Full-Endoscopic Foraminotomy with a Novel Large Endoscopic Trephine for Severe Degenerative Lumbar Foraminal Stenosis at L5 S1 Level: An Advanced Surgical Technique

Abstract

To (i) introduce the technical notes of a novel full-endoscopic foraminotomy with a large endoscopic trephine for the treatment of severe degenerative lumbar foraminal stenosis at L₅ S₁ level; (ii) assess the primary clinical outcomes of this technique; (iii) compare the effectiveness of this full-endoscopic foraminotomy technique and other previous techniques for lumbar foraminal stenosis. From January 2019 to August 2019, a retrospective study of L₅ S₁ severe degenerative lumbar foraminal stenosis was performed in our center. All patients who were diagnosed with severe foraminal stenosis at L₅ S₁ level and failed conservative treatment for at least 6 weeks were identified. Patients with segmental instability or other coexisting contraindications were excluded. A total of 21 patients were enrolled in the study. All patients were treated by full-endoscopic foraminotomy using large endoscopic trephine. The visual analogue scale (VAS) and Oswestry disability index (ODI) were evaluated preoperatively and at 1, 3, 6 months, and 1 year after the surgery, and the modified MacNab criteria were used to evaluate clinical outcomes at the last follow-up. There were 10 males and 11 females with a mean age of 66.38 ± 9.51 years. Five patients had a history of lumbar surgery. The mean operative time was 63.57 ± 25.74 min. The mean follow-up time was 13.29 ± 1.38 months. The mean postoperative hospital stay time was 1.29 ± 0.56 days. The mean preoperative VAS score significantly decreased from 7.38 ± 1.02 to 2.76 ± 1.09 (t = 19.759, P < 0.01), 2.25 ± 1.02 (t = 21.508, P < 0.01), 1.60 ± 1.05 (t = 31.812, P < 0.01), and 1.45 ± 1.10 (t = 25.156, P < 0.01) at 1 month, 3 months, 6 months, and 1 year after the operation. The mean preoperative ODI score significantly decreased from 64.66% ± 4.91% to 30.69% ± 4.59% (t = 33.724, P < 0.01), 29.44% ± 4.50% (t = 32.117, P < 0.01), 24.22% ± 4.14% (t = 33.951, P < 0.01), and 22.44% ± 4.94% (t = 30.241, P < 0.01) at 1 month, 3 months, 6 months, and 1 year after the operation. At the last follow-up, 19 patients (90.48%) got excellent or good outcomes. One patient suffered postoperative dysesthesia, and the symptoms were controlled by conversion treatment. One patient took revision surgery due to the incomplete decompression. There were no other major complications. Percutaneous endoscopic decompression is minimally invasive spine surgery. However, the application of endoscopic decompression for L₅ S₁ foraminal stenosis is relatively difficult due to the high iliac crest and narrow foramen. Full-endoscopic foraminotomy with the large endoscopic trephine is an effective and safe technique for the treatment of degenerative lumbar foraminal stenosis.

Keywords: Endoscopic trephine; Foraminal stenosis; Full-endoscopic foraminotomy; Lumbar spinal stenosis.

Fig. 1

Endoscopic trephine system. (A, B): Specially designed instruments of endoscopic trephine system. (A) Special trephine (left), working cannula (medial), secondary bevel‐ended working cannula (right). (B) Schematic illustration of the endoscopic trephine system. Endoscopic trephine was inserted between the working cannula and endoscope, which could remove the bone under endoscopic observation.

Fig. 2

Schematic illustration of the foraminotomy by using the endoscopic trephine. (A) A flow chart of the key steps for full‐endoscopic foraminotomy surgery. (B) The initial decompression started at the shoulder of SAP, and the working cannula was placed in contact with the surface of SAP. (C) The procedure of bony decompression was from outside to inside and from caudal to cranial. (D) Decompression cranially to the partial ventral side of the isthmus and inferior side of superior pedical until the cranial attachment of foraminal ligamentum flavum exposed. (E) Removed thickened LF, nucleus pulposus fragments and foraminal ligament, the decompression was completed. Upper was coronal illustration, and the lower was sagittal illustration. LF was figured in gray, dura and nerve root were figured in yellow, disc and nucleus fragments were figured in blue, bony structure was figured in light yellow.

Fig. 3

Placement of working cannula. (A) The patient was placed in the lateral position. The entry point was located 8 cm lateral from midline. (B) Reconstructed 3D illustration showed the cannula was placed parallel to L₅S₁ disc space, and targeted at the shoulder of the SAP. (C, D) Intraoperative radiography showed the extraforaminal placement of the working cannula. (E) The endoscopic views of the SAP. (F) The endoscopic trephine was inserted for bony decompression. SAP, superior articular process; Endo, endoscopic.

Fig. 4

Intraoperative endoscopic views of the decompression by endoscopic trephine. (A) The facet joint capsule was exposed. (B) Endoscopic trephine was inserted to remove the shoulder of SAP. (C) Partial SAP was removed by endoscopic trephine, and a layer of fragile cortical bone preserved on the ventral side. It could prevent the injury of the nerve root. (D) LF and joint space were exposed after partial SAP and IAP was removed. (E) The cranial attachment of foraminal LF was exposed. It should be removed carefully. (F) The complete full‐range decompression of the exiting nerve root.

Fig. 5

VAS and ODI were improved significantly after the surgery. (A) VAS before surgery (pre‐op) and at 1 month, 3 months, 6 months, and 1 year after surgery. (B) ODI before surgery (pre‐op) and at 1 month, 3 months, 6 months, and 1 year after surgery.

Fig. 6

The case of a 56‐year‐old female patient. (A, B) Preoperative MRI and CT showed the severe foraminal stenosis at the left L₅S₁ level. (C, D) Postoperative CT showed complete foraminal decompression was achieved. Preoperative (E) and postoperative (F) reconstructed 3D illustrations showed the exiting nerve root was completely decompressed. The gray part was L₅ vertebral and structures above L₅. The red part was S₁ vertebral and structures below S₁. The green part was the iliac crest. The orange line was the exiting nerve root. The orange dotted line was the exiting nerve root covered by the bony structures. The hypertrophied SAP, ventral side of the isthmus and the transition zone of the posterolateral side of the superior pedical and the base of the transverse process were removed.