18.1 Introduction
Conventional thoracic laminectomy remains the standard surgical approach for treating thoracic spine pathologies such as thoracic spinal stenosis and ossified ligamentum flavum (OLF) . However, this procedure can involve extensive removal of bony and musculoligamentous structures, necessitating fusion surgery to prevent iatrogenic instability, which can lead to postoperative back pain and complications .
Unilateral biportal endoscopy (UBE) is a minimally invasive endoscopic spine surgery that addresses degenerative spinal diseases in the cervical, lumbar, and thoracic spine . The concept of unilateral laminectomy for bilateral decompression (ULBD) has been effectively used for lumbar spinal stenosis and is now being adapted for thoracic spinal stenosis and OLF.
Thoracic ULBD by UBE aims to reduce postoperative instability and back pain by preserving the contralateral facet joint, lamina, and musculoligamentous structures. The technique offers a clear, magnified surgical view under continuous saline irrigation, allowing independent movement of surgical instruments and the endoscope. This method facilitates complete spinal cord decompression, improving neurological and functional outcomes while avoiding complications associated with conventional thoracic laminectomy.
This chapter discusses the indications, surgical techniques, and tips for thoracic ULBD by UBE, focusing on specific anatomical landmarks to prevent complications.
18.2 Indications and Contraindications
Indications:
Thoracic spinal stenosis
Ossified ligamentum flavum (OLF)
Synovial cysts
Contraindications:
Central disc herniation
Spinal tumor
Vascular malformations
Spinal column instability
High-grade deformity
For beginner UBE surgeons: fused-type OLF, severe dural ossification, or severe thoracic stenosis due to safety and technical difficulties.
18.3 Special Instruments
Instruments necessary for thoracic ULBD by UBE include a diamond drill and a 1-mm Kerrison punch, similar to other UBE surgeries.
18.4 Anesthesia and Position
The surgery is performed under general anesthesia with intraoperative neurophysiological monitoring. The patient is placed in a prone position on a table, ensuring no abdominal compression to avoid inadequate venous return and engorgement of the epidural venous plexus. This precaution helps prevent excessive intraoperative bleeding, which could lead to overuse of the RF probe and potential cord injury. Generally, a left-side approach is preferred for right-handed surgeons, with a left-side portal for the endoscope and a right-side portal for surgical instruments. An assistant on the opposite side holds the semi-tubular retractor.
18.5 Surgical Steps
18.5.1 Skin Marking and Making Portal
C-arm fluoroscopy is used to confirm the surgical level, compared with preoperative images to avoid errors. The docking point is identified on the AP view of the C-arm fluoroscopy as the lower part of the cranial lamina. Two incisions are made approximately 2.5 cm apart, centered at the lower part of the cranial lamina and the midline of the proximal and distal pedicles. In obese patients, the incisions should be wider and laterally located from the midline.
Serial dilators and an endoscopic sheath are inserted to the docking point under C-arm guidance. The portals are confirmed on AP and lateral fluoroscopy. The muscle detacher is used to reach the inferior edge of the cranial lamina and the base of the spinous process. The endoscope and semi-tubular retractor are positioned, creating an initial working space under fluoroscopic guidance. The semi-tubular retractor maintains fluid output and retracts paraspinal muscles.
18.5.2 Bone Working (Video 18.1)
With both portals correctly placed, the RF probe coagulates soft tissues to expose the cranial lamina, base of the spinous process, and interlaminar space. The outer cortex of the cranial lamina is removed to expose the cancellous bone. A round cutting burr is used to remove the cranial lamina down to the ligamentum flavum (LF). Care must be taken to avoid compressing the LF with the burr or Kerrison punch. The base of the spinous process is removed to create space for safe bone working, especially during contralateral decompression.
The midline gap of the LF, an anatomical landmark, is identified to guide the extent of bone working. The cranial lamina is removed until the cranial attachment of the LF is exposed. The LF is left as a protector to avoid neural injury during bone working. After completing a sufficient laminectomy for bilateral decompression while preserving the LF, the medial aspect of the facet joint is partially removed. The lateral end of the laminectomy overlaps with the medial aspect of the facet joint, which should be preserved as much as possible for stability.