The purpose of this study was to evaluate the clinical and radiologic
outcomes of bilateral decompression via a unilateral paramedian approach for
transforaminal lumbar interbody fusion. Forty consecutive patients satisfying
the inclusion criteria were divided randomly into groups 1 and 2. Patients were
treated with unilateral (group 1) or bilateral (group 2) pedicle screw fixation
and bilateral decompression via 1-sided (group 1) or bilateral (group 2)
paramedian approach. Perioperative parameters (operation time, blood loss,
hospital stay, complications, and implant cost), clinical outcome parameters
(Japanese Orthopedic Association [JOA] scores, visual analog scale [VAS]
scores, and Oswestry Disability Index [ODI] preoperatively and at 1 week and 3
months postoperatively), and radiologic parameters (radiograph and computed
tomography [CT] scan preoperatively and at 1 week postoperatively) were
No differences were seen between groups 1 and 2 with respect to
operation time, blood loss, or hospital stay. No complications were observed in
either group. The ODI, JOA, and VAS values of both groups showed significant
differences between the preoperative and 1-week or 3-month postoperative
values. No significant differences were seen in the improvements of the ODI,
JOA, and VAPS values between groups 1 and 2 at any postoperative time point.
Postoperative CT indicated that the contralateral decompression was sufficient
in both groups.
The short-term results indicate that bilateral decompression via a
unilateral paramedian approach for transforaminal lumbar interbody fusion with
unilateral pedicle screw fixation is safe, feasible, and effective over the
short-term and is more cost-efficient than a bilateral paramedian approach.
In 1982, Harms and Rolinger1 described an innovative
improvement to posterior surgical approaches to the disk space for interbody
arthrodesis, designated transforaminal lumbar interbody fusion. Use of the
transforaminal lumbar interbody fusion technique with a bilateral pedicle screw
has since been widely accepted as a standard operation for lumbar fusion,
achieving fusion rates as high as 90% to 100%.2 The technique was
further improved by Salehi et al3 in 2004, with the development of
the minimally invasive transforaminal lumbar interbody fusion technique. In the
latter method, a paramedian approach is used to expose the neural scute and
articular processes by splitting the sacrospinalis, leaving the spinous
processes and supraspinous/interspinous ligament complex intact.
However, a 1-sided paramedian approach allows only unilateral pedicle
screw fixation, and bilateral pedicle screw fixation seems to require a
bilateral paramedian approach. Although in vitro studies have shown that
unilateral pedicle screw fixation is less stable than bilateral
fixation,4,5 the clinical fusion rate does not appear to encounter
the same stability problems.6-9 The use of unilateral fixation could
reduce the surgical time, blood loss, and implant cost of performing
transforaminal lumbar interbody fusion.
When treating bilateral nerve root compression, most surgeons take a
back-to-midline approach or use a bilateral paramedian approach for the
complete decompression of both sides. Although McCulloch10 achieved
bilateral decompression through unilateral laminotomy as early as 1991, and
other groups11-14 have since performed bilateral microdecompression
using a unilateral approach, each of these studies was performed via a midline
approach. Unilateral transforaminal lumbar interbody fusion via a paramedian
approach and bilateral decompression via a midline incision were described in
various studies,10,15-19 but to our knowledge, bilateral
decompression with unilateral pedicle screw fixation via a unilateral
paramedian approach incision has not been reported.
Accordingly, we integrated these initial techniques and describe a
novel procedure in which a unilateral pedicle screw instrument was used and
bilateral decompression was accomplished via a unilateral paramedian approach.
The short-term objective of this prospective randomized study was to evaluate
the feasibility, safety, and efficacy of bilateral decompression via a
unilateral paramedian approach. The long-term objective was to evaluate the
fusion rate of transforaminal lumbar interbody fusion with unilateral pedicle
screw fixation after 2-year follow-up.
Materials and Methods
Approval for this study was obtained from the Institutional Review
Board of Zhongshan Hospital. Consecutive patients who satisfied the following
inclusion criteria were considered eligible: an age of 20 to 75 years and
1-level lumbar stenosis or spondylolisthesis (grade I or II) with bilateral
nerve root compression symptoms. Exclusion criteria included any prior lumbar
surgery or unilateral nerve root compression symptoms.
Enrolled patients were randomized into 2 groups using a
computer-generated random number program. Group 1 was treated via 1-sided
paramedian approach for transforaminal lumbar interbody fusion with unilateral
pedicle screw fixation and bilateral decompression. Group 2 was treated with
bilateral pedicle screw fixation and bilateral decompression via bilateral
paramedian approach. A single surgeon (X.X.J.) performed all surgeries and was
blinded to the patient group until the start of the surgery.
After general endotracheal anesthesia was induced, patients were
placed in a prone position on a radiolucent table. The pedicles of the
vertebral arch of the operating level were marked on the skin with a C-arm
machine. A paramedian incision was made between the pedicle skin markers on the
severe side in both groups. Through the posterior lumbar fascia, the
sacrospinalis was split to expose the ipsilateral facet joint, transverse
processes, and vertebral lamina. According to the standard transforaminal
lumbar interbody fusion procedure, the inferior and superior articular
processes and part of the vertebral lamina were removed with high-speed drills,
curettes, and Kerrison rongeurs. These bones were kept for use as an autograft
during interbody fusion. The underlying disk space was exposed. The nerve root
was decompressed by removal of the ligamentum flavum and bone spur. A sharp
knife was used to create a rectangular window on the annulus fibrosus. The disk
materials and endplate cartilage were completely removed. The local autograft
was implanted, and 1 Capstone cage implant (Medtronic Sofamor Danek, Memphis,
Tennessee) and 2 pedicle screws (Legacy; Medtronic Sofamor Danek) were inserted
and fixed on the ipsilateral side.
In group 1, the standard transforaminal lumbar interbody fusion
procedure was performed. The more ipsilateral lamina was removed to the midline
under the spinous process. The space between the contralateral dural and
ligamentum flavum was divided. While protecting the nerve retractor, the
contralateral ligamentum flavum and osteophytes that had proliferated on the
medial margin of the contralateral lamina and facet joint were ground and
removed using high-speed drills, curettes, and Kerrison rongeurs through the
spinal canal inside.
In group 2, in addition to the standard transforaminal lumbar
interbody fusion procedure, the same pedicle screw incision was also made on
the other side (for a total of 1 cage implant and 4 pedicle screws). As on the
first side, the sacrospinalis was split to expose the articular and transverse
processes, laminotomy was performed to decompress the nerve root, and the
system was fixed with pedicle screw.
Finally, the wound was irrigated with saline, and drains were placed
as needed. Patients wearing a lumbar corset were able to leave the bed as soon
as the drain was removed (ie, 1 or 2 days postoperatively).
Perioperative parameters included sex, age, hospital stay, blood loss,
operation time, implant cost, and complications. These data were compared to
evaluate safety and feasibility.
Clinical outcome parameters included Japanese Orthopedic Association
(JOA) scores, visual analog scale (VAS) scores for the lumbar and leg, and
Oswestry Disability Index (ODI). Scores were obtained preoperatively and at 1
week and 3, 6, 12, and 24 months postoperatively. These data were compared to
Radiologic parameters included anteroposterior (AP) and lateral
radiographs preoperatively and at 1 week and 3, 6, 12, and 24 months
postoperatively, additional flexion–extension radiographs preoperatively
and at 6, 12, and 24 months postoperatively, and 3-D computed tomography (CT)
preoperatively and at 1 week and 12 and 24 months postoperatively. Radiographic
analyses mainly evaluated the fusion rate and will be reported in a future
article after all follow-ups are completed. The efficacy of the contralateral
decompression was judged by comparing the preoperative CT scan with that
obtained 1 week postoperatively.
Statistical analysis was performed using SPSS 17.0 for Windows (SPSS
Inc, Chicago, Illinois). The Wilcoxon rank-sum and t test were used for
statistical analysis of the differences in noncategorical variables between the
unilateral and bilateral groups. A P value <.05 was considered
From March 2008 to December 2008, a total of 40 patients were included
in the study. Group 1 included 8 men and 12 women with a mean age of 53.8 years
(range, 37-72 years). The vertebral levels involved included L3-4 (1 patient),
L4-5 (11 patients), and L5-S1 (8 patients). Diagnoses included lumbar canal
stenosis (11 patients), spondylolisthesis grade I (6 patients), and
spondylolisthesis grade II (3 patients). Group 2 included 10 men and 10 women
with a mean age of 53.2 years (range, 25-73 years). The vertebral levels
involved included L3-4 (2 patients), L4-5 (12 patients), and L5-S1 (6
patients). Diagnoses included lumbar canal stenosis (10 patients),
spondylolisthesis grade I (6 patients), and spondylolisthesis grade II (4
patients). No significant differences in age, sex, or surgical level were
observed between the 2 groups.
No neurological injuries, dural tears, or infections were seen in
either group. Blood loss, operation time, hospital stay duration, and implant
costs are shown in Table 1. No differences were seen between the 2 groups with
respect to operation time, blood loss, or hospital stay, although both blood
loss and operation time are slightly lower in group 1. Group 1 used 2 pedicle
screws plus 1 cage implant, and group 2 used 4 pedicle screws plus 1 cage
implant. Accordingly, significant differences in implant cost were observed
between the 2 groups.
Data from the 3-month postoperative follow-up were received for all 40
patients (Table 2). Postoperative ODI, JOA, and VAS values were significantly
different at all times from the preoperative values in both groups. No
significant differences in either group were seen in the results at 1 week and
3 months postoperatively. To counteract interference by the basal condition
among the 40 patients, groups were compared with the data calculated by the
mean robustness regression. These statistics revealed no significant difference
in the improvement of ODI, JOA, or VAS values between the 2 groups at any
postoperative time point (Table 3).
Results of CT scans preoperatively and at 1 week postoperatively
indicated that the contralateral decompression was sufficient in group 1
(Figure 1). Sufficient decompression was seen, and no osteophyma or disk
material in the vertebral canal or bilateral recesses were seen. Radiographic
results at 3 months postoperatively revealed no cage collapse, broken drafts,
loose pedicle screws, or pseudoarticulation formation (Figure 2). We will
continue collecting data through the 24-month follow-up visit, at which time we
will compare differences in the fusion rates between the 2 groups.
|Figure 1: Pre- (A,
B) and postoperative (C, D) CT scans in group 1. The contralateral
decompression appears sufficient.
|Figure 2: AP (left)
and lateral (right) radiographs of group 1 patients preoperatively (A) and at 3
months postoperatively (B).
The short-term objective of this prospective randomized study was to
evaluate the feasibility, safety, and efficacy of bilateral decompression via a
unilateral paramedian approach. No significant differences were seen in terms
of hospital stay, blood loss, operation time, or complication rate between
groups 1 and 2 (Table 1), indicating that the surgical procedure is feasible
and safe. As surgeons become familiar with this technique, we believe blood
loss and operation time can be lower. The ODI, JOA, and VAS values differed at
all postoperative time points when compared with the preoperative values in
both groups, with no significant difference between groups 1 and 2 (Tables 2,
3). These results indicate the efficacy of the surgical procedure. Computed
tomography scan also showed that the contralateral decompression was sufficient
(Figure 1). Therefore, the most important advantage of the unilateral procedure
is that it can substantially reduce implant cost.
Degenerative lumbar spinal stenosis is a common disease worldwide,
with the number of surgeries performed for lumbar stenosis increasing each
year. Since its first description in 1982,1 transforaminal lumbar
interbody fusion has become widely accepted as a standard surgical treatment
for lumbar fusion. The standard transforaminal lumbar interbody fusion
procedure includes a midline incision, bilateral pedicle screw fixation, and 1
or 2 cages for interbody fusion. The minimally invasive approach with
transforaminal lumbar interbody fusion was first reported in 2004.3
Since that time, some surgeons have opted to use a paramedian approach
incision, which facilitates pedicle screw insertion and diminishes muscle
stripping.8,20 Compared to a midline incision, a paramedian approach
incision can preserve the spinous processes and supraspinous/interspinous
ligament complex and avoid the atrophy of paravertrebral muscles. In 26
patients who underwent transforaminal lumbar interbody fusion via a median
approach on 1 side and a paramedian approach on the other, muscular atrophy was
more serious on the side with the median incision, according to postoperative
Alternatively, some surgeons attempt to use unilateral pedicle screw
fixation as a substitute for bilateral pedicle screw. Bilateral pedicle screw
fixation requires bilateral pedicle screws, and unilateral fixation seems more
suited for minimally invasive surgery. However, in addition to reducing blood
loss and operation time, unilateral fixation also reduces implant cost.
Therefore, unilateral fixation is the preferred method, assuming that the
stability is sufficient. Using in vitro, model, and animal experiments, Goel et
al4 observed that unilateral fixation is less stable than bilateral
fixation to support interbody fusion. The stability of the unilateral pedicle
screw fixation group was 18% to 57% of those in the bilateral fixation group.
Similar results were also obtained from vitodynamic measurements on
In contrast, in a clinical study of 87 patients undergoing
posterolateral lumbar interbody fusion of 1 or 2 levels, treatment with
unilateral or bilateral pedicle screw fixation achieved statistically similar
fusion rates (91.5% or 97.5%, respectively).9 In a study by
Fernández-Fairen et al,6 eighty-two patients who accepted
either unilateral or bilateral pedicle screw fixation were followed up for 3
years, at which time lateral flexion and extension radiographs were taken and
the motion between the fusion segments was measured. The fusion rates in the
unilateral and bilateral groups were statistically similar (92.7% and 90%,
respectively). Thus, although the stability of unilateral pedicle screw
fixation seems to be less than that with bilateral fixation, this change is not
reflected clinically or in the fusion rate. The stability and fusion rates in
the current study will be discussed in a later article, as part of the
long-term analysis after 2-year follow-up.
Young et al18 first reported the use of contralateral
decompression via the vertebral canal in 1988. A few years later,
McCulloch10 used endoscopy to accomplish ipsilateral decompression,
expose the contralateral vertebral structure by removing part of ligamenta
interspinalia and vertebral lamina, separate the ligamentum flavum and dura,
and remove the ligamentum flavum and osteophytes that compressed the nerve
root. After finishing these procedures, the bilateral nerve roots were
decompressed and free. With the increasing use of endoscopic surgery, numerous
studies have addressed the clinical outcomes of unilateral laminotomy for
bilateral decompression,11-12,14,22-25 with clinical success rates
ranging from 87% to 100%. In contrast to the present study, most previous
studies have used a midline incision with the aid of endoscopy. However,
previous results suggest the feasibility, efficacy, and safety of using
decompression from inside the lumbar canal.
The novelty of our procedure was combining decompression with
minimally invasive transforaminal lumbar interbody fusion and unilateral
pedicle screw. Because of the pedicle screw fixation, we do not need to
consider iatrogenic instability. Because a paramedian approach incision is used
and the transforaminal lumbar interbody fusion procedure requires that the
facet joint be cut, it is easier to perform contralateral decompression under
direct vision, even without endoscopic assistance. Our short-term results
indicate that the procedure is safe (no complications), feasible (hospital
stay, blood loss, and operation time are not prolonged, and the operation time
may be able to be shortened), and effective (improved VAS, JOA, and ODI
values). Computed tomography also showed that the contralateral decompression
was sufficient. The main benefit to this approach is that it can substantially
reduce implant cost.
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Drs Feng, Cao, Jiang (Chun), and Jiang (Xiao-Xing) are from the
Department of Orthopedics, Zhongshan Hospital, Fudan University, Shanghai,
Drs Feng, Cao, Jiang (Chun), and Jiang (Xiao-Xing) have no relevant
financial relationships to disclose.
Correspondence should be addressed to: Xiao-Xing Jiang, MD, PhD,
Department of Orthopedics, Zhongshan Hospital, Fudan University, 130 Yixueyuan
Rd, Shanghai, 20032 China (firstname.lastname@example.org).