Transverse Process and Needles of Medial Branch Block to Facet Joint as Landmarks for Ultrasound-Guided Selective Nerve Root Block

Abstract

Selective lumbar nerve root block (SNRB) is generally accepted as an effective treatment method for back pain with sciatica. However, it requires devices producing radioactive materials such as C-arm fluoroscopy. This study evaluated the usefulness of the longitudinal view of transverse process and needles for medial branch block as landmarks under ultrasonography.
We performed selective nerve root block for 96 nerve roots in 61 patients under the guidance of ultrasound. A curved probe was used to identify the facet joints and transverse processes. Identifying the lumbar nerve roots under the skin surface and ultrasound landmarks, the cephalad and caudal medial branch blocks were undertaken under the transverse view of sonogram first. A needle for nerve root block was inserted between the two transverse processes under longitudinal view, while estimating the depth with the needle for medial branch block. We then injected 1.0 mL of contrast medium and checked the distribution of the nerve root with C-arm fluoroscopy to evaluate the accuracy. The visual analog scale (VAS) was used to access the clinical results.
Seven SNRBs were performed for the L2 nerve root, 15 for L3, 49 for L4, and 25 for L5, respectively. Eighty-six SNRBs (89.5%) showed successful positioning of the needles. We failed in the following cases: 1 case for the L2 nerve root; 2 for L3; 3 for L4; and 4 for L5. The failed needles were positioned at wrong leveled segments in 4 cases and inappropriate place in 6 cases. VAS was improved from 7.6 ± 0.6 to 3.5 ± 1.3 after the procedure.
For SNRB in lumbar spine, the transverse processes under longitudinal view as the ultrasound landmark and the needles of medial branch block to the facet joint can be a promising guidance.

Full text

Transverse Process and Needles of Medial Branch
Block to Facet Joint as Landmarks for Ultrasound-
Guided Selective Nerve Root Block
Daehee Kim, MD, Donghyuk Choi, MD, Chungyoung Kim, MD,
Jeongseok Kim, MD, Yongsoo Choi, MD
Department of Orthopaedic Surgery, Kwangju Christian Hospital, Gwangju, Korea
Original Article
Clinics in Orthopedic Surgery 2013;5:44-48 • http://dx.doi.org/10.4055/cios.2013.5.1.44
Received July 7, 2012; Accepted August 17, 2012
Correspondence to: Yongsoo Choi, MD
Department of Orthopedic Surgery, Kwangju Christian Hospital, 30
Yangrim-ro, Nam-gu, Gwangju 503-715, Korea
Tel: +82-62-650-5064, Fax: +82-62-650-5066
E-mail: stemcellchoi@hanmail.net
Selective nerve root block (SNRB) has a therapeutic po-
tential for lower back pain accompanied by sciatica, and
many studies have reported good results.
1,2)
Furthermore,
SNRB can help to confirm the surgical level and range
before the operation as a diagnostic tool. It also alleviates
pain effectively to delay the operation. However, the tra-
ditional method, using computed tomography (CT) or C-
Background: Selective lumbar nerve root block (SNRB) is generally accepted as an effective treatment method for back pain with
sciatica. However, it requires devices producing radioactive materials such as C-arm fluoroscopy. This study evaluated the useful-
ness of the longitudinal view of transverse process and needles for medial branch block as landmarks under ultrasonography.
Methods: We performed selective nerve root block for 96 nerve roots in 61 patients under the guidance of ultrasound. A curved
probe was used to identify the facet joints and transverse processes. Identifying the lumbar nerve roots under the skin surface and
ultrasound landmarks, the cephalad and caudal medial branch blocks were undertaken under the transverse view of sonogram first.
A needle for nerve root block was inserted between the two transverse processes under longitudinal view, while estimating the
depth with the needle for medial branch block. We then injected 1.0 mL of contrast medium and checked the distribution of the
nerve root with C-arm fluoroscopy to evaluate the accuracy. The visual analog scale (VAS) was used to access the clinical results.
Results: Seven SNRBs were performed for the L2 nerve root, 15 for L3, 49 for L4, and 25 for L5, respectively. Eighty-six SNRBs
(89.5%) showed successful positioning of the needles. We failed in the following cases: 1 case for the L2 nerve root; 2 for L3; 3
for L4; and 4 for L5. The failed needles were positioned at wrong leveled segments in 4 cases and inappropriate place in 6 cases.
VAS was improved from 7.6 ± 0.6 to 3.5 ± 1.3 after the procedure.
Conclusions: For SNRB in lumbar spine, the transverse processes under longitudinal view as the ultrasound landmark and the
needles of medial branch block to the facet joint can be a promising guidance.
Keywords: Lumbar spine, Spinal injections, Ultrasound
arm fluoroscopy as a guidance, is not free from exposure
to radiation. Also, the space required for the devices is not
always available in the outpatient departments. Recently,
the ultrasound guided SNRB has been introduced to over-
come these disadvantage, so as to be applied easily in the
outpatient department.
3,4)
However, its application is re-
stricted due to the more difficult anatomical assessment to
nerve roots as compared to the facet joint block. Regarding
this limitation, we have attempted an ultrasound guided
selective lumbar nerve root block. We evaluated the use-
fulness of longitudinal view of the transverse process and
needles of medial branch block to facet joint as landmarks
under ultrasonography.
Copyright ©
2013 by e Korean Orthopaedic Association
is is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0)
which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Clinics in Orthopedic Surgery
•
pISSN 2005-291X eISSN 2005-4408

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Kim et al. Landmarks for Ultrasound-Guided Selective Nerve Root Block
Clinics in Orthopedic Surgery
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Vol. 5, No. 1, 2013
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METHODS
The patients had visited our hospital for chronic lower
back pain and radiating pain to the leg, from September
2010 to February 2011. They were diagnosed lumbar
spinal stenosis, based on the medical history, physical
examination, radiography, magnetic resonance imaging
(MRI) or CT. Sixty-one patients showed no satisfactory
improvement of symptoms following medication, physi-
cal therapy, and rehabilitation programs for more than 6
weeks. Ultrasound-guided selective nerve root block was
done in 96 nerve roots for 61 patients. There were 26 male
and 35 female. The mean age of the patients was 60.4 years
(range, 35 to 83 years). They were selected for the lumbar
nerve root for nerve block, based on clinical symptoms
and radiological pathology, including foraminal stenosis
on MRI or CT. During the procedure, the patients were
in the prone position, and the lumbar lordotic curve was
countervailed. A surface landmark of the spinous process,
iliac crest line, and needle target points were marked using
anteroposterior lumbar radiograph after the spinous pro-
cess, and the posterior iliac crest line of patients were pal-
pated (Fig. 1). To develop the necessary ultrasound views,
the spinous processes were first examined under high-
resolution ultrasound with 5-MHz curved transducer
(LogiQ P5, GE Medical Systems, Milwaukee, WI, USA).
Ultrasound-guided identification of the desired segment
for nerve block was not described exactly, in contrast to
C-arm fluoroscopy. Longitudinal facet views were ob-
tained by curved tranducer to identify the different spinal
segments (Fig. 2). The physicians were well aware of the
anatomical landmark of the lateral facet and the transverse
process for pedicle screw placement in the lumbar spine.
The facet joint is a useful ultrasonic landmark for the iden-
tification of anatomical level. We identified the target level
by counting up the facet joint from the lumbosacral facet
joint or counting down from the twelfth rib. After finding
the location of the desired target level, the transverse axial
images were obtained by rotating the probe 90 degrees.
The spinous process, facet joint, and transverse process
were delineated by transverse sonograms at each level.
The target point for the medial branch block was defined
as on the upper edge of the transverse process. Confirm-
ing lumbar nerve roots under the surface and ultrasound
Fig. 1. (A) Distance from the spinous
process to the needle target point was
measured on the radiograph. (B) Surface
landmarks such as spinous process,
iliac crest, and needle target point were
marked.
Fig. 2. (A) Longitudinal facet views were
obtained by curved transducer to identify
the different spinal segments. (B) The
longitudinal facet view shows L3-4, L4-5,
and L5-S1 facet joints.

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landmarks, the cephalad and caudal medial branch block
to the nerve root was undertaken in the transverse view
of sonogram, using 21 gauge needle. The needle for the
medial branch block was inserted approximately 30 de-
grees to the skin and exactly in line with the transducer
and echo plane as short axis in plane approach (Fig. 3). A
needle of length equal to that for medial branch block was
inserted for SNRB, between the two transverse processes
under longitudinal view. The angle of the needles was the
same for medial branch block as short axis out of plane ap-
proach (Fig. 4). At this point we estimated the depth of the
needle for SNRB, comparing with the needles for medial
branch block, and we inserted the needle 10 mm deeper
than medial branch block. Then we injected 1 mL contrast
medium and evaluated the position of the needles and dis-
tribution of the contrast medium with C-arm fluoroscopy
(Fig. 5). We used a mixture of 1 mL of 2% lidocaine and
1 mL of triamcinolone acetate (40 mg/mL). The clinical
assessment was performed by visual analog scale (VAS)
at one to three days after the procedure at the outpatient
Fig. 3. (A) Medial branch block to the facet
joint was performed on the transverse
view as short axis in plane approach. (B)
The needle is targeted just lateral to the
facet joint. SP: spinous process, FJ: facet
joint, TP: transverse process.
Fig. 4. (A) The needle for selective nerve root (NR) block was inserted at the same angle with the needle for medial branch block as short axis out of
plane approach. (B) The NRs are seen just caudal to the each transverse process (TP) and the needle is approaching the L3 NR.
Fig. 5. The position of the needles and distribution of the contrast medi-
um were evaluated with C-arm fluoroscopy. The two arrows indicate
needles for medial branch block and the two arrowheads for selective
nerve root block.

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Kim et al. Landmarks for Ultrasound-Guided Selective Nerve Root Block
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clinic. Independent
t
-tests were used to compare between
pre- and postoperative VAS. Statistical analysis was carried
out using SPSS ver. 12.0 (SPSS Inc., Chicago, IL, USA).
Significance was set at
p
< 0.05.
RESULTS
Seven SNRBs were performed at the L2 nerve root (fora-
men between the L2 and L3), 15 at the L3, 49 at the L4,
and 25 at the L5, respectively. Of total 96 needles, 86 SN-
RBs (89.5%) showed successful positioning of the needles.
We failed one case at the L2-3 level, and 2 at L3-4, 3 at L4-
5, and 4 at L5-S1. The failed needles were positioned in
wrong leveled segments in 4 cases and inappropriate place
in 6 cases. VAS was improved from 7.6 ± 0.6 to 3.5 ± 1.3
after the procedure (
p
= 0.001). Before injecting the mix-
ture of medicine, we corrected the wrong-positioned nee-
dles to the appropriate places under C-arm fluoroscopy.
We had all patients rest in the recovery room for an hour
before leaving the hospital. No case showed any complica-
tion such as aggravation of the pain, numbness, headache,
dizziness, and allergic reaction.
DISCUSSION
The use of ultrasonography has recently been increasing
in musculoskeletal intervention treatment.
4-6)
However,
there are some limitations in using ultrasound for SNRB.
The most challenging part in the use of ultrasound is in
placing the needle in the exact position and estimating
the depth of the nerve roots. Loizides et al.
7)
reported that
all 10 needles were correctly placed using costal process
and inter-transverse ligament as landmarks by in-plane
method in their cadaveric study. However, it is not easy to
obtain inter-transverse ligament clearly in practical situa-
tions. Chumnanvej et al.
8)
reported that successful needle
position under ultrasound was resulted in 63% for SNRB.
But they did not mention the approaching method of the
needle, and reported that facet echo edge was identified
by ultrasound. It is not easy to have a clear view for facet
echo edge in all patients, and it is more difficult to place
the needle tip at the facet echo edge under ultrasound. We
think this is the reason for their low success rate of 63%.
In order to overcome this limitation, we undertook the
SNRB on the longitudinal ultrasound view for short axis
out of plane approach. This could show both the caudal
and cephalad transverse processes at one plane, and it
was easier to apprehend the structural correlation during
the procedure than transverse view. Additionally, prior to
SNRB, we performed medial branch block as the needle
for another guide. We took the same length of needle for
SNRB and medial branch block, and inserted the needle
for SNRB at the same angle (approximately 30°) of the
needle for medial branch block. Preoperatively, we mea-
sured the distance from the basal portion of the transverse
process to posterior margin of the vertebral disc on mag-
netic resonance imaging; and the mean distance was 5.7
± 1.6 cm. We could estimate the depth of the needle com-
paring the head of the needles. The needle for SNRB was
inserted deeper by 5 to 10 mm than medial branch block.
To make a decision for the final depth of the needle, it is
possible to get an image for motion echo of final needle tip
in ultrasound by a small movement of the needle tip.
Most previous studies which performed ultrasound
guided SNRB assumed successful positioning of the
needle depending on whether the symptoms were relieved
or not.
9)
The relief of symptoms could be obtained by sys-
temic drug effect even if the needle was not placed at the
appropriate position, leading to inadequate estimation of
the accuracy. Hence, we evaluated the accuracy by check-
ing the placement of the needle and distribution of the
contrast medium, especially the tip, with C-arm fluorosco-
py after injecting contrast medium under ultrasonic view.
Eighty-six roots (89.5%) could be guided successfully for
SNRB by ultrasound.
In comparison with CT or C-arm fluoroscopy, ul-
trasonography newly draws attentions for some of its ad-
vantages. First, there is no exposure to radiation. Although
the radiation dose during the nerve block by CT or C-arm
fluoroscopy for single procedure is ignorable, the physi-
cians are repeatedly exposed to radiation during many
procedures besides C-arm fluoroscopy, including nerve
blocks. Thus when the total radiation dose for one year is
examined, the level is of a concern. It can be argued that
the hand region of orthopedic surgeons who use the irra-
diator may be excessively damaged by the radiation.
10)
Lee
et al.
11)
reported on a hand lesion that was damaged due to
radiation in Korea. The second advantage is that the ad-
ditional equipments necessary for the protection against
radiation are not required; and with the small size of the
equipment which easily movable, the procedure can be
performed in outpatient clinics.
Despite such advantages, the acoustic impedance of
bone is high, and thus it has limitations in taking a good
quality image of spinal structures. In addition, the repro-
ducibility among doctors is low.
12)
These drawbacks may
be overcome with practice and further development of
ultrasound equipment in the future.
In conclusion, the transverse processes under lon-
gitudinal view as ultrasound landmark and the needles of

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Kim et al. Landmarks for Ultrasound-Guided Selective Nerve Root Block
Clinics in Orthopedic Surgery
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Vol. 5, No. 1, 2013
•
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medial branch block to the facet joint can be a promising
guidance for SNRB in lumbar spine. It can be performed
with 89.5% effectiveness, and we expect it to be performed
in the outpatient departments without the concern for the
radiation exposure.
CONFLICT OF INTEREST
No potential conflict of interest relevant to this article was
reported.
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