General
- Aka:
- Unilateral Biportal Endoscopic (UBE) fusion
- Unilateral Biportal Endoscopic Lumbar Interbody Fusion (ULIF)
- Percutaneous biportal endoscopic lumbar interbody fusion
Indications
- Low-grade (1/2) spondylolisthesis
- Spinal stenosis:
- Herniated nucleus pulposus (HNP): (weak)
Contraindications
- High-grade (>2)spondylolisthesis:
- Severe forms of spondylolisthesis often necessitate a subtotal to total resection of the bilateral facet joints
- Multilevel spinal stenosis:
- Other aetiologies
- Cases involving infection, spondylodiscitis, vertebral fractures, or tumours are contraindications.
- Complex spondylolisthesis:
- ULIF is not suitable for spondylolisthesis with a fused segment that would necessitate a subtotal or total resection of the bilateral facet joints.
Surgical technique
- Patient Preparation and Positioning
- Prone position under general or epidural anaesthesia.
- A waterproof surgical drape is considered necessary for the endoscopic surgery.
- C-arm fluoroscopy is used to align the view, ensuring the endplates of the targeted disc are clearly visible at the centre of the image.
- Establishing Portals
- Two ipsilateral portals (channels) are created under C-arm fluoroscopic guidance. The transverse incisions for these portals are made about 3 cm apart.
- One source specifies a common approach for a right-handed surgeon operating on the L4–5 level from the left side:
- Endoscopic portal (proximal) is created at the level of the L4 pedicle. This channel is used for a 4-mm diameter, 0° endoscope housed within a 5.5-mm trocar.
- Working portal (distal) is created at the level of the L5 pedicle. This channel is used for surgical instruments like drills, radiofrequency probes, Kerrison punches, and dissectors.
- Continuous saline irrigation is maintained, flowing from the endoscopic channel to the working channel to ensure a clear operative view. A trocar in the working portal aids in the smooth insertion of instruments, prevents muscle injury, and facilitates good drainage.
- Decompression of Neural Structures
- An initial submuscular working space is created on the laminar surface under endoscopic guidance.
- An ipsilateral laminotomy is performed using a drill and Kerrison punches to access the spinal canal.
- The ipsilateral inferior articular process of the upper vertebra and the superior articular process of the lower vertebra are resected using punches, a drill, and a micro-osteotome. This step serves two purposes:
- It decompresses the neural elements
- Allows for the collection of local autologous bone for the fusion graft.
- For thorough decompression of the exiting nerve root, the superior articular process may need to be removed completely or more laterally.
- Finally, the ligamentum flavum is resected to finalize the decompression. This includes removing both the ipsilateral and contralateral ligamentum flavum to achieve complete decompression of the central canal and the bilateral traversing nerve roots.
- Discectomy and Endplate Preparation
- After the disc is exposed, any vessels on its surface are coagulated with a radiofrequency probe.
- An annulotomy (an incision in the annulus fibrosus) is made, and the disc material is removed.
- Thorough endplate preparation is performed under the clear, magnified endoscopic view. The goal is to completely remove the cartilaginous endplate from the osseous endplate without causing injury. Various instruments such as curettes, endplate shavers, and curved dissectors are used for this step.
- Interbody Fusion and Fixation
- A large amount of fusion material is inserted into the prepared disc space, often using a specialised funnel. The graft material consists of local autologous bone chips harvested during the decompression, sometimes supplemented with allograft bone chips or demineralized bone matrix (DBM).
- The working-portal skin incision may be slightly extended to accommodate the interbody cage.
- A large-sized TLIF cage, filled with fusion materials, is inserted into the disc space. This is done under both endoscopic and C-arm fluoroscopic guidance. During insertion, a retractor can be anchored at the annulotomy site to protect the thecal sac and nerve roots.
- The procedure is completed with percutaneous pedicle screw fixation. The two ipsilateral portals can be used for the screw insertion.
- Closure
- A drainage catheter is inserted through the working channel to prevent the formation of an epidural haematoma.
- Local anaesthetic is injected at each skin incision area before closure.
- The skin is closed using subcutaneous sutures and skin bond materials, avoiding the need for traditional sutures.
- Management of Intraoperative Issues
- Bleeding: Epidural bleeding can be controlled with a radiofrequency probe on low power or by packing hemostatic materials like gel foam. Bone bleeding is managed with bone wax.
- Dural Tear (Durotomy): If a small dural tear occurs, it can be managed by attaching a fibrin collagen patch and maintaining a lumbar drain for 5 to 7 days post-operatively. For larger tears, direct dural repair is recommended.
Pros and cons
Pros of UBE Fusion
- Minimally Invasive with Less Tissue Damage
- Reduced Blood Loss
- No patients in the UBE fusion group required a blood transfusion, compared to 20% of patients in the PLIF group.
- Reduced back pain
- Significantly less back pain in the immediate postoperative period (e.g., days 1 and 2).
- Effective Decompression and Clinical Outcomes:
- UBE fusion allows for thorough, direct decompression of the central canal, lateral recess, and bilateral nerve roots, similar to what can be achieved with conventional open surgery.
- High Fusion Rates:
- Fusion rates of over 90%
- Which is not significantly different from conventional fusion techniques.
- Technical Advantages of the Biportal Approach:
- The use of two separate portals allows for a clear, magnified view via the endoscope while simultaneously using various surgical instruments through the working portal.
- This facilitates complete preparation of the vertebral endplates, which is critical for a successful fusion.
- Unlike some uniportal endoscopic systems that restrict cage size, the UBE technique allows for the insertion of large-sized TLIF cages, as the cage does not need to pass through a narrow cannula.
- A large amount of bone graft material can be packed into the disc space using a funnel before the cage is inserted.
- Possible Lower Complication and Readmission Rates:
- One study observed that the UBE fusion group had a lower overall incidence of postoperative complications (2 cases vs. 6) and readmissions (0 vs. 2) compared to the microscopic TLIF group, although this difference was not statistically significant.
Cons of UBE Fusion
- Longer Operative Time:
- Average time of 152.4 minutes for UBE fusion versus 122.4 minutes for microscopic TLIF.
- Another found it to be 158 minutes for UBE versus 137 minutes for PLIF.
- Due to
- Complexities of working in a limited space
- Operating under continuous water irrigation
- Time required for percutaneous screw fixation.
- Steep Learning Curve:
- It is recommended that surgeons become proficient in UBE decompression techniques before attempting the more complex UBE fusion.
- Technical Challenges:
- Bleeding Control:
- Epidural or bone bleeding can easily blur the operative vision, making the surgery difficult. Specialised tools like radiofrequency probes and materials like bone wax are essential for management.
- Dural Tears:
- Durotomy (a tear in the dura mater) can occur, particularly when using instruments blindly. While small tears can often be managed with patches and drainage, larger tears may necessitate a direct suture repair.
- Cage Insertion:
- A "blind space" is created between the skin and the endoscopic field during cage insertion, though a specialised retractor is used to protect the nerves.
- Potentially Lower Fusion Quality:
- Although the overall fusion rate is comparable to PLIF, one study found that the UBE group had significantly fewer cases of 'definite fusion' and more cases of 'probable fusion'.
- The authors suggest this may reflect that the technique is still on the learning curve with regard to optimising the fusion grade.
- Limited Indications:
- Not recommended for high-grade spondylolisthesis (Meyerding grades III and IV) or other conditions requiring extensive bilateral resection of the facet joints.
Outcomes
- Clinical Outcomes (Pain and Disability)
- Pain Relief:
- Both UBE fusion vs conventional fusion significantly reduce leg pain and improve disability scores (Oswestry Disability Index - ODI). At the final follow-up (12 months or more), there were no significant differences in back pain, leg pain, or ODI scores between the UBE groups and the conventional surgery groups.
- Postoperative Back Pain:
- A key advantage of UBE fusion is significantly less back pain in the immediate postoperative period.
- Back pain in the UBE (ULIF) group improved significantly by the first week, whereas in the PLIF group, significant improvement was not seen until the one-year mark.
- Perioperative and Surgical Outcomes
- Blood Loss:
- UBE fusion results in significantly less blood loss.
- 190.3 ml for the UBE group,vs 289.3 ml for the microscopic TLIF group.
- Another study found that no patients in the UBE group required a blood transfusion, compared to 20% of patients in the PLIF group.
- Operative Time:
- Mean operative time
- 152.4 minutes for the UBE group versus 122.4 minutes for the microscopic TLIF group.
- 158 minutes for UBE fusion compared to 137 minutes for PLIF.
- Complications and Readmissions:
- The rates of surgical complications are low and not significantly different from conventional fusion.
- 2 postoperative complications (symptomatic hematoma and cage subsidence) and no readmissions in the UBE group, compared to 6 complications and 2 readmissions in the microscopic TLIF group.
- No significant difference in the rates of dural tear, nerve root injury, hematoma, or infection between UBE and PLIF groups.
- Radiological Outcomes (Fusion)
- Fusion Rate:
- 78.3% - 90% for the UBE group.
- Fusion Quality:
- The UBE fusion group had significantly fewer cases of 'definite fusion' and more cases of 'probable fusion' compared to the conventional PLIF group.
- Instrumentation:
- Rates of cage subsidence and screw loosening were not significantly different between the UBE and conventional fusion groups.
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