[Orthopedic UBE Section] Advanced Guide to Unilateral Dual-Channel Endoscopy (UBE): 10 Key Details for Overcoming the Learning Curve

In recent years, unilateral biportal endoscopy (UBE) has been changing the landscape of minimally invasive spinal surgery at an astonishing pace.

With its unique dual-port design—one for visualization and one for instrument manipulation—UBE perfectly blends the flexibility of traditional open surgery with the minimally invasive advantages of modern endoscopic technology. For younger generations of spine surgeons, UBE is highly attractive not only because of its clear visualization and easy instrument manipulation, but also because it maximizes the preservation of paravertebral muscles. However, transitioning from open surgery or single-port endoscopy to UBE is not straightforward. Beginners often face a steep learning curve. How can this stage be navigated safely and efficiently? This article summarizes 10 crucial technical details and strategies, aiming to provide a practical roadmap for your UBE advancement.

I. Patient Positioning: The Starting Point. This is the most crucial first step in preoperative planning. The vast majority of UBE surgeries are performed in the prone position.

• Key Positioning: Maintaining a kyphotic spinal position is paramount. This effectively opens the intervertebral spaces, widening access to common compression sites within the spinal canal (such as intervertebral discs and ligamentum flavum), a prerequisite for achieving ideal decompression.

• Abdomen Suspension: Regardless of the type of spinal surgical frame used, it is essential to ensure the patient's abdomen is suspended. This prevents epidural venous distension and significantly reduces intraoperative bleeding.

II. Portal Placement: UBE is a typical "targeted" surgery, and the location of the portal directly determines the difficulty of the procedure.

• Incision Selection: In the early stages of learning, it is recommended to choose a longitudinal skin incision rather than a transverse incision. If difficulties arise, a longitudinal incision is easier to convert to microscopic or open surgery.

• Fascial Management: Do not neglect the deep fascia. It is recommended to make a cruciate incision in the fascial layer, which is crucial for ensuring smooth drainage of saline solution during the operation.

• Special Cases: For patients with excessive lumbar lordosis or herniated discs, portal placement is extremely challenging. It is recommended that beginners accumulate more experience before attempting such cases.

III. Triangulation: The Core of Operation

For orthopedic surgeons, the "triangle technique" is familiar from arthroscopic training, and UBE follows the exact same principle: under fluoroscopic guidance, the instrument tip in the working channel is inserted into the endoscopic field of view in the observation channel.

• Overcoming Challenges: This can be the most challenging step for beginners. Maintaining a stable triangle structure is even more difficult when dealing with patients with high BMI or soft tissue hypertrophy.

• Recommendation: Stay calm and don't rush. Attending cadaveric training is a shortcut to quickly mastering this technique.

IV. Hydrodynamics: Ensuring a Clear View (Saline Dynamics)

Unlike arthroscopy, there is no true natural cavity behind the spine. UBE, as a "water-based" procedure, requires the artificial creation of space.

• Space Construction: Early on, this is achieved by dissecting the paraspinal muscles; later, it's done through bony decompression to maintain operating space.

• Inflow and Outflow Balance: During the procedure, constant monitoring of the inflow and outflow of saline solution is essential. Smooth outflow not only removes bone fragments and soft tissue debris, ensuring a clear view, but more importantly, it prevents iatrogenic nerve damage caused by excessive hydraulic pressure.

V. Case Selection: A Step-by-Step Approach (Location of the Pathology) Wise case selection is key to a smooth learning curve.

• Initial Stage: Prioritize lumbar spine lesions over cervical or thoracic spine lesions; prioritize familiar interlaminar approaches over foraminal or extraforaminal approaches.

• Advanced Stage: Once you are confident in the ipsilateral approach, try the "over-the-top" technique for contralateral lesions.

• Advanced Challenges: Calcified lesions (calcified intervertebral discs, ossification of the ligamentum flavum), multi-segment surgeries, and UBE fusion surgeries should be reserved for those with more refined techniques. Master simple decompression before considering fusion.

VI. Side Selection: Side of the Lesion The vast majority of surgeons are right-handed.

• Strategy: Initially, it is recommended to choose lesions on the left side. This allows instruments to be held in the dominant hand (right hand), resulting in more precise and controllable manipulation.

• Flexibility: Some surgeons even choose to stand on the patient's left side when dealing with right-handed lesions, using a contralateral approach for decompression to utilize the dexterity of the dominant hand.

• Goal: As techniques mature, regardless of dominant hand, surgeons should train themselves to operate freely bilaterally.

VII. Hand-Eye Coordination: Depth Perception In UBE, the endoscope and instruments converge at a certain angle to the lesion. This means that the surgeon must establish a three-dimensional spatial sense on the two-dimensional screen.

• Distance Control: During the procedure, it is necessary to accurately predict the distance between the endoscope lens and surgical instruments (such as drills and forceps) to avoid lens wear and to prevent nerve damage caused by blind spots.

• Experience Transfer: Experience using a burr in microscopic spinal surgery can accelerate this process, even though the magnification of the UBE is much higher than that of a microscope. VIII. Anatomical Recognition: Endoscopic Familiarity. Spinal anatomy under endoscopy differs significantly from that under open surgery.

• Microstructure: Many structures easily overlooked in open surgery, such as the synovial tissue of the facet joints, the meningeal vertebral ligaments, and the midline dural folds, are clearly visible under endoscopy.

• Key Landmarks: Beginners must be familiar with the J point (lumbar spine), V point (cervical spine), and the V-cleft of the ligamentum flavum. These anatomical landmarks are "lighthouses" for locating and avoiding complications.

Ⅸ.Dealing with the "Red Screen Phenomenon": Hemostasis Strategies (Tackle the 'Red Screen')

Bleeding is one of the most troublesome problems during UBE surgery. Once the field of vision is completely obscured by blood, the so-called "red screen phenomenon" occurs.

• Stay calm: Do not panic. This is the dividing line between a novice and an expert.

• Coping techniques: 1. Place the endoscope close to the bleeding point to accurately locate the blood vessel using magnified vision. 2. Use radiofrequency ablation for precise coagulation. 3. Instantly increase water pressure or use a fluid hemostatic agent.

• Remember: Early detection and timely treatment of even minor bleeding can effectively prevent the red screen phenomenon.

Ⅹ. Terminal Hemostasis: Preventing Hematoma. The final step before wound closure often determines the success or failure of the surgery.

• Risk: Unlike open surgery, UBE results in a very small dead space. Incomplete hemostasis can lead to severe nerve root compression even with a small amount of hematoma buildup.

• Solution: Optimal hemostasis must be ensured before closure. In our experience, placing a drainage tube for 24-48 hours significantly reduces the risk of symptomatic postoperative hematoma.

In conclusion, unilateral dual-channel endoscopy (UBE) perfectly combines a surgeon's anatomical familiarity with the precision of the endoscope. Although the learning curve is steep, a safe and standardized operating system can be established by following the 10 key principles mentioned above—from patient positioning to terminal hemostasis.