Chapter 26 Selective Percutaneous Posterolateral Endoscopic Lumbar Nuclectomy

A percutaneous endoscopic lumbar discectomy (PELD) through a posterolateral approach is one of many newly developed minimally invasive spine surgery (MISS) techniques. These techniques require only a small skin incision, present less traumatic sequelae to the muscles, epidural space, and neural tissues passing through the intervertebral foramen, and allow an early recovery after the procedure.

The three distinct mechanisms for pain relief by selective percutaneous posterolateral endoscopic lumbar discectomy are a manageable bulk decompression under direct endoscopic visualization and fluoroscope guidance, dilution of inflammatory peptides through continuous irrigation, and denervation of ingrown nerves by means of radiofrequency and laser (Fig. 26-1).

Figure 26–1 The three distinct mechanisms of pain relief after endoscopic discectomy are decompression under direct endoscopic visualization and fluoroscopic guidance, continuous irrigation to dilute inflammatory peptides, and denervation of sensory nerve endings by means of radiofrequency and laser ablation.

Selective chromoendoscopy (Table 26.1) in spine surgery is based on using the specific indicator (a blue color) of indigo carmine that is highly reactive with acidic extracellular matrix in degenerated nucleus pulposus. There is strong evidence for the usefulness of applying indigo carmine for selective endoscopic intervertebral nuclectomy in degenerated nucleus. However, there is no strict difference between normal aging and degeneration in the intervertebral disc (IVD), and an acidic condition of the IVD does not always indicate a pathologic condition. Removal of all blue-colored nucleus pulposus ensures the removal of all degenerated nucleus pulposus, whether or not the IVD is pathologically degraded. To remove the neural compression of herniated nucleus, decompression must become the primary purpose. Therefore, selective nuclectomy must be performed only when the targeted herniated nucleus turned blue in the posterior third of the IVD during chromoendoscopy.

Table 26.1 Concept of Selective Percutaneous Posterolateral Endoscopic Lumbar Nuclectomy

Contraindications

Selective percutaneous posterolateral endoscopic lumbar nuclectomy is contraindicated in patients with the following conditions:

Cauda equina syndrome

Spinal stenosis, except when due to disc herniation

Postlaminectomy recurrent herniation (a relative contraindication)

Complications

The informed consent discussion with the patient should include the following possible complications and their management (Table 26.2):

The surgeon may be unable to access the involved area owing to a high iliac crest, especially in men, or because of an extremely narrow intervertebral disc space. This situation is rare but would require the surgeon to change to an interlaminar approach.

Transient dysesthesia (sunburn syndrome), lasting about 4 weeks, can be caused by searching for the structures during the approach, or by decompressing and detaching the protruded disc from adhesion with the neural component. Selective dorsal ganglion block and gabapentin medication can be prescribed in these cases.

Lumbar plexopathy can be caused by blunt trauma from approaching too close to the midline (within 8 cm). This complication can be prevented by keeping at least 10 cm from the midline. Lumbar plexopathy is verified by electromyography and nerve conduction velocity measurements and is treated with selective dorsal ganglion block and gabapentin medication when necessary.

Superficial or deep-layer hematoma in the can occur in the subcutaneous tissue or between the psoas major and psoas minor muscles, respectively. Compression is necessary for superficial hematoma; observation by magnetic resonance imaging for absorption of blood is required for deep-layer hematoma.

Further instability can result from the procedure in patients with spondylolisthesis and disc herniation. This instability would be repaired through percutaneous external pedicle screw fixation.

Table 26.2 Potential Complications, Their Causes, and Their Management

Potential Complication	Cause(s)	Management
Inability to access the involved area	A high iliac crest, especially in men An extremely narrow intervertebral disc space

Requires conversion to an interlaminar approach Transient dysesthesia (sunburn syndrome)

Intraoperative probing for the structures

Detachment of a protruded disc from adhesion

Gabapentin and/or selective dorsal root ganglion block Lumbar plexopathy Blunt trauma by an approach that is too near the midline, i.e., within 8 cm

Confirmed by electromyography and nerve conduction testing

Gabapentin and/or lumbar plexus block

Superficial or deep-layer hematoma Occurs in the subcutaneous tissue or between the psoasas major and minor muscles

Superficial hematoma requires compression

Deep-layer hematoma requires observation by magnetic resonance imaging for confirmation of absorption of blood

Aggravation of instability In patients with spondylolisthesis combined with disc herniation Percutaneous external pedicle screw fixation

Preoperative prepations

Physical Examination

Low back pain upon performance of the straight-leg raising test defines the positive tension sign (essential for diagnosis) (Fig. 26-2).

The location of the pain can help localize the nerve root involved. Pain may radiate to small, isolated areas along the course of a dermatome (Figs. 26-3 and 26-4).

Figure 26–2 The supine straight-leg raising test.

Figure 26–3 Dermatome hyperalgesia, pain, and tenderness in the distribution of the lower limb from herniation of intervertebral disks. (A) Pattern of distribution of the L4 segment from herniation of the L3 intervertebral disc. (B) Dermatome hypalgesia, pain, and tenderness in the distribution of the L5 segment resulting from herniation of the L4 intervertebral disc. (C) Dermatome hyperalgesia, pain, and tenderness in the distribution of the S1 segment resulting from herniation of the L5 intervertebral disc.

(Modified from Keegan JJ. Dermatome hyperalgesia associated with herniation of the lumbar intervertebral disc. J Bone Joint Surg 1944;26:238-248.)

Figure 26–4 Meaningful locations of pain radiating from the various nerve roots.

Imaging Diagnosis

The following imaging evaluations are used:

Magnetic resonance imaging demonstrates intervertebral disc herniation corresponding to physical findings.

Plain films enable intervertebral space measurement prior to the operation.

Discography reveals concordant pain, shape, and pressure during the preoperative or intraoperative period.

Medications

The following medications are prescribed if needed:

For major analgesia, nonsteroidal anti-inflammatory drugs and/or acetaminophen containing a weak opioid (codeine).

For adjuvant analgesia, gabapentin for neuropathic pain.

Related anatomy and physiology

A Kambin’s triangular working zone is the site of surgical access for posterolateral endoscopic discectomy; it is defined as a right triangle over the dorsolateral disc. The hypotenuse is the existing nerve root, the base (width) is the superior border of the caudal vertebra, and the height is the dura and traversing nerve root (Fig. 26-5).

Figure 26–5 (A) Kambin’s triangular working zone (dotted circle). (B) L3-L4 and L4-L5 intervertebral discogram.

Instrumentation

Necessary instrumentation and preparation for posterolateral endoscopic discectomy (Figs. 26-6 to 26-8) consists of the following:

Multichannel, 20-degree oval spinal endoscope with 2.7-mm working channel and integrated continuous irrigation (inflow and outflow) ports

7-mm working cannulas with various open slotted, beveled, and tapered ends

Two-channel tissue dilator/obturator

Specialized single- and double-action rongeurs for visualized fragmentectomy

Larger straight and hinged rongeurs for discectomy and targeted fragmentectomy

Trephines for anulotomy and foraminoplasty

Microrasps, curettes, and Penfield probes

Anulotomy knife

Flexible bipolar radiofrequency or laser probe for hemostasis, thermal contraction of the anular collagen, and thermal ablation of the anular nociceptors

Fluoroscope

Local anesthetics: 1% lidocaine

Conscious sedation: 50 μg fentanyl, 30 mg ketorolac, and 2 to 3 mg midazolam, if necessary

Fluid pump for continuous irrigation, consisting of 2 mg epinephrine and 80 mL gentamicin per 1000 mL cold saline for the prevention of bleeding and infection

Figure 26–6 Arrangement of personnel and instrument for endoscopic discectomy. Schematic drawing around the patient (A) and intraoperative photography (B).

Figure 26–7 The Yeung Endoscopic Spine System YESS™ endoscope (Richard Wolf Medical Instruments, Knittlingen, Germany) features multichannel irrigation and a 2.8-mm working channel. Complementary access cannulas and instruments improve visualization of the epidural space and the foramen. CCD: charge-coupled device

(Illustration by David Azarello.)

Figure 26–8 Instrumentation for percutaneous endoscopic lumbar discectomy. (A) Spinal endoscope. (B) Spine needle set. (C) Dilator. (D) Various types of working sleeves. The beveled cannula is used for an intracanalicular disc herniation and the round cannula proves more useful in foraminal and extraforaminal disc herniations. (E) Trephines with different cutting diameters (top to bottom): 3.0, 5.3, and 6.3 mm. (F) Dissectors, with different outside diameters (top to bottom): 2.5, 3.0, and 3.5 mm. (G) Intradiscal rongeurs, articulating (top) and nonarticulating (bottom). (H) Micro-rongeurs, scissors, and micro-punches. (I) Driving sleeve (impactor; top) and mallet (bottom). (J) Radiofrequency unit (Ellman Trigger-Flex Bipolar System, Ellman Innovations, Hewlett, NY) (left) or laser unit (Trimedyne 1210 VHP 80w Holmium Laser. Trimedyne, Inc, CA) (right).

Procedure

1. The patient’s written informed consent is obtained.

2. The appropriate antibiotics are administered 30 minutes before the skin incision; for example, an intravenous injection of 1 gram cefazolin could be given after a skin test has been completed.

3. Basic monitoring is set up, including measurements of blood pressure, pulse rate, respiration rate, pulse oximetry, and electrocardiography.

4. Conscious sedation/analgesia, as listed previously, is given if needed.

5. The appropriate markings are made with a marking pencil on the skin under the fluoroscope (see Figs. 26-9 and 26-10 for details).

6. Local anesthetic, 1% lidocaine, is injected using a 2-inch-long, 26-gauge needle, into the skin and subcutaneous tissue, but not into the psoas major and psoas minor muscles, through which the lumbar plexus passes.

7. A 6-inch-long, 18-gauge needle is inserted at a 25- to 30-degree angle from the coronal plane (reciprocal of 60-65 degrees from the parasagittal plane), targeting the foraminal anular window.

8. The surgeon should feel the sequential different sensations of approaching the outer anulus, penetrating the anulus, and reaching the center, on the posteroanterior (PA) fluoroscopic view, and posterior third of the nucleus.

9. Chromodiscography is performed to identify the targeted acidic degenerated nuclectomy with a mixture of contrast agent and indigo carmine, such as 2 mL and 8 mL, respectively, while recording the patient’s experience of pain according to the volume, the pressure according to the volume, the volume injected, and the shape of spreading of the contrast agent and indigo carmine on anteroposterior and lateral fluoroscopic views (Fig. 26-11).

10. A long, thin guidewire is inserted through the 18-gauge needle channel and the nucleus.

11. The needle is then removed.

12. A small incision about 1 cm in length is made along the skin crease.

13. The bluntly tapered, tissue-dilating obturator is slid over the guidewire until the tip of the obturator is firmly engaged in the anular window (Fig. 26-12).

14. The working cannula is advanced over the obturator (Fig. 26-13).

15. The obturator is then removed (see Fig. 26-13).

16. With use of the endoscope with irrigation, the outer anular fibers are inspected before the anulotomy to ensure that no neural structures are in the path of the cannula.

17. A four-quadrant anular infiltration of 0.5 mL of 1.0% lidocaine is performed with a 6-inch-long, 18-gauge needle, care being taken to avoid the spinal nerves.

18. Anular fenestration is completed with small and large cutting trephines or anulotomes (Fig. 26-14).

19. After the endoscope is removed, the blue-stained nucleus pulposus is extracted with endoscopic rongeurs or with the larger straight and hinged rongeurs directly through the cannula (Figs. 26-15 and 26-16).

20. The patient is asked to cough to increase the abdominal pressure and ensure sufficient disc decompression.

21. The flexible radiofrequency trigger-flex bipolar probe or a side-firing holmium:yttrium-aluminum-garnet (Ho:YAG) laser is inserted for intradiscal denervation and contraction of anular collagen at the herniation site, and the degenerated and extruded portions of the disc are removed (Fig. 26-17; see Fig. 26-16).

22. The endoscope is used to confirm the discectomy is complete at the anulotome site, neural structures, and epidural space.

23. The endoscope and cannula are removed under direct vision.

24. The subcutaneous tissue is sutured with an absorbable material (Fig. 26-18).

25. The incision is dressed with an adhesive bandage, and a 2-day piroxicam patch is applied for analgesia (see Fig. 26-18).

Figure 26–9 Yeung protocol for needle and instrument placement Yeung AT, Yeung CY: Posterolateral selective endoscopic diskectomy: The YESS technique. (A) Posteroanterior (PA) fluoroscopic (C-arm) exposure enables topographic location of the spinal column midline and the transverse planes of the target discs. Intersections of drawn lines mark the PA disc centers (arrows). (B) Lateral fluoroscopic exposure enables topographic location of the lateral disc center and allows visualization of the plane of inclination for each disc. Intersections of drawn lines mark the lateral disc centers (arrows) (C) The inclination plane of each target disc (red lines) is drawn on the skin from the lateral disc center (plus signs) to the posterior skin surface. (D) The distance between lateral disc centers (plus signs) and the posterior skin surface plane is measured along each disc inclination line (red line). (E and F) This distance is then measured from the midline along the respective transverse plane line for each disc. At the end of this measurement, a line parallel to the midline (long black horizontal line) is drawn to intersect each disc inclination line (red line). This intersection marks the skin entry point or “skin window” for each target disc. Needle insertion at this point toward the disc is angled approximately 25 to 30 degrees to that the needle enters the disc at the dorsal quadrant, traversing just under the superior facet of the inferior vertebra to get as dorsal and close to the posterior anulus as possible. Lateral disc centers (black Xs). In DH Kim, RG Fessler, JJ Regan (eds). Endoscopic Spine Surgery and Instrumentation. New York, Thieme, 2005, pp 201-211.

Figure 26–10 Schematic drawing of passage of percutaneous endoscopic lumbar discectomy (PELD). Fig 29-10 A shows a working channel of the PELD, B shows schematic drawing of needle insertion angle and distance. The 6-inch-long, 18-gauge needle is inserted at a 25- to 35-degree angle from the coronal plane (reciprocal of 60-65 degrees from the parasagittal plane), targeting the foraminal anular window. Three-dimensional figures of passage of PELD related with surrounding structures (C and D), QL, quadratus lumborum muscle; ES, erector spinae muscle; P, psoas major muscle; L, length from the midline to needle insertion; H, height from the skin to the middle of the intervertebral disc.

Figure 26–11 Confirmatory chromodiscography and guidewire insertion. The contrast agent is running over the posterior anulus and posterior epidural space with downward leakage on fluoroscopic AP (A) and lateral view (B). The pain is found to be concordant with the patient’s previously described pain.

Figure 26–12 An obturator tube passes over the guidewire with confirmation on fluoroscopic AP (A) and lateral view (B).

Figure 26–13 A working sleeve is inserted, and the obturator tube is removed with confirmation on fluoroscopic AP (A) and lateral view (B).

Figure 26–14 An anulotome with small trephines with confirmation on fluoroscopic AP (A) and lateral view (B) and large trephines. (C)

Figure 26–15 (A) The endoscope is placed through the sleeve. (B) Selective nuclectomy is performed and confirmed on flurouoscopic lateral view. (C and D) The disc fragments which were removed by focep. (E) The nuclectomy material was stained with hematoxylin and eosin stain. Nonstained white and red regions of nucleus pulposus had a normal chondrocyte arrangement with regular matrix (×4). (F) Stained nucleus pulposus had chondrocyte aggregation with an irregular matrix agreement, including increased vascular infiltration (×200).

(From Kim IS, Kim KH, Shin SW, et al. Indigo carmine for the selective endoscopic intervertebral nuclectomy. J Korean Med Sci 2005;20:702-703.)

Figure 26–16 Radiofrequency application for denervation of ingrown innervation and vascularization and for anuloplasty.

Figure 26–17 Schematic illustrations of endoscopic discectomy with the direction of disc material decompression (arrow) (A) and denervation using radiofrequency or laser (B).

Figure 26–18 Skin closure with surgical adhesive skin closures (Steri-Strips). (A) Subcutaneous suture with absorbable material. (B) Almost 1 cm-long small incision. (C) Skin colsure with adhesive band.

See also Table 26.3 and Figure 26-19 for a summary of the operative steps and Figures 26-20 and 26-21 for endoscopic views of the procedure.

Table 26.3 Steps of Percutaneous Selective Chromoendoscopic Nuclectomy

Step	Chapter Figure(s)
Drawing for placement of needle and instrument	26-9, 26-10
Confirmatory chromodiscography and guidewire insertion	26-11
An obturator tube passes over the guidewire	26-12
Working sleeve inserted and obturator tube removed	26-13
Anulotome with small and large trephines	26-14
Endoscope placement through the sleeve	26-15A
Selective nuclectomy	26-15-B to F
Denervation and anuloplasty	26-16, 26-17
Skin closure	26-18

Figure 26–19 The five major steps of endoscopic discectomy.

Figure 26–20 Schematic illustration of the percutaneous lumbar endoscopic discectomy with beveled working sleeve toward dura sac (left) and corresponding endoscopic views (right)

Figure 26–21 Endoscopic views of percutaneous endoscopic discectomy. (A) After anulotomy, the inflammatory membrane containing in-grown engorged blood vessels is floating in the center and at the 6 to 8-o’clock position. This obscures the nucleus pulposus (NP). The glistening bright yellow epidural fats covered parts of the blue-stained bulging NP at the 12 to 3-o’clock position. (B) The forceps are inserted to extract bulging NP. (C) The tip of the side-firing radiofrequency ablation (RFA) laser approaches through the site of the anulotomy toward the intervertebral space to remove in-grown nerves and blood vessels after removal of the bulging NP. (D) The tip of the RFA laser is aimed to remove the blood vessels in the inflammatory membrane around the 5-o’clock position. (E) After removal of the blue-stained bulging NP, the blue-tinged white anulus fibrosus (AF) is located in the center of the endoscopic field. The glistening bright yellow epidural fats are located at the 12 to 3-o’clock position. At the 6 to 8-o’clock position, the epidural fats are seen after removal of the inflammatory membrane. The red congested inflammatory membrane-covered AF is located at the 9 to 12-o’clock position.

Postoperative care and follow-up

The straight-leg raising test result is improved immediately, and a postoperative nonenhanced computed tomography scan shows an air-filling shadow around the detached area (Fig. 26-22).

Figure 26–22 Postoperative computed tomography scan. Right lateral and anterior epidural space is occupied with air-filled shadow.

Walking is encouraged 2 hours after the procedure. Nonsteroidal anti-inflammatory drugs, muscle relaxants, and gabapentin are prescribed for 1 week after the procedure. At a follow-up visit 1 week after the procedure, the adhesive dressing is removed for examination of the incision.

Caveats

For prevention of neural damage, the speed of advancement of the needle and obturator should be reduced.

Local anesthetics should never be infiltrated around lumbar plexus.

Before anulotomy, sufficient analgesia, such as local infiltration of the anulus with intravenous ketorolac or remifentanil, is needed.

To confirm sufficient disc decompression, the patient should be told to cough before decompression is considered finished.

Case Study 26.1

A 19-year-old woman with a 1-year history of mild low back pain and intermittent left leg pain sustained an acute exacerbation of the left leg pain 21 days prior to visiting to our clinic. She was preparing for a university entrance examination at the time and was unable to sit to study, and she had to sleep in a reclining position to reduce the left leg pain. The standing and reclining positions provided some relief. She had received an epidural steroid injection in the back at the local clinic near her home; the symptoms recurred 3 days later. A large left paracentrally-foraminally extruded herniated nucleus with slight downward migration on the L4-L5 intervertebral space was found to be causing compression on the exiting nerve root. Open surgery was recommended.

The patient chose to delay the operation in order to continue preparing for the university entrance examination. She was concerned about a long-term hospital admission, a cosmetic problem, and possible complications after back surgery. She then decided to undergo minimally invasive spine surgery after suffering intractable pain that prevented sleep. She complained of a new onset of weakness, tingling, and constant numbness during the 2-hour trip to the clinic.

Physical examination at this time found that the patient was experiencing constant pain around the left posterior buttock, tenderness in the left sciatic notch, and numbness radiating down the left lower leg to the great toe and the dorsum of the left foot. The straight-leg raising test result was positive result, less than 20 degrees. A decreased sensation of light touch over the dorsum of the foot and great toe were also observed.

A confirming discogram of L4-L5 was performed. Intradiscal pressure was high until an injection of 1 mL of contrast agent and indigo carmine mixture was given and concordant radiating pain on the left leg occurred. With 1 mL to 2 mL of injected volume, the pressure was acutely decreased, and posterior downward leakage was observed on the lateral discographic view.

Selective posterolateral lumbar endoscopy was performed as described in the text of this chapter. During the discectomy, the patient felt relief of the radiating pain. Immediately after the procedure, tension signs had disappeared. The postoperative computed tomography scan demonstrated a decompressed extruded disc (see Fig. 26-22).

After being moved to a hospital room, the patient dressed and voided without assistance. When the surgeon visited 2 hours later, the patient could walk with some dysesthesia on the previous lesion site. When she came to the clinic 1 week later for follow-up, the wound was clean and she reported no discomfort during basic activities. The patient was advised that she could shower or bathe at this point, 1 week after the operation.