Available via license: CC BY 4.0
Content may be subject to copyright.
R E S E A R C H A R T I C L E Open Access
Comparison between posterior dynamic
stabilization and posterior lumbar interbody
fusion in the treatment of degenerative disc
disease: a prospective cohort study
Haodong Fei
1†
, Jiang Xu
2†
, Shouguo Wang
1
, Yue Xie
1
, Feng Ji
1*
and Yongyi Xu
1
Abstract
Background: Few studies compared radiographic and clinical outcomes between posterior dynamic stabilization
(PDS) and posterior lumbar intervertebral fusion (PLIF) in treating degenerative disc disease (DDD).
Methods: A total of 176 consecutive patients who underwent posterior instrumented spinal surgery for
degenerative disc disease between January 2007 and January 2009 were prospectively divided into two
groups—PDS and PLIF. All patients includ ed in the analysis were followed up for 3 years. Demographic distribution,
perioperative complications, and radiographic and clinical outcomes were compared between the two groups.
Results: The amount of intraoperative blood loss and drained volume was significantly greater in the PLIF group
compared with the PDS group (881.1 ml versus 737.4 ml, p = 0.004). The length of stay of patients who had PLIF
surgery (20.9 days) was significantly longer (p = 0.033) than that of patients who underwent PDS surgery (18.9 days).
Patients with PLIF surgery had higher total costs than those with PDS s urgery (US$12826.8 vers us U S$116 54.5,
p = 0.002). No statistically significant differences existed in back v isual a nalogue scale (VAS), leg VAS, o r
Oswestry disability index (ODI) scores between the PDS and PLIF groups of patients at each time point.
Conclusions: Compared with PLIF, PDS have advantages on blood loss, length of stay in hospital, total charges,
and radiographic outcomes, but no advantages on leg and back VAS or ODI scores. High-quality randomized controlled
trials are still required in the future.
Keywords: Dynamic stabilization, Dynesys, Lumbar spine, Posterior lumbar interbody fusion, Degenerative disc disease
Introduction
Instrumented fusion in the treatment of degenerative con-
ditions of the lumbar spine is known to have potential
complications such as pseudoarthrosis, nonunion, instru-
mentation failure, infection, donor site pain, and adjacent
segment disease [1–3]. The Dynesys Spinal Stabilization
System (Zimmer, Inc., Minneapolis, MN, USA) uses ped-
icle screws, polyethylene-terephthalate cords, and polycar-
bonate urethane spacers to stabilize a functional spinal
unit. The concept of these devices is to reduce the load
and restrict the motion of the affected level to stop or
delay its degeneration. While studies have indicated posi-
tive outcomes with improved Oswestry disability index
(ODI) scores and visual analogue scale (VAS) pain scores,
as well as shorter recovery time than the fusion for
patients with degenerative disc disease (DDD) of the lum-
bar spine treated with the Dynesys system [4–6], to our
knowledge, literature is lacking in studying differences in
radiographic and clinical outcomes between posterior dy-
namic stabilization (PDS) and posterior lumbar interbody
fusion (PLIF).
This prospective cohort study was designed to evaluate
radiographic and clinical outcomes between posterior dy-
namic stabilization and posterior lumbar interbody fusion
in patients with degenerative disc disease. Furthermore,
* Correspondence: habest126@126.com
†
Equal contributors
1
Department of Orthopaedics, Huai’an First People ’s Hospital, Nanjing
Medical University, Huai’an, Jiangsu 223300, People’s Republic of China
Full list of author information is available at the end of the article
© 2015 Fei et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License
(http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium,
provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://
creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Fei et al. Journal of Orthopaedic Surgery and Research (2015) 10:87
DOI 10.1186/s13018-015-0231-7
we hypothesized that PDS would lead to shortened length
of hospital stay, reduced medical costs, and fewer peri-
operative complications.
Materials and methods
The study protocol was approved by the local institu-
tional review board and ethics committee. Informed
consent was obtained from all study participants. A total
of 176 consecutive patients undergoing posterior instru-
mented spinal surgery for degenerative disc disease be-
tween January 2007 and January 2009 at a hospital were
prospectively divided into two groups according to their
clinic sequences. There were 51 males and 44 females
subject to PDS, with the mean age of 47.3 years. The im-
planted level included L2–L5 in 1 case, L3–L4 in 5
cases, L3–L5 in 7 cases, L4–L5 in 45 cases, L4–S1 in 10
cases, and L5–S1 in 27 cases. In the PLIF group, there
were 40 males and 41 females, with the mean age of
52.9 years. The implanted level included L2–L5 in 2
cases, L3–L4 in 4 cases, L3–L5 in 5 cases, L4–L5 in 47
cases, L4–S1 in 13 cases, and L5–S1 in 10 cases. The
statistical information of patients, including comorbidi-
ties , was presented in Table 1. Degenerative lumbar disc
disease had been diagnosed in all of these patients , and
they all suffered from severe neurogenic claudication
and leg, buttock, or groin pain with back pain that was
aggravated in sitting or lumbar flexion and relieved by
upright position. In all cases, conservative treatment had
failed to control these patients’ symptoms. Patients who
underwent surgical treatment for nondegenerative condi-
tions (trauma, tumor, or infection) were excluded. We also
excluded patients with osteoporosis (bone mineral density
T-score less than −2.5) and those who had undergone pre-
vious lumbar fusion surgery and those with degenerative
deformity.
On admission to the hospital for the surgery, all patients
underwent re-examination including routine lumbar pos-
terior–anterior and flexion–extension position radiographs,
lumbar computed tomography (CT), and magnetic reson-
ance imaging (MRI); lumbar myelography was provided
for some patients to ascertain whether there was compli-
cated lumbar intervertebral disc protrusion, canal stenosis,
or spondylolisthesis. A summary of findings and the clin-
ical history were then documented on a standardized
evaluation form and entered into the hospital’s computer-
ized patient records system.
Dynesys implantation was performed in the prone pos-
ition. A midline approach, with dissection of the erector
spinae muscles , provided access to the bony anatomy of
the lumbar spine. If indicated, decompression of the
spinal canal was performed first. Insertion of the pedicle
screws was carried out under radiographic control using
a C-arm. The polycarbonate urethane spacer was cut ac-
cording to the measured distance between the screws,
with the length being chosen to compensate for any exist-
ing lordosis or kyphosis. The central cord and the spacer
were then locked within the screw heads. A soft brac e
was administered after surgery until wound healing
had occurred.
PLIF was performed in a standard manner. Where re-
quired, extensive decompression and facetectomy were
performed for cage insertion. Autologous bone graft using
decompressed bone chips was used within and around the
cage, followed by pedicle screw instrumentation and fix-
ation. A posterolateral fusion was also performed for these
patients. Surgery was performed by a single senior sur-
geon. Blood loss was estimated through the evaluation of
the amount of blood in the suction canister and that in
soaked lap pads. The surgery was performed with the pa-
tient under hypotensive anesthesia in which systolic blood
pressure was kept lower than 90 mm Hg. All wounds were
closed over hemovac drains which were placed on con-
tinuous suction. Drains were discontinued no sooner than
postoperative day 3, with the output less than 100 ml over
24 h. The same blood transfusion guidelines were used for
all patients. Allogenic blood transfusion was performed if
hemoglobin decreased to less than 7.0 mg/dL or if anemic
symptoms developed, such as a decrease in blood pressure
to less than 100 mmHg systolic, tachycardia greater than
100 beats/min, or a low urine output less than 30 mL/h,
even after initial fluid challenge with 500 mL normal sa-
line in patients with a hemoglobin level between 7.0 and
8.0 mg/dL [7, 8].
Table 1 Demographics of the groups
Characteristics Dynesys group
(n = 95)
PLIF group
(n = 81)
p
Age (years)
a
47.3 ± 12.9 52.9 ± 11.2 0.002
Sex 0.569
Male 51 40
Female 44 41
BMI (kg/m
2
)
a
26.9 ± 3.9 22.9 ± 3.3 <0.001
Comorbid medical conditions 0.136
Yes 12 17
No 83 64
Implanted level, n (%) 0.158
L2–L5 1 (1.1) 2 (2.5)
L3–L4 5 (5.3) 4 (4.9)
L3–L5 7 (7.4) 5 (6.2)
L4–L5 45 (47.4) 47 (58.0)
L4–S1 10 (10.5) 13 (16.0)
L5–S1 27 (28.4) 10 (12.3)
Comorbid medical conditions include cardiovascular disorders, respiratory
diseases, digestive system disorders, diabetes mellitus, renal insufficiency
BMI body mass index
a
Data are displayed as mean ± SD
Fei et al. Journal of Orthopaedic Surgery and Research (2015) 10:87 Page 2 of 7
Information was compiled about perioperative compli-
cations occurring within 30 days after operation, including
surgical complicatio ns (postoperative bleed ing, wound
breakdown, infection, implant failure, neurologic com-
promise, etc.) and nonsurgical complications (pulmonary
disease, arrhythmia, hemodynamic instability requiring
inotropic support, etc.). All patients had at least 3 years of
follow-up (3.0–5.5 years) physical and radiographic exami-
nations postoperatively.
Data collected included flexion, extension, neutral ra-
diographs, range of motion (ROM) in sagittal view, an-
terior and posterior disc heights, ODI score, VAS pain
score, preoperative BMD, and total charges. Total charge
was defined as hospital charges during index hospitalization
alone, not including costs for follow-up care and readmis-
sion. Radiographs were measured and analyzed by two ex-
perienced spine surgeons. Flexion and extension views
were taken with patients in the lateral position. The ROM
in the sagittal (flexion–extension) view was obtained by
the following formula: ROM sagittal = angle (extension) −
angle (flexion). Disc height was determined on radio-
graphs taken with the patient in the neutral position and
was assessed by measurement of lines drawn at the most
prominent points of the endplate anteriorly and poster-
iorly. Total disc height measured from L1 to S1 was the
sum of the disc height at each level. VAS scores were de-
termined on a scale ranging from 0 (no pain) to 100
(worst pain imaginable).
In the PLIF group, fusion status was recorded for each
surgically treated segment at each follow-up interval using
X-ray film. The level was regarded as fused if there was
radiographic evidence of bone bridging the disc space with
no lucency. For patients undergoing multiple-level fusion,
all surgically treated segments needed to be fused for the
patient to be considered as a fusion success.
The data analysis was conducted using SPSS version 19.0
(Chicago, IL, USA). Normal distribution was validated by
Shapiro–Wilk test. Continuous data were compared be-
tween the PDS and PLIF groups through Student’s t test,
whereas discontinuous data were analyzed through the
chi-squared test. Fisher’s exact test was conducted for
small data subsets (n < 5). All significance tests were two-
tailed, with p < 0.05 representing statistical significance.
Post hoc power analyses were conducted for the change in
VAS, ODI scores, ROM, and anterior disc height and pos-
terior disc height in the PDS and PLIF groups.
Results
Surgical characteristics
All variables were in normal distribution. There were no
significant differences in mean operation time, mean peri-
operative red blood cell transfusion unit, and perioperative
complications between the two groups (Table 2). However,
the mean amount of intraoperative blood loss and drained
volume was significantly greater in the PLIF group com-
pared with the PDS group (881.1 ml versus 737.4 ml, p =
0.004); in addition, patients who had PLIF surgery had a
significantly longer mean length of stay (20.9 days) than pa-
tients who underwent PDS surgery (18.9 days) (p = 0.033).
Mean total charges of patients with PLIF surgery were
higher than that of patients with PDS surgery (US$12,826.8
versus US$11,654.5, p = 0.002).
Clinical outcomes
In the PDS group, the mean VAS scores for back pain
obtained preoperatively 1 year after surgery and in the
final follow-up visit were 43.7 ± 14.5, 19.5 ± 11.7, and
10.6 ± 9.1, respectively. The corresponding mean VAS
scores for leg pain were 51.6 ± 15.7, 13.2 ± 8.9, and 6.7 ±
8.3. The corresponding ODI scores were 57.1 ± 7.7, 33.5 ±
6.6, and 25.9 ± 5.7. In the PLIF group, the mean VAS
scores for back pain obtained preoperatively 1 year after
surgery and in the final follow-up visit were 45.3 ± 13.9,
18.6 ± 11.3, and 11.4 ± 8.5, respectively. The correspond-
ing mean VAS scores for leg pain were 52.3 ± 16.3, 11.5 ±
8.2, and 7.1 ± 7.5. The corresponding ODI scores were
56.1 ± 8.1, 33.9 ± 7.1, and 24.9 ± 5.9. In both groups, VAS
and ODI scores decreased after surgery, and there was a
statistically significant difference between preoperative
and final follow-up scores for back VAS, leg VAS, and
ODI scores (p < 0.001). However, no statistically significant
differences can be seen in back VAS, leg VAS, or ODI
scores between the PDS and PLIF groups of patients at
each time point (Table 3).
Radiological outcomes
Range of motion
ROM values of the implanted segment and L1–S1 levels
were measured preoperatively, 1 year after surgery and
in the final follow-up visit. There were no significant dif-
ferences in the mean ROM values for the implanted seg-
ments and the mean ROM values for the L1–S1 levels
between patients in the PDS group and PLIF group pre-
operatively (6.8° ± 2.7° versus 6.6° ± 3.0°, p = 0.579; 18.1° ±
Table 2 Comparing variables in patients with posterior
dyn amic sta biliza tion (PDS) an d with posterior lumbar
interb ody fusion (PLIF)
Characteristics Dynesys group (n = 95) PLIF group (n = 81) p
Op time (min)
a
162.3 ± 41.4 167.3 ± 37.2 0.404
EBL (mL)
a
737.4 ± 307.2 881.1 ± 373.9 0.004
Transfusion (U/pt)
a
0.12 ± 0.79 0.09 ± 0.51 0.869
Length of stay (d)
a
18.9 ± 5.3 20.9 ± 6.9 0.033
Total charge (USD)
a
11654.5 ± 1889.3 12826.8 ± 2946.8 0.002
Complication, n (%) 2 (2.1) 4 (4.9) 0.416
Op time operation time, EBL estimated blood loss, U blood units: U/pt units
per patient
a
Data are displayed as mean ± SD
Fei et al. Journal of Orthopaedic Surgery and Research (2015) 10:87 Page 3 of 7
5.9° versus 17.9° ± 6.4°, p = 0.852) (Table 4). However, there
were statistical differences in the mean ROM values of the
implanted segment and L1–S1 levels between the PDS
group and the control group (3.5° ± 1.2° versus 0.9° ± 0.9°,
p < 0.001; 15.3° ± 4.9° versus 13.1° ± 3.3°, p = 0.001) (Table 5)
1 year after surgery. In the final follow-up visit, the mean
ROM values of the implanted segment and L1–S1 levels
in the PDS group were significantly higher than that
in the control group (3.7° ± 1.4° versus 0.6° ± 0.6°, p <0.001;
15.8° ± 4.7° versus 13.6° ± 3.4°, p < 0.001) (Table 6).
Posterior disc height
Posterior disc height was assessed with standing neutral
lateral radiographs preope ratively, 1 year after surgery
and in the final follow-up visit for both groups. The mean
posterior disc height of the implanted segment for the
PDS group was 7.7 ± 1.8 mm preoperatively, 8.8 ± 1.5 mm
1 year after surgery, and 8.3 ± 1.6 mm in the final follow-
up visit. In the control group, the mean posterior disc
height of the implanted segment was 7.8 ± 1.2 mm pre-
operatively, 7.8 ± 1.4 mm 1 year after surgery, and 7.5 ±
1.3 mm in the final follow-up visit. The mean posterior
disc height of the implanted segment was greater 1 year
after Dynesys placement than the preoperative one but
then gradually decreased; no statistically significant differ-
ence was found between the two groups in the preopera-
tive stage and midterm and final follow-up visit in
posterior disc heights of the L1–S1 levels, but there was a
statistically significant difference between the two groups
in the disc height of the implanted segment 1 year after
Table 3 Clinical outcome
Dynesys group (n = 95) PLIF group (n = 81) p
ODI (%)
a
Pre op 57.1 ± 7.7 56.1 ± 8.1 0.391
Mid-term 33.5 ± 6.6 33.9 ± 7.1 0.738
Final 25.9 ± 5.7 24.9 ± 5.9 0.271
VAS
back
(mm)
a
Pre op 43.7 ± 14.5 45.3 ± 13.9 0.451
Mid-term 19.5 ± 11.7 18.6 ± 11.3 0.633
Final 10.6 ± 9.1 11.4 ± 8.5 0.568
VAS
leg
(mm)
a
Pre op 51.6 ± 15.7 52.3 ± 16.3 0.752
Mid-term 13.2 ± 8.9 11.5 ± 8.2 0.199
Final 6.7 ± 8.3 7.1 ± 7.5 0.782
VAS visual analogue scale, ODI Oswestry disability index, VASback VAS score
for back pain, VASleg VAS score for leg
a
Data are displayed as mean ± SD
Table 4 Preoperative radiographic outcome
Dynesys group
(n = 95)
PLIF group
(n = 81)
p
ROM (°)
a
Operated level 6.8 ± 2.7 6.6 ± 3.0 0.579
L1–S1 18.1 ± 5.9 17.9 ± 6.4 0.852
Anterior disc height (mm)
a
Operated level 12.3 ± 2.4 12.3 ± 2.1 0.796
L1–S1 56.6 ± 4.9 56.7 ± 4.9 0.798
Posterior disc height (mm)
a
Operated level 7.7 ± 1.8 7.8 ± 1.2 0.774
L1–S1 36.3 ± 7.2 36.2 ± 4.5 0.911
Disc height was determined on radiographs taken with the patient in the
neutral position and was assessed by measurement of lines drawn at the most
prominent points of the endplates anteriorly or poste riorly. Total disc height
measured from L1 to S1 was the sum of the disc height of each level
ROM range of motion
a
Data are displayed as mean ± SD
Table 5 Radiographic outcome at midterm follow-up (1 year
postoperatively)
Dynesys group
(n = 95)
PLIF group
(n = 81)
p
ROM (°)
a
Operated level 3.5 ± 1.2 0.9 ± 0.9 <0.001
L1–S1 15.3 ± 4.9 13.1 ± 3.3 0.001
Anterior disc height (mm)
a
Operated level 13.1 ± 2.1 11.9 ± 2.1 <0.001
1L1–S1 57.1 ± 7.4 56.6 ± 4.8 0.670
Posterior disc height (mm)
a
Operated level 8.8 ± 1.5 7.8 ± 1.4 <0.001
L1–S1 38.0 ± 7.0 36.7 ± 5.6 0.171
Disc height was determined on radiographs taken with the patient in the
neutral position and was assessed by measurement of lines drawn at the most
prominent points of the endplates anteriorly or poste riorly. Total disc height
measured from L1 to S1 was the sum of the disc height of each level
ROM range of motion
a
Data are displayed as mean ± SD
Table 6 Radiographic outcome at final follow-up
Dynesys group
(n = 95)
PLIF group
(n = 81)
p
ROM (°)
a
Operated level 3.7 ± 1.4 0.6 ± 0.6 <0.001
L1–S1 15.8 ± 4.7 13.6 ± 3.4 <0.001
Anterior disc height (mm)
a
Operated level 12.8 ± 2.2 11.7 ± 2.2 0.001
L1–S1 57.0 ± 4.9 56.2 ± 4.9 0.267
Posterior disc height (mm)
a
Operated level 8.3 ± 1.6 7.5 ± 1.3 <0.001
L1–S1 37.9 ± 6.5 37.0 ± 4.5 0.281
Disc height was determined on radiographs taken with the patient in the
neutral position and was assessed by measurement of lines drawn at the most
prominent points of the endplates anteriorly or poste riorly. Total disc height
measured from L1 to S1 was the sum of the disc height of each level
ROM range of motion
a
Data are displayed as mean ± SD
Fei et al. Journal of Orthopaedic Surgery and Research (2015) 10:87 Page 4 of 7
surgery and in the final follow-up visit (p < 0.001) (Tables 4,
5, and 6).
Overall complication rates
In the PDS group, perioperative complications occurred
in two (2.1 %) cases, deep venous thrombosis in one case
and increasing motor deficit required reoperation in one
case. In the PLIF group, perioperative complications oc-
curred in four (4.9 %) cases. Two deaths occurred intraop-
eratively, one of which was caused by excessive bleeding
and the other one of which was caused by massive myo-
cardial infarction. Two broken screws were found (in two
patients) and all of the broken screws have been replaced
by reoperation. There was no statistically significant differ-
ence between two groups (Table 2).
Discussion
Fusion is generally considered to be the treatment of choice
for painful degenerative conditions of the lumbar spine that
have proven unresponsive to nonoperative therapy [9, 10].
For a long time, good results were thought to be dependent
on radiologically confirmed solid fusion. However, several
studies in which patients had pseudarthrosis showing the
same clinical outcome as patients with solid fusion have
challenged this notion [11–13]. Therefore, it is hypothe-
sized that it is the reduction in (rather than the elimin-
ation of) segmental motion brought about by partial
fusion or perhaps even simply by an alteration of the
structure of spinal tissues or by the surgery itself that re-
sults in the alleviation of pain. As pain relief represents
one of the most important outcomes in achieving a good
result after surgery for degenerative spinal disorders, it
would thus appear that solid fusion no longer represents
a prerequisit e for achieving this goal. If this were so, it
would present several advantages, including a reduction in
the extensiveness of surgery required and the number of
complications, as well as the elimination of undesirable
late side effects of fusion, such as adjacent segment degen-
eration [14] and consequent hypermobility [15].
In our study, back and leg pain VAS scores in the PDS
group improved from 43.7 to 10.6 and from 51.6 to 6.7,
respectively. In the PLIF group, back and leg pain VAS
scores decreased from 45.3 to 11.4 and from 52.3 to 7.1,
respectively. In the present study, VAS scores for leg and
back pain improved in both groups in the final follow-up
visit compared with preoperative scores, indicating that
both methods were effective for the treatment of degen-
erative lumbar diseases. As assessed by multiple measures,
patients who underwent a PDS performed as well as those
who underwent a PLIF. However, this effect is only evi-
dent in the result of 3-year follow-up visit. Many studies
[16–18] have reported positive results of the Dynesys,
while some reports have indicated that results are no
better than those obtained with rigid fusion [19, 20]. We
contribute VAS improvemen t to the biome chanics of
the Dynesys, which is a load-sharing device that results
in less stiffness than PLIF and may provide immediate
stabilization of the diseased segment and neutralize the
abnormal forces caused by the pathological bony and soft
tissue changes [21–23].
There are conflicting reports on the maintenance of disc
height with Dynesys. In our study, changes in posterior
disc heights in implant segments showed a contrary pat-
tern of changes compared to those 1 year after surgery
and in the final follow-up visit, which were similar to pre-
operative values. Additionally, CT showed that there was
an increase in intervertebral foramen cross-sectional areas
and heights immediately after Dynesys implantation but
that it subsequently decreased in extent. Thus, no signifi-
cant difference was evident between preoperative and final
follow-up values. It could be concluded from this study
that the Dynesys increased spinal canal and intervertebral
foramen sizes and local kyphosis with increasing posterior
disc height in implanted segments immediately after sur-
gery, but that these returned to their preoperative levels
during follow-up visit. However, Yu found that Dynesys
implantation resulted in an increase of posterior disc
height and that posterior disc height in the follow-up visit
3 years after surgery was maintained at both the operated
level and L1–S1 [21]. Beastall et al. reported a reduction
of anterior disc height without a significant increase in
posterior disc height 9 months after surgery in 24 patients
treated with Dynesys [24]. Kim et al. compared the results
of single- and multiple-level stabilization with Dynesys in
patients with degenerative spinal disease and found no de-
crease of disc height in either group with a mean follow-
up visit of 31 ± 14 months [25].
In line with the studies of Yu et al. [22], our study dem-
onstrated that both blood loss and the length of hospital
stay were significantly less in the Dynesys group. The re-
duction of blood loss in the Dynesys group is presumably
caused by the insertion of the Dynesys device requiring
less bone and soft tissue dissection as compared to PLIF.
Likewise, the shorter hospital stay of patients in the Dynesys
group is most likely due to the insertion of the device
which is less invasive as compared to PLIF [6, 26]. The lat-
ter benefits may be of particular importance for elderly pa-
tients, or those with significant co-morbidities.
The present study shows the hospital charge in one in-
stitution for PDS and PLIF procedures in hospitalization.
The results show a significantly higher cost of patients
subject to surgical treatment via PLIF fusion than those
with PDS. The mean costs of these two procedures dif-
fered by US$1172. The underlying meaning of these re-
sults can be interpreted in various ways. First, as the mean
hospital cost for both PDS and PLIF surpasses US$10,000,
a discrepancy of more than US$1000 in the cost calls into
question the real relevance of these data to the economic
Fei et al. Journal of Orthopaedic Surgery and Research (2015) 10:87 Page 5 of 7
impact of the decision to use one procedure over the other.
Our analysis also suggests another nonmonetary means of
measuring value. Though hospital charges were signifi-
cantly greater for PLIF procedure, there may be no signifi-
cant differences in charges for materials or services in the
operating room. This suggests that the greatest difference
in charges for these two procedures may arise from peri-
operative care. Several potential risk factors may influence
the perioperative care such as aging and comorbid medical
conditions.
Our data showed no significant differences in compli-
cations between two groups, although the percentage of
complications in the PLIF group (4.9 %) was higher than
that in the Dynesys group (2.1 %). The relatively small
sample size may be the reason. Screw loosening and ad-
jacent level instability in the Dynesys group were not
significantly greater than those in the PLIF group. Al-
though short-term clinical studies have reported that 6.5
to 20.0 % of patie nts available for follow-up visit showed
screw loosening [20, 27, 28], screw loosening had no ad-
verse impact on clinical improvement. In our study, only
two cases of screw loosening occurred in each group and
no revision surgeries were required. The lower rate of screw
loosening noted in our study as compared with other pre-
viously reported studies might be caused by the fact that
patients selected for study were relatively young and had
normal bone mineral density. Thus, Dynesys system may
be especially effective for younger patients for whom sur-
gical intervention is most needed.
Several potential limitations of this study should be
mentioned. First, though the follow-up period in this study
was 3 years, a much longer follow-up visit is required to
fully understand radiographic and clinical outcomes be-
tween PDS and PLIF or determine segmental instability at
adjacent levels and long-term outcomes. Moreover, the
nature of single-surgeon studies raises the possibility that
results may not be externally valid and not reproducible
elsewhere. Although there is an advantage, i.e., surgical
techniques applied throughout the study were consistent
and were not contaminated by multiple surgeons perform-
ing surgery with inevitable technique differences, variable
implants, and inconsistency in bone grafting techniques
with the use of substitutes and osteobiologics. In addition,
we also acknowledge limitations caused by our patients’
clinical heterogeneity. The difference in age and BMI be-
tween two groups may have influence on the result, which
will induce bias in the current cohort study.
In conclusion, in this prospective cohor t study by a
single surgeon, the short-term and long-term functional
outcomes clearly demonstrate that PDS have advantages
on blood loss, length of stay in hospital, total charge,
and radiographic outcomes, but no advantages on leg and
back VAS or ODI scores. This indicates that Dynesys
stabilization technique requires less extensive surgery than
PLIF but does not result in a superior improvement of the
clinical outcome compared with PLIF in the last follow-up
visit of a minimum 3-year period.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
The design of the study was done by FJ. HF and JX prepared the manuscript
and assisted in the study processes. SW, YX (Xie), and XY (Xu) assisted in the
data collections. All authors read and approved the final manuscript.
Acknowledgements
We thank Dr. Yongyi Xu for his support in obtaining the approval of the
ethics committee in this study.
Author details
1
Department of Orthopaedics, Huai’an First People ’s Hospital, Nanjing
Medical University, Huai’an, Jiangsu 223300, People’s Republic of China.
2
Department of Rehabilitation Medicine, Huai’an Second People’s Hospital,
Xuzhou Medical College, Huai’an, People’s Republic of China.
Received: 5 November 2014 Accepted: 24 May 2015
References
1. Resnick DK, Choudhri TF, Dailey AT, Groff MW, Khoo L, Matz PG, et al.
Guidelines for the performance of fusion procedures for degenerative
disease of the lumbar spine. Part 5: correlation between radiographic and
functional outcome. J Neurosurg Spine. 2005;2(6):658–61.
2. Kumar MN, Baklanov A, Chopin D. Correlation between sagittal plane
changes and adjacent segment degeneration following lumbar spine
fusion. Eur Spine J. 2001;10(4):314–9.
3. Okuda S, Iwasaki M, Miyauchi A, Aono H, Morita M, Yamamoto T. Risk
factors for adjacent segment degeneration after PLIF. Spine (Phila Pa 1976).
2004;29(14):1535–40.
4. Putzier M, Schneider SV, Funk JF, Tohtz SW, Perka C. The surgical treatment
of the lumbar disc prolapse: nucleotomy with additional transpedicular
dynamic stabilization versus nucleotomy alone. Spine (Phila Pa 1976).
2005;30(5):E109–14.
5. Lee SE, Park SB, Jahng TA, Chung CK, Kim HJ. Clinical experience of the
dynamic stabilization system for the degenerative spine disease. J Korean
Neurosci Society. 2008;43(5):221–6.
6. Welch WC, Cheng BC, Awad TE, Davis R, Maxwell JH, Delamarter R, et al.
Clinical outcomes of the Dynesys dynamic neutralization system: 1-year
preliminary results. Neurosurg Focus. 2007;22(1):E8.
7. Parker MJ, Roberts CP, Hay D. Closed suction drainage for hip and knee
arthroplasty. A meta-analysis. J Bone Joint Surg Am. 2004;86-A(6):1146–52.
8. Ovadia D, Luger E, Bickels J, Menachem A, Dekel S. Efficacy of closed
wound drainage after total joint arthroplasty. A prospective randomized
study. J Arthroplasty. 1997;12(3):317–21.
9. Andrews CL. Evaluation of the postoperative spine: spinal instrumentation
and fusion. Semin Musculoskelet Radiol. 2000;4(3):259–79.
10. Nakai S, Yoshizawa H, Kobayashi S. Long-term follow-up study of posterior
lumbar interbody fusion. J Spinal Disord. 1999;12(4):293–9.
11. Agazzi S, Reverdin A, May D. Posterior lumbar interbody fusion with cages:
an independent review of 71 cases. J Neurosurg. 1999;91(2 Suppl):186–92.
12. Andersen T, Christensen FB, Hansen ES, Bunger C. Pain 5 years after
instrumented and non-instrumented p ostero lateral lumbar spinal fusion.
Eur Spine J. 2003;12(4):393–9.
13. France JC, Yaszemski MJ, Lauerman WC, Cain JE, Glover JM, Lawson KJ, et al.
A randomized prospective study of posterolateral lumbar fusion. Outcomes
with and without pedicle screw instrumentation. Spine (Phila Pa 1976).
1999;24(6):553–60.
14. Guigui P, Wodecki P, Bizot P, Lambert P, Chaumeil G, Deburge A. Long-term
influence of associated arthrodesis on adjacent segments in the treatment
of lumbar stenosis: a series of 127 cases with 9-year follow-up. Rev Chir
Orthop Reparatrice Appar Mot. 2000;86(6):546–57.
15. Chou WY, Hsu CJ, Chang WN, Wong CY. Adjacent segment degeneration
after lumbar spinal posterolateral fusion with instrumentation in elderly
patients. Arch Orthop Trauma Surg. 2002;122(1):39–43.
Fei et al. Journal of Orthopaedic Surgery and Research (2015) 10:87 Page 6 of 7
16. Fay LY, Wu JC, Tsai TY, Wu CL, Huang WC, Cheng H. Dynamic stabilization
for degenerative spondylolisthesis: evaluation of radiographic and clinical
outcomes. Clin Neurol Neurosurg. 2013;115(5):535–41.
17. Li Z, Li F, Yu S, Ma H, Chen Z, Zhang H, et al. Two-year follow-up results of
the Isobar TTL Semi-Rigid Rod System for the treatment of lumbar degenerative
disease. J Clin Neurosci. 2013;20(3):394–9.
18. Hoppe S, Schwarzenbach O, Aghayev E, Bonel H, Berlemann U. Long-term
outcome after monosegmental L4/5 stabilization for degenerative
spondylolisthesis with the Dynesys device. J Spinal Disord Tech. 2012.
19. Haddad B, Makki D, Konan S, Park D, Khan W, Okafor B. Dynesys dynamic
stabilization: less good outcome than lumbar fusion at 4-year follow-up.
Acta Orthop Belg. 2013;79(1):97–103.
20. Grob D, Benini A, Junge A, Mannion AF. Clinical experience with the
Dynesys semirigid fixation system for the lumbar spine: surgical and
patient-oriented outcome in 50 cases after an average of 2 years. Spine
(Phila Pa 1976). 2005;30(3):324–31.
21. Yu SW, Yen CY, Wu CH, Kao FC, Kao YH, Tu YK. Radiographic and clinical
results of posterior dynamic stabilization for the treatment of multisegment
degenerative disc disease with a minimum follow-up of 3 years. Arch
Orthop Trauma Surg. 2012;132(5):583–9.
22. Yu SW, Yang SC, Ma CH, Wu CH, Yen CY, Tu YK. Comparison of Dynesys
posterior stabilization and posterior lumbar interbody fusion for spinal
stenosis L4L5. Acta Orthop Belg. 2012;78(2):230–9.
23. Fayyazi AH, Ordway NR, Park SA, Fredrickson BE, Yonemura K, Yuan HA.
Radiostereometric analysis of postoperative motion after application of
dynesys dynamic posterior stabilization system for treatment of
degenerative spondylolisthesis. J Spinal Disord Tech. 2010;23(4):236–41.
24. Beastall J, Karadimas E, Siddiqui M, Nicol M, Hughes J, Smith F, et al. The
Dynesys lumbar spinal stabilization system: a preliminary report on
positional magnetic resonance imaging findings. Spine (Phila Pa 1976).
2007;32(6):685–90.
25. Kumar A, Beastall J, Hughes J, Karadimas EJ, Nicol M, Smith F, et al. Disc
changes in the bridged and adjacent segments after Dynesys dynamic
stabilization system after two years. Spine (Phila Pa 1976). 2008;33(26):2909–14.
26. Schnake KJ, Schaeren S, Jeanneret B. Dynamic stabilization in addition to
decompression for lumbar spinal stenosis with degenerative
spondylolisthesis. Spine (Phila Pa 1976). 2006;31(4):442–9.
27. Bothmann M, Kast E, Boldt GJ, Oberle J. Dynesys fixation for lumbar spine
degeneration. Neurosurg Rev. 2008;31(2):189–96.
28. Stoll TM, Dubois G, Schwarzenbach O. The dynamic neutralization system
for the spine: a multi-center study of a novel non-fusion system. Eur Spine J.
2002;11 Suppl 2:S170–8.
Submit your next manuscript to BioMed Central
and take full advantage of:
• Convenient online submission
• Thorough peer review
• No space constraints or color figure charges
• Immediate publication on acceptance
• Inclusion in PubMed, CAS, Scopus and Google Scholar
• Research which is freely available for redistribution
Submit your manuscript at
www.biomedcentral.com/submit
Fei et al. Journal of Orthopaedic Surgery and Research (2015) 10:87 Page 7 of 7
