Full-Endoscopic Decompression Combined with Oblique Lumbar Interbody Fusion for Treating Lumbar Spinal Stenosis with Prolapsed Nucleus Pulposus

We describe a minimally invasive surgery using a full-endoscopy system to complete the spinal canal decompression visually in oblique lumbar interbody fusion surgery for lumbar spinal stenosis with prolapsed nucleus pulposus.

Oblique lumbar interbody fusion (OLIF) has been widely used to treat lumbar spinal stenosis. However, patients with prolapsed nucleus pulposus are not suitable for this surgery. We introduce a hybrid surgical procedure combining OLIF and full-endoscopic spinal canal decompression to address this issue. During the OLIF procedure, after completing the discectomy, the endoscopic system is inserted into the intervertebral space to perform the latter half of the discectomy, remove the loose nucleus pulposus, and achieve direct decompression of the nerve root under visualization. After decompression, the free nerve root can be seen under the endoscopic view. With the assistance of endoscopy, the indications for OLIF surgery can be expanded, allowing for the treatment of cases with sciatica caused by the nucleus pulposus. Intraoperative X-ray fluoroscopy can determine the direction and location of decompression under the endoscopy. All patients experienced satisfactory relief from their lumbar and leg pain after the surgery with no complications. Full-endoscopic decompression combined with oblique lumbar interbody fusion is an effective, safe surgical technique for lumbar spinal stenosis with prolapsed nucleus pulposus.

Oblique lumbar interbody fusion (OLIF) has been widely used for the treatment of lumbar spinal stenosis^1,2,3,4. It has many advantages, such as the oblique approach reducing the need for extensive dissection of muscles, ligaments, and nerves, large interbody cages, and extensive bone grafting, leading to higher fusion rates and more durable outcomes^4,,5,6. However, due to the technical principle of tightening the ligament to achieve indirect decompression, patients with prolapsed nucleus pulposus are not suitable for this surgery^3,5,7.

For patients without compromised spinal stability, full-endoscopic decompression surgery can effectively relieve the nerve to achieve satisfactory clinical outcomes^8,9,10. The magnified and illuminated view can help the surgeon achieve a direct decompression. However, endoscopic decompression surgery is not appropriate for cases with preoperative spinal instability^8,11.

Based on the strengths and weaknesses of the two surgeries, we introduce a hybrid minimally invasive surgery that combines OLIF with full-endoscopic spinal decompression for the treatment of lumbar spinal stenosis patients for whom direct decompression is necessary. The prolapsed nucleus pulposus can be completely removed without neurological complications. The clinical outcome is satisfactory.

This study has been approved by the Ethics Committee of Hebei General Hospital. Informed consent has been obtained from all individual participants.

NOTE: A flow diagram of full-endoscopic decompression combined with OLIF surgery is shown in Figure 1.

1. Preoperative preparation (Radiographic study)

1. Determine the surgical segment for the patient according to the physical examination and radiological study.Use the imaging evaluation to locate the herniated disc, determine the height of the intervertebral space, and check whether there is calcification (Figure 2).
2. Measure the window between the psoas major muscle and the artery to ensure sufficient width for the operation space and to find whether there are anatomical variations (Figure 3).

2. Position and skin marking

1. Place the patient in a lateral (usually left side above) decubitus position to allow access to the lumbar spine after general anesthesia. Achieve the pelvis traction by bending the surgical bed to enlarge the operation space.
2. Secure the patient's thorax and pelvis to the operating table with wide tape, and position the hips in flexion to relax the psoas major muscle and lumbar plexus nerves (Figure 4).
3. Use a fluoroscope to determine the center point of the intervertebral disc in the lateral position. Make a marking on the skin. Mark the contour of the iliac wing on the skin surface (Figure 5).

3. Approach and exposure

1. Make the surgical incision approximately 4 cm long, 3 cm anterior to the center of the disc (Figure 6). Bluntly dissect the three layers of abdominal muscles successively along the direction of the muscle fibers, namely the external oblique muscle, the internal oblique muscle, and the transversalis muscle (Figure 7).
2. Expose the retraperitoneal fat to the surgical field. Bluntly dissect these fats to expose the anterior border of the psoas (Figure 8). Retract the anterior border of the psoas posteriorly using the Cobb dissector to expose the surface of the disc (Figure 9).
3. Nail two Kirschner wires into the proximal and distal vertebral bodies of the intervertebral disc. Block the psoas muscle on the dorsal side. Expose the lateral side of the intervertebral disc and vertebral body clearly (Figure 10).

4. Discectomy and decompression

1. Incise the annulus fibrosus of the disc with a 10-blade scalpel. Remove the degenerated disc material from the intervertebral space using the forceps and reamer (Figure 11).
2. Insert the endoscope system into the intervertebral space (Figure 12). Perform the surgical procedure under continuous saline irrigation. Saline can freely overflow from the skin incision. Control the flow rate of water by the height of the saline bag.
3. Remove the posterior portion of the intervertebral disc material under direct endoscopic visualization. The spinal canal is located at the 12 o'clock position in the visual, the right annulus fibrosus is at the 6 o'clock position, and the endplates are located at the 9 o'clock and 3 o'clock positions, respectively (Figure 13).
4. Perform spinal canal decompression carefully from the inside of the disc to the outside. Use graspers, forceps, and the probe for this. It is easier to decompress the right lateral recess than the left due to the limited tilting angle of the endoscope.
5. Use a diamond burr in decompression when there are osteophytes on the posterior edge of the vertebral body or when the intervertebral disc is calcified (Figure 14). Ensure the decompressed nerve root is clearly seen under the endoscope (Figure 15). Visualize the position of the forceps by X-ray fluoroscopy to confirm the adequacy of decompression (Figure 16).
   NOTE: The complete removal of the nucleus pulposus during surgery and the direct visualization, wider, and more direct decompression of the spinal canal are key factors for postoperative neurological function recovery.

5. Interbody fusion and instrumentation

1. After spinal canal decompression, remove the endoscope system.
2. Perform the next steps under direct visualization: First, penetrate the contralateral annulus fibrosus using a reamer. Insert a peek cage filled with artificial bone and recombinant human bone morphogenetic protein-2 (rhBMP-2) vertically into the intervertebral space. Confirm the location and size of the cage by X-ray fluoroscopy.
3. Insert two 7 mm diameter screws into the vertebral bodies on the cephalic and caudal sides. Use a rod to connect the two screws together (Figure 17).
4. After careful hemostasis and irrigation of the surgical field, suture the incision layer by layer and place a drainage tube in the surgical area (Figure 18).

6. Postoperative care

1. The patient can get out of bed with a brace 24 h after the operation. Remove the drainage tube when the drainage volume is less than 50 mL/24 h.

From December 2023 to October 2024, this surgery was performed on 8 patients in our hospital, including 5 males and 3 females aged 44-78 years with an average of 67.9 years. The average operation time was 135.8 min.

Patients presented relief of their symptoms including Intermittent claudication and sciatica. The neurological function on each follow-up greatly improved compared with that before surgery.

Postoperative MRI shows that the free nucleus pulposus had been completely removed (Figure 19). However, long-term clinical efficacy requires longer follow-up. At present, the average follow-up time is 6 months, and long-term clinical effects will be reported in subsequent studies.

Figure 1: Flow diagram of full-endoscopic decompression combined with OLIF surgery. Please click here to view a larger version of this figure.

Figure 2: Determining the surgical segment using radiography. (A) "→" shows the nucleus pulposus that is migrating towards the cranial end. (B) "-" shows the distance between the psoas major muscle and the artery. (C) "-" shows the height of the intervertebral space. Please click here to view a larger version of this figure.

Figure 3: Radiography showing the artery, vein, and the psoas major muscle. "→" shows the artery. "" shows the vein. "○" shows the psoas major muscle. Please click here to view a larger version of this figure.

Figure 4: The patient's position during surgery. The surgical bed is bent. Please click here to view a larger version of this figure.

Figure 5: Fluoroscopy and marking. (A) The center point of the intervertebral disc under X-ray fluoroscopy. (B) Markers on the skin: The solid line shows the iliac wing. The dashed line shows the planned surgical incision. "" shows the center point of the intervertebral disc on the skin surface. Please click here to view a larger version of this figure.

Figure 6: The surgical incision. Please click here to view a larger version of this figure.

Figure 7: Bluntly dissect the three layers of abdominal muscles. (A) The external oblique muscle, (B) the internal oblique muscle, and (C) the transversalis muscle. Please click here to view a larger version of this figure.

Figure 8: Expose the retroperitoneal fat and psoas. "→" shows the psoas. "○" shows the retroperitoneal fat. "-" shows the anterior border of the psoas. Please click here to view a larger version of this figure.

Figure 9: Expose the disc using the Cobb dissector. "→" shows the intervertebral disc. Please click here to view a larger version of this figure.

Figure 10: Two Kirschner wires in the proximal and distal vertebral bodies to expose the disc clearly. Two arrows show the Kirschner wires. "○" shows the intervertebral disc. Please click here to view a larger version of this figure.

Figure 11: Discectomy. (A) Incise the annulus fibrosus with the surgical knife. (B) Discectomy with forceps. (C) Discectomy with the reamer. Please click here to view a larger version of this figure.

Figure 12: The endoscope system in the intervertebral space. (A) Real-time intraoperative photographs and (B) the diagram. Please click here to view a larger version of this figure.

Figure 13: The endoscopic view of the intervertebral space. "→" shows the spinal canal at 12 o'clock position; "" shows the right annulus fibrosus at 6 o'clock position. "○" shows the endplates at 9 o'clock and 3 o'clock positions. Please click here to view a larger version of this figure.

Figure 14: Removal of the osteophytes on the posterior edge of the vertebral body with the diamond burr. Please click here to view a larger version of this figure.

Figure 15: The nerve root under the endoscopic view. "→" shows the nerve root. "○" shows the epidural fat. Please click here to view a larger version of this figure.

Figure 16: The image of the X-ray fluoroscopy indicate that the forceps is located in the lateral recess. (A) The A-P X-ray fluoroscopy shows that the forceps is located on the inner edges of the superior and inferior pedicles. (B) The lateral X-ray fluoroscopy shows that the forceps is located on the posterior edge of the vertebral body. Please click here to view a larger version of this figure.

Figure 17: The images of the X-ray fluoroscopies show the screws and cage. (A) The A-P X-ray fluoroscopy and (B) the lateral X-ray fluoroscopy. Please click here to view a larger version of this figure.

Figure 18: The sutured incision and the drainage system. Please click here to view a larger version of this figure.

Figure 19: Preoperative and postoperative MRI images. The arrows show the free nucleus pulposus. (A) Preoperative sagittal MRI image. (B) postoperative sagittal MRI image. (C) Preoperative axial MRI image. (D) Postoperative axial MRI image. Please click here to view a larger version of this figure.

This surgery alleviates symptoms caused by both spinal stenosis and prolapsed nucleus pulposus, resulting in satisfactory clinical outcomes for the patients. The satisfactory clinical outcomes are attributed to the direct decompression of the spinal canal under the endoscopy, which differs from the traditional OLIF surgery where spinal canal decompression relies on the tension of the posterior longitudinal ligament after increasing the intervertebral height^4,6,12,13. This is why a prolapsed nucleus pulposus is one of the contraindications for OLIF surgery^6,14.

Various posterior minimally invasive fusion surgeries, such as minimally invasive surgical transforaminal lumbar interbody fusion (MIS-TLIF) and endoscopic transforaminal lumbar interbody fusion (endo-TLIF), can also be used to treat patients with spinal stenosis combined with prolapsed nucleus pulposus^9,14. Many studies have proved that those minimally invasive fusion surgeries have achieved satisfactory clinical outcomes^11,13,15. However, some studies have found that although these minimally invasive posterior lumbar fusion surgeries can reduce the paraspinal muscle damage and thus lower the incidence of postoperative lower back pain, some patients still experience varying degrees of multifidus muscle damage one year after surgery, which can affect the core stability of the spine and cause secondary damage to the lumbar spine^6,16,17. From the perspective of iatrogenic injury to the paraspinal muscles, OLIF is the most minimally invasive lumbar fusion procedure. Additionally, OLIF offers advantages such as a larger fusion cage, broader bone grafting area, stronger support, and better reduction of spondylolisthesis^2,3,4,6,12.

Full-endoscopic decompression surgery has achieved satisfactory clinical outcomes in the treatment of lumbar spinal stenosis and lumbar disc herniation^8,9,10,11. This minimally invasive surgery has a definitive effect on the removal of the free nucleus pulposus and the decompression of the spinal canal. However, unlike traditional full-endoscopic spine surgery, which removes the nucleus pulposus through the intervertebral foramen or interlaminar space, this innovative procedure utilizes an endoscope inserted from the oblique lateral side of the intervertebral disc to perform the discectomy. Under this new approach, identifying the direction and location of the herniated nucleus pulposus under endoscopic view is a key point. Firstly, the position of the annulus fibrosus can be used as a reference point, and the transition from the lateral annulus fibrosus to the posterior can be observed under the endoscope. Secondly, intraoperative X-ray fluoroscopy can also assist in determining the orientation of the endoscope and the location of the prolapsed nucleus pulposus.

For spinal surgeons who already have a grasp of both OLIF and Full-endoscopic decompression surgery, the learning curve for this technique is gentle. This technique is a hybrid of the above two surgeries, so theoretically, complications from both surgeries may occur during this surgery. Vertebral endplate injury (13.3%) and thigh numbness/pain (10.6%) are the two most common complications during OLIF process^18,19. The biggest difficulty during endoscopic decompression is determining the position of nerve roots, which sometimes requires intraoperative X-ray fluoroscopy to assist in localization. The probability of nerve injury is low because the endoscopic view is magnified and irrigated with water. So overall, after mastering OLIF and endoscopic spine surgery, the surgery can be performed safely. In addition to this technology, TLIF can treat such diseases, but the surgical trauma will significantly increase.

It is difficult to remove the nucleus pulposus located in the left lateral recess of the spinal canal under the endoscope. The obstruction from the abdominal cavity and the anterior longitudinal ligament prevents the endoscope from achieving a wider angle²⁰. This shortcoming needs to be addressed through subsequent improvements in surgical instruments and equipment, such as by using a unilateral biportal endoscope. With the assistance of spinal endoscopy, OLIF surgery can achieve direct spinal canal decompression, which can be considered a revolutionary improvement in the development of OLIF surgery. It is an effective and innovative minimally invasive surgical technique that could play a significant role in advancing minimally invasive spinal surgery. However, more clinical cases and longer-term applications are needed to verify its clinical efficacy.

The authors declare that there are no conflicts of interest in this study.

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