Minimally Invasive Multilevel Percutaneous Pedicle Screw Fixation for Lumbar Spinal Diseases

Abstract

There are rare reports on the result of multilevel (≥3 levels) percutaneous pedicle screw fixation (PPF). The purpose of this study was to report the clinical experiences for multilevel PPF of the lumbar spine.
A total of 17 patients of lumbar spinal disease (7 degenerative diseases, 6 infectious diseases, and 4 traumatic instabilities) underwent neural decompression and multilevel PPF. There were 8 men and 9 women with a mean age of 61.4 years (range, 25-84) and a mean follow-up period of 23.2 months (range, 13-48). The average PPF level was 3.7. A retrospective review of clinical, radiological, and surgical data was conducted.
"Excellent" or "good" clinical results were obtained in 15 patients (88.2%) according to the Odom's criteria. The average improvement of visual analogue scale was 5.2 points (from 9.3 to 4.1), and the average improvement of Oswestry Disability Index was 36.2 (from 71.2 to 35.0) at the last visit (p<0.05). The fusion rate was 88.2%, but, screw loosening was occurred in 2 patients, and adjacent segmental degeneration was occurred in 2 patients. There was no statistical significance in the change of total lumbar lordotic angle. The average operation time was 5.9 hours, with an estimated blood loss of 550 ml and bed rest duration of 2.0 days.
Although the current study examined a small sample with relatively short term follow up periods, our study results demonstrate that multilevel PPF is feasible and safe for selective lumbar spinal diseases.

Full text

CLINICAL ARTICLE
pISSN 1738-2262/eISSN 2093-6729
Korean J Spine 9(4):352-357, 2012
www.e-kjs.org
352
Copyright
© 2012 The Korean Spinal Neurosurgery Society
Minimally Invasive Multilevel Percutaneous Pedicle
Screw Fixation for Lumbar Spinal Diseases
Seong Son, Sang Gu Lee, Chan Woo Park, Woo Kyung Kim
Department of Neurosurgery, Gachon University, Gil Hospital, Incheon, Republic of Korea
Objective: There are rare reports on the result of multilevel (
≥
3 levels) percutaneous pedicle screw fixation (PPF). The pur-
pose of this study was to report the clinical experiences for multilevel PPF of the lumbar spine.
Methods: A total of 17 patients of lumbar spinal disease (7 degenerative diseases, 6 infectious diseases, and 4 traumatic
instabilities) underwent neural decompression and multilevel PPF. There were 8 men and 9 women with a mean age of
61.4 years (range, 25-84) and a mean follow-up period of 23.2 months (range, 13-48). The average PPF level was 3.7. A retro-
spective review of clinical, radiological, and surgical data was conducted.
Results: “Excellent” or “good” clinical results were obtained in 15 patients (88.2%) according to the Odom’s criteria. The
average improvement of visual analogue scale was 5.2 points (from 9.3 to 4.1), and the average improvement of Oswestry
Disability Index was 36.2 (from 71.2 to 35.0) at the last visit (p<0.05). The fusion rate was 88.2%, but, screw loosening was
occurred in 2 patients, and adjacent segmental degeneration was occurred in 2 patients. There was no statistical significance
in the change of total lumbar lordotic angle. The average operation time was 5.9 hours, with an estimated blood loss of 550
ml and bed rest duration of 2.0 days.
Conclusion: Although the current study examined a small sample with relatively short term follow up periods, our study results
demonstrate that multilevel PPF is feasible and safe for selective lumbar spinal diseases.
Key Words: Spinal fusion
ㆍ
Lumbar vertebrae
ㆍ
Bone screw
●
Received: November 12, 2012
●
Revised: December 18, 2012
●
Accepted: December 24, 2012
Corresponding Author: Sang Gu Lee, MD, PhD
Department of Neurosurgery, Gil Hospital, 1198 block, Guweol-Dong,
Namdong-Gu, Incheon 405-220, Republic of Korea
Tel: +82-32-460-3304, Fax: +82-32-460-3899
Email: samddal@gilhospital.com
INTRODUCTION
Minimally invasive spine surgery may allow for surgery of
the lumbar spine with considerably less blood loss and soft tis-
sue damage. Recently, to reduce the adverse effect of the open
technique of pedicle screw, the percutaneous pedicle screw fixa-
tion (PPF) is becoming more widespread in spinal surgery. Many
studies about PPF have been reported, but still, there are rare
reports about the result of multilevel (≥3 levels) PPF
4,10,12,18)
.
This study analyzed the clinical, radiological, and surgical results
of the multilevel PPF in various lumbar spinal diseases.
MATERIALS AND METHODS
1. Patient population
From March 2008 to April 2011, a total of 17 patients of
lumbar spinal disease underwent neural decompression, inter-
body fusion and multilevel PPF by one neurosurgeon. There were
8 men and 9 women with a mean age of 61.4 years (range, 25-
84) and a mean follow-up period of 23.2 months (range, 18-43).
Below is a group list of our indications for the procedure.
1) Multilevel degenerative diseases such as spinal stenosis,
spondylolisthesis (Grade I), or instability with symptoms refra-
ctory to conservative treatment.
2) Severe bone destruction with a spinal cord compression
or a nerve root compression due to infectious diseases such
as tuberculous spondylitis or pyogenic spondylitis.
3) Spinal instability with a spinal cord compression or a nerve
root compression due to trauma.
Out of 17 patients, 7 patients were degenerative diseases (5
spinal stenosis with instability, 2 spondylolisthesis), 6 patients
were infectious diseases (4 pyogenic spondylitis, 2 tuberculous
spondylitis) and 4 patients were burst fractures with thecal
sac compression and instability (Table 1). The patients, with
excessive spondylolisthesis or severe spinal deformity such as
scoliosis, kyphosis, and rotational deformity, were excluded
from PPF procedure.
2. Procedures and instruments
We performed neural decompression and interbody fusion

Multilevel percutaneous pedicle screw fixation
Korean J Spine 9(4) December 2012
353
Table 1. Summary of patients’ data patients’ data
Case Sex Age Diagnosis Decompression (levels) PPF levels
Degenerative
disease
1 F 70 Stenosis with instability L2‐5 LN
*
(1), PLIF
†
(2) 3
2 M 61 Stenosis with instability L1‐4LN(1), PLIF(1) 3
3 F 61 Stenosis with instability L2‐5LN(2), PLIF(1) 4
4 M 53 Stenosis with instability L2‐5LN(1), pLIF(2) 3
5 F 69 Stenosis with instability L3‐S1 LN (1), PLIF 2 3
6 F 55 Stenosis and spondylolisthesis L2‐5PLIF(3) 3
7 M 84 Stenosis and spondylolisthesis L2‐5PLIF(3) 5
Infectious
disease
8 M 70 Pyogenic spondylitis L2‐3LN(1), PLIF(2)4
9 M 71 Pyogenic spondylitis L3‐5Ant Co
‡
(3) 5
10 M 25 Tuberculous spondylitis L2‐3 Ant Co (2) 3
11 F 76 Tuberculous spondylitis T12‐L1 Post Cu (3) 6
12 M 69 Pyogenic spondylitis L1‐2Post Cu(2) 3
13 M 49 Pyogenic spondylitis L4‐5PLIF(1) 3
Traumatic
instability
14 F 67 Instability with cord injury T12‐L2 LN (2), Post Cu
§
(2) 5
15 F 57 Instability with cord injury L1‐2Ant Co(2) 4
16 F 60 Instability with cord injury L1‐2LN(1), Post Cu(1) 3
17 F 47 Instability with cord injury T12‐L1 LN (1), Post Cu (1) 3
Mean 61.4 3.7
*
LN=laminectomy and foraminotomy,
†
PLIF=posterior lumbar interbody fusion,
‡
Ant Co=anterior corpectomy and interbody fusion,
§
Post Cu=posterior curettage and interbody fusion
first. The posterior lumbar terbody fusion (PLIF) with face-
ctectomy via midline incision was performed in 9 patients,
the posterior lumbar currettage and interbody fusion in 5 pa-
tients, and the anterior lumbar corpectomy and interbody fu-
sion in 3 patients. Allograft iliac bone, mesh cage containing
allograft bone chips, or polyetheretherketone (PEEK) cage con-
taining allograft bone chips were used in interbody fusion.
And then, multilevel PPF was performed in prone position
using CD Horizon
®
Longitude
®
(Medtronic Sofamor Danek,
Memphis, TN,USA), CD Horizon
®
Sextant
®
II (Medtronic Sofa-
mor Danek, Memphis, TN, USA), Viper
®
II (DePuy Spine,
Raynham, MA, USA), or AnyPlus
®
(GS Spine, Santa Cruz, CA,
USA). The screws were placed percutaneously using fluoro-
scopic guidance. The cannulated screws, which were inserted
over a guide wire, had extenders attached to them, which had
a slot to receive the rod. Since the entry point of screw inser-
tion in the middle pedicle is most important for alignment of
spine, the insertion of screw in the middle pedicle was carried
out lastly.
The slot was large enough in the unreduced position to
accept a rod that was passed again percutaneously. The rod
is contoured according to the sagittal contour desired and then
passed free hand through the slots under direct fluoroscopic
control. Once the rod is appropriately positioned through all
the screw extender slots, the extender is reduced to seat the
rod into the tulip of the screw head. Once reduced, the top
locking nut is inserted to fix the rod to the screw starting
from the caudal screw and working proximally in sequential
fashion. Once all the nuts are in place, the extender is unsea-
ted and detached from the screw. Compression or distraction
can be applied to the extenders as desired, to gain further
correction.
The average PPF level was 3.7 (range, 3-6).
3. Outcome parameters
A retrospective review of clinical, radiological, and surgical
data was conducted.
Of the back pain or leg pain, the severity of main symptom
was recorded using visual analog scale (VAS). Functional out-
comes were measured using the Oswestry Disability Index
(ODI) scores, and patient’s satisfactions were recorded using
Odom’s criteria during follow-up period.
For radiological evaluation, we examined the dynamic X-
rays, magnetic resonance imaging (MRI), and computed to-
mography (CT) prior to surgery, and also, the dynamic X-rays
and CT consecutively during follow-up period.
The accuracy of screw position was analyzed by immediate
postoperative CT. In CT scan, screw perforation of any aspects
of cortex was checked, and when all parts that constitute the

S Son, et al.
354 www.e-kjs.org
Fig. 1. The sagittal angle measurement by Cobb’s angle method
on plain X-ray. The adjacent segmental angle (ASA) was measu-
red as total sum of intervertebral angles between flexion and
extension lateral radiographs (A). To measure it, line along the end
plate of adjacent vertebra body and line along the end plate
of the most superior or inferior fused vertebra body were drawn.
The total lumbar lordotic angle (TLA) was defined as the angle
subtended by the superior end plate line of L1 and the superio
r
end plate line of S1 (B).
Table 2. Description of fusion result by Brantigan and Steffee
Grade 1 Obvious collapse of construct due to pseudoarthrosis, loss of disc height, vertebral slip, broken screws, displacement of the
cage, resorption of bone graft
Grade 2 Probable significant resorption of the bone graft due to pseudoarthrosis, major lucency, or gap visible in fusion area (2 mm
around the entire periphery of graft)
Grade 3 Uncertain non‐union, bone graft visible in the fusion area at approximately the density originally achieved at surgery.
A
small lucency or gap may be visible involving a portion of the fusion area with at least half of the graft area.
Grade 4 Probable fusion bone bridges entire fusion area with at least the density achieved at surgery. There should be no lucency
between the donor and vertebral bone.
Grade 5 Fusion bone in the fusion area is radiographically more dense and mature than originally achieved by surgery. Optimally,
there is no interface between the donor bone and the vertebral bone, although a sclerotic line between the fusion area, resorption
of the anterior traction spur, anterior progression of the graft within disc space, and fusion of facet joints.
screw were located in pedicle and vertebral cortex, it was
considered as screw accurately inserted.
To evaluate sagittal alignment, total lumbar lordotic angle
(TLA) was measured on lateral radiograph in neutral position,
and adjacent segmental angle (ASA) was measured on flexion-
extension view (Fig. 1). We defined definite change of ASA
on the standing lateral film as sagittal translation of the ad-
jacent vertebral body above fused level greater than 3 mm
and/or ASA greater than 10 degrees
19)
. TLA and ASA were
checked at the preoperative period, 1 month after the oper-
ation, 6 months after the operation, and the last follow-up.
The bony fusion rate of interbody fusion and screw failure
such as fracture or loosening were evaluated by dynamic X-
rays and CT during follow-up period. The degree of bone fu-
sion was based on the classification of Brantigan and Steffee
2)
(Table 2), and we regarded Grade 4 or 5 as a state of bone
fusion. The screw loosening was confirmed when we observed
more than 1 mm thick radiolucent zone (halo sign) around
screw on plain radiographs. Also, we have identified the devel-
opment of the late postoperative complications such as in-
stability and instrument failure.
Surgical outcomes were evaluated by checking the opera-
tion time, estimated blood loss (EBL), duration of postopera-
tive bed rest and length of hospital stay. The occurrence of
perioperative morbidities such as neurologic deterioration,
cerebrospinal fluid (CSF) leakage, wound infection, pneumo-
nia, heart problem, urinary difficulty, epidural hematoma, and
deep vein thrombosis were checked. Also, we tracked the fre-
quency of reoperation.
4. Statistical methods
For statistical analysis, paired samples t test was conducted
using SPSS software (version 17.0, SPSS Inc, Chicago, IL, USA).
A probability value of less than 0.05 was considered significant.
RESULTS
1. Clinical outcomes
The mean VAS score at the 1 month after the surgery 6.7
(range, 5-9) was significantly lower than the preoperative score,
9.3 (range, 9-10). The mean VAS score decreased at each follow-
up evaluation and was significantly lower at the last follow-up
4.1 (range, 2-5) compared with the preoperative score (Fig. 2).
The mean ODI score also improved from 71.2 (range, 67-

Multilevel percutaneous pedicle screw fixation
Korean J Spine 9(4) December 2012
355
Fig. 2. Graph showing visual anolog scale (VAS) before the sur-
gery and during the follow-up period. The mean improvement
of VAS from the pre-operation to the last follow-up was 5.2
points (from 9.3 to 4.1) (p<0.05). Months 1, 6, 12 and the las
t
follow- up are represented on the X axis. The Y axis represents
the score.
Fig. 3. Graph showing Oswestry Disability Index (ODI) before th
e
surgery and during the follow-up period. The mean improve-
ment of ODI from the pre-operation to the last follow-up was
36.2 (from 71.2 to 35.0) (p<0.05). Months 1, 6, 12 and the las
t
follow-up are represented on the X axis. The Y axis represents
the score.
Fig. 4. The number of patients according to Odom’s criteria a
t
the 6 months after surgery and at the last follow-up. The Y axis
represents the number of patients.
81) preoperatively to 38.0 (range, 29-61) at the last follow-up
(Fig. 3). Both VAS and ODI score improved after the surgery
and the improvement maintained during the follow-up period
with statistical significance (p<0.05).
According to the Odom’s criteria, the results were excellent
in 6 patients (35.3%), good in 7 patients (41.2%), and fair in
4 patients (23.5%) at the 6-month follow-up, and excellent in
7 patients (41.2%), good in 8 patients (47.0%), and fair in 2
patients (11.8%) at the last follow-up. Therefore, the clinical
success rate according to the Odom’s criteria was 88.2%(Fig. 4).
2. Radiological outcomes
In all the patients, by CT scan immediately after the surgery,
the cases of screw malposition were 6 (4.1%) out of 146 screws.
However, there was no occurrence of neurological deficit or
vascular complications, and also no need of screw correction.
The mean TLA increased from 34.7° before the surgery
to 38.0° at the 1 month after the surgery, however, decreased
to 35.9° at the last follow-up. The mean ASA was 5.7° at pre-
operation and 7.0° at the last follow-up. The mean ASA of the
caudal adjacent segment was 5.6° at pre-operation and 5.3°
at the last follow-up. There was no statistical significance in
the changes of the TLA and ASA. Only 2 patients (11.8%) sho-
wed definite change of ASA of cranial adjacent segment, and
all of them were asymptomatic.
During follow-up period, there were bony fusions in 15
patients out of 17 patients who underwent interbody fusion,
and thus fusion rate was 88.2%. On the other hand, there
were screw loosening in 2 patients, but there was no pull-out
or fracture of screw. Among 2 patients of screw loosening,
1 patient showed progressive lumbar kyphotic change without
aggravation of symptom, and 1 patient showed instrument
related infection and underwent removal of screw at 1 year
after the surgery.
3. Surgical outcomes
The mean operation time was 5.9 hours (range, 5.0-9.5),
EBL was 550 ml (range, 300-1,500) with need of average 1.2
packs (range, 0-4) of transfusion, and duration of bed rest
was 2.0 days (range, 1-4). The mean length of hospital stay
was 26.4 days (range, 8-59), which was longer period than
expected, maybe due to long-term antibiotic therapy for infe-
ctious patients. Except for 6 infectious patients, mean length
of hospital stay was 13.6 days (range, 8-22).
Fortunately, there was no major perioperative morbidity
except for a single case of reoperation for resolving hemoper-
itoneum in patient who underwent anterior corpectomy and
fusion.

S Son, et al.
356 www.e-kjs.org
DISCUSSION
The pedicle screw fixation has been used as a universal
spinal fusion surgery method for many spinal disorders. Stan-
dard open technique for pedicle screw fixation, however, has
been associated with several disadvantages. During the open
technique, extensive tissue dissection and longtime retraction
are inevitable to expose entry points of screw and to provide
orientation of lateral to medial for optimal screw trajectory.
The excessive retraction of muscle can cause ischemic damage
and permanent pathological changes of the muscle
7,8,20,21)
.
Already, some authors reported that the degree of damage of
muscles and back pain after surgery were proportionate to
the size and time of retraction during surgery
5,17)
. In addition,
extensive dissection of paraspinal muscle can cause excessive
blood loss and necrosis of tissue, which can be said to increase
the need for transfusion and the chance of postoperative infe-
ction
20)
. Such problems cause longer bed rest duration, lengthy
hospital stay, and significant cost
22)
. Moreover, some authors
have suggested that the open technique can cause adjacent
segment degeneration due to extensive dissection of paraspi-
nal muscle or iatrogenic injury of facet joint
14,19)
.
As these problems become important matter, recently, mini-
mally invasive PPF was introduced and developed. PPF uses
small muscle splitting approach to allow placement of hard-
ware under fluoroscopic guidance. This technique permits ac-
curate hardware placement while avoiding adverse effects of
open technique. Based on this concept, many authors have
reported about advantages of single- or two-level PPF such
as shorter operative time, less paraspinal muscle damage, less
need for postoperative oral analgesics, and lower blood loss
than open technique
9,13)
. For multilevel (more than 3 levels)
PPF, the longer the length of rod is more difficult to insert, and
adjusting alignment of pedicle is difficult. However, recently,
with introduction of new instruments, multilevel PPF method
that can do a wide range of spinal fusion was developed. Multi-
level PPF has usually been carried out for degenerative sco-
liosis patients1, but it is still not widely carried out yet, and so
the clinical result of the operation method are not known well.
The results of the author’s present study demonstrated favo-
rable clinical and radiological outcomes. In the current study,
with regard to patient’s symptom and satisfaction, improve-
ment of clinical outcomes such as VAS and ODI were signifi-
cant. Also, radiological outcomes including rate of screw mal-
position (4.1%), fusion rate (88.2%), occurrence of definite
change of ASA (11.8%), and occurrence of screw looseing (11.8
%) were satisfactory. Although it is difficult to compare our
results with the other studies because there are many factors
affecting outcomes, such as the patient’s medical condition,
surgeon’s experience, surgical indication, surgical method, and
outcome assessment criteria, the outcomes in the present study
are comparable to other reports
11,23)
.
Multilevel lumbar fusion surgery is needed for multilevel
decompression and spinal stability. However, in some special
cases, the choice of multilevel fusion is cautious. For example,
elderly patients may be at increased risk of surgical morbidities
such as pneumonia, cardiovascular event, or wound infection.
Also, the patients with medical comorbidities such as cardio-
vascular disease, renal disease, and diabetes may represent a
significant challenge for surgery. The open technique for multi-
level fusion, which has the disadvantage of increased operative
time and blood loss, may not be tolerated in these elderly
patients with poor preoperative general conditions. However,
multilevel PPF can be tolerable in even these patients. Com-
pared to the literature
6,16)
, based on surgical outcomes of cur-
rent study, we can demonstrate multilevel PPF to be techni-
cally feasible, to be accomplished within tolerable operative
times, to be associated with less blood loss than the open tech-
nique, and to be associated with short hospital stays. Moreo-
ver, there was no surgical complication except for a single case
of reoperation due to hemoperitoneum.
Despite all the above, limitations of multilevel PPF have
been described, including steep learning curves and theoret-
ically increased radiation exposure
3)
. Also, in rare cases, the
inserted instrument comes to be positioned close to skin, which
can cause serious skin stimulating symptom, and so instrument
removal is needed
15)
.
With development of various instruments of multilevel PPF,
it is possible to insert contoured long rod as required for the
spinal curvature, and to correct malalignment by compression
or distraction. However, the indication is more limited than
open technique. In cases of the significant malalignment of
pedicle before the surgery due to severe spondylolisthesis (Grade
II or more), severe scoliosis, or rotational deformity, it is diffi-
cult to carry out reduction of spinal curvature with percuta-
neous method. Also, since this surgery is carried out under
C-arm fluoroscope, the pedicle should be within the range
of anatomical structure that can be predicted under fluoro-
scope by the performing physician. For example, in cases of
excessive degeneration and formation of osteophyte, it is hard
to find pedicle under fluoroscope, and so accurate test is nec-
essary and attention should be paid before the surgery. More-
over, as the shape of rod which is inserted percutaneously
is limited in lordotic or mild kyphotic curved form, it is diffi-
cult to apply for severe kyphotic deformity. So, as mentioned
above, patients with excessive spondylolisthesis or severe spi-
nal deformity were excluded from this multilevel PPF.
There are some limitations to the present study that should

Multilevel percutaneous pedicle screw fixation
Korean J Spine 9(4) December 2012
357
be dealt with. This study was retrospective and had a small
patient group with too short follow-up period. Furthermore,
the study population is heterogeneous with varying indica-
tions for spinal fixation, and there is no comparison with open
techniques. Additional study is required to compare the multi-
level PPF to the open technique in cases of identical operative
indications.
CONCLUSION
Using newer posterior percutaneous instruments, it is possible
to achieve multilevel PPF for various lumbar spinal diseases,
with favorable clinical, radiological, and surgical outcomes.
It remains to be seen whether long-term outcomes are also
favorable. Also, the preoperative pedicle alignment is an impor-
tant factor in multilevel PPF.
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