes
of bone and soft tissue adjacent to the nerve, and their
relationship to each other. Causes of radiculopathy may include
From the Chattanooga Orthopaedic Group, Foundation for Research; Chattanooga,
TN (Drs. Humphrey, Hodges); the Department of Orthopaedic Surgery (Drs. Chase,
Patwardhan) and Department of Radiology (Dr. Lomasney), Loyola University
Chicago, Maywood, IL,; and the Department of Orthopaedic Surgery, University of
South Carolina, Columbia, SC (Dr. Shuster).
Submitted for publication January 6, 1998. Accepted in revised form April 7, 1998.
Presented at the 1995 Cewical Spine Research Society Annual Meeting, November
30 to December 2,1995, Sante Fe, NM.
No commercial party having a direct financial interest in the results of the research
supporting this article has or will confer a benefit upon the authors or upon any
organization with which the authors are associated.
Reprint requests to S. Craig Humphyeys, MD, Chattanooga Ortbopaedic Group,
605 Glenwood Avenue, Suite 303, Chattanooga, TN 37404.
0 1998 by the American Congress of Rehabilitation Medicine and the American
Academy of Physical Medicine and Rehabilitation
0003-9993/98/7909-4812$3.00/O
PhD, John Shuster, MD,
congenital abnormalities, traumatic, metabolic, oncologic, vascular, infectious, or degenerative diseases.
Various tests have been developed to aid in detecting the
source of radicular pain. Spurling’s and Scoville’s test3 rotates
and laterally bends the patient’s head maximally toward the
affected side. With the head and neck in this position, a vertical
force is applied to the uppermost portion of the cranium. This
position is believed to bulge the intervertebral disc and decrease
the foraminal height, causing foraminal impingement. The
force to the head is transmitted to the intervertebral disc, which
are further bulged, causing maximum encroachment on the
intervertebral foramen. The extension test applies maximal extension for 15 to 25 seconds, causing posterior disc bulging and
foraminal impingement.4 Finally, the shoulder abduction relief
test puts the patient’s affected arm in maximum abduction with
the hand resting on the head. This can offer relief from radicular
symptoms by opening the foramen. These tests suggest that
head and arm position affect the foraminal area available for the
exiting nerve root and thus affect radiculopathy.
Previous studies have investigated the effect of head position
on foraminal area and pressure. Farmer and Wisneski4 took
pressure measurements in the neural foramina of the C5, C6,
and C7 nerve roots at various positions of the head and
ipsolateral arm in cadaver specimens. Increasing neck extension resulted in significantly greater pressure at each root tested.
Abduction of the arm was shown to significantly reduce
pressure measurements. It was concluded that head and arm
position could be adjusted to reduce neuroforaminal pressure by
increasing foraminal area. Yoo et al5 investigated changes in
foraminal area at the C5, C6, and C7 levels. They determined
that increases in foraminal area occurred with neck flexion,
whereas extension decreased the area.
Many nonsurgical modalities exist to alleviate cervical
radiculopathy and pain. These include rest, antiinflammatory
medication, physical therapy, injections, and traction. The
mechanism of action of cervical traction is controversial. Some
suggest that traction alleviates muscular spasm and enlarges the
neural foramen. Others have suggested that the rest and
immobility of traction provides relief by decreasing the inflammation, and still others have suggested that flexion in combination with traction and/or immobilization is beneficial.7
Based on the results of studies that showed a correlation
between head position and foraminal area, it was hypothesized
that a combination of llexion and traction could benefit
foraminal anatomy. In the current study computed tomography
(CT) was used to investigate foraminal area/volume, and to
determine the effects of varied flexion angles and traction on the
foraminal space. The purpose of this study was to determine
whether combined flexion and traction was capable of increasing foraminal area in cadaver spines in an attempt to reduce
radiculopathy.
METHODS
Ten fresh frozen human spine specimens (age range, 65 to 80
years) were obtained with intact ligaments, paravertebral
muscles, and nervous tissue, as well as overlying muscle and
soft tissues. The skin and soft cutaneous tissues were removed.
Cl through T3 was separated from the remainder of the spine.
Arch
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1106
EFFECTS
OF FLEXION
AND
TRACTION
ON FORAMEN,
Humphreys
The superficial tissueswere dissected, preserving the ligaments.
Care was taken to avoid disrupting the relationship of the
osseous anatomy and the intervertebral discs. Specimens were
stored at -2O”C, which has been shown to have no significant
effect on the dimensions of the intervertebral foramen Specimens were kept moist to avoid desiccation. To exclude any
specimen with significant pathologic condition, anteriorposterior, lateral, and oblique x-rays were taken. Additionally,
all specimens were evaluated with magnetic resonance imaging
(MRI). Tl-weighted sagittal and TZweighted axial and sagittal
images were obtained. X-ray and MRI data were reviewed by a
musculoskeletal radiologist. X-ray and MRI were reviewed
independently for each specimen. Two grades were given to
each specimen, one for disc degeneration and the other for
changes in osseous anatomy. Disc degeneration was graded as
follows: 0, normal; 1, mild (minimal disc height loss); 2,
moderate (disc height loss with moderate proliferative changes);
3, severe (obliteration of disc space). Changes in osseous
anatomy were graded on the following scale: 0, normal; 1, mild
(mild degenerative changes); 2, moderate (facet spurring with
encroachment of foraminal space); 3, severe (severe encroachment of foraminal space from bony spurs). One specimen was
excluded from the study after plain radiographic analysis and
MRI because of fusion at C3-C4 and severe degenerative
changes, leaving nine specimens for testing.
Experimental Setup
A radiolucent apparatus was designed to simulate cervical
traction (fig 1). This was then custom-fit to the CT table. The jig
allowed for different-sized specimens and control of flexion
angle and traction weight. Proximal (Cl-2) and distal (T2-3)
portions of the specimen were potted using bone cement.
Specimens were secured to the jig, and each specimen was
CT imaged on a GE High Speed Advantage spiral CT scanner.a
Tube current was 200nA, and tube potential was 1OOkV.There
was no gantry tilt. Scans were performed in both the standard
and bone algorithm. A large field of view was used for scanning
and a 15 field of view for display. Anteroposterior and lateral
scouts were taken before each scan to confirm flexion angle and
standardize cuts. Specimens were scanned at 3-mm increments
with 1: 1 pitch, from the superior endplate of C3 to the inferior
endplate of C7. Specimens were scanned without traction
weight and with 25-lb axial traction at neutral, 15” flexion from
neutral, and maximum flexion as measured by the Cobb method
Fig 1. Experimental
Arch
Phys
Med
Rehabil
apparatus
Vol79,
with
September
specimen
1998
attached.
Fig 2. Reformatted
sagittal
CT images
for one specimen
at one
condition.
Image at top left is at the medial margin
of the foraminal
canal, with the other
5 images
moving
laterally
through
the foramen. Arrow
indicates
C5-C6 foramen.
from C2 to C7. This resulted in six scansper specimen. Traction
was applied with a direction of pull perpendicular to the
endplate of C2. A 30-minute interval was observed before
scanning after the weight was applied or removed to allow for
stretching and recovery of the soft tissues.Axial image data was
reformatted to 3-mm slices at l-mm increments.
Reformatted images were constructed in the sagittal plane.
The image was then manipulated to a plane parallel to the
medial margin of the C5-C6 foramen based on the morphologic
appearance of the vertebrae, pedicles, and facets to accommodate canal obliquity. Sequential l-mm images along the foramen were obtained from medial to lateral for a total of six
images. All images to be measured were saved, coded, and
stored on optical disk with annotation on the image to mark the
foramen of interest.
Measurements
Measurements were performed independently by three orthopedic surgeons. Each image was digitized (Lasico 1280b) from
hard copy films to obtain the cross-sectional area of the C5-C6
foramen (fig 2). The six areas were stacked end to end, and the
volume of the foramen was calculated. The digitizer was
calibrated using known magnification scales that appear on
each CT image.
EFFECTS
OF FLEXION
AND
TRACTION
Confirmation of Methods
A radiopaque (Teflon) block was prepared with six holes
from 3 to 8mm at l-mm increments. The block was imaged with
CT at different obliquities to simulate the cadaveric anatomy.
The block was imaged, reformatted, reconstructed, and measured in a manner identical to the cadaveric specimens.
The measured volume and area of the Teflon standard were
found to be within lmm3 and lmm* of actual values, respectively, which is within the limits of error of the imaging
software and testing parameters.
Statistical Analysis
A descriptive statistical analysis was performed to calculate
the means and standard deviations of all dependent variables
(area and volume). The differences between the dependent
variables were calculated by using a repeated measures analysis
of variance (ANOVA), with post hoc multiple comparisons
where indicated. Because of multiple comparisons, the level of
significance for rejecting the null hypothesis was set at the 1%
probability level (0~= .Ol).
RESULTS
The average grade for both disc degeneration and changes in
osseousanatomy was between 1 and 2. The average volume and
isthmus areas from the nine specimens, along with standard
deviations, are shown in fig 3. The shape of the foramen
approximates an hourglass with its narrowest aspect (isthmus) 3
to 4mm from the medial margin of the foramen. This was
determined by examining the changes in the cross-sectional
areas through the foramen as shown in figure 4. This general
appearance was seen in all specimens regardless of flexion
angle of traction.
Flexion alone significantly increased foraminal volume and
isthmus area, but as the specimens assumed an increasingly
flexed position there was a smaller incremental increase in
foraminal size. The addition of 15” flexion increased the
volume 23% (p = .003), and the area 23% (p = .007) from
neutral. Maximal flexion increased the volume 34% (p = ,002)
and the area 36% (I, = ,002) from neutral.
Although traction at each flexion angle increased the foraminal volume and isthmus area as compared with flexion alone,
these changes were not statistically significant (significance of
traction on volume: neutral, p = .057; 15”, p = .015; maximal
Fig 3. Results
area (mms).
(standard
deviations):
n,
volume
(mm3);
tZI, isthmus
ON FORAMEN,
Humphreys
300
zi
E
A
A
200 -
:L
m
A
A
3
4
0
-1
0
1
2
Distance
from
spinal
Fig 4. Area along the foraminal
canal for
the six tested
conditions
are shown.
between
these two extremes.
canal
5
6
(mm)
one specimen.
The remaining
Only two of
plots
fall
flexion, p = .209; significance of traction on area: neutral,
p = .046; 15”, p = .050; maximal flexion, p = .322). Traction
at neutral position did approach significance (p = .046). The
largest volume and the largest isthmus area were found with
maximal flexion and traction, but these were not significantly
larger than the values with maximal flexion alone.
As the area of each foramen was directly measured, these
values were used to assess interobserver and intraobserver
error. There was no significant difference between observers
0, = .151), with standard deviation consistently less than 10%
of the mean. There was also no significant interaction between
the observers and the condition tested (p = .973).
DISCUSSION
In patients in whom foraminal encroachment is the culprit in
radicular pathology, cervical traction and flexion are thought to
increase the foraminal area and volume, hypothetically allowing increased vascularity, decreased compression on the nerve
root, and a subsequent decrease in inflammation.6x7
The intervertebral foramen is comprised of the vertebral
bodies anteriorly, pedicles superiorly and inferiorly, and lamina
posteriorly as they meet the posterior aspect of the pedicles to
form the pillars that support the facets of the zygapophyseal
joints. The foramen is most often studied radiographically using
45” oblique views. Qualitative assessment of its size and
encroachment are limited. Looking at the spine threedimensionally, as with our CT reconstructions, has allowed us
to create the cervical chamber through which the nerve root and
accompanying meninges traverse. The chamber is illustrated in
figure 5, which shows a 45” oblique view of the intervertebral
foramen and the nerve root. Segnarbieux and coworkers9 have
termed this the interpedicular compartment, whereas Giles and
KaverilO call it the intervertebral canal. Because this chamber is
obliquely oriented the foramen, as seen on plain radiographs, it
is not necessarily an accurate, nor clinically a reliable indicator
of spinal nerve encroachment. Therefore, CT with the option of
reformation in any plane was the imaging technique of choice
in this study. It is a reliable portrayal of cervical spine anatomy
and can localize anatomic lesions.‘r Intravenous contrastenhanced CT studies can accurately delineate the epidural
space.‘* Preoperative assessment and planning is enhanced by
Arch
Phys
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Fiehabil
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1999
1108
EFFECTS
OF FLEXION
AND
TRACTION
Fig 5. A 45O oblique
view
of the intervertebral
foramen
and the
nerve root. The anterior
root (a) lies anteroinferiorly,
adjacent
to the
uncovertebral
joint, and the posterior
root (p) is close to the superior
articular
process.
its use. Newer two-dimensional dynamic reconstruction and
three-dimensional reconstruction allow additional precision
and representation of anatomy. Zinreich6,13reported that threedimensional CT gave additional information in more than 50%
of cases.6,13 Smith and associatest4 showed that threedimensional reconstruction gives a better representation of the
lumbar intervertebral tunnel than plain CT. Our reconstructed
images reconfirmed that the cervical foramen is shaped like an
hourglass with the isthmus positioned close to the center of the
foramen or 3 to 4mm from the spinal canal. Volumetric
measurements could also be made allowing repeated measurements under various conditions.
We investigated the effects of flexion with and without
traction at C5-C6 in cadaver spines, the level most commonly
involved in cervical radiculopathy.15 Traction weight must be
great enough to overcome friction of the head and body on the
traction table and the dynamic state of the patient and tissues.16,17Only then will it lead to anatomic changes. In the
current study, the dynamic state of the patient tissues was not
taken into account. Traction is also limited by the development
of pain, radicular symptoms, or constitutional changes in the
patient. Judovichls found that at least 251bs was needed to
change posterior cervical spine elements, Jackson19 showed
that distraction was produced with 20 to 251bs., and Colachis
and Strohm1,s,20used 301bsin their in their experiments. Others
Arch
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Rehabil
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79, September
1998
ON FORAMEN,
Humphreys
found that 1201bsof traction was needed to cause disc rupture at
C5-C6.21 Therefore, we chose 251bs as a reasonable amount
both clinically and experimentally.
The cervical spine in its neutral position assumes a lordotic
curve. This is due to the greater height of the intervertebral disc
anteriorly. Using the Cobb angle, the normal neutral position is
10 to 15” of lordosis. The normal range of motion has been
determined to be 35” of flexion and 26” of hyperextension,20
which is consistent with Holmes and coworkers,22 who found a
total range of motion of 60” to 70”. They discuss other studies
showing slightly larger ranges (SO’ to 90”) using different
methods of angular assessment,which if taken into account are
not inconsistent with their results. Thus, using the Cobb angle,
normal range of motion is 35” to 50” of lordosis to 20” to 30” of
kyphosis. Crue23 studied foraminal height using plain radiographs and no traction and showed that llexion increases
foraminal height. Yoo and associates showed this fact in
cadaver specimens by inserting calibrated cylindrical probes
into the cervical foramen. Compared with foraminal diameter in
the neutral position, he showed statistically significant reductions in foraminal diameter of 10% and 13% at 20” and 30” of
extension, respectively. Conversely, in flexion there was a
statistically significant increase of 8% and 20% at 20” and 30”
of flexion, respectively. This is easily confirmed and universally
accepted and is primarily due to intervertebral separation
posteriorly, which also increased with traction. As discussed
earlier, this two-dimensional view, though helpful, may be
incomplete. The degree of foraminal narrowing on plain
radiographs correlates poorly with electromyographic and
clinical findings, as well as with myelographic findings. Duration of traction is dependent on method of traction used, but it
must allow for optimal anatomic change. Collachis and
Strohm,1,s,20using intermittent traction and human subjects,
showed that 301bs of traction for 7 seconds produced separation
of the vertebral interspace. No significant difference in separation was noted at 7, 30, and 60 seconds, and the maximal mean
separation took place at 25 minutes with minimal anterior
residual separation 20 minutes after traction was removed.
Therefore, we allowed an interval of 30 minutes between the
application of a load and foraminal space.
This study used fresh frozen cadaveric spine specimens
without the cranium and spine musculature. As such, the role of
the spinal musculature was not assessed.
Traction may play a role in neutralizing the weight of the
head and in alleviating spasm in the paravertebral and cranial
muscles. Smith14 found that foraminal measurements from
reformatted three-dimensional CT images underestimated true
foraminal measurements as measured by calipers. However,
this is not likely to affect the conclusions of this study on the
relative effects of flexion and traction on the foraminal space.
Maximal flexion as defined in our study may not be tolerated
well by patients and may be impractical as a treatment option.
Our results supported the use of flexion with or without 251bs
of traction to increase the foraminal volume and the crosssectional area at the isthmus of the foramen. In our trials with
flexion at 15” and at maximal flexion, traction provided little
additional benefit. Traction in the neutral position, however, did
provide some degree of foraminal enlargement in both volume
and isthmus area. The initial enlargement with traction alone
likely represents the limit of elastic deformation by the soft
tissues. The enlargement of the foramen with 15” of llexion and
maximum flexion represents the posterior aspect of the superior
vertebra as it is distracted away from the inferior vertebra. The
small subsequent area and volume added by traction in flexion
indicates that flexion pretensions the posterior soft tissues. A
EFFECTS
OF FLEXION
AND
TRACTION
limitation of this study was that it used a static model without
spinal musculature. It is possible that in the dynamic model
traction may alleviate symptoms, including muscle spasms.
Cervical neural impingement is a significant clinical problem
with disability requiring treatment. Controversy exists as to
treatment method. This cadaveric study indicates that Aexion
plays a dominant role in increasing foratninal volume and area,
with little additive effect of traction.
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Suppliers
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1998