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Clinical Neurology and Neurosurgery 147 (2016) 11–17

Contents lists available at ScienceDirect

Clinical Neurology and Neurosurgery

jo ur nal home p age: www.elsev ier .com/ locate /c l ineuro

ransforaminal percutaneous endoscopic lumbar discectomy for veryigh-grade migrated disc herniation

ong Ahna,∗, Il-Tae Jangb, Woo-Kyung Kima

Department of Neurosurgery, Gachon University Gil Medical Center, Incheon, South KoreaDepartment of Neurosurgery, Nanoori Hospital, Seoul, South Korea

r t i c l e i n f o

rticle history:eceived 17 March 2016eceived in revised form 12 May 2016ccepted 16 May 2016vailable online 17 May 2016

eywords:iscectomyull-endoscopicumbarigrated disc herniation

ercutaneous endoscopicransforaminal

a b s t r a c t

Objectives: Transforaminal percutaneous endoscopic lumbar discectomy (PELD) for high-grade migrateddisc herniation has been regarded as a challenging task, but because of the remarkable improvementin navigable instruments and advanced epiduroscopic technique, it can be used for the treatment ofhigh- or very high-grade migrated disc herniation. The purpose of this study was to describe in detailthe standardized technique of transforaminal PELD for very high-grade migrated disc herniation anddemonstrate the clinical results.Methods: Very high-grade lumbar migrated disc herniation was defined as a disc migration beyond theinferior margin of the pedicle. Thirteen consecutive patients with very high-grade lumbar migrated discherniation were treated with transforaminal PELD, which has three stages: (1) direction-oriented trans-foraminal approach, (2) release of periannular anchorage, and (3) epiduroscopic fragmentectomy withnavigable instruments. The surgical outcomes were assessed using the visual analogue pain score (VAS),Oswestry disability index (ODI), and modified Macnab criteria.Results: The operated levels were L3-4 in 2 (15.4%) patients, L4-5 in 10 (76.9%), and L5-S1 in 1 (7.7%). Thedirections of migration were cranial in 8 patients and caudal in 5. The mean VAS for leg pain improved from7.86 ± 1.28 preoperatively to 2.54 ± 1.51 at 6 weeks postoperatively and 1.85 ± 1.07 at 1 year postopera-

tively (P < 0.01). The mean preoperative ODI improved from 84.92 ± 6.36 preoperatively to 27.83 ± 7.34at 6 weeks postoperatively and 17.54 ± 13.40 at 1 year postoperatively (P < 0.01). Excellent or good globaloutcomes were obtained in 84.6%, and the rate of symptomatic improvement was 92.3%.Conclusion: Transforaminal PELD can be effective for very high-grade migrated lumbar disc herniation,and a standardized technique may provide a reliable and reproducible result.

© 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND

. Introduction

Transforaminal percutaneous endoscopic lumbar discectomyPELD) is regarded as a practical alternative to conventional openiscectomy in the treatment of lumbar disc herniations, with ben-fits of less tissue trauma and day-surgery setting [1–8]. As theoncept of transforaminal PELD has been changed from intradiscalecompression to epidural selective discectomy, advanced endo-copic decompression techniques for migrated disc herniation have

een developed [9–16]. Other authors reported the use of mini-ally invasive or percutaneous endoscopic discectomy using an

nterlaminar approach for migrated disc herniation [17–22]. How-

∗ Corresponding author at: Department of Neurosurgery, Gachon University Giledical Center, ADD 21, Namdong−daero 774 beon−gil, Namdong−gu, Incheon

1565, South Korea.E-mail address: ns-ay@hanmail.net (Y. Ahn).

ttp://dx.doi.org/10.1016/j.clineuro.2016.05.016303-8467/© 2016 The Authors. Published by Elsevier B.V. This is an open access article uhttp://creativecommons.org/licenses/by-nc-nd/4.0/).

license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

ever, the feasible degree of migration has been limited to low-gradedisc migration with transforaminal PELD, whereas high-grade discmigration can be the main cause of operative failure after PELD[10,23]. Lee et al. [10] classified the type and degree of migrateddisc herniation. They defined the possible extent of disc migrationand recommended open surgery for far-migrated disc herniationbeyond the limitation. Since then, some authors reported the useof transforaminal or interlaminar approach to treat far-migrateddisc herniation [11–13,20]. The grading system of migrated discherniation for PELD was first suggested by Lee et al. [10] and latermodified by Kim et al. [20]. Based on previous studies, migrateddisc herniation can be classified into 3 categories: low-, high-,and very high-grade migration. Lee et al. [10] and Choi et al. [13]defined “high-grade” disc migration as migration greater than the

measured height of the posterior marginal disc space. Kim et al.[20] described “very high-grade” migrated disc herniation as discmigration that extends beyond the inferior margin of the pedicle in

nder the CC BY-NC-ND license

12 Y. Ahn et al. / Clinical Neurology and Neurosurgery 147 (2016) 11–17

nds beyond the inferior margin of the pedicle in either cranial or caudal direction.

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Table 1Demographics of the 13 patients with very high-grade migrated lumbar discherniation.

No. Age Sex Level Migration Zone Global result

1 72 M L4-5 Superior P Good2 59 F L3-4 Superior P Fair3 46 M L4-5 Superior F + P Excellent4 52 F L4-5 Inferior LR Good5 53 M L3-4 Superior P Good6 40 M L4-5 Inferior LR Excellent7 33 M L4-5 Inferior LR Excellent8 30 M L5-S1 Superior P Excellent9 54 M L4-5 Inferior LR Good10 36 M L4-5 Superior P Excellent11 42 M L4-5 Superior F + P Good12 36 M L4-5 Inferior LR Good13 34 M L4-5 Superior P Poor

Fig. 1. Very high-migrated lumbar disc herniation: a disc migration that exte

ither upward or downward direction (Fig. 1). There are only fewase reports on the use of percutaneous endoscopic technique inhe treatment of very high-grade disc migration. If any, they arexceptional cases that used the interlaminar approach, which isot standardized [13,20]. Owing to the latest technical improve-ent in navigational instruments, the migrated disc fragment can

e accessed by the transforaminal epiduroscopic approach. Weave developed a practical technique in removing high-grade discigration through the transforaminal endoscopic approach with

piduroscopic use of navigable instruments and demonstrated thearly clinical outcomes.

. Materials and methods

.1. Patients and evaluation

Thirteen patients (2 women and 11 men; mean age, 45.2 years;ange, 30–72 years) with unilateral radicular leg pain with orithout sensory change, motor weakness, or decreased deep ten-on reflex; intractable symptoms despite more than 4 weeks ofonservative treatment including selective nerve root blockade;ymptoms corresponding with magnetic resonance images (MRI)nd computed tomography (CT) scans; very high-grade migratedumbar disc herniation at single level on imaging studies; andnderwent transforaminal PELD were included in this cohort studynd were longitudinally followed-up [10,20]. Very high-grade discigration was defined as disc migration that extends beyond the

nferior margin of the pedicle in either upward or downwardirection [20] (Fig. 1). The exclusion criteria were spinal steno-

is, segmental instability, and other pathological conditions suchs acute inflammation, infection, fracture, or tumor. Cases with

high iliac crest in which the pelvic shadow overlay is beyondhe middle of the upper pedicle were excluded from the study

P: paracentral, F: foraminal, LR: lateral recess.

[24]. The clinical outcomes were evaluated using the visual ana-logue pain score (VAS), Oswestry disability index (ODI) [25], andmodified Macnab criteria [26,27]. Data were collected from patientcharts, patient-based outcome questionnaires on regular visit, andtelephone interviews. Patient demographics are summarized inTable 1. The study was approved by our institutional review board,and informed consent was obtained from the patients.

2.2. Surgical technique

The surgical procedure can be categorized into 3 stages (Fig. 2):

(1) direction-oriented transforaminal approach, (2) release of peri-annular anchorage, and (3) epiduroscopic fragmentectomy usingnavigable instruments.

Y. Ahn et al. / Clinical Neurology and Neurosurgery 147 (2016) 11–17 13

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ig. 2. Schematic illustrations of transforaminal percutaneous endoscopic lumbar dransforaminal approach and discectomy using a semi-flexible forceps for inferior dn articulating forceps for superior disc migration.

.3. Patient preparation and direction-oriented transforaminalpproach

Preoperative evaluation from MRI and CT scan is essential toetermine the shape of the migrated disc and the adequate land-

ng point with approach angle. The procedure is usually performednder local anesthesia with conscious sedation. The patients are

njected with midazolam (0.05 mg/kg) intramuscularly and fen-anyl (0.8 �g/kg) intravenously before surgery. Thereafter, themount of sedatives can be adjusted according to the patient’s con-ition and the surgeon’s need. The patient is placed in the proneositioned on a radiolucent table. A typical skin entry point is0–15 cm lateral to the midline according to the patient’s bodyize. For the proper transforaminal epiduroscopic approach, skinntry can be determined using the lateral fluoroscopic view, whichhould be at the skin point between the tip of the spinous pro-ess and the posterior surface of the facet joint on the lateraluoroscopic view. For a shallower approach, the point should beetermined anteriorly, while for a steeper approach, the pointhould be determined posteriorly on the lateral fluoroscopic view.he disc landing and approach angle is determined depending onhe zone and direction of disc migration (direction-oriented trans-oraminal approach). The landing point on the disc should be aslose as possible to the annular tear point. For a cranially migratedisc, a caudal-to-cranial approach angle is recommended, whereasor a caudally migrated disc, a cranial-to-caudal approach angle isecommended (Fig. 2). An 18-gauge spinal needle is inserted intohe disc along the planned trajectory line through the foraminalindow. Preemptive epidurogram and epidural block before discenetration may help determine the shape of the disc herniationnd reduce approach-related pain. Once the needle is inserted into

he disc, discography with indigo carmine is performed to stainhe disc material and determine the leakage pattern through thennular fissure. Then, a staged dilation technique from the guideire, obturator, and final working sheath is performed. The bevel-

tomy (PELD) for very high-grade migrated disc herniation. Left. A cranial-to-caudaligration. Right. A caudal-to-cranial transforaminal approach and discectomy using

ended working sheath is typically placed on the disc to see boththe intradiscal and the epidural space (half-and-half configuration).Thereafter, a working channel endoscope is inserted and a delicateendoscopic exploration can begin.

2.4. Intradiscal and annular release

The release of annular anchorage should be performed aroundthe annular fissure. Initial endoscopic exploration can confirmthe anatomical layer of the periannular structures: the intradiscallayer with the nucleus, the outer layer with the annulus-posteriorlongitudinal ligament (PLL) complex, and the epidural layer withperineural fat and dural sac. Thereafter, intradiscal subannulardebulking is performed until the border of the annular fissure isexposed. Intradiscal release can be performed using grasping for-ceps, radiofrequency bipolar ablator, and side-firing laser. The outerlayer of the annulus and the PLL can be cut using annulus scis-sors. Then, the epidural layer can be released after confirming theepidural space and the migrated disc fragment. Before the adequatereleasing step, the epidural space is hardly opened because of thetight adhesion between the disc and the fibrous anchoring tissues.Once the intradiscal and epidural release is completed, the her-niated mass can be defined, and the epidural working space forinstruments can be obtained.

2.5. Epiduroscopic fragmentectomy using navigable instruments

The use of navigable instruments such as semiflexible forceps,articulating forceps, and flexible curved probe is effective for com-plete removal of very high-grade migrated disc (Fig. 2). Beforeinserting a grasping forceps, the shoulder osteophyte can be cut by

endoscopic cutters. This ventral decompression can create a furtherworking space to approach the migrated disc in a cranial or cau-dal direction. Then, articulating forceps or semi-flexible forceps areapplied toward the tip of the migrated disc under endoscopic and

14 Y. Ahn et al. / Clinical Neurology and Neurosurgery 147 (2016) 11–17

Fig. 3. Illustrated case of a 39-year-old female patient. (A) Preoperative magnetic resonance images (MRI) showing very high-grade cranially migrated disc herniation at theright L4-5 level. (B) Postoperative MRI showing full-scale epidural decompression after selective removal of migrated disc.

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ig. 4. Illustrated case of a 45-year-old male patient. (A) Preoperative magnetic rest the right L4-5 level. (B) Postoperative MRI showing complete epidural decompre

uoroscopic guidance. A flexible curved probe can track the trajec-ory of disc migration and dissect the fragment. The use of navigablenstruments can avoid the need for time-consuming bony resec-ion. The migrated disc can be gently removed in one piece or in

ultiple pieces. Complete herniotomy can be performed by remov-ng the whole herniation mass including the intradiscal fragment,eriannular fragment, and far-migrated remote site fragment. Sup-

e images (MRI) showing severe very high-grade caudally migrated disc herniationafter selective removal of migrated disc.

plementary use of radiofrequency coagulator and side-firing laser isuseful for hemostasis and delicate decompression. After completeherniotomy, the decompressed dural sac and nerve root becomefreely movable. The end point of the procedure is a strong pul-

sation of the dural sac and nerve root with respiration, coughing,or Valsalva maneuver. Finally, careful endoscopic examination isperformed if there is any adverse event such as dural damage or

Y. Ahn et al. / Clinical Neurology and Neurosurgery 147 (2016) 11–17 15

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ig. 5. (A) Visual analogue pain score (VAS) for back pain preoperatively and at 6 w weeks, 6 months, and 1-year postsurgery. (C) Oswestry disability index (ODI) sco

pidural bleeding. After adequate hemostasis, the endoscope isaken out, and a sterile dressing is applied on the surgical wound.

. Results

The operated levels were L3-4 in 2 (15.4%) patients, L4-5 in 10

76.9%), and L5-S1 in 1 (7.7%). The directions of migration wereranial in 8 patients (Fig. 3) and caudal in 5 (Fig. 4). The tails ofhe migrated discs were typically located at the paracentral zone inranially migrated cases and at the lateral recess zone in caudally

6 months, and 1-year postsurgery. (B) VAS for radicular pain preoperatively and atoperatively and at 6 weeks, 6 months, and 1-year postsurgery.

migrated cases (Table 1). The mean ± standard deviation value ofpreoperative VAS score for back pain was 7.15 ± 1.14. The scoreimproved to 2.77 ± 1.01 at 6 weeks postoperatively, 2.38 ± 1.26 at6 months postoperatively, and 2.08 ± 1.12 at 1 year postoperatively(P < 0.01, Fig. 5A). The mean VAS for leg pain was 7.86 ± 1.28 andimproved to 2.54 ± 1.51 at 6 weeks postoperatively, 1.92 ± 1.26 at 6

months postoperatively, and 1.85 ± 1.07 at 1 year postoperatively(P < 0.01, Fig. 5B). The mean preoperative ODI was 84.92 ± 6.36,with 27.83 ± 7.34 at 6 weeks postoperatively, 18.92 ± 13.33 at 6months postoperatively, and 17.54 ± 13.40 (P < 0.01. Fig. 5C). The

16 Y. Ahn et al. / Clinical Neurology and Neurosurgery 147 (2016) 11–17

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ig. 6. The global outcome according to the modified Macnab criteria. Eleven (84.6%xperienced symptomatic improvements.

lobal results according to the modified Macnab criteria were excel-ent in 4 patients (30.8%), good in 7 patients (53.8%), fair in 1atient (7.7%), and poor in 1 patient (7.7%). Therefore, excellent orood results were obtained in 84.6%, and the rate of symptomaticmprovement was 92.3% (Fig. 6). There was 1 postoperative casef dysesthesia, but the patient’s symptom and neurological sta-us were improved in 6 months with repeated epidural block and

edications.

. Discussion

.1. Transforaminal PELD for migrated disc herniation

The PELD technique has been considered as a minimally invasivelternative to conventional open discectomy for soft lumbar discerniation. However, its application in the treatment of migratedisc herniation is limited. The use PELD for high-grade migratedisc herniation is technically demanding and results in less favor-ble outcome [10,23]. For high-grade disc migration, additionaloraminoplasty is required for clinical success [9,11]. Some authorseported that the interlaminar approach offers access to high-gradeigrated disc herniation [13,20]. Thus far, treatment of very high-

rade disc herniation that is beyond the inferior margin of theedicle level with PELD is a challenging task. However, transforam-

nal PELD is increasingly used in the treatment of very high-gradeisc migration owing to the advent of revolutionary develop-ent in surgical instruments and advanced endoscopic approach

echnique. Navigable instruments such as semi-flexible forceps,rticulating forceps, curved forceps, and flexible curved probe [12]an reach the remote site more easily and take out the sequesteredragment without additional bone resection or foraminoplasty. Theexible curved probe can dissect the remote site pathologies andelease the soft tissue adhesion. Thereafter, articulating forceps andurved forceps make the removal of near-migrated disc hernia-ion easier via epiduroscopic approach. Semiflexible forceps canrace the disc migration and grab out the migrated fragment orven sequestered fragment under both endoscopic and fluoro-copic guidance.

.2. Advantage of transforaminal PELD

The transforaminal approach to the migrated disc herniationas several advantages over the interlaminar approach. First, there

s low risk of dural sac damage with the transforaminal approach.s the dural sac is already pushed away by the bulk of the herni-

13 patients experienced excellent or good results, and 12 (92.3%) of the 13 patients

ated fragment in the ventral epidural space, the risk of dural sacinjury is relatively low with the transforaminal approach than theinterlaminar approach. Moreover, there is no need for dural sac ornerve root retraction to expose the herniated fragment with thetransforaminal approach. Second, there is no overhanging laminablocking the endoscopic approach. Resection of the lamina underendoscopic view may be time-consuming and ineffective. Trans-foraminal epiduroscopic exploration can be applied to all lumbarlevels regardless of overhanging lamina. Third, the maternal disc aswell as migrated fragments can be decompressed with transforami-nal approach, which means the “removal of the whole iceberg” fromthe origin of the herniation to the tip of the migrated fragment(complete herniotomy). When using the interlaminar approach,the hidden intradiscal fragment in the maternal disc can possiblyremain, which might lead to recurrent herniation or incompletedecompression. Therefore, removal of only the tip of the iceberg,with the base remaining, can cause delayed reherniation. In con-trast, when using the transforaminal approach, the maternal discand the base of the iceberg would be decompressed first and onlythen would the migrated portion be treated. Finally, the wholeprocedure can be performed under local anesthesia with con-scious sedation, unlike in interlaminar approach. The interlaminarapproach requires general or epidural anesthesia for a safe pro-cedure. In this sense, the transforaminal approach can achieve aminimally invasive procedure than the interlaminar approach.

4.3. Prevention of epidural bleeding and dural tear

One of the most important concerns in this procedure isepidural bleeding. There may be flourishing epidural vessels andcongestions around the herniated fragment. Thus, considerableepidural bleeding may occur during the epidural discectomy anddecompression. Uncontrolled epidural bleeding, by obstructing thesurgeon’s vision, may be the cause of operative failure or epidu-ral hematoma. To prevent this complication, blind insertion of theinstrument into the epidural space should be avoided. A carefuland gradual approach along the migrated fragment going to thetip of the hernia mass is essential. Sometimes, epidural bleedingis inevitable. In that case, direct hemostasis with radiofrequencycoagulator or compression with hemostatic material to the bleed-ing focus for several minutes can stop the bleeding. Dural tear is

another concern during the epidural instrumentation. This com-plication is relatively rare because there is usually clear boundarybetween the dural membrane and the hernia capsule. However,once the dural tear happens during the procedure, conversion

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Y. Ahn et al. / Clinical Neurology

o open surgery may be required. Therefore, the surgeon shouldlways confirm the anatomical relationship between the nerve andoft tissues through the endoscopic visual field.

.4. Limitations

The limitations of this study are the relatively short follow-p period and small number of cases. However, the 12-monthollow-up results can reflect the neural decompression effect of

minimally invasive discectomy technique. Considering the lowncidence of very high-grade migrated disc herniation in actualractice, our number of cases may be considerable. We believe that

longer follow-up period with a larger number of cases is neces-ary to evaluate the long-term effect of transforaminal PELD on discegeneration and relapse of disc disease.

. Conclusion

The advanced technique of transforaminal PELD can be effectiveor very high-grade migrated lumbar disc herniation, and a stan-ardized technique may provide reliable and reproducible results.

unding

The authors have no relevant affiliations or financial involve-ent with any organization or entity with a financial interest in

r financial conflict with the subject matter or materials discussedn the manuscript. This includes employment, consultancies, hon-raria, stock ownership or options, expert testimony, grants oratents received or pending, or royalties.

onflict of interests

The authors declare that there is no conflict of interest regardinghe publication of this paper.

cknowledgments

The authors would like to thank Sang-Ho Lee, MD, PhD, Ho Kim,S, Nayoung Choe, BS, Jae Eun Park, BS, and Sol Lee, BS, for theirupport and assistance with this study.

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