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Chapter Summary
• Context: Unilateral Biportal Endoscopy (UBE) represents a paradigm shift in minimally invasive spine surgery by separating the optical viewing channel from the working instrument corridor. By placing a standard arthroscope through one portal and handling conventional micro-surgical and power instruments freely through a second independent portal under continuous saline irrigation, UBE overcomes the instrumental restriction and visual co-axial constraints inherent to uniportal working-channel endoscopes. This dual-portal freedom allows wide viewing angles, unconstrained triangulation, use of standard high-speed burrs and osteotomes, and efficient bilateral decompression via a unilateral approach (ULBD). UBE has established widespread utility across the cervical, thoracic, and lumbar spine for discectomy, decompression of central and lateral recess stenosis, foraminal unroofing, and biportal endoscopic lumbar interbody fusion (ULIF/BE-LIF). Successful implementation requires mastering water outflow dynamics, triangulating triangulation geometry, managing epidural bleeding, and preventing fluid extravasation.
• Chapter Objective: Detail the biomechanical, anatomical, and practical foundations of Unilateral Biportal Endoscopic (UBE) spine surgery. The chapter teaches the triangulation geometry of viewing and working portals, continuous fluid irrigation mechanics, surgical steps for lumbar decompression and biportal interbody fusion, and the recognition and prevention of complications such as epidural hematoma, incidental durotomy, and hydrostatic pressure overload.
• Biportal philosophy and triangulationUBE decouples visualization from instrumentation. The viewing portal accommodates a 0° or 30° arthroscope, while the adjacent working portal allows unrestricted movement of conventional Kerrisons, high-speed burrs, curettes, and radiofrequency wands (Figure 67.1). This separation enables broad triangulation, tactile feedback identical to open microsurgery, and rapid bone resection.
• Fluid irrigation and hydrostatic safetyContinuous saline irrigation keeps the surgical field crystal clear and compresses low-pressure epidural venous bleeding. However, maintaining adequate outflow through the working portal is vital: blocked outflow leads to fluid extravasation into paraspinal muscles, elevated epidural pressure, and risk of increased intracranial pressure.
• Indications across the spineUBE is applied in the lumbar spine for disc herniations, central canal stenosis, lateral recess stenosis, and foraminal decompression. In the cervical and thoracic regions, it facilitates posterior foraminotomy, laminotomy, and cord decompression. Furthermore, UBE enables biportal endoscopic lumbar interbody fusion (BE-LIF), offering endplate preparation and large cage insertion with minimal muscle trauma.
• Surgical technique and bilateral decompression (ULBD)Under fluoroscopic guidance, the two portals are established over the target laminofacet junction. Creating an initial working cavity with radiofrequency ablation exposes bony landmarks. Ipsilateral laminotomy and flavectomy are completed; tilting the scope across the base of the spinous process achieves contralateral over-the-top decompression with complete preservation of the contralateral facet and dorsal paraspinal musculature.
• Complication managementDural tears, epidural hematoma, incomplete decompression, and facet over-resection are the main risks. Dural tears can be managed endoscopically with patches, clips, or fibrin sealant. Epidural hematoma is prevented by rigorous radiofrequency hemostasis with reduced pump pressure prior to portal closure and routine subfascial drain placement.
• Clinical Application: When planning a UBE procedure, precise skin marking under fluoroscopy is essential to position the viewing and working portals roughly 1.5 to 2.5 cm apart, aligned with the target interlaminar window. Maintaining continuous fluid egress around the working portal cannula is mandatory throughout the entire operation; any decrease in outflow should immediately prompt widening of the skin portal. During bilateral over-the-top decompression, the ligamentum flavum should be kept intact as long as possible to protect the thecal sac while the contralateral lamina and superior articular process are undercut. Before concluding the surgery, irrigation inflow pressure should be lowered to reveal hidden venous oozing, and meticulous radiofrequency coagulation performed. Routine subfascial drainage is advised to prevent postoperative epidural hematoma formation.
