Observational Study Medicine ®

Percutaneous endoscopic lumbar discectomy for

L5-S1 disc herniation based on image analysis
and clinical findings
A retrospective review of 345 cases
Shih-Chieh Shen, MDa,b, Hung-Chieh Chen, MDc,d, Hsi-Kai Tsou, MD, PhDe,f,g,h,* , Ruei-Hong Lin, MDe,
Yu-Tung Shih, MDi,j, Chih-Wei Huang, MDk, Chien-Lun Tang, MDk, Hsien-Te Chen, MD, PhDl,m,n,
Chien-Chun Chang, MDm,n, Chung-Yuh Tzeng, MD, PhDo,p

Abstract
The effect of spinal anatomical anomalies on the efficacy of percutaneous endoscopic lumbar discectomy (PELD) for disc herniation
repair is unclear. This retrospective review aims to assess the safety and effectiveness of PELD for treating L5-S1 disc herniation
with a range of characteristics and to determine the prevalence of lumbosacral transitional vertebrae (LSTV) anatomical anomalies
to facilitate pre-surgical planning. From July 2005 to June 2019, 345 patients with L5-S1 disc herniations were treated with PELD.
The primary outcome was 1-year postoperative visual analogue scale scores for low back and lower limb pain. The secondary
outcomes included the surgical approach used, lumbosacral bony anomalies, presence of a ruptured disc or severely calcified
disc, pediatric lumbar disc herniation, recurrent disc herniation management, and the long-term outcome. visual analogue scale
scores for most patients were significantly improved after surgery. The prevalence of LSTVs was 4.05% (14/345 patients) in
lumbar sacralization and 7.53% (26/345 patients) in sacral lumbarization. The prevalence of ruptured and severely calcified discs
was 18.55% (64/345) and 5.79% (20/345), respectively. The prevalence of pediatric lumbar disc herniation was 2.02% (7/345).
The recurrence rate was 4.34% (15/345). Two durotomy cases without sequelae and 8 cases of lower limb dysesthesia lasting
longer than 3 months postoperatively were reported. PELD is safe and effective for treating L5-S1 disc herniation, including cases
complicated by calcified lumbar disc herniation, disc rupture with migration, and the presence of LSTV. Appropriate imaging is
essential to identify case-specific factors, including the prevalent LSTV anatomical anomalies, before surgery.
Abbreviations: CT = computed tomography, IL = interlaminar, IV = intravenous, LDH = lumbar disc herniation, LSTV =
lumbosacral transitional vertebrae, MRI = magnetic resonance imaging, PELD = percutaneous endoscopic lumbar discectomy,
TF = transforaminal, VAS = visual analogue scale.
Keywords: calcified disc, lumbosacral transitional vertebrae, pediatric lumbar disc herniation, percutaneous endoscopic lumbar
discectomy, ruptured disc

SCS and H-CC contributed equally to this work. Institute, Taichung Veterans General Hospital, Taichung, Taiwan, R.O.C, l
Department of Sports Medicine, College of Health Care, China Medical University,
The authors have no conflicts of interest to disclose.
Taichung, Taiwan, R.O.C, m Department of Orthopedic Surgery, China Medical
The datasets generated during and/or analyzed during the current study are University Hospital, China Medical University, Taichung, Taiwan, R.O.C, n Spine
available from the corresponding author on reasonable request. Center, China Medical University Hospital, China Medical University, Taichung,
This study was approved by the Institutional Review Board (IRB) of Taichung Taiwan, R.O.C, o Department of Orthopedics, Taichung Veterans General
Veterans General Hospital (#CE19352B) and performed in accordance with the Hospital, Taichung, Taiwan, R.O.C, p Department of Medicinal Botanicals and
Declaration of Helsinki. Due to the retrospective nature of this study, informed Health Applications, Da-Yeh University, Changhua County, Taiwan, R.O.C.
consent (written/verbal) of the patients was waived by the IRB of Taichung * Correspondence: Hsi-Kai Tsou, Functional Neurosurgery Division, Neurological
Veterans General Hospital because the study analyzed anonymous clinical data. Institute, Taichung Veterans General Hospital, 1650 Taiwan Boulevard Sec. 4,
a
Department of Surgery, Tri-Service General Hospital Songshan Branch, Taichung, Taiwan 40705, R.O.C (e-mail: tsouhsikai@gmail.com).
National, Defense Medical Center, Taiwan, R.O.C, b Department of Biomedical Copyright © 2023 the Author(s). Published by Wolters Kluwer Health, Inc.
Engineering, National Yang Ming Chiao Tung University, Taiwan, R.O.C, c This is an open access article distributed under the Creative Commons
Department of Radiology, Taichung Veterans General Hospital, Taichung, Attribution License 4.0 (CCBY), which permits unrestricted use, distribution, and
Taiwan, R.O.C, d School of Medicine, National Yang Ming Chiao Tung University, reproduction in any medium, provided the original work is properly cited.
Taipei, Taiwan, R.O.C, e Functional Neurosurgery Division, Neurological Institute, How to cite this article: Shen S-C, Chen H-C, Tsou H-K, Lin R-H, Shih Y-T,
Taichung Veterans General Hospital, Taichung, Taiwan, R.O.C, f Department of Huang C-W, Tang C-L, Chen H-T, Chang C-C, Tzeng C-Y. Percutaneous
Rehabilitation, Jen-Teh Junior College of Medicine, Nursing and Management, endoscopic lumbar discectomy for L5-S1 disc herniation based on image
Miaoli County, Taiwan, R.O.C, g Department of Post-Baccalaureate Medicine, analysis and clinical findings: A retrospective review of 345 cases. Medicine
College of Medicine, National Chung Hsing University, Taichung, Taiwan, R.O.C, 2023;102:5(e32832).
h
College of Health, National Taichung University of Science and Technology,
Taichung, Taiwan, R.O.C, i Department of Neurosurgery, Jen-Ai Hospital, Received: 14 January 2022 / Received in final form: 10 January 2023 / Accepted:
Taichung, Taiwan, R.O.C, j Institute of Biomedical Sciences, National Chung Hsing 11 January 2023
University, Taichung, Taiwan, R.O.C, k Department of Neurosurgery, Neurological http://dx.doi.org/10.1097/MD.0000000000032832

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1. Introduction 2.2. Surgical technique

Percutaneous endoscopic lumbar discectomy (PELD) is a min- All PELD procedures were performed by the same neurosur-
imally invasive treatment for lumbar disc herniation (LDH). geon. All patients were given prophylactic antibiotics (1000 mg
The benefits of PELD over open lumbar discectomy include cefazolin sodium or 2000 mg cefazolin sodium if body
less intraoperative blood loss, better paravertebral muscle weight > 80 kg) within 30 minutes of surgery. In those patients
preservation, and shorter hospital stays. Because PELD results treated with the IL approach, surgery was performed with the
in less epidural scarring by preserving the ligamentum fla- patient under intravenous (IV) anesthesia but clearly conscious
vum,[1,2] disc re-treatment is safer and more effective. PELD and lying prone on a radiolucent table.[9] The skin incision was
is also proven safe and effective for the treatment of pediat- made as close as possible to the medial area of the craniocaudal
ric LDH.[3,4] Thus, PELD has become an alternative to con- center of the IL window, facilitated by insertion of a 2-chan-
ventional open discectomy for LDH management. For the nel dilator into the lateral edge of the IL window. A working
treatment of LDH, PELD can be performed using a transfo- sleeve with an 8.0 mm outer diameter and beveled opening was
raminal (TF) or interlaminar (IL) approach. Appropriate sur- then directed toward the ligamentum flavum. The remainder of
gical planning, including the choice of approach, is informed the procedure was performed under direct visual control and
by case-specific characteristics of the lesion and contributes with constant irrigation. A lateral incision window (6–8 mm)
to successful PELD outcomes for LDH. Such characteristics was made in the ligamentum flavum to expose the neural struc-
include the presence of lumbosacral transitional vertebrae tures and epidural fat tissue. The working sleeve with beveled
(LSTV), the direction of disc material migration in the herni- opening could be turned and used as a nerve hook. Using the
ated disc, and the presence of calcified LDH. joystick principle, medial and lateral as well as cranial and cau-
Present in 4% to 30% of the general population,[5,6] LSTV are dal mobility within the spinal canal could be manipulated to
common congenital vertebral anomalies that range in morphol- search for and remove the protruding disc with the aid of con-
ogy from broadened transverse processes to complete fusion.[6] trol optics and a bipolar probe. All surgical instruments and
Preoperative detection of an LSTV is essential to determining the endoscopic system were supplied by Richard Wolf GmbH
the correct spinal level for surgery and to avoiding procedural (Knittlingen, Germany). The high-resolution endoscope had a
and surgical errors. Anomalous articulation or fusion between 4.1 mm intra-endoscopic working channel, and the direction of
LSTV and the sacrum makes the TF approach difficult; thus, view was 25°. The combination of the 8.0-mm outer diameter
the spinal level should be identified preoperatively. In addition, and beveled opening of the working sleeve enabled us to create
disc rupture involves extrusion of the disc nucleus out of the visual and working fields in an area without a clear, anatomi-
annulus, into the spinal canal, commonly causing leg pain. cally pre-formed cavity. A high radiofrequency low temperature
Ruptured disc migration refers to disc material displacement bipolar probe (Elliquence, LLC, Baldwin, NY) was used.
away from the open annulus where the disc has extruded.[7] Based on preoperative MRI findings, the IL axillary or shoul-
Upward or downward migration should be identified during der approach was chosen depending on the location of the disc
preoperative planning so that surgical management can be herniation and the presence or absence of migration. For patients
adjusted accordingly. Finally, calcified LDH is rare and is most treated with the TF approach, surgery was performed under IV
prevalent in China.[8] The hard texture of a calcified disc makes anesthesia, with the patient clearly conscious and lying prone on
the TF approach difficult, requiring the IL approach in such a radiolucent table. The insertion site was localized at the highest
cases. Postoperative lower limb dysesthesia seems to be more laminal level of the symptomatic side using the fluoroscopic lat-
common in cases involving a calcified disc. Thus, calcified LDH eral view. A spinal cannula was gently inserted into the selected
identified preoperatively requires careful consideration in the disc at the dorsal aspect. A guide wire was then placed along the
surgical plan. spinal cannula, and the spinal cannula then was removed. A skin
The purpose of this retrospective review is to assess the safety incision about 8 mm in length was made and a 2-channel dilator
and effectiveness of PELD for treating L5-S1 disc herniation with inserted into the disc space along the guide wire. The working
a range of characteristics and to determine the prevalence of LSTV sleeve and endoscope were then inserted as previously described.
anatomic anomalies to assist medical professionals with pre-surgi- Under direct visual control, the bulging disc was removed and
cal planning. The use of different surgical techniques to accommo- the posterior annulus fibrosus adequately decompressed.
date case-specific disc herniation characteristics is also discussed. All patients treated with the TF approach had a low iliac crest
or LSTV, eliminating the need for foraminoplasty (Fig. 1). Among
our patients, the TF approach was used in 9.27% (32/345), the
2. Materials and methods IL axillary approach in 72.75% (251/345), and the shoulder
2.1. Patient demographics approach in 18.26% (63/345). One patient with a huge bulging
disc underwent both the axillary and shoulder approaches.
We retrospectively reviewed the data of 345 consecutive patients
treated with PELD for L5-S1 disc herniation at Taichung Veterans
General Hospital between July 2005 and June 2019. The patient
age, sex, and diagnosis were extracted from the medical records. 2.3. Outcome assessment
Preoperative radiographs (anteroposterior and lateral) and magnetic The primary outcome was the mean 1-year post-PELD VAS
resonance image (MRI) of the lumbar spine were also evaluated. score for low back and low limb pain. The secondary out-
Computed tomography (CT) of the lumbar spine was carried out if comes included patient satisfaction, the site of disc herniation,
a calcified disc was suspected. Thoracic spine radiography (antero- LSTV, migration of ruptured disc herniation, severe calcified
posterior) was used to detect the presence and lumbosacral level disc herniation, surgical approach, and pediatric disc hernia-
of LSTV. To evaluate the effectiveness of PELD, preoperative and tion. Adverse events including complications from PELD were
postoperative visual analogue scale (VAS) pain scores were recorded recorded. The MacNab scale score was used as the indicator
for each patient with low back and lower limb pain. Complications of clinical outcomes and pain relief.[10] The MacNab approach
arising from PELD included cerebrospinal fluid leakage, wound classifies clinical symptoms into 4 groups (excellent, good, fair,
infection, postoperative sequelae, and recurrent disc herniation. and poor), but this score was not accurate enough to classify
This study was approved by the institutional review board pain. Thus, we modified the MacNab score to include the VAS
of Taichung Veterans General Hospital (#CE19352B) and per- score (post-PELD 1-year VAS compared with pre-PELD VAS)
formed in accordance with the Declaration of Helsinki. Due to in the clinical outcomes for the MacNab score. The modified
the retrospective nature of this study, informed consent (written/ MacNab score classified pain as follows: excellent (no pain;
verbal) of the patients was waived. VAS = 0 and 100% pain relief); good (50–99% pain relief), fair

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Figure 1. The transforaminal approach on the L5-S1 level was used to indicate the lower iliac crest condition. (a, b) A 41-years-old female presented with low
back pain and painful numbness radiating to the left buttock and a history of more than 1 year of left lower limb pain.

(1–49% pain relief), and poor (0% pain relief and no overall Table 1
improvement).
Baseline characteristics of the study cohort of 345 patients.
Number of patients
2.4. Statistical analysis
Male/Female 219/126
All data are presented as the mean and standard deviation (SD).
Age (yr) 39.40 (range,
All analyses were conducted using Microsoft Excel 2016 soft-
13–84)
ware (Microsoft, Inc, Redmond, WA). Mean preoperative VAS score (low back pain/lower limb pain) 5.75/7.41
Surgical approach*
 Interlaminar axillary 251 (72.75%)
3. Results  Interlaminar shoulder 63 (18.26%)
The patient cohort included a total of 345 patients (219 males;  Transforaminal 32 (9.27%)
126 females) with a mean age of 39.40 years (range, 13–84 Site of disc herniation
years) (Table 1). The mean VAS scores for low back pain and  Left 212 (61.44%)
 Right 133 (38.55%)
lower limb pain decreased dramatically from baseline within 1 LSTVs
week after surgery and continued to decrease through the fol-  Lumbar sacralization 14 (4.05%)
lowing year of follow up (Table 2; Fig. 2). Of the 256 patients  Sacral lumbarization 26 (7.53%)
followed for a year, the mean low back pain VAS score decreased  6th lumbar vertebra 3 (0.86%)
from 5.75 (± 2.75) preoperatively to 0.26 (± 0.57) 1-year post- Ruptured disc herniation** 64 (18.55%)
PELD. The mean lower limb pain VAS score decreased from  Upward 8 (12.5%)
7.41 (± 1.74) preoperatively to 0.29 (± 0.58) 1-year post-PELD  Downward 27 (42.18%)
(Table 2; Fig. 2). Excellent outcomes on the modified MacNab  No migration 30 (46.87%)
scores[10] were reported by 60.14% of the cohort for low back Severe calcified disc herniation 20 (5.79%)
pain and 72.69% for lower limb pain. Good outcomes were Pediatric disc herniation 7 (2.02%)
reported by 33.94% for low back pain and 21.40% for lower Recurrent disc herniation 15 (4.34%)
limb pain. Nearly 4% had a fair outcome for relief of low back * One patient underwent both axillary and shoulder approaches owing to a huge bulging disc.
and lower limb pain. A poor outcome was reported by 2.21% ** One patient exhibited both large upward and large downward migrated discs.
for low back and lower limb pain. Fifteen patients required LSTV = lumbosacral transitional vertebrae, VAS = visual analogue scale.
repeated surgery.
The prevalence of specific LDH characteristics and spinal
anomalies in our cohort was revealed by analysis of medical Patient satisfaction with PELD (defined as at least 50% pain
record data. Herniated discs occurred more frequently on the left relief[11]) measured 1-year post-PELD was 94.09% (255/271)
side (61.44%; 212/345) than on the right (38.55%; 133/345). for low back pain and lower limb pain.
The prevalence of lumbar sacralization and sacral lumbarization All surgeries were performed under IV sedation, and all
were 4.05% (14/345) and 7.53% (26/345), respectively (Fig. 3). patients were conscious during the procedures. No patients were
The prevalence of a sixth lumbar vertebra was 0.86% (3/345) converted to other surgical techniques. Postoperative complica-
(Fig. 4). The prevalence of ruptured disc was 18.55% (64/345). tions included 2 durotomy cases without sequelae and no need
Migration was upward in 12.5% (8/64) of cases, downward in for repairs; 8 patients had a history of lower limb dysesthesia
42.18% (27/64), and absent in 46.87% (30/64). (Fig. 5). One lasting longer than 3 months. Six lower limb dysesthesia cases
patient exhibited large upward and downward disc migration. involved severely calcified discs, and 2 cases involved recurrent
The prevalence of severe disc calcification was 5.79% (20/345) herniated discs. Thus, severely calcified discs and recurrent her-
(Fig. 6). The incidence of pediatric disc herniation was 2.02% niated disc surgery are risk factors for dysesthesia. No infections
(7/345) (Fig. 7). or surgical failures occurred.
The rate of herniated disc recurrence was 4.34% (15/345).
Ten cases of recurrent disc herniation at the same site were
4. Discussion
treated with repeated endoscopic surgery; the other 5 cases were
treated with major surgery. In addition, 11 cases of recurrent In this study of PELD outcomes for LDH repair in 345 patients,
herniated intervertebral disc occurring after a previous major we observed a dramatic improvement in median postoperative
operation were successfully treated with PELD. The characteris- VAS scores compared to preoperative scores starting 1 week
tics of the herniated discs are detailed in Table 1. after surgery with continued improvement over the next year

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Table 2
Patient mean VAS scores before and after PELD.
Post-PELD Post-PELD Post-PELD
Pre-PELD 1 wk 3 mo 1 yr

Mean VAS score

 Low back pain 5.75 1.12 0.52* 0.26*
 Lower limb pain 7.41 1.45 0.62* 0.28*
Number of patients 345 343 251* 256*
*The mean VAS at 3-month post-PELD is the mean of 251 patients and 1-year post-PELD is the mean of 256 patients; 15 patients who underwent repeated operations were excluded.
PELD = percutaneous endoscopic lumbar discectomy, VAS = visual analog scale.

Figure 2. The number of patients followed and the mean VAS score according to the medical record before surgery, then at 1 week, 3 months, and 1-year
post-surgery. The line graph showed VAS scores for low back pain and lower limb pain, respectively, in the follow-up period. VAS = visual analogue scale.

of follow up. The LDH recurrence rate was 4.34%. Patient sat- with LDH.[15] Another study, however, failed to confirm signif-
isfaction was high, with a median of 94.09% at 1-year post- icant asymmetry in the multifidus muscle above, at, or below
PELD. Our cohort included patients with LSTV anatomical the disc herniation site.[16] This hypothesis will require further
anomalies (lumbar sacralization, 4.05%; sacral lumbarization, examination.
7.53%). The prevalence of ruptured discs was 18.55% and that LSTV is a congenital spinal anomaly involving sacralization
of severely calcified discs was 5.79%. The prevalence of pediat- of the lowest lumbar segment or lumbarization of the most supe-
ric lumbar disc herniation was 2.02%. These results suggest that rior sacral spinal segment. The reported prevalence of LSTV in
PELD L5-S1 disc repair has excellent clinical outcomes and few symptomatic patients ranges from about 7% to 30%[17,18] and
surgical complications for treating LDH with a broad range of was 11.59% (40/345) in our patient cohort. LSTV is of clini-
characteristics. cal significance due to the altered spinal biomechanics result-
Previous studies have shown that PELD using either the IL or ing from these anatomic anomalies. Disc degeneration and disc
TF technique yields favorable outcomes for patients with her- herniation are associated with LSTV.[17,19] In younger patients,
niated lumbar discs.[1,9,12] Yeung et al reported an 89.3% satis- disc herniation and spondylosis are more common in those with
factory result rate among 307 patients treated by posterolateral LSTV than without.[19,20] We observed no significant difference
endoscopic discectomy.[1] Ruetten et al reported a 91% satis- in LSTV prevalence according to age (average age of all patients,
faction rate among 331 patients treated with the endoscopic IL 39.40; average age of patients with LSTV, 39.32 years). Local
technique.[12] Cao et al[13] reported satisfaction rates of 89.8% stress caused by LSTV leads to increased disc degeneration at
(day surgery mode) and 91.0% (non–day-surgery mode) in their the transitional level and above. The observation of a smaller
study of 402 patients. Consistent with the above reports, nearly lordotic curve in the lumbosacral segment and a “squared”
all of our 345 patients gained immediate relief from low back appearance of the transitional vertebrae during surgery suggests
pain and lower limb pain after nerve root decompression, as that the spinal level might have been misidentified. For accu-
indicated by postoperative VAS scores. And based on the mod- rate spinal segmentation assessment before surgery, a complete
ified MacNab scores,[10] around 94.09% of patients reported radiographic spinal survey (including T-L-S spinal x-ray films)
excellent and goods outcomes for low back and lower limb pain. is recommended. Anomalous articulation or bony fusion of the
We observed that more herniated discs occurred on the left transverse process with the sacrum (Castellvi types II, III, and
(212 patients) than on the right side (133 patients). A previ- IV) can obstruct access via the TF approach; thus, such cases
ous study reports that paramedian annular tears were more should be accessed using the IL approach.[21]
common on the left than on the right side.[14] This difference A ruptured disc displaces mainly along the horizontal and
likely reflects the fact that the right back muscles tend to be vertical planes,[7,14] but the direction of disc migration observed
stronger because most people are right-handed. The distance on MRI differs between studies. In our study, downward migra-
from the multifidus muscle to the lamina has been shown to tion of the ruptured disc at the L5-S1 level (27 cases) was more
correlate significantly with multifidus asymmetry in patients prevalent than was upward migration (8 cases). One patient

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Figure 3. Two patients with lumbosacral transitional vertebrae. (a-d) A 36-year-old male presented with low back pain with pain radiating to the right lower limb
for 3 months. (a, b) Radiographs of the lumbar spine showed L5 sacraliation. (c, d) Preoperative MRI showed L4-S1 disc herniation with downward migration
of the right ruptured disc. (e-h) A 26-years-old male presented with right buttock pain radiating to the right lower limb. (e, f) Radiographs of the lumbar spine
showed S1 lumbarization. (g, h) Preoperative MRI showed L5-S1 disc herniation on the right side. MRI = magnetic resonance imaging.

Figure 4. A 23-years-old male presented with low back pain and a 2-year history of painful numbness radiating to the left lower limb. (a, b, c) Radiographs
of the whole spine showed the presence of the sixth lumbar vertebra. (d, e) Preoperative MRI showed L6-S1 disc herniation to the left side. MRI = magnetic
resonance imaging.

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Figure 5. Three patients with a ruptured disc with or without migration. (a, b) A 41-year-old male with a ruptured disc and upward migration. (c, d) A 36-years-
old male with a ruptured disc and downward migration. (e, f) A 37-years-old female with a ruptured disc and no migration.

exhibited equally large upward and downward migrated discs. and microscopically confirmed data, was 5.79%. Preoperative
Schellinger et al[22] suggested that extruded LDH has an equal identification of disc calcification is a key step to successful
chance of displacing upward or downward because the anterior treatment. The endoscopic IL approach may provide superior
epidural space configuration is similar at both the superior and access to calcified herniated discs, with better visualization
inferior vertebral bodies. Daghighi et al[23] reported that cau- of the interface between the herniated disc, nerve root, and
dal (72.2%) and paracentral (74.2%) migrations were the most dural sac. Dural adhesion to the calcified disc is usually found
common extruded LDH patterns noted in 1020 patients, also during surgery. A trephine, burr, or punch used during sur-
confirmed by Son et al[24] in 164 patients with extruded LDH. gery should be manipulated carefully to avoid injury to the
Daghighi also noted that the incidence of upward migration nerve root and dural sac. Even if complete removal of the
increased with patient age and decreased in the lower lumbar calcified disc is not possible, decompression of the affected
spinal levels. To explain this observation, Fries et al[25] hypoth- root is essential.
esized that the anterior epidural space rostral to the disc space Pediatric LDH, a rare condition, is treated surgically in 0.5%
is more available in older patients, who have less fatty tissue to 5% of patients.[3] The prevalence of pediatric patients in our
and whose bodies are widely patent in the higher lumbar inter- cohort was 2.02% (7/345). PELD is an ideal technique for pedi-
space. In our study, the 7 patients with ruptured discs with atric LDH because of its lower level of traumatization compared
upward migration only (mean age: 40.57 years) were slightly to other methods. Wang et al found satisfactory outcomes with
older than the patient population as a whole (mean age: 39.40 low complication rates when using percutaneous endoscopic IL
years). Surgical management and preoperative plans should be discectomy in pediatric patients. Despite significant pain relief
adjusted for each patient to accommodate the migration pattern following open discectomy for pediatric LDH, long-term data
of the ruptured disc.[24] suggest that 20% to 30% of pediatric patients will require addi-
Calcified LDH is challenging to treat surgically, with an tional surgery later in life.[28]
increased risk of incomplete decompression and nerve root Recurrent disc herniation after surgical repair remains a con-
injury. The reported prevalence of intervertebral disc calcifica- cern. In a meta-analysis of 63 studies of PELD for LDH, the
tion varies between studies, from rare[26] to as high as 50% to range of reported rates of recurrence was 0% to 12.5%, with an
70% of patients.[8,27] Because preoperative imaging studies are overall pooled prevalence of 3.6%.[29] Similarly, 15 patients in
based on MRIs, not CTs, evaluating every patient for calcified our cohort experienced recurrent disc herniation at the same site
discs can be difficult. In our study, the prevalence of severe after PELD, a rate of 4.34%. Of these patients, 10 were treated
disc calcification (defined as a disc that is primarily hard) with repeated PELD. All experienced significant improvement
based on preoperative CT imaging, intraoperative findings, with no major complications.

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Figure 6. A 21-year-old female presented with low back pain and a 3-month history of painful numbness radiating to the right lower limb. (a, b) Preoperative
CT showed calcified disc herniation at the L5-S1 level. (c, d) Preoperative MRI showed disc herniation dominant to the right side. CT = computed tomography,
MRI = magnetic resonance imaging.

Many studies have reported a lower incidence of serious 5. Conclusions

complications such as durotomy, neurological deficits, and PELD is safe and effective for treating L5-S1 disc herniation,
infection with PELD than with conventional open discec- including cases complicated by calcified LDH, disc rupture with
tomy.[30,31] Injury to traversing and exiting nerve roots that migration, and the presence of LSTV. Appropriate imaging is
results in persistent leg pain, dysesthesia, and weakness can essential to identify case-specific factors and anatomical anom-
be avoided by performing PELD under IV sedation with the alies before surgery.
patient clearly conscious. By working with patient responses,
manipulation of the working sleeve can be immediately
adjusted to reduce over-traction of the nerve root. Of our 345 Acknowledgments
patients, 2 had durotomy without sequelae and 8 experienced
lower limb dysesthesia longer than 3 months postoperatively. The authors thank Mr. Jun-Peng Chen at the Biostatistics Task
No complications of cerebrospinal fluid leakage, wound infec- Force of Taichung Veterans General Hospital for statistical
tion, poor healing, or permanent neurological deficit were analysis.
noted.
The primary limitation of our study is its retrospective design.
Author contributions
We had no control group with which to perform a comparative
study. We lost 74 patients (74/345; 21.44%) to follow-up 1 year Conceptualization: Shih-Chieh Shen, Hsi-Kai Tsou, Hsien-Te
post-surgery, which may have introduced statistical bias in those Chen, Chien-Chun Chang, Chung-Yuh Tzeng.
results. Further randomized, prospective studies are needed to Data curation: Hung-Chieh Chen, Hsi-Kai Tsou, Yu-Tung Shih.
verify the efficacy of PELD at the L5-S1 level, especially in pedi- Investigation: Hung-Chieh Chen, Yu-Tung Shih.
atric patients. Methodology: Ruei-Hong Lin.

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Figure 7. A 14-year-old girl presented with low back pain and an 8-month history of painful numbness radiating to the right lower limb. (a, b) Preoperative MRI
showed disc herniation at the L4-5 and L5-S1 levels, especially at the L5-S1 level. (c, d) Postoperative MRI showed that the herniated disc had been removed,
and both S1 roots were decompressed. MRI = magnetic resonance imaging.

Project administration: Hsi-Kai Tsou, Chih-Wei Huang, Chien- [4] Wang X, Zeng J, Nie H, et al. Percutaneous endoscopic interlaminar
Lun Tang. discectomy for pediatric lumbar disc herniation. Childs Nerv Syst.
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[5] Delport EG, Cucuzzella TR, Kim N, et al. Lumbosacral transitional
Visualization: Hsien-Te Chen, Chien-Chun Chang.
vertebrae: incidence in a consecutive patient series. Pain Physician.
Writing – original draft: Shih-Chieh Shen, Hsi-Kai Tsou. 2006;9:53–6.
Writing – review & editing: Hsi-Kai Tsou, Chung-Yuh Tzeng. [6] Konin GP, Walz DM. Lumbosacral transitional vertebrae: classifica-
tion, imaging findings, and clinical relevance. AJNR Am J Neuroradiol.
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[7] Lee S, Kim S-K, Lee S-H, et al. Percutaneous endoscopic lumbar discec-
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