Biportal Endoscopic Transforaminal Lumbar Interbody Fusion: The Double-Cage Technique
Article information
Abstract
Biportal endoscopic transforaminal lumbar interbody fusion (BETLIF) is a novel spinal fusion procedure using the unilateral biportal endoscopic technique. The hydrostatic pressure of saline irrigation suppresses bleeding, enabling us to perform delicate surgery in a crystal-clear and magnified surgical field with almost no bleeding. Adequate neural decompression, disc space preparation, and bony endplate preservation can be achieved safely. The sturdy endplate reduces the incidence of cage subsidence and provides good initial stability. We use 2 interbody fusion cages and a large amount of bone graft to promote fusion. Reduction of the spondylolisthesis can also be achieved using a modern pedicle screw system. This article presents a step-by-step demonstration of the BETLIF technique in a 68-year-old patient with degenerative scoliosis and spondylolisthesis at L4-5, including his clinical presentation and treatment results. BETLIF is a safe, effective, and revolutionary minimally invasive solution for spinal fusion. Its advantages include a magnificent surgical field, direct decompression, minimum blood loss, radical discectomy, meticulous endplate preparation, cage insertion under direct visual control, and excellent treatment results with a high fusion rate and few complications.
WRITTEN TRANSCRIPT
0:00 Introduction
This article will demonstrate biportal endoscopic transforaminal lumbar interbody fusion (BETLIF) surgical techniques using double cages.
0:11 Anesthesia, Patient Positioning, and Drapping
BETLIF is performed under endotracheal general anesthesia, with the patient placed in the prone position on a radiolucent spine table [1-3]. Because the surgery is performed with continuous saline irrigation, watertight draping is essential to prevent the patient from soaking, which could result in hypothermia. The table should be adjusted to ensure the fluoroscope's free passage to obtain clear anteroposterior and lateral images. A transparent covering hood for the fluoroscope is handy when checking the lateral image. The following procedures will be demonstrated at the L4–5 level from the right-side approach (Figure 1).
The preoperative radiologic studies, including x-rays (A–C) and magnetic resonance images (D, E), showed degenerative scoliosis and spondylolisthesis at L4–5 with severe spinal canal stenosis in a 68-year-old male patient.
1:00 Localization and Skin Marking
We prefer the mini-open Wiltse’s approach between the multifidus and longissimus dorsi muscles. The skin markings include the disc line, the medial and lateral pedicle lines, the inferior pedicle line of the upper vertebra, and the superior pedicle line of the lower vertebra. The longitudinal skin incision is 1 or 1.5 cm lateral to the lateral pedicle lines, which is also used for insertion of pedicle screws. The length of the skin incision is about 2.5 to 3 cm for a one-segment fusion and 4 to 5 cm for a 2-segment fusion. Another 0.5-cm incision at the intersection of the lower vertebra's medial and lower pedicle lines is created to insert the endoscope.
2:02 Approach
After incising the deep fascia and gentle dissection of the intermuscular plane down to the facet joint, we use a blunt dilator to dissect a small space over the lamina and facet joint. Then, we insert the radiofrequency wand and endoscope to establish the triangulation. Then, we start saline irrigation, use the radiofrequency wand to clean the soft tissue, and create the working space. We prefer the 30° endoscope because it provides a wide visual field and easier access to the disc space.
2:24 Direct Decompression
We use the high-speed bur with a 4-mm coarse diamond ball tip to start the laminotomy. The starting point of laminotomy is the conjoined part of the spinous process and lamina, also known as the spinolaminar junction. After the cranial margin of the ligamentum flavum is exposed, we use the straight and curved osteotomes to chop off the inferior articular process into small pieces. These bone chips are used as autologous bone grafts. Direct neural decompression is achieved by sublaminar decompression to the contralateral lateral recess, and then the ligamentum flavum is removed as a whole piece. Finally, the ipsilateral superior articular process of the lower vertebra is resected using osteotomes or high-speed bur to complete the total facetectomy and shape the transforaminal route for the next step. The lateral portion of ligamentum flavum, which covers the exiting nerve root, should be preserved at this stage to prevent potential root injury while inserting the cage trials or interbody fusion cages.
3:43 Radical Discectomy and Endplate Preparation
For effective disc removal and preserving the bony endplate, we designed a new set of endplate strippers with 3 different angles to strip the cartilaginous endplate away from the bony endplate [4]. The various angles of the strippers can reach the deep contralateral corner in the disk space. The disc is removed in large pieces along with the cartilaginous endplate. We never use the disc shavers or curettes due to concerns about bony endplate injury. After thorough disc space preparation, we will place the endoscope into the disc space to check the result. In most cases, the amount of disc removed from a single disc space usually exceeds 10 mL.
4:41 Cage Insertion
The cage size is determined by serial cage trials of 1-mm increment starting from 7 mm. We prefer to insert 2 TLIF cages into the disc space, one vertically oriented and the other obliquely oriented [5]. We insert some bone grafts into the ipsilateral side of the disc space in advance. The fusion cages are filled with demineralized bone matrix. The vertical cage is usually inserted first. The Kambin's triangle is generally big enough that we do not need to use any retractor to protect the dura, traversing or exiting nerve roots. After the first cage is inserted, the disc space is well maintained so that we can impact a large amount of bone grafts inside. Local autografts harvested from laminotomy, allografts prepared by our bone bank, and the remaining demineralized bone matrix are impacted into the remaining disc space using a specially designed funnel [6]. The dura and traversing nerve root are retracted medially and anchored on the disc using our specially designed cannulated dural retraction anchor [7]. Then, we can safely insert the second oblique cage beside the fixation pin. The oblique cage can be inserted horizontally to distract the contralateral disc space if indicated. The cages should be inserted as anteriorly as possible to prevent posterior cage migration and to restore the lumbar lordosis (Figure 2). Cage insertion and its final position are monitored and confirmed using the fluoroscope.
The fluoroscopic images demonstrate the ideal positions of interbody cages. AP, anterior-posterior.
6:37 Final Check
Use the endoscope to check the adequacy of neural decompression. Ipsilateral foramen decompression can be accomplished now to release the exiting nerve root. The final check should include the cranial and caudal portions of the central canal, contralateral lateral recess and traversing nerve root, ipsilateral lateral recess and traversing nerve root, and the ipsilateral exiting nerve root. Temporarily stop the irrigation to check the dural pulsation and identify any active bleeders. Use the radiofrequency wand to coagulate the bleeders and use bone wax to seal the cancellous bone. A drain tube is mandatory to reduce the risk of epidural hematoma.
7:12 Pedicle Screws Fixation
We use cannulated transpedicle screws with long reduction barrels. Insertion of the pedicle screws is guided by fluoroscopy through the same surgical wounds and the intermuscular planes. The connecting rods are prebent to obtain better lordotic alignment. Reduction of spondylolisthesis can be achieved by securing the caudal pedicle screws first and then pulling up the cranial vertebra using the cantilever maneuvers. After confirming the final position of the pedicle screws, we secure the entire construct and break off the barrels to complete the instrumentation. The wounds are closed in layers.
7:30 Treatment Results
The patient experienced significant improvement in his lower back pain, leg pain, and neurological symptoms. Three days after the surgery, he was discharged from the hospital. One year after the surgery, the postoperative x-ray and computed tomography scan showed reduced spondylolisthesis, solid interbody fusion, and no cage subsidence (Figure 3).
The postoperative x-rays (A, B) and computed tomography scans (C, D) one year after the surgery showed a reduction of the spondylolisthesis, solid interbody fusion, and no cage subsidence.
Notes
Conflict of Interest
JLP, a member of the Editorial Board of Journal of Minimally Invasive Spine Surgery & Technique, is the corresponding author of this article. However, he played no role whatsoever in the editorial evaluation of this article or the decision to publish it. Author has no conflict of interest to declare.
Funding/Support
This video article is funded by a research grant (FEMH-2023-C-065) from the Far-Eastern Memorial Hospital.
Informed Consent
The research was approved and monitored by the Research Ethics Review Committee of Far-Eastern Memorial Hospital (IRB 112021-E). The committee waived the participant's informed consent.