Clinical Outcomes of Interlaminar Percutaneous Endoscopic Uniportal Pars Decompression for Lumbar Spondylolysis

Abstract

Background: To evaluate the clinical and radiological outcomes of a novel full endoscopic procedure performed via an interlaminar approach to decompress entrapped nerve roots in patients with lumbar spondylolysis.

Methods: Patients who underwent interlaminar percutaneous endoscopic pars decompression were included in this retrospective cohort study. Patients with back pain and dynamic lumbar instability were excluded from the study. Clinical parameters related to outcomes, including the Oswestry Disability Index (ODI) and visual analog scale (VAS) for leg pain, were assessed before and after surgery. The radiological outcomes, vertebral slippage percentage, and motion radiographs were evaluated preoperatively and postoperatively.

Results: Of the 11 patients included in the study, 5 had spondylolysis alone, 1 of whom had spondylolysis at L3-L4 and L4-L5, and 4 of whom had it at L5-S1; and 6 patients had spondylolysis in combination with spondylolisthesis, of whom 4 had involvement at L5-S1, 1 had involvement at L4-L5, and 1 had involvement at L3-L4. At a mean follow-up period of 22.64 months, 63.3% of patients achieved more than 50% improvement in ODI score and 90.91% of patients achieved more than 50% improvement in VAS score. Spondylolysis with vertebral slippage had inferior ODI improvement outcomes as compared with spondylolysis alone, but the VAS was not significantly different. No significant difference was observed on the slippage percentage observed between the pre- and postoperative periods. However, 1 patient experienced vertebral slippage after surgery, but fusion surgery was not required.

Conclusions: Interlaminar percutaneous endoscopic pars decompression is a safe and successful treatment for patients with stable lumbar spondylolysis and nerve root compression. Even in situations in which vertebral slippage occurs, spinal fusion may not be the best option for all patients with lumbar spondylolysis.

Clinical relevance: The interlaminar percutaneous endoscopic pars decompression is a safe and successful procedure for treatment of patients with stable lumbar spondylolysis and nerve root compression.

Keywords: interlaminar percutaneous endoscopic uniportal pars decompression; nerve root compression; spondylolysis.

Figure 1

The entry point of endoscope for L4 spondylolysis (L4-L5 spondylolisthesis) is the L3-L4 interlaminar window.

Figure 2

The bony hook is the hook-like remnant of the proximal deficient lamina of the L5 lamina below the pars defect in L5-S1 spondylolisthesis, which compresses the L5 exiting nerve root (red arrow).

Figure 3

Steps of percutaneous endoscopic pars decompression in L5 spondylolysis (L5-S1 spondylolisthesis). (A) The facet joint of L4-L5 is identified. (B, C) The endoscope cannula is moved to the caudal region adjacent to the facet joint to find the pars defect of L5. (D) The soft tissue and fibrocartilaginous mass in the gap are removed with a burr. (E) After the gap is clear, the S1 traversing nerve is identified. (F) The bony hook below the gap is identified and removed using a Kerrison rongeur until the L5 exiting nerve root is free.

Figure 4

The red arrow indicates L5 pars defect. The iliolumbar ligament binds between the L5 transverse process and the ilium (white arrow).

Figure 5

Comparison of pre- and postoperative magnetic resonance images of L5 spondylolysis in a patient who underwent percutaneous endoscopic right L5 pars decompression. (A) The pars defect at L5 observed in a lateral radiograph. (B, C) The right L5 pars defect and L5 exiting nerve root compression in the L5-S1 intervertebral foramen. (D, E) The right L5 exiting nerve root is free after surgery.