Cost-effective unilateral biportal endoscopic microdiscectomy: illustrative case

Abstract

BACKGROUND

Unilateral biportal endoscopic (UBE) spine surgery is an ultra–minimally invasive technique that provides enhanced visualization while minimizing the tissue disruption associated with traditional open surgery. It utilizes separate portals for visualization and instrumentation, which allows for tactile feedback and freedom of movement similar to open procedures.

OBSERVATIONS

Despite these advantages, a significant barrier to the widespread adoption of endoscopic spine surgery can be capital expense for specialized endoscopic systems. This technical paper aims to overcome that barrier by providing a detailed, step-by-step guide for performing a UBE microdiscectomy utilizing standard arthroscopic and basic spine equipment that are widely available.

LESSONS

The authors describe patient positioning, operating room setup, portal placement, fluid management, and a systematic approach to decompression. Key steps, including establishing the visualization window and managing hemostasis, are detailed. The authors also discuss postoperative considerations and provide technical tips to shorten the learning curve. By leveraging standard instrumentation, this technique makes the benefits of UBE surgery more accessible to surgeons and institutions, thereby lowering the financial barrier to adoption without compromising surgical goals.

https://thejns.org/doi/10.3171/CASE2678

Degenerative spinal conditions represent one of the most significant burdens and costs to society in terms of direct healthcare costs, as well as indirect cost from lost work/duty hours.¹ In the military population, it represents one of the main reasons for lost duty days and significantly affects service member readiness.^2,3 Recent technological advances, including endoscopic spine surgery techniques, have allowed spine surgeons the ability to accomplish the same goals of surgery with the potential benefits of significantly less tissue disruption and blood loss, smaller incisions, faster return to duty, and decreased narcotic use.^4–6

Barriers remain to the broader adoption of endoscopic techniques in spine surgery, including the capital expenses for endoscopic systems, which can surpass $330,000.^7–9 This can be particularly true for smaller military treatment facilities (MTFs) or ambulatory surgery centers (ASCs).

The objective of this technical paper is to illustrate a unilateral biportal endoscopic (UBE) technique performed in an ambulatory surgery setting utilizing existing arthroscopic equipment and basic spine equipment without additional capital cost, lowering the cost barrier to adoption.

The surgical steps are demonstrated through an illustrative case and video of a patient who underwent this economic technique (Video 1). This technical paper consists of one illustrative case report and is a medical educational activity that does not meet the US Department of Health and Human Services definition of “research,” which is “a systematic investigation, including research development, testing, and evaluation, designed to develop or contribute to generalizable knowledge.” This paper was written following the Case Report (CARE) guidelines.

VIDEO 1.Illustrative video of right L4–5 UBE microdiscectomy utilizing standard arthroscopic equipment. Lig. Flav. = ligamentum flavum. Click here to view.

Illustrative Case

A 56-year-old male presented with several months of right foot drop and pain. He had a history of chronic low back pain; however, 4 months earlier he developed onset of new stabbing pain, and numbness and tingling radiating from the right low back buttock, thigh, and leg into the top of the foot with associated right foot drop. He could only walk about 10–14 steps until he began dragging his right foot. He had previously tried physical therapy, epidural steroid injection, gabapentin, meloxicam, and home exercises with transient relief and persistent symptoms. Examination revealed 3/5 strength in right ankle dorsiflexion, extensor hallucis longus with an inability to heel walk on the right foot, and diminished sensation to the dorsum of the right foot and a positive straight leg raise on the right. MRI demonstrated a right paracentral L4–5 disc herniation with caudal migration and severe compression of the transiting right L5 nerve root (Fig. 1). Given his severe right L5 radiculopathy, foot drop, and failure to achieve the desired relief with nonoperative management, a right L4–5 UBE microdiscectomy was offered.

FIG. 1.

MR images demonstrating right paracentral L4–5 disc herniation with caudal migration and severe compression of the transiting right L5 nerve root.

Methods

This technique leverages equipment readily available in ambulatory surgery settings with an existing arthroscopic program.

Equipment

The following equipment was used in this study: a standard endoscopy or arthroscopy tower with a camera and light source, a 4-mm 30° arthroscope, an arthroscopic trocar and cannula system for irrigation inflow/outflow, a 90° radiofrequency (RF) ablation wand for hemostasis and soft tissue debridement, a high-speed drill with a 3- or 4-mm burr, and an arthroscopic slotted cannula to pass a 2-0 suture with a knot pusher. Standard spine and arthroscopy instruments included Kerrison rongeurs, pituitary rongeurs, straight and angled curettes, Penfield elevators, a ball-tip probe, and arthroscopic scissors and punches.

Patient Positioning and Operating Room Setup

The patient was placed prone on a Wilson frame atop a Jackson table. The Wilson frame was maximally opened to increase interlaminar space. A standard drape with a collection pouch was connected to suction for fluid outflow management. The surgeon stood on the affected side, and the assistant, surgical technician, and C-arm fluoroscope were positioned on the opposite side. The endoscopic viewing tower was placed directly across from the surgeon at eye level to maintain ergonomic posture.

Fluid Management

UBE surgery relies on a fluid medium for visualization. Continuous irrigation is required to maintain a clear viewing window and wash away debris.¹⁰ Water pressure must be carefully controlled to avoid neurological injury from excessive hydrostatic pressure. Ideal pressure is maintained between 25 and 40 mm Hg.¹⁰ This can be achieved using an arthroscopic pump or, more simply, by gravity with a saline bag hung at eye level.^10,11 In addition to pressure, hemostasis is aided by infiltrating the incision sites with epinephrine, administering tranexamic acid (e.g., a 1-g bolus preincision), and maintaining relative hypotension with a systolic blood pressure goal of < 110 mm Hg.¹¹

Portal Placement and Establishing the Viewing Window

Accurate portal placement is critical for operative efficiency. For this illustrative case, the target was the patient’s right L4–5 spinolaminar junction for his right L5 radiculopathy with foot drop from an inferiorly migrated right L4–5 disc herniation. Using intraoperative fluoroscopy, we planned the incisions. For the interlaminar approach, the working portal was typically placed at the medial border of the caudal pedicle, in line with the disc space, and the viewing portal was placed approximately 3 cm cranially, creating a 30° angle of convergence (Fig. 2).

FIG. 2.

Intraoperative fluoroscopic image with spinal needles showing the planned trajectory and incisions for a biportal approach to the L4–5 spinolaminar junction.

The caudal (working) portal was incised 7–8 mm. The first dilator from a standard tubular retractor set was used to carefully probe the anatomy and elevate the erector spinae muscle off the spinolaminar junction to help create potential space for the later introduction of saline. Care was taken to avoid applying significant downward force and plunging through the interlaminar space into the thecal sac. Appropriate localization was confirmed with lateral fluoroscopy. The cranial portal was made with a stab incision (4 mm), and the trocar was carefully introduced to triangulate with the caudal port (Fig. 3).

FIG. 3.

Intraoperative fluoroscopic image showing localization of the initial dilator in the caudal working channel and the endoscope trocar cranially triangulated to the L4–5 spinolaminar junction.

The length of the dilator was noted, and the arthroscopic slotted cannula was then notched with bandage scissors to a length 2–3 cm longer than the measured dilator depth and bent so that it broke to the desired length. Pliers were used to make a slight bend at the distal cut side of the cannula. The slotted cannula was not inserted along the dilator. Alternatively, a 10-ml syringe barrel with the tip removed and cut in half lengthwise could be used as a cannula for the working channel in a nonobese patient. Next, the dilator was removed and the RF probe was then inserted into the working channel along the cannula. The endoscope was inserted through the trocar with irrigation and light source now active. It is critical not to activate the RF probe until visualized by the camera. The camera was maneuvered to visualize the caudal L4 lamina at the spinolaminar junction, and the RF probe was brought into the same field. Under direct visualization, the RF probe was used to complete the soft tissue debridement and achieve hemostasis, establishing a clear working window. Lateral fluoroscopy should be used to confirm appropriate localization (Fig. 4).

FIG. 4.

Intraoperative fluoroscopic image demonstrating the RF probe in the caudal working channel and the endoscope cranially triangulated to the L4–5 spinolaminar junction.

Decompression and Discectomy

Before beginning the decompression, key bony landmarks must be clearly identified: the spinolaminar junction (medial), medial facet (lateral), and the cranial edge of the caudal lamina (inferior). Using a high-speed burr, we performed a small laminotomy to expose the ligamentum flavum and medial facetectomy, as indicated. Initial entry through the ligamentum flavum and into the canal can be made with arthroscopic punch scissors. This maneuver eliminates the need for additional laminotomy to identify the superior attachment of the ligamentum flavum, allowing its release using an upgoing curette. The arthroscopic punch scissors also have a 1- to 2-mm foot, making entry into the canal safer, by pushing the underlying epidural fat or thecal sac away from the cutting action and allowing endoscopic irrigation to rush in. This helps push the thecal sac away from the instrument. Kerrison rongeurs can then be used to further decompress the lateral recess. Once the traversing nerve root is clearly identified, the Penfield 4 instrument can be used to mobilize the root medially. If epidural veins overlying the disc space are encountered, the RF probe turned to the lowest setting can be used to achieve hemostasis. Care must be taken to not cause thermal injury to the nerve root. A rent in the annulus can then be entered with the Penfield instrument or nerve hook. Small loose fragments were washed out through the working channel. The micropituitary instrument was used to resect additional fragments. The endoscope was used to visualize the tip of the pituitary; it should always be introduced closed and then opened beside or ventral to the root, ensuring that when closed there is no potential for injury to the traversing root. Direct visualization with the endoscope confirmed adequate decompression of the traversing root and hemostasis (Fig. 5).

FIG. 5.

Intraoperative images showing microdiscectomy being performed with a micropituitary instrument under direct visualization (left) and confirming decompression of the traversing right L5 nerve root (right).

Closure

After hemostasis was achieved, irrigation was performed under direct visualization and a steroid was applied in the epidural space. The instruments were removed, fluid was suctioned, and the small portal incisions were closed with dermal sutures and sterile dressing was applied.

Results

Our patient awoke from anesthesia without complication. On postoperative examination, his preoperative right foot numbness and pain were improved and his examination findings were stable compared to the preoperative assessment. He had minimal discomfort at the incision site, rating pain at 0 of 10 on the Defense and Veterans Pain Rating Scale. He was able to ambulate, tolerate oral intake, and void and was discharged home in improved condition, without any narcotic pain medication.

At the 30-day postoperative visit, he had complete resolution of his preoperative symptoms and was neurologically intact. The incisions were well healed. He was given a physical therapy referral for structured outpatient rehabilitation and cleared for return to military duty.

Informed Consent

The necessary informed consent was obtained in this study.

Discussion

Observations

Traditional lumbar microdiscectomy has long served as the gold standard for operative treatment of lumbar disc herniation. However, innovations in minimally invasive spine surgery, including tubular microdiscectomy, percutaneous endoscopic techniques, and UBE discectomy (UBED), have been developed to minimize muscle dissection and collateral tissue injury.¹¹ UBED utilizes two small portals, allowing surgeons to work with a bimanual technique under continuous irrigation.⁴ This configuration improves visualization, preserves normal anatomy, and may reduce postoperative pain and recovery times.

The primary strength of the described technique is its cost-effectiveness, which makes UBED accessible without large capital expenditures by using existing orthopedic arthroscopic equipment. This allows for successful adoption of this ultra–minimally invasive technique for use at overseas MTFs. It successfully combines the benefits of minimally invasive surgery, less tissue trauma, and faster recovery with the use of familiar instruments and skills from both arthroscopy and open spine surgery.

The main limitation is the initial learning curve. Surgeons must become adept at maintaining proper orientation with the 30° endoscope, working in a fluid medium, triangulating instruments through separate portals, and achieving hemostasis with arthroscopic equipment.

Economic Comparison With Other Surgical Techniques

Compared to traditional open microdiscectomy, UBED offers significantly less muscle and soft tissue disruption. Choi et al. found that, when compared with open microdiscectomy, endoscopic microdiscectomy resulted in lower direct hospital cost savings ($3806 vs $4302 for open microdiscectomy, p < 0.01) and higher quality-adjusted life years at 1 year ($8064).¹² A study by Wan et al. found significantly higher surgical equipment cost per case with uniportal endoscopy compared to UBED ($3337 vs $0) due to the equipment rental cost of the uniportal system.¹³ Consumable costs were not significantly different ($3775 uniportal and $4420 biportal).¹³

Comparison of Surgical Proficiency and Outcome

When compared to uniportal endoscopy, the UBED technique allows for greater instrument freedom and utilizes more traditional instruments, which may shorten the learning curve for surgeons transitioning from open procedures. Chan et al. found that proficiency in biportal discectomy was achieved within 40 cases.¹⁴ Qiao et al. found that proficiency was obtained after 27 cases with UBED and 36 cases for uniportal endoscopy.¹⁵ Chan et al. demonstrated that proficiency was typically reached after 10–15 UBED cases, compared with 27–31 uniportal cases, highlighting its intuitive bimanual technique.¹⁴ Lower early complication rates in the UBED cohort (7.1% vs 29.0% in the uniportal cohort) underscore the safety of the learning curve.¹⁴

Qiao et al. further reported no significant differences in clinical outcomes between UBED and uniportal endoscopy, with both cohorts achieving similar reductions in Oswestry Disability Index and visual analog scale pain scores compared to preoperatively and similar patient satisfaction rates (91% for UBED and 92% for uniportal endoscopy, p > 0.05).¹⁵ Minor complication rates were also comparable for UBED and uniportal endoscopy (6.9% and 3.17%, respectively; p = 0.683).¹⁵ Özer and Demirtaş found a minor complication rate of 3.7% in their series of 54 patients who underwent UBED.¹⁶ The safety profile of UBED has been well established in prior studies.^17–19 Park et al. compared outpatient versus inpatient biportal endoscopic surgery (n = 84) and demonstrated a significantly shorter length of stay (0.1 ± 0.3 vs 1.6 ± 0.9 days) and reduced operative time (115.7 vs 146.2 minutes) for outpatient cases, underscoring UBED’s efficiency in ambulatory settings.¹⁸

Lessons

This cost-effective UBE technique has significant implications for expanding access to endoscopic spine surgery. We recommend a structured adoption process for surgeons, beginning with mentorship or observation, followed by cadaveric training and a deliberate progression from simple to more complex cases. This methodical approach helps ensure efficiency in the operating room, minimizing surgeon frustration and increasing safety.

This technical paper demonstrates an economic method for unilateral biportal endoscopy by utilizing standard arthroscopic and spine instrumentation. This may allow wider use of this ultra–minimally invasive approach in patients without the associated financial barrier of other techniques, making it more accessible to ASCs, small community hospitals, and MTFs.

Acknowledgments

We used Google Gemini 3 in the initial literature search.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: Lawless, Chang. Acquisition of data: Lawless. Analysis and interpretation of data: Lawless, Mody, Kinoshita. Drafting the article: Lawless, Mody. Critically revising the article: Lawless, Mody, Steed, Chang. Reviewed submitted version of manuscript: Lawless, Mody, Steed, Chang. Approved the final version of the manuscript on behalf of all authors: Lawless. Administrative/technical/material support: Mody, Steed. Study supervision: Lawless.

Supplemental Information

Videos

  Video 1. https://vimeo.com/1170316629.

Correspondence

Michael H. Lawless: Naval Medical Center San Diego, CA. michael.h.lawless2@gmail.com.