CliniCAl outComes in PAtients After lumbAr disk surgery with

Acta Clin Croat 2013; 52:87-91
Professional Paper
Clinical outcomes in patients after lumbar
disk surgery with Annular Reinforcement
Device: two-year follow up
Duje Vukas1, Darko Ledić1, Gordan Grahovac2, Zlatko Kolić1, Krešimir Rotim3 and Milorad Vilendečić 2
Rijeka University Hospital Center, Rijeka; 2Dubrava University Hospital; 3Sestre milosrdnice University Hospital
Center, Zagreb, Croatia
SUMMARY – Annular Reinforcement Device represents a modification of operative treatment
of intervertebral disk herniation. It is a prosthesis that is anchored into the body of the vertebra.
The intradiscal part of the implant is placed in the inner part of the annulus fibrosus defect. The
aim of this technique is to reduce the incidence of reherniation and the degree of intervertebral
space collapse, which is the most frequent adverse effect of diskectomy. Clinical outcomes of the
treatment group indicated a statistically significant improvement with respect to the control group.
Furthermore, over the period of two years, no cases of symptomatic reherniation were recorded.
Considering that no serious complications occurred during the procedures, it would appear that
this is an implant that, given its encouraging results, should be further verified in carefully designed
future studies.
Key words: Annular closure device; Lumbar spine; Intervertebral disk; Disk herniation; Diskectomy,
The most frequent cause of radicular pain in the
leg among the working population is disk herniation.
In most cases, the symptoms remit spontaneously following conservative treatment, with no indication for
surgery1. In some patients, however, operative treatment is indicated 2. These are patients with serious
neurologic deficits, thxose with cauda equina syndrome, and, most frequently, those patients that show
no improvement following conservative treatment in
the period of six weeks after the onset of symptoms3.
Microdiskectomy and sequestrectomy are the most
frequent types of operative treatment for treating disk
herniation. These are standard operative procedures
with positive clinical outcomes; 70%-80% of patients
report satisfactory recovery2.
Correspondence to: Duje Vukas, MD, Clinical Department of Neurosurgery, Rijeka University Hospital Center, Tome Strižića 3,
HR-51000 Rijeka, Croatia
Received April 18, 2012, accepted January 17, 2013
Acta Clin Croat, Vol. 52, No. 1, 2013
Microdiskectomy is a standard operative procedure for herniated disk4. An alternative approach in
patients with sequestered disk herniation is sequestrectomy, which represents a less invasive surgical procedure, producing comparable clinical results5.
It has also been proven that the incidence of reherniation is reduced when more aggressive diskectomy is performed, but such an aggressive approach
increases degenerative changes6. On the other hand,
less invasive diskectomy leads to a higher incidence of
The idea of modified surgical procedures that would
partially replace the disk tissue in order to reduce the
impact of the procedure on biomechanical relations has
been developed for a number of years now. The first
attempts included hard intradiscal materials (stainless
steel, PEEK)8,9 that are implanted inside the disk itself.
Next, nucleus replacement implants made of different
biochemical structures (hydrogel, polyvinyl-alcohol,
hydrolyzed polyacrylonitrile polymer, polyurethane,
protein hydrogel)10-14 that are inserted inside the disk
D. Vukas et al.
Prospective study of lumbar disk herniation treated by mechanical nucleus implant
and primarily function so as to absorb water, have been
developed. The goal of this has been to try and re-establish the anatomical relations as they were prior to
surgical procedure, and keep them as such.
There are also implants that function mechanically, with the aim of closing the defect in the annulus
fibrosus and protect the remaining disk tissue. Clinical results obtained with the latter technique were the
focus of this study.
There are a few main consequences for the biomechanics of the treated segment. The collapse of the intervertebral disk space speeds up degenerative changes, especially in the facet joints. The most frequent
adverse consequences of the procedure are the increase
in the speed of degenerative changes, accompanied by
chronic pain. Another frequent complication, occurring in up to 25% of surgical patients, is reherniation
within ten years after surgical procedure15, which is
the leading cause of repeated surgical procedures.
The first approach described was suture of the
annulus following diskectomy16. Then, over the past
fifteen years, injectable hydroactive substances and
mechanical implants have been developed. The most
frequent complication of the aforementioned surgical
procedures was migration of the implanted material
from the intervertebral space, inflammatory reaction
of the endplates, and implant subsidence17,18.
The study reported below presents comparison of
patients treated prospectively by standard microdiskectomy (control group), and patients who, following
evacuation of the disk tissue during microdiskectomy,
had the Annular Reinforcement Device (Barricaid
ARD, Intrinsic Therapeutics, Woburn, MA USA)
(Fig. 1) inserted, with the aim of preserving the anatomical structures.
Distal Platinum Iridium Marker
Proximal Platinum
Iridium Marker
Polymer Mesh
Mesh Guide Pocket
Titanium Anchor
Fig. 1. Barricaid Annular Reinforcement Device.
Patients and Methods
In this prospective study, we followed two groups
of patients non-concurrently in an identical way.
Control group comprised 72 patients who were
treated with standard diskectomy between 2003 and
2007, before the Annular Reinforcement Device
was available. Treatment group patients received the
Annular Reinforcement Device in 2008 and 2009.
Treatment group consisted of 30 patients, 16 male
and 14 female, mean age 38.2 years, treated and followed up by the same physicians as the control group.
In the control group, there were 49 male and 23 female patients, mean age 40.6 years. The aim of this
study was to compare and contrast clinical outcome
in patients of the two groups over the study period
of 24 months. Patients were treated at two hospitals
(Dubrava University Hospital, Zagreb, and Rijeka
University Hospital Center, Rijeka, Croatia). The
patients were followed up in identical manner. First
examination was carried out prior to surgery, second
examination immediately after the surgery, and then
at 6 weeks, 3 months, 6 months, 12 months, and
finally two years after surgical procedure. At both
hospitals, the treatment group was approved by the
institution’s ethics committee, although changes to
the device and protocol were made with subsequent
ethics committee review. The control group was an
investigator initiated study approved by each institution’s ethics committee. During the follow up period,
any patient reporting symptoms would be physically
examined and referred for magnetic resonance imaging (MRI) to confirm suspected reherniation.
Similar inclusion/exclusion criteria were applied
to both groups. All patients suffered from neurologic deficit (radiculopathy) for at least six weeks. The
deficit did not improve with conservative treatment.
All patients underwent preoperative MRI to confirm
disk herniation as the cause of neurologic deficit. Patients with leg pain measured by the visual analog
scale (VAS) of the intensity 40/100 or more and disability graded by means of the Oswestry Disability
Index (ODI) higher than 40/100 were included in
the implant group. No minimum ODI was applied
in the group undergoing only diskectomy. VAS
and ODI at all time points were administered and
graded by the same physicians in the treatment and
Acta Clin Croat, Vol. 52, No. 1, 2013
D. Vukas et al.
Prospective study of lumbar disk herniation treated by mechanical nucleus implant
Table 1. Oswestry Disability Index
Time point
Week 6
Month 3
Month 6
Month 12
Month 24
Mean SD
49.4 18.3
30.7 15.5
25.6 13.9
21.6 15.5
19.8 15.8
19.8 17.1
Mean SD
62.7 13.7
31.4 14.6
22.6 10.9
17.7 11.5
15.6 12.2
11.6 10.4
*Wilcoxon rank-sum
Week 6
Month 3
Month 6 Month 12 Month 24
control groups. All patients were in the age range
18-70 years. Patients who had previously had some
spine surgery were not included in the study. Also,
patients suffering from foraminal or extraforaminal
disk herniation were also excluded from the study,
as well as those who suffered from some other spinal
Fig. 2. Annular Reinforcement Device in situ.
Acta Clin Croat, Vol. 52, No. 1, 2013
pathology. Patients unable or unwilling to take part
in the study, as well as those suffering from systemic
or metabolic diseases were not included either. The
annulus fibrosus defect was measured during the
surgery, and, following the prosthesis manufacturer’s instructions, the prosthesis was not implanted in
those patients with annulus defect greater than 6x10
mm (height x width).
Surgical technique
All patients were treated with lumbar diskectomy.
All surgeries were performed under general anesthesia. The patients were in the prone position, with
knees and hips flexed. Prior to surgical procedure,
each surgical patient was administered antibiotic prophylaxis (cefazolin). Medial incision of the skin was
used for unilateral approach to the intralaminar space.
Fluoroscopy was used to verify appropriateness of the
space. Flavectomy was performed, most frequently
accompanied by cranial lamina undercutting. In all
treatment group patients, prosthesis for annular reinforcement was implanted. The prosthesis is made of
a titanium anchor and polymer mesh. The planned
location of the mesh is between the remaining material of the nuclear tissue and annulus fibrosus. The
mesh contains markers that are visible on x-rays, and
are used for visual control of the implant position (Fig.
2). The implant (prosthesis) is inserted following the
manufacturer’s recommendations. Each step is guided
by fluoroscopy.
The implant was inserted in all patients
who were planned to receive prosthesis and
satisfied the criteria for inclusion in the study.
There were no intraoperative complications
due to the modification of the standard procedure. The procedure was not significantly
prolonged, and the postoperative course was
identical in both groups. Postoperative care
in the hospital was identical (a mean of 4
days). In terms of complications, we report
durotomy in one patient from the treatment
and control group each.
The mean preoperative ODI was 49.4 in
control group and 62.7 in treatment group.
In both groups, there was considerable (ex89
D. Vukas et al.
Prospective study of lumbar disk herniation treated by mechanical nucleus implant
Table 2. Visual analog scale – back
Time point
Week 6
Month 3
Month 6
Month 12
Month 24
Mean SD
*Wilcoxon rank-sum
Mean SD
66.3 16.6
18.1 18.0
12.1 11.2
14.1 11.6
13.2 15.9
10.5 19.5
Week 6
Month 3
Month 6 Month 12 Month 24
Table 3. Visual analog scale – ipsilateral leg
Time point
Mean SD
Preoperative 58.8
Week 6
Month 3
Month 6
Month 12
Month 24
Mean SD
79.8 12.8
12.7 18.4
12.3 19.3
*Wilcoxon rank-sum
Week 6
Month 3
Month 6 Month 12 Month 24
pected) improvement following the surgery. In the
first 6 months of surgical procedure, the improvement
was relatively the same in both groups, whereas at 24
months of the procedure ODI score was 11.6 in treatment group and 19.8 in control group (Table 1).
VAS was analyzed separately for back pain and for
pain in the affected leg. In this case, too, treatment
group showed higher preoperative values. The mean
preoperative VAS-back was 43.1 in control group and
66.3 in treatment group. At 24 months of the surgery,
the difference in VAS-back was 8.6 (19.1 in control
group and 10.5 in treatment group) (Table 2).
VAS-affected leg was statistically better in treatment group at both 12 (p=0.016) and 24 months
(p=0.0046) of the procedure. At 24 months, the difference between the two groups was 12.3 (21.2 in
control group and 8.9 in treatment group) (Table 3).
In treatment group, not a single symptomatic reherniation occurred. In control group, a 6.9% (5/72)
symptomatic reherniation rate was recorded over
2-year period, with two of the five reherniations occurring in the first three months following the procedure. All of these were reoperated on. There were no
instances of implanted material migration out of or
subsidence into the vertebral body.
Discussion and Conclusion
Intradiscal implants represent a relatively new
technology for treating disk herniation. The implant
we used is simple to use and does not lengthen the duration of surgical procedure. Its use led to significant
clinical improvement as compared with patients who
underwent standard diskectomy. Furthermore, there
was no case of symptomatic reherniation at the operated level among treatment group patients. Outcomes
in both groups were good, with treatment group outcomes being even better; however, the difference was
generally nonsignificant. The significance in leg pain
on later follow ups, along with the near significance
at three months, may have been closely related to the
occurrence of symptomatic reherniations in control
group. A larger study would be useful to clarify these
results. Since our postoperative follow up was quite
short (two years), the study needs to be continued.
Good clinical results obtained in this study are very
encouraging with respect to positive attitudes toward
the implant as a treatment method.
Acta Clin Croat, Vol. 52, No. 1, 2013
D. Vukas et al.
Prospective study of lumbar disk herniation treated by mechanical nucleus implant
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POMOĆU proteze za rekonstrukciju defekta anulusa: REZULTATI DVOGODIŠNJEG
D. Vukas, D. Ledić, G. Grahovac, Z. Kolić, K. Rotim i M. Vilendečić
Ugradnja proteze za rekonstrukciju defekta anulusa čini modifikaciju operacijskog liječenja hernije intervertebralnog
diska. Radi se o protezi koja se ugrađuje (usidri) u korpus kralješka. Intradiskalni dio implantata postavlja se s unutarnje
strane defekta anulusa fibrozusa. Cilj navedene tehnike je smanjivanje incidencije rehernijacija te smanjivanje stupnja kolapsa intervertebralnog prostora kao najčešćih neželjenih posljedica diskektomije. Klinički ishod ispitivane skupine pokazao je statistički značajan napredak u odnosu na kontrolnu skupinu. Također tijekom dvije godine nije zabilježen nijedan
slučaj simptomatske rehernijacije. S obzirom na to da nije bilo ozbiljnih komplikacija tijekom samog zahvata, smatramo da
se radi o implantatu čiji početni rezultati ohrabruju te se moraju potvrditi u slijedećim dobro dizajniranim prospektivnim
Ključne riječi: Proteza za rekonstrukciju defekta anulusa; Lumbalni segment kralježnice; Intervertebralni disk; Hernija diska;
Diskektomija; Ishod
Acta Clin Croat, Vol. 52, No. 1, 2013