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Year : 2022  |  Volume : 70  |  Issue : 2  |  Page : 510--514

Unilateral Biportal Percutaneous Transforaminal Endoscopic Lumbar Foraminal Decompression and Discectomy: A Technical Note

Edmond Jonathan Gandham1, Nalli Ramanathan Uvaraj2, Jin Hwa Eum3,  
1 Department of Neurological Sciences, Christian Medical College, Vellore, Tamil Nadu, India
2 Department of Spine Surgery, Madras Medical College, Chennai, Tamil Nadu, India
3 Department of Spine Surgery Bumin Hospital, Busan, South Korea

Correspondence Address:
Edmond Jonathan Gandham
Associate Professor Neurosurgery, Department of Neurological Sciences, Christian Medical College, Vellore 632 004, Tamil Nadu


Background and Introduction: Minimally invasive spine surgery (MISS) is a set of techniques and procedures that reduces the local tissue injury while achieving the same results through traditional open surgery. The techniques for the treatment of lumbar disc herniation and degenerative canal stenosis have evolved from tubular discectomy to endoscopic discectomy. This helps in preserving spine function. Good clinical outcomes have been reported with the use of an endoscope for degenerative lumbar disc disease. Objective: In this video abstract, we present a case lumbar foraminal stenosis in an elderly man that was treated successfully using unilateral biportal endoscopic spine surgery. (UBESS). Surgical Technique: A 70-year-old man presented with progressive neurogenic claudication and left L4 numbness and paresthesias. His claudication distance was 200 m. His MRI Lumbosacral spine showed severe left L4-5 foraminal stenosis due to a disc prolapse. The patient underwent a left-sided unilateral biportal endoscopic transforaminal decompression and discectomy at L4-5 successfully. Postoperative period was uneventful and the patient had significant relief in his symptoms. Postoperative MRI Lumbosacral spine showed no muscle damage with adequate decompression at left L4-5 level. Results: The patient had an uneventful recovery. Conclusion: Biportal percutaneous transforaminal endoscopic discectomy/decompression is an ideal alternative to the uniportal endoscopic and minimal invasive microsurgery for foraminal and paracentral disc herniations and lateral recess and foraminal stenosis.

How to cite this article:
Gandham EJ, Uvaraj NR, Eum JH. Unilateral Biportal Percutaneous Transforaminal Endoscopic Lumbar Foraminal Decompression and Discectomy: A Technical Note.Neurol India 2022;70:510-514

How to cite this URL:
Gandham EJ, Uvaraj NR, Eum JH. Unilateral Biportal Percutaneous Transforaminal Endoscopic Lumbar Foraminal Decompression and Discectomy: A Technical Note. Neurol India [serial online] 2022 [cited 2022 Aug 18 ];70:510-514
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Full Text

Minimal invasive spine surgery (MISS) using the percutaneous transforaminal endoscopic discectomy/decompression (PTED) is commonly performed and is found to be safe and effective in experienced hands.[1],[2] This can be performed by either a uniportal or biportal endoscopic technique. This article describes in detail the technique of PTED using a biportal endoscopic spine surgery technique.


The video in the article describes the technique of unilateral biportal endoscopic spine surgery for lumbar foraminal stenosis. The video describes the relevant surgical anatomy required to perform this surgery. Using this technique the left L4-5 foramen was decompressed and discectomy was done.

Case description: A 70-year-old man presented with progressive neurogenic claudication and with numbness in the left L4 dermatome for six months. His claudication distance was 200 m. He had decreased sensation in the left L4 dermatome to all modalities of sensation by 50%. His MRI showed severe canal stenosis of left L4-5 foramen secondary to disc prolapse. X-ray showed degenerative changes at L4-5 level. There was no listhesis. This is depicted in [Figure 1].{Figure 1}

 Relevant Surgical Anatomy

To effectively perform PTED one should be familiar with the surgical anatomy of the neural foramen and its contents. The neural foramina is occupied by the exiting nerve root, radicular artery, and venous plexus. The radicular arteries are the direct branches from the abdominal aorta. They are frequently paired and well seen from L1 to L4 levels and infrequent at L5 level. The radicular artery is located superior to the exiting nerve root.[3]

The exiting nerve root and the dorsal root ganglion occupy the superior aspect of the neural foramina. Kambin's triangle an empty zone (E) described by Parviz Kambin in 1980 is the safe surgical corridor for the paraspinal approach to the disc space. The triangle's hypotenuse is formed by the exiting nerve root. The inferior border is formed by the inferior end plate of the target disc space. The posterior or the vertical part of the triangle is formed by the lateral edge of the superior articular process (SAP). The superior articular process of the lower vertebrae is the key anatomical landmark for the foraminal approach.[4] This is depicted in [Figure 2].{Figure 2}

Indications and contraindications

PTED technique can be safely applied in treating paracentral lumbar disc herniations (LDH) and is very effective in dealing with far lateral LDH and foraminal LDH. It is also effective in treating lateral recess and foraminal stenosis.[1],[2]

PTED is contraindicated in patients with spondylolisthesis, discitis and bleeding diathesis.[2]

 Surgical Technique

Anesthesia: All PTED surgeries are performed under Propofol sedation with erector spinae regional block. Under ultrasound guidance, a 20-G epidural needle is inserted along the plane of the transducer until the tip hits the transverse process of L1. A volume of 30 ml of 0.5% ropivacaine along with 2.5 mg of dexamethasone and 0.1 mg epinephrine is injected selectively at the L1 transverse process, erector spinae, muscle, and fascia. This is repeated on the other side. This is ideal for surgeries being performed from L1 to L5 levels. There are no hemodynamic changes associated with this block. This paraspinal block also provides good postoperative analgesia.[5],[6]


Patient is positioned prone on Wilson's frame. Care is taken to protect the eyes and the abdomen and to avoid pressure at bony prominences. The area is cleaned and prepped using standard surgical principles.


The procedure requires a 3.5-mm spherical bur (Conmed Linvatec), 0°(Zero degree arthroscope) 4-mm-diameter endoscope (Conmed Linvatec), bipolar flexible radiofrequency probe (Ellman Trigger-Flex probe, Ellman International), 3.5 mm VAPR radiofrequency (RF) electrode (DePuy Mitec), Working cannula (designed by senior author Eum), serial dilators (size 1, 2, 3) a specially designed T shaped soft tissue dissector, standard laminectomy instruments, such as hook dissectors, Kerrison punches, straight and curved curettes and pituitary forceps [Figure 3].{Figure 3}

Placement of portals

Under C arm fluoroscopic guidance, the upper and lower pedicles at the required disc space, and the upper and lower endplates along with the transverse processes are marked. Using a spinal needle (22G) the isthmus or the pars interarticularis (P) is identified and marked. Since identification of the superior articular process (SAP) is difficult on an AP and lateral fluoroscopic imaging it is emphasized that identification of pars interarticularis helps in correct placement of the portals. After confirming the level of pars interarticularis, the skin incisions are made 1 cm above and below to facilitate the working portal and the scopy portal. Usually skin incision is made 2-3 cm from the midline. For a right-handed surgeon approaching from a left side the working portal is below and scopy portal is above [Figure 4] and [Figure 5]. It is vice versa if approached from the right side. This arrangement of the working and scopy portal is interchangeable.{Figure 4}{Figure 5}


This is the most important step of a biportal endoscopic spine surgery (UBESS). After confirming the foramen of interest, the thoracolumbar fascia is infiltrated with local anesthesia (lidocaine). Then the first dilator is used to identify the pars, followed by creating the working space with the second and third dilator. The working cannula specially designed by the senior author (Eum) is used to facilitate easy passage of instruments. The scopy portal is made 2 cm above the distal portal. The T shaped dissector helps in detaching the muscles and soft tissues attached to the bony boundaries of the neural foramen. Triangulation between the scope and the RF probe is the key step before the foraminal dissection. Once the triangulation is complete it is ensured that there is adequate and free egress of normal saline used for irrigation [Figure 6].{Figure 6}

Creation of surgical corridor

RF probe is used to achieve hemostasis and to coagulate the muscle and fascia. Saline irrigation facilitates a clear visual field at the area of interest. The first step of surgery is to identify the pars-interarticularis (P) which is followed by identification of the superior articular process (SAP). The tip of the superior articular process (SAP) is excised using a drill and the empty zone (E) is reached by dissection. The attachments of the ligamentum flavum is identified and is excised. This will expose the fat and the exiting nerve root. Any bleeding during the dissection is controlled by the RF probe. Dissection is carried up to the pars interarticularis and by partially drilling the pars interarticularis the foraminal surgical corridor is created. This can be summarized as Pars interarticularis – Superior articular process—Empty zone–UP (dissection). (PSE-UP) [Figure 7].{Figure 7}

Decompression is complete when we see the pulsations of the exiting nerve root and the thecal sac. If there is disc bulge or disc prolapse annulotomy is performed using a penfield dissector and the sequestered disc is removed. [Figure 8] At each level, C arm is used to confirm the position of the disc space.{Figure 8}


Hemostasis is achieved and after making sure the surgical corridor is clean the working portal is removed. Excess saline retained in the working space is drained by manual squeezing and suction aspiration. A suction drain (Hemovac, 50 ml) is placed and anchored with a stitch. The portals are closed with a subcutaneous stitch/ethilon and tissue adhesive is used to approximate the skin edges. Adequate sterile dressings are applied. [Figure 9]{Figure 9}

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Video timeline with audio transcript:

0.1 to 0.09: We present a case of lumbar foraminal stenosis in an elderly man treated successfully by – unilateral biportal endoscopic spine surgery referred as (UBESS).0.19 to 0.42: This is an MRI of a 70-year-old man who presented with neurogenic claudication and progressive numbness in the left L4 dermatome. As seen here there is severe L4-5 foraminal stenosis secondary to a disc prolapse on the left side. Patient is positioned prone and care is taken to pad the pressure points. Procedure is done using regional anesthesia. Region of interest is marked with pedicle marker, confirmed by an II. Pars interarticularis acts as a guide to placement of portals.0.48 to 1.15: Level is confirmed using a spinal needle and at this point it's important to memorize about Kambin's triangle. The exiting nerve root occupies the superior aspect of the neural foramina. Empty zone as described by Kambin is a safe surgical corridor for the paraspinal approach to disc space. This is depicted by triangle in the picture. Superior articulating process (SAP) is the key anatomical landmark for the foraminal approach. This picture shows the instruments used for UBESS; regular laminectomy instruments can be used.1.16 to 2.06: This is the caudal side and this is the cranial side. Caudal side is the working portal, cranial side is the scopy portal. Skin incisions are made 3 cm from the midline, 1 cm above and below the foramen of interest. After making skin incisions serial dilators are inserted to create a working channel. For a left side approach the scopy portal is above and the working portal is below, for a right-sided approach its vice versa. This is interchangeable. Soft tissue and muscle are detached using the T handle. This allows the widening of working portal to facilitate smooth passage of instruments.2:12 to 2:59: Skin incisions are made on the cranial side to create a scopy portal. Serial dilators are inserted to widen the space. Triangulation is made between the T handle and the dilators. Zero-degree arthroscope is inserted in the scopy portal. Triangulation is the most important step in UBESS. Triangulation is made between the endoscope and dilator inserted in the working portal. At each step we have to ensure there is adequate and free flow of saline. Specially designed Eum's working cannula is inserted into the working portal to allow the passage of radiofrequency (RF) probe and the instruments used for foraminotomy.3:02 to 3:31: Using A RF probe muscle and soft tissue are coagulated and cleared. RF probe helps in attaining hemostasis, Using the RF probe the bony landmarks, i.e pars interarticluaris and SAP are identified. Soft tissue around the SAP is cleared using the RF probe. SAP is defined. Identification of SAP in the early part of the surgery is key to successful foraminal approach. The next step is to identify pars interarticularis.3:36 to 3:49: The tip of sap is drilled partially using a high-speed diamond burr. Adequate flow of saline dissipates the heat generated during drilling. This maneuver increases the working space.3:52 to 5:12: Using a curette the ligamentum flavum is partially disconnected. E denotes the empty zone. Part of pars and SAP is removed to define the empty zone. Dissection is carried to free the ligamentum flavum from its attachments using a curette. The ligamentum flavum is removed in a piece meal fashion using a Kerisson rongeur. This exposes the exiting nerve root and the pad of fat. Nerve root is gently transposed to expose the disc space. Annulotomy is done using the Indian knife, the disc fragments are curetted. Ball tip probe is introduced at this stage to separate the disc fragments.5:14 to 6:16: The disc fragments are removed using the disc forceps. Using the curettes and disc forceps the residual disc fragments are removed till the root is free of compression. Extreme care is taken not to damage the root. Adequate flow of saline helps in better visualization. Annuloplasty is done using the RF probe. Final inspection is done using the ball tip probe to look for residual disc fragments. As noted here the root is free of compression. The field of vision is clear. Surgiflow is used to attain hemostasis.6:17 to 6:24: Postoperative picture showing the skin incisions with in situ drain, the incisions are closed with ethilon.6:26 to 6:31: Postoperative MR showing adequate decompression of the nerve root on the left side.


After surgery patient had significant improvement in his symptoms. His postoperative period was uneventful. Postoperative MRI of the lumbosacral spine showed adequate decompression at the left L4-5 foramen, the root was free. There was no evidence of muscle damage. [Figure 10]{Figure 10}

 Pearls and Pitfalls

The most crucial step in the surgery is early identification of pars interarticularis (P), followed by identification of superior articular process (SAP), dissection in the empty zone of the Kambin's triangle. This can be summarized as P-S-E.[5] In contrast to open microsurgery, PTED has a steep learning curve. PTED is associated with complications related to the neural and arterial structures around the neural foramen. The incidence of nerve root injury and postoperative dysesthesias reported in the literature is close to 5% following a uniportal transforaminal endoscopic technique. The incidence of dural tear is less than 5%. Inadequate separation of the ligamentum flavum, due to incomplete sectioning of epidural ligaments which connects the flavum to the dura can lead to dural tear. This can be managed with tachycomb.[5],[7],[8] If the dural tear is over 1 cm endoscopic suturing can be done, if this is not successful, we need to convert to open surgery. In author's experience conversion of endoscopic surgery to open surgery to manage a CSF leak was required in only 1% of his case series. Epidural bleeding can be controlled with radiofrequency probe. Surgiflow helps in controlling the epidural bleeding.


Unilateral biportal endoscopic spine surgery (UBESS) provides a wider and clearer view of the surgical field, obviates the need for special endoscopic instruments, facilitates greater freedom of movement, is versatile, and enables better surgical manipulation and effective decompression, discectomy as compared to the uniportal technique and open surgeries.[5],[6],[9] UBESS is performed under sedation and regional anesthesia thereby reducing the chances of nerve injury as the patient can perceive pain and warn the surgeon if there is any inadvertent nerve handling.[5],[6] UBESS can be safely applied for degenerative pathologies from L1-S1. Iliac crest at L5-S1 level does not pose any surgical challenge as the approach is always medial to the iliac crest. UBESS offers many advantages with minimal pain at the operative site, reduced hospital stay, early rehabilitation, and less tissue damage at the site of surgery. It has a steep learning curve and offers excellent results in experienced hands.


UBESS is an ideal alternative to the uniportal endoscopic and minimal invasive microsurgery for foraminal, paracentral disc herniations, lateral recess, and foraminal stenosis.

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Conflicts of interest

There are no conflicts of interest.


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