Full-Endoscopic Spinal Canal Decompression After Direct Midline Splitting of the Spinous Process: A Technical Note

For lumbar spinal canal stenosis, endoscopic spine surgery typically employs a unilateral approach. While this approach has the advantage of early access to the lamina, it risks damage to the facet joint on the entry side. Additionally, decompression of the ipsilateral lateral recess can be challenging, sometimes resulting in inadequate decompression laterally, leading to incomplete symptom relief. To address these issues, a midline approach after midline splitting of the spinous process has been developed. However, this technique often uses a relatively large 16mm cylindrical retractor, resulting in skin incisions of approximately 20-25mm according to various reports. In our case, we performed a full-endoscopic spinal canal decompression underwater using a 7mm diameter through a 12mm skin incision, after directly splitting the spinous process along the midline. This technique achieved sufficient decompression with favorable outcomes. We report the details of this less invasive surgical procedure. The patient was a 62-year-old male who was independent in activities of daily living with a history of degenerative spondylolisthesis. This patient underwent posterior lumbar interbody fusion for L4/5 degenerative spondylolisthesis eight years ago. He had experienced pain in the left groin and perineal area (Numerical Rating Scale 6) for five months without improvement, which led him to our outpatient clinic. At the time of his visit, there was no apparent muscle weakness in either lower limb, only sensory disturbance. Lumbar MRI examination led to a diagnosis of lumbar spinal canal stenosis (L1/2) and conus medullaris syndrome. He requested endoscopic treatment, and we decided to perform an underwater full-endoscopic spinal canal decompression. The surgery involved a 12mm midline skin incision and direct splitting of the spinous process (L1) by approximately 10mm using a chisel and hammer. After placing a straight sheath, trumpet-shaped laminectomy was performed under endoscopic visualization. Trumpet-shaped refers to a laminectomy technique where the surgical field gradually widens as bone removal progresses deeper into the lamina. The yellow ligaments on both sides were removed as much as possible, resulting in sufficient decompression. Both facet joints were preserved, and extensive decompression was achieved. Postoperatively, although the patient still had some perineal pressure sensation, the sensory disturbance in the groin area improved, and he was discharged home on the second postoperative day with a modified Rankin Scale of 1. We report a case of successful spinal canal decompression using an endoscopic approach after midline splitting of the spinous process for lumbar spinal canal stenosis. We consider this surgical method to be valuable as it is less invasive, provides a good symmetrical view, and allows sufficient decompression on both sides.