All Endoscopic Procedures Require a Working Space
Endoscopic procedures, by nature, require a designated working space to perform effectively. The history of endoscopy dates back to 1853 when Antoine Jean Desormeaux of France developed the first instrument to examine the urinary tract and bladder, coining the term "endoscope". In 1868, Kussmaul performed the first gastroscopy, and by 1901, Gorge Kelling attempted endoscopic examination of the peritoneal cavity, laying the groundwork for modern laparoscopic and robotic abdominal surgeries. Professor Kenji Takagi is credited with performing the first arthroscopic examination of a knee joint in 1918, which is now a cornerstone in orthopedic surgeries.
Endoscopic spinal surgery began as percutaneous endoscopic discectomy, with early attempts by Kambin (1973) and Hijikata et al. (1975). However, this field has lagged behind other surgical specialties due to the lack of natural working space in the spine. Unlike the stomach, abdominal cavity, or joints, the spine does not have a pre-existing cavity that can be easily accessed. The concept of Kambin’s triangle provided a crucial corridor for initial approaches to lumbar disc lesions in endoscopic surgery.
Unilateral biportal endoscopy (UBE) is a technique in endoscope-assisted spinal surgery that creates working spaces using the potential space around the spine. Depending on the pathological region, approaches can be posterior or transforaminal. "Son's space" is a key anatomical working space in the posterior approach. This space includes the interfascicular space between multifidus muscles and the space between the multifidus and the lamina. Converting these spaces into an atraumatic working corridor allows UBE to achieve minimally invasive surgery similar to conventional spinal surgery.
Steps for Creating a Working Corridor in UBE Surgery:
- Verify the true anteroposterior view using C-arm radiography.
- Target the junction of the spinous process and the lamina.
- Make a skin incision for the working portal at the medial margin of the lower pedicle.
- Make a scopic portal incision 3 cm cranially from the working portal.
- Insert the core dilator through the interfascicular space.
- Sequentially insert and move dilators to widen the working space.
- Insert the directional guide to maintain the working portal.
- Position the scopic portal and ensure triangulation between portals.
- Insert the sheath with an obturator through the scopic portal.
- Clear soft tissue from the sheath tip using the directional guide.
- Insert the endoscope to visualize the lamina.
- Retract the multifidus muscle using a semi-tubular retractor.
- Ensure proper irrigation with saline for visibility.
- Drill out bone to establish a true working space.
UBE Is Fluid-medium Surgery, Not Air-based
Endoscopic spinal surgery, such as UBE, differs from open surgery because it uses a fluid medium, similar to joint arthroscopy, which uses saline for irrigation. In UBE surgery, two portals are created: one for the endoscope and one for surgical instruments. Continuous saline circulation is crucial for maintaining a clear visual field and successful surgery (Fig. 2.2).
Unlike knee arthroscopy, which operates within a natural joint cavity, the spine does not have an inherent space for surgery. UBE creates an artificial working space that is close to the epidural space, making control of saline pressure critical to avoid neural damage. The anatomical distance from the skin to the lamina in the spine is greater than in the knee, complicating fluid outflow and increasing the risk of complications from high hydrostatic pressure.
Key Points for Safe Fluid-medium Surgery:
- Maintain optimal hydrostatic pressure (30–50 mmHg) by adjusting the height of the saline bag relative to the patient.
- Use specially designed semi-tubular retractors to control outflow and pressure.
- Avoid excessive saline pressure to prevent neural complications like headaches, bleeding, or delayed awakening from anesthesia.
- Minimize risks of abdominal fluid collection and hypothermia by using tepid saline and heating pads.
By understanding and addressing these anatomical and procedural nuances, UBE can provide effective and minimally invasive treatment for various spinal pathologies.