Journal of Spinal Surgery

: 2022  |  Volume : 9  |  Issue : 4  |  Page : 205--211

Interlaminar full-endoscopic discectomy for L5-S1 disc herniations: Surgical technique and early outcomes during the learning curve

Umesh Srikantha, Yadhu K Lokanath, Akshay Hari, BS Deepak 
 Department of Neurosurgery, Aster CMI Hospital, Bengaluru, Karnataka, India

Correspondence Address:
Umesh Srikantha
Department of Neurosurgery, Aster CMI Hospital, Bengaluru-74, Karnataka


Background: Interlaminar full endoscopic discectomy has been the least invasive and preferred route to treat disc herniations at L5-S1 and are being increasingly accepted and adopted in many centres. Compared to transforaminal approach, it offers the advantage of a familiar posterior approach with presumably easier transition for surgeons who have been doing another form of minimally invasive spine surgery. Objective: The article describes the surgical steps and early outcomes along the initial learning curve of Interlaminar Endoscopic discectomy for herniated disc at L5-S1 level. Material and Methods: This retrospective study included the first 20 patients who underwent Interlaminar Endoscopic Lumbar Discectomy (IELD) at our center. Patients with unilateral symptoms, failed conservative treatment, and good interlaminar window were selected for IELD. Visual Analog Scale (VAS) score s and McNab criteria were used to assess the outcome. Postoperative magnetic resonance imaging (MRI) was done in the majority of patients to assess and correlate the adequacy of root decompression and extent of discectomy. Results: The mean age of the 20 patients was 41 years (17 to 60 yr) with a male: female ratio of 3:2. The median surgical time was 80 min (40 to 150 min). The mean VAS scores for leg pain reduced from 8.2 preoperatively to 2.1 in the postoperative period. All patients had a minimum follow-up for 6 months. Postoperative MRI was done in 14 patients, which showed complete fragment removal with the good decompression of the nerve root in 12 patients. There was no early recurrence of radicular symptoms in any patient. According to Modified McNab criteria, 8 patients had excellent outcome, 9 patients had good outcome, and 3 patients did fairly well. Conclusion: IELD offers an excellent alternative to tubular surgeries for treating disc pathologies at L5-S1. This series represents the early reports from the first 20 cases at the author's center who have been performing tubular surgeries for more than a decade. With the learning curve been overcome, the technique could be used in a wider array of lumbar spine pathologies henceforth.

How to cite this article:
Srikantha U, Lokanath YK, Hari A, Deepak B S. Interlaminar full-endoscopic discectomy for L5-S1 disc herniations: Surgical technique and early outcomes during the learning curve.J Spinal Surg 2022;9:205-211

How to cite this URL:
Srikantha U, Lokanath YK, Hari A, Deepak B S. Interlaminar full-endoscopic discectomy for L5-S1 disc herniations: Surgical technique and early outcomes during the learning curve. J Spinal Surg [serial online] 2022 [cited 2023 Apr 2 ];9:205-211
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Lumbar disc prolapse is one of the most common pathology encountered by spine surgeons in day-to-day practice.[1] Symptomatic cases refractory to conservative treatment will benefit from surgical discectomy and nerve root decompression to alleviate the pain.[2],[3] With advances in technology and refinement in surgical techniques, there have been several developments in surgical techniques for removing a herniated disc, each claiming to have its advantages and aiming to cement its own place as a standard of care in surgical treatment of lumbar disc prolapse.[3],[4],[5]

Endoscopic spine surgery techniques, especially in the past two decades, have emerged with wider applications and have found greater acceptance among the spine surgeons.[6],[7],[8],[9] Claiming to be the least invasive approach for a surgical discectomy, the transforaminal endoscopic lumbar discectomy, initially described by Kambin and Sampson in 1986[10] and later modified to a direct visualised approach by Yeung in 1999,[11] utilized the natural opening of the foramen to enter the disc and address its pathology. Being a completely new trajectory and approach, spine surgeons needed a considerably longer learning curve to understand the anatomy and re-orient oneself to visualizing the pathology and canal from anteriorly, as against to seeing them from posteriorly during a standard posterior approach.[9],[12]

However, with the introduction of interlaminar full endoscopic techniques in 2006,[13],[14] the technique could be used in a route familiar to most spine surgeons, thus expecting to have a shorter learning curve and utility in a wider array of pathologies than what most surgeons would be comfortable using the transforaminal route for.[15] Furthermore, surgeons who have already been practising another form of minimally invasive spine surgery (Tubular surgery; Destendau) could easily shift to this less invasive technique without worrisome hiccups in the course of their learning curve.

This article describes the steps in interlaminar full endoscopic discectomy and enumerates outcomes in our first 20 cases.

 Materials and Methods

The first twenty cases of IELD done for a herniated disc at L5-S1 by the principal author (U.S) were retrospectively analyzed. Patient with L5-S1 disc herniations who had failed conservative treatment and willing for surgery was assessed regarding the feasibility of undergoing IELD at our center. Patients who were undergoing surgery for L5-S1 disc herniations were chosen and counseled to undergo IELD if they fulfilled the following selection criteria –

Acute disc herniations (chronic cases with calcified annulus or collapsed disc space were excluded and underwent tubular microdiscectomy)Good anatomical interlaminar window at L5-S1Unilateral symptomsAbsence of major neurological deficits/Cauda equina featuresAbsence of instability or severe facet arthrosis.

The cases that underwent IELD were retrospectively analyzed. Their demographic data, clinical symptoms, preoperative Visual Analog Scale (VAS) scores for back pain and leg pain and intraoperative factors were collected. Any intra-operative complications or difficulty faced and postoperative clinical status and outcome including VAS scores were collected. Postoperative magnetic resonance imaging (MRI) was done on first postoperative day in majority of cases, as a routine protocol to document extent of discectomy and decompression to correlate with intra-operative findings. Patients were followed up at 1 week, 6 weeks, 6 months, and 1 year. Any complaints were noted and outcome was assessed according to the modified McNab criteria. All patients were put on a regular physical exercise program under the care of a spine physiotherapist.

Planning and operative room set-up

It is very important to select an appropriate case for IELD, especially when we are starting to do the technique. Prior detailed anatomical knowledge, attending lectures, video sessions, live surgeries, and cadaveric courses conducted by more experienced faculty helps to understand the technique in detail and makes the initial journey smoother. Once the case is identified, detailed radiological evaluation should be done to note the characteristics of the herniated disc (location, size, nerve root displacement, migration, etc.) and to rule out instability (dynamic standing radiographs).

It is also equally important to keep everything ready in the operating room and make sure that the operating room staff are aware of the requirements of the case and have the knowledge to operate the necessary equipment that are going to be used during the surgery. The operating room set-up should be explained to both the staff and anesthetist so that they are aware of their role and position of specific equipment in the operating room.

In general, surgeon and assistant stands on the symptomatic side and endoscopic tower (including the camera unit, monitor, light source, and irrigation pump) is placed in the front of surgeon [Figure 1]b. Endoscope is held in the left hand, thumb is placed between irrigation inlet end and light source (Endoscope C), rest of fingers can used to hold the working cannula and index finger is projected down to guide the working cannula [Figure 1]c. Right hand is used to hold and guide the instruments through the working cannula. The important aspect is prevent surgeons hand fatigue while holding the endoscope in most ergonomic position.{Figure 1}

The entire armamentarium consists of interlaminar endoscope, camera system, viewing monitor, light source, irrigation system, radiofrequency unit and access instruments (rongeurs, grasping forceps, straight dissector, straight and articulated punches, annulotome, radiofrequency probe, and endoscopic burrs) [Figure 1]a. RF probe used in endoscopy is 360° rotatable instrument which help coagulate, cut soft tissue and attain hemostasis. Distal end of RF device is flexible and proximal end of device has rotating unit which guide toward the direction tip of RF probe.

Surgical technique

Positioning and planning skin incision

Patient is positioned prone in the standard fashion and entire procedure is performed under general anesthesia at our center. The target disc is identified on a lateral fluoroscopic image and skin entry is marked approximately 1 cm off the midline with a slight inferior to superior angle to reach the disc [Figure 2]. Craniocaudal localization can also be altered based on the nature of disc prolapse and extent of migration.{Figure 2}

Dilatation and introducing endoscope

After local infiltration, a stab incision is made all the way to the lumbar fascia, followed by insertion of the dilator. The dilator can be used to palpate the inferior edge of the cranial lamina and separate the soft tissue along its edge and over the interlaminar space. Care should be taken not to exert too much downward pressure to avoid inadvertent pressure while dissecting soft tissue over the interlaminar space. A bevelled working sleeve is guided over the first dilator with bevel opening medially. The endoscope is inserted after removing the first dilator and subsequent procedure is performed under constant saline irrigation.

Soft-tissue dissection and exposure of interlaminar window

Soft-tissue dissection to expose the Interlaminar Window (ILW) is performed with help of punches and RF probe. If bony diameter of IL window is small, window can be enlarged using endoscopic diamond burr drilling inferior border of cranial lamina [Figure 3]a and [Figure 3]b.{Figure 3}

Widening the interlaminar window

Prior to flavum resection, it is important to ascertain if the interlaminar space is adequate for the sheath to enter the epidural space. If the space is inadequate, it needs to be widened by drilling the inferior part of the upper lamina, upper part of lower lamina, or the medial part of facet to facilitate the sheath to enter the epidural space. Which bony part to be resected and how much to be resected can be tailored based on the pathology and individual patient's anatomy.

Flavectomy and entering epidural space

Once the flavum is adequately exposed, a linear (horizontal) flavotomy is done perpendicular to the direction of fibers. Using a cutting forceps, the flavum is opened in layers carefully until the epidural fat is visualized through a small opening [Figure 3]c. This opening can then be enlarged using straight and angled cutting forceps or an endoscopic upcutting kerrisons punch. The flaval opening is extended laterally till lateral border of the nerve root is visualized and should be adequate to introduce the sheath into epidural space, deliver the sequestered fragments and access the neural structures.

Identifying neural structures and disc herniation

Once the flavectomy is adequate, any excess epidural fat can be removed using grasping forceps and cauterised with RF, following which a smooth dissector (straight or angled at tip) can be used to identify the lateral border of nerve root [Figure 3]d. Using gentle movements, the nerve root can be dissected and mobilised medially to expose the disc fragment or bulging annulus underneath it [Figure 3]e. Once the retraction is adequate, the sheath is introduced into the epidural space with bevel facing medially and then rotated so that the flange of the sheath itself acts as a nerve root retractor [Figure 3]f. In cases with large axillary fragment, care should be taken to avoid excessive root retraction against the fragment. Removing the fragment partially through the axilla will facilitate safe root retraction and sheath manipulation.


Once root is retracted, an extruded fragment can be directly visualized and removed. The disc fragments can be removed partially or in toto depending on morphology, consistency and chronicity of the herniation. In contained herniations, a small annulotomy using a dissector or annulotome will expose the fragment, which can then be removed. In chronic cases, a larger annular resection may be needed to remove the hardened fragments [Figure 3]g.

Lateral recess decompression

In cases with chronic and broad annular bulging, additional lateral recess decompression can be done by removing the medial lip of superior articular process and its junction with upper part of lower lamina to deroof the traversing root over a longer distance. This bony work is easily accomplished by an endoscopic drill. If this step is done after flavectomy and discectomy, care should be taken to avoid any inadvertent injury to the nerve root while drilling in the lateral recess. Using a sheathed drill bit is helpful in such cases.

Checking adequacy of decompression

The end points of decompression is considered when neural elements are floating free in irrigation fluid. Axillary and shoulder region of root should be thoroughly inspected. Any free floating fragments should be removed and haemostasis is achieved using RF [Figure 3]h.

Withdraw endoscope and closure

The access instruments are removed and wound closed with a single subcutaneous suture and steri-strips.


In total of 20 subjects, the mean age was 41 years (range from 17 to 60). There were 12 males and 8 females. All patients were operated at the last mobile spinal segment. This was L5-S1 level in 18 patients and L4-5 (Sacralised L5) in 2 patients (Both patients had a favourable interlaminar window for IELD). All patients underwent a unilateral approach with 8 patients undergoing a right sided approach and the remaining, a left sided approach. The sheath could be introduced into the epidural space with just a flavotomy in 12 patients and 8 needed some form of drilling to enlarge the interlaminar window to introduce the sheath and endoscope. The median surgical time was 80 min (range - 40 to 150 min). No quantifiable blood loss occurred in any patient. A small dural tear occurred in one patient on the root sleeve, which was left uncorrected. There were no postoperative deficits or wound related complications in this patient in the postop period. In another case (3rd case in the timeline), the intraoperative extent of decompression (fragment removal) was not clear with the endoscope and hence a 16mm tubular retractor was placed to confirm it. No additional decompression or disc removal was necessary after placing the tubular retractor. There were no technical difficulties and equipment malfunction encountered in any case.

All patients were ambulated within 6 hours of the surgery and discharged the next morning. All patients reported good relief in preoperative symptoms on the same evening. The mean VAS score for leg pain decreased from preoperative mean of 8.25 (range - 6 to 10) to 2.1 in the immediate postoperative period. Postoperative MRI was done in 14 patients, which showed complete fragment removal with good decompression of the nerve root in 12 patients [Figure 4]. There were small residual disc fragments in 2 patients, both of which were asymptomatic, hence no further intervention was done and it was decided to monitor and follow them up [Figure 5].{Figure 4}{Figure 5}

A follow-up duration of 6 months was available for all patients. For patients who had not come to the hospital for follow-up, a telephonic consultation was done to note down their complaints (if any) and level of activity. Intermittent back pain was the most common complaint during follow-up. Three patients complained of some residual intermittent paresthesias in the legs. All patients had resumed their job or full household activity. According modified McNab criteria 8 patients had excellent outcome, 9 patients had good outcome and 3 patients did fairly well.


Lumbar disc herniation remains one of the common spinal degenerative condition across any generation and race.[16] With emphasis on early postoperative recovery and return to work, minimally invasive techniques have become popular in the surgical treatment of lumbar disc herniations.[5],[6],[17] Amongst the several minimally invasive techniques available in present day practice, Full-endoscopic techniques are probably the least invasive means of removing a disc herniation under direct vision. They provide direct access to the spinal canal either through the transforaminal or interlaminar windows, minimise paraspinal muscle injury and tissue damage with the transforaminal route offering additional advantages of minimising bone resection and dural sac retraction as well.[6],[9] Transforaminal surgeries approach the spinal canal and disc pathology from a different angle than the commonly performed posterior midline routes, necessitating surgeons to re-orient their pathoanatomical points to be able to perform the procedure effectively and with ease.[12],[18],[19] The authors presume that his could be one of the reasons behind transforaminal surgeries not gaining traction in their centre, which has been performing Tubular retractor assisted surgeries for more than a decade now.

On the other hand, Interlaminar full endoscopic technique utilise the commonly used posterior route to approach the intraspinal pathology, avoiding the need to re-orient oneself to visualising the pathology from anteriorly, as demanded by the transforaminal approach. The authors believe that this was an easier transition from the routinely performed Tube retractor assisted surgeries and one of the reasons for an easier and quicker adaptation of the technique at their centre. They report their early outcomes in a small group (of first 20) patients undergoing IELD for L5-S1 disc herniation with acceptable short-term outcomes and a low complication profile in the course of their learning curve.

IELD also offers several additional advantages over the transforaminal route. Due to the overhang of the iliac crest, narrow foramen owing to a broad pedicle and transverse process of L5, combined with a steep disc inclination angle, approach to L5-S1 disc through a transforaminal route is fraught with limitations and technical difficulty, sometimes necessitating a trans-iliac approach.[20],[21],[22] This combined with an advantage of a wide interlaminar window makes the Interlaminar approach favourable for treating pathologies at L5-S1.[6],[9] IELD has also increased the versatility of pathologies treated by full-endoscopic techniques, particularly for Lumbar canal stenosis.[17]

Full endoscopic discectomy has shown equivalent results to conventional/open discectomy as well as tubular discectomy in several studies.[5],[17] The earliest reports of IELD in 2006 by two independent groups showed favourable outcomes in around 90% of patients with a recurrence rate of 2.4% over 2 years follow-up period.[14],[13] Zelenkov et al. reported favourable outcomes in 94% of their patients with nearly 90% of their patients opting to undergo IELD again if need arises.[23] Hua et al. similarly reported favourable outcomes in 90% of their patients with a recurrence rate of 1.2%.[24] Seventeen of the 20 patients in our series reported favourable outcomes (85%).

Several authors have put the learning curve for IELD at 20 cases.[23],[25] A recent review concluded that the operative time and rate of complications reduced after around 22 cases,[15] with the complication rates reducing from 6.8% in the early group to 3.6% in the late group. The most common critical complication in the early group was an intraoperative dural tear. One patient in our series had a dural injury around the root sleeve. There weren't any other intraoperative complications encountered in our study. The main difficulties faced during the learning curve and methods to overcome them are listed in [Table 1].{Table 1}

In summary, IELD offers an excellent alternative to tubular surgeries for treating disc pathologies at L5-S1. This series represents the early reports from the first 20 cases at the authors centre who have been performing tubular surgeries for more than a decade. With the learning curve been overcome, the technique could be used in a wider array of lumbar spine pathologies henceforth.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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