Keywords
lumbar disc herniation - complications - full-endoscopic lumbar discectomy - introduction
- surgical result
Introduction
Full-endoscopic lumbar discectomy (FELD) is a minimally invasive surgical treatment
for symptomatic lumbar disc herniation (LDH) that removes the herniation through an
8-mm diameter cannula using a microforceps under microendoscopic visualization ([Fig. 1A]).[1]
[2] Full-endoscopic techniques can be used to treat recurrent and upper level LDH, nerve
root compression due to degenerative spondylosis, as well as purulent discitis/spondylitis.[2] However, spine surgeons are often hesitant to introduce FELD into their practice
because specialized equipment and training are required.[3] The Japanese Society for Minimally Invasive and Endoscopic Techniques of Spinal
Neurosurgery (JASMETS), formerly known as the Society for Minimally Invasive and Endoscopic
Techniques of Spinal Neurosurgery (SMET-SNS), has been conducting seminars and hands-on
training and dispatching surgical experts around the country to educate and assist
fellow neurosurgeons in adopting FELD. As a result, we began to use FELD in our institution
in 2019. This article provides an overview of our adoption of FELD and compares our
early short-term FELD outcomes with those of microscopic lumbar discectomy performed
during the same period.
Fig.1 (A) An endoscope (→) and a cannula (△) used for a full-endoscopic lumbar discectomy
(FELD). An endoscope is inserted into a cannula in FELD, and instruments are manipulated
through the endoscope. (B) Schematic illustration of the three approaches in FELD. TF, transforaminal approach;
PL, posterolateral approach; IL, interlaminar approach. (C) Schematic diagram of the operating room setup for FELD.
Materials and Methods
FELD Introduction
An experienced spinal surgeon from our institution participated in two technical certification
seminars and a hands-on spine endoscopy certification course organized by JASMETS.
This training was supplemented by direct guidance from a SMET-SNS-certified endoscopic
spine surgeon during the surgeon's first three FELD cases. Proficiency was further
increased by participating in cadaver training.
Patients
Fifty-one consecutive patients who underwent surgical treatment for LDH from July
2019 to December 2021 were retrospectively analyzed. The indication for surgery in
all patients was symptomatic LDH despite conservative treatment. The patients selected
the type of lumbar discectomy (FELD or microdiscectomy) after being informed of the
details of each approach; they were also informed that FELD was in the introductory
stage. The study was approved by the Ethics Committee of Kagawa Rosai Hospital on
May 15, 2020 (No. R2–2).
Pre- and postoperative visual analog scale (VAS) and Japan Orthopaedic Association
(JOA) scores, operative time, blood loss volume, surgical complications, and LDH recurrence
were recorded. Twenty-one patients elected FELD (15 men and 6 women; mean age, 57.0±17.0
years) and 30 elected microdiscectomy (22 men and 8 women; mean age, 58.3±15.9 years).
Outcomes were evaluated using the VAS and JOA score recovery rates. The VAS recovery
rate was defined as (preoperative VAS score−postoperative VAS score)/preoperative
VAS×100 (%). The JOA recovery rate was defined as (preoperative JOA score−postoperative
JOA score)/(29−preoperative JOA score)×100 (%). Recovery rate of 75% or higher was
considered excellent, 74 to 50% was considered good, 49 to 25% was considered fair,
and 24% or lower was considered poor.[4]
Continuous variables are expressed as means±standard deviation and were compared using
the t-test. Categorical variables are expressed as numbers with percentage and were compared
using Fisher's exact test. A p-value of less than 0.05 was considered significant.
FELD Surgical Technique
All patients underwent surgery in the prone position under general anesthesia and
free-running motor evoked potential monitoring. One of three FELD approaches was used:
transforaminal (TF), posterolateral (PL), or interlaminar (IL)[1] ([Fig. 1B]). The TF approach was performed by puncturing 10 to 12cm from the midline at an
angle of 22 to 24degrees from the horizontal plane and entering the disc through the
safety triangle in the intervertebral foramen. The PL approach was performed by puncturing
5 to 8cm from the midline at an angle between 30 and 60degrees from the horizontal
plane; this approach was mainly applied to LDHs outside the intervertebral foramen.
The IL approach was mainly applied to L5/S1 disc herniations in which the TF approach
was considered difficult because of the anatomical position of the iliac crest. This
approach was usually performed by puncturing 1 to 2cm from the midline and drilling
off the vertebral arch if necessary; the LDH was then removed via the same route as
microdiscectomy. The operating room setup for FELD is shown in [Fig. 1C]. Fluoroscopy and endoscopy monitors were placed opposite to the approach side. The
scrub nurse was positioned to the right of the surgeon to ensure smooth handing of
surgical instruments. In the TF approach, the patient was placed in a flexed position
under fluoroscopy to open the intervertebral foramen. After induction of anesthesia,
1 to 2mL of a 1:1 mixture of indigo carmine dye and Omnipaque 240 contrast (GE Healthcare,
Tokyo, Japan) was injected into the disc under fluoroscopic guidance to increase disc
visibility before surgery. In addition, a wide scaffold was prepared and used to facilitate
operation of the foot switches of the bipolar electrocautery and drill at a height
that would allow the surgeon to operate the endoscope in a natural position without
shoulder strain[3] ([Fig. 2A], ⇨). In addition, a draping method was applied to prevent water leakage from the
intraoperative irrigation system ([Fig. 2B], △).
Fig. 2 (A) To enable the easy operation of bipolar and drill foot switches at a height that
allows the endoscope to be operated naturally (⇨), we prepared and used a wide scaffold.
(B) Because full-endoscopic lumbar discectomy (FELD) is performed with saline perfusion,
the technical instructor taught the draping method, less likely to cause water leakage
(△).
Results
Among the 21 patients in the FELD group, the TF, PL, and IL approaches were performed
in 8, 3, and 10 patients, respectively. The preoperative VAS and JOA scores in the
FELD group were 4.9±0.8 and 15.9±3.2, respectively, and did not significantly differ
from those in the microdiscectomy group. Intraoperative dural tears occurred in one
patient in each group; these were closed with suture during surgery. The dural tear
in the FELD group occurred in the nerve root axilla during an IL approach and was
addressed by converting to microdiscectomy. No other serious complications occurred.
Both JOA and VAS scores significantly improved in both groups. The VAS and JOA recovery
rates in the FELD group were 71%±12% (good) and 75%±12% (excellent), respectively.
In the microdiscectomy group, the corresponding scores were 74%±21% (good) and 86%±9%
(excellent), respectively. Operative time did not significantly differ between the
FELD and microdiscectomy groups (138.5±62.5 vs. 112.8±31.9minutes). Blood loss volume
was small (32.6±25.3mL) in the microdiscectomy group and almost negligible (≤ 5mL)
in the FELD group. Mean follow-up was 10.4±7.5 months in the FELD group and 9.1±5.3
months in the microdiscectomy group. Recurrent LDH occurred in one patient in each
group ([Table 1]).
Table 1
Surgical results of the FELD and microdiscectomy groups
|
FELD
(n=21)
|
Microdiscectomy
(n=30)
|
p-Value
|
|
Age
|
56.5±17.6
|
58.3±15.9
|
0.71
|
|
Sex (M:F)
|
15:06
|
22:08
|
1
|
|
Level
|
L2/3
|
3 (TF)
|
1
|
0.097
|
|
L3/4
|
4 (TF)
|
7
|
|
L4/5
|
4 (TF)
|
14
|
|
L5/S1
|
10 (IL)
|
8
|
|
VAS
|
Preop
|
5.4±1.3
|
6.0±1.9
|
0.15
|
|
Postop
|
1.8±1.3[a]
|
1.5±0.7[a]
|
0.36
|
|
Rate of improvement
|
0.67±0.17
|
0.73±0.16
|
0.21
|
|
JOA score
|
Preop
|
15.9±3.2
|
14.4±4.9
|
0.24
|
|
Postop
|
25.8±2.7[a]
|
25.9±1.8[a]
|
0.89
|
|
Rate of improvement
|
0.76±0.16
|
0.78±0.12
|
0.57
|
|
Complication
|
Dural injury: 1
|
Dural injury: 1
|
1
|
|
Operative time
|
131.5±45.2min
|
111.0±29.3min
|
0.057
|
|
Blood loss
|
Small amount
|
32.6±25.3mL
|
–
|
|
Follow-up (mo)
|
8.9±5.8
|
7.3±5.6
|
0.076
|
|
Recurrence
|
1
|
1
|
1
|
Abbreviations: F, female; FELD, full-endoscopic lumbar discectomy; IL, interlaminar;
JOA score, Japan Orthopaedic Association score; M, male; TF, transforaminal; VAS,
visual analog scale.
a Significantly different (p<0.05) compared with the preoperative values of each group.
Illustrative Cases
Case 1: L5/S1 Disc Herniation Removed Using the IL Approach
A 20-year-old male presented with lumbago and right lower extremity pain for 3 months
that persisted despite analgesic treatment. Magnetic resonance imaging (MRI) showed
a right L5/S1 disc herniation ([Fig. 3A, B]). Right S1 sensory disturbance was noted on neurological examination. JOA and VAS
scores were 17 and 5, respectively. After informed consent was obtained, FELD using
the IL approach was performed. After the yellow ligament was removed during surgery,
the blue-stained prolapsed herniated mass was identified lateral to the right S1 nerve
root ([Fig. 3C]) and removed. This decompressed the nerve root, which moved laterally. After confirming
no lateral or ventral S1 nerve root compression ([Fig. 3D]), the operation was terminated. Immediately after surgery, the patient reported
symptom relief without pain at the surgical site. He was discharged on the third postoperative
day with JOA and VAS scores of 28 and 1, respectively. The MRI at discharge showed
a sufficient reduction in the size of the hernia ([Fig. 3E, E]). No symptom recurrence was observed at the 2-month follow-up.
Fig. 3 Images of a 20-year-old male who underwent full-endoscopic lumbar discectomy (FELD)
with the interlaminar approach. Preoperative right paramedian sagittal (A) and axial (B) T2-weighted magnetic resonance images showing a right herniated disc at L5/S1. Endoscopic
view showing a blue-stained herniated disc compressing the right S1 nerve root (*)
medially (C). After removing the herniated disc medial to the right S1 nerve root, we confirmed
sufficient decompression of the right S1 nerve root (D). Postoperative magnetic resonance imaging (MRI) at 3 days showed a reduction in
the size of the hernia. (E) Left paramedian sagittal image. (F) Axial image at L5/S1.
Case 2: L3/4 Disc Herniation Using the TF Approach
A 72-year-old male was referred to us by his local physician to evaluate lumbago and
severe right lower extremity pain. MRI showed a left L3/4 disc herniation that reached
the left intervertebral foramen ([Fig. 4A, B]). A left L3 nerve root block provided temporary relief. Preoperative JOA and VAS
scores were 11 and 8, respectively. After informed consent was obtained, FELD was
performed using the TF approach. During surgery, the blue-stained disc was identified
([Fig. 4C]) and a cavity in the disc was created. As the angle of the endoscope shifted more
horizontally, the epidural dissection was performed and the traversing nerve root
was identified ([Fig. 4D]). The endoscope and cannula were then gradually shifted superiorly until the exiting
nerve root was visible and the migrated herniated disc fragment was dissected ([Fig. 4E]). The cannula was then withdrawn under fluoroscopy to confirm nerve root decompression.
The patient's symptoms improved immediately and he was discharged 7 days later with
JOA and VAS scores of 28 and 1. MRI at discharge showed a sufficient reduction in
the size of the hernia ([Fig. 4E, F]). No symptom recurrence was observed at the 3-month follow-up.
Fig. 4 Images of a 72-year-old man who underwent full-endoscopic lumbar discectomy (FELD)
with the transforaminal approach. Preoperative left paramedian sagittal (A) and axial (B) T2-weighted magnetic resonance imaging (MRI) demonstrating a left herniated disc
at L3/4 that reached the right intervertebral foramen. The endoscopic view shows a
blue-stained disc (C). The traversing nerve root (*) was identified after the epidural dissection was
performed (D). The endoscope and cannula were then gradually shifted cranially, and the migrated
herniated disc fragment was dissected, then the exiting nerve root (#) was decompressed
(E). Postoperative MRI at 3 days confirmed a reduction in the size of the hernia. (F) Left paramedian sagittal image. (G) Axial image at L3/4.
Discussion
Microdiscectomy for LDH is associated with good surgical outcomes[5] and has been commonly performed by surgeons in our department. Since the introduction
of FELD in Japan in 2003,[6] its use has been increasing; however, some spine surgeons have been reluctant to
adopt it. Reasons include good microdiscectomy outcomes and the fact that FELD is
a completely different technique that requires new skills and training.[7] Surgeons usually experience a higher incidence of FELD complications in the period
early after adopting the technique[8]; therefore, it is important to obtain good outcomes in this phase. In Japan, JASMETS
regularly holds seminars and hands-on sessions to educate fellow surgeons regarding
minimally invasive spinal endoscopic surgery, FELD in particular. Certified surgeons
are also available to attend FELD surgeries upon request to assist in operating room
setup and provide guidance. By participating in JASMETS seminars and workshops and
inviting a certified surgeon to provide guidance, we were able to safely perform 21
FELD cases in the first 2 years and 6 months after adopting the technique. We found
that direct detailed instruction regarding surgical instrument handling and operating
room setup was essential to our success.
We were able to invite a certified physician to our institution for guidance only
three times because of the coronavirus disease 2019 pandemic; however, our relationship
with him has continued and he has been available to respond to any questions. Our
surgical skill improvement has relied on his continued direct guidance. We consider
such a relationship to be essential.
FELD has several advantages. It causes little damage to muscle tissue, the vertebral
arch, yellow ligament, and posterior longitudinal ligament. In addition, it provides
a view of the LDH that is not possible with microscopy and the operative field is
kept clean owing to water irrigation. Furthermore, the TF approach can be used for
revision surgery without passing through adherent scar tissue.[7]
A LDH located inside or outside the intervertebral foramen, as in case 2, often does
not respond to conservative treatment.[9]
[10] The conventional posterior median and paraspinal methods are highly invasive, while
FELD is less so.[10] Our case series included three such cases and all experienced good results. We consider
these to be a good indication for FELD.
Another advantage of FELD is that the technique and skills required can be applied
to diseases other than LDH as the surgeon's skills improve. Other full-endoscopic
spine surgery techniques include percutaneous endoscopic laminoplasty for lumbar spinal
stenosis, percutaneous endoscopic cervical keyhole foraminotomy for cervical radiculopathy,
and percutaneous endoscopic discectomy and drainage for pyogenic spondylitis. Further
developments in full-endoscopic spine surgery are expected in the future.[7]
Complications of FELD include postoperative dysesthesia (owing to surgical nerve root
stimulation), intra-abdominal organ injury during disc puncture in the high lumbar
spine, and less frequently, massive bleeding from an intraforaminal artery. Dural
injury is a relatively common complication of the TF and IL approaches.[11]
[12] The one we experienced occurred during an IL approach to an L5/S1 disc herniation.
In this case, the herniation appeared axillary on preoperative MRI; however, it was
actually in the shoulder region. After the injury, we immediately switched to microscopic
surgery and performed a successful repair. Such a possibility should be explained
to the patient before surgery.
On a technical note, meticulous hemostasis at the time of endoscope removal is essential.
Moreover, discontinuation of antiplatelet agents and anticoagulants before surgery
is required. Even a small wound hematoma can cause symptoms because of the small size
of the wound.[13] Intracranial hypertension must also be considered, as it has been reported in cases
of high perfusion pressure or prolonged surgery. Furthermore, epileptic seizures may
occur after neck pain or headache. However, we have not experienced any such complications
to date, probably because of our participation in the JASMETS seminars and training.
Conclusion
Spine surgeons who adopt FELD can achieve good surgical outcomes similar to those
of microdiscectomy, even in the early period. Participation in JASMETS seminars and
training and proctoring by a certified endoscopic spine surgeon were instrumental
in our experience.
