8 Percutaneous Endoscopic Interlaminar Lumbar Diskectomy: Structural Preservation Technique for L5–S1 Herniated Nucleus Pulposus

Microscopic lumbar diskectomy has been the standard operation in lumbar disk surgery for herniated nucleus pulposus (HNP), but recently, percutaneous endoscopic lumbar diskectomy (PELD) has developed significantly.1,2,3,4,5 PELD can be classified into transforaminal PELD (PETLD)^{1,6,7,8,9,10,11,12,13,14,15} and interlaminar PELD (PEILD)^{1,16,17,18,19,20,21} according to the approach. Each method has its own advantages and disadvantages. The indications and anatomical and surgical tips for the two kinds of PELD are discussed in this chapter.^{6,17,18,19,20,21,31}

8.2 Anatomical Considerations

8.2.1 Classification

See Table 8.1, Table 8.2, and Fig. 8.1.

8.2.2 Anatomical Limitations of PETLD and Rationale for PEILD

The condition of the foramen and the iliac crest should be checked before using the transforaminal approach, because in cases associated with a narrow foramen, a shallow suprapedicular area, or a high iliac crest, it will be difficult to approach the target point (Fig. 8.2).^22,23,24,25 The rationale for PEILD in L5–S1 HNP is shown in Fig. 8.3. Anatomical features of the interlaminar space are shown in Fig. 8.4.

Table 8.1 Advantages and disadvantages of PELD procedures for L5–S1 HNP

Table 8.2 Advantages and disadvantages of two different percutaneous interlaminar approaches

Fig. 8.5 shows the standard set-up for the operating room, including the positions of the surgeon, nurse, and instrument table, as well as the positions of the X-ray machine and the video and image-processing equipment.

8.4.2 Anesthesia

For the interlaminar approach, an epidural block or general anesthesia is an appropriate choice, because the nerve roots are directly retracted, which causes severe pain. General anesthesia reduces the patient’s anxiety and intraoperative pain, but it lacks the benefit of neural monitoring.

8.4.3 Positioning and Skin Marking

The patient is placed in the prone position for PELD (Fig. 8.6). Planning the entry point of the working channel is important in PEILD for successful disk removal and for avoiding structural damage, including neural damage (Video 8.1).

The entry point for PEILD is the “V” point:

• The V point is the intersection of the ligamentum flavum, inferior articular process, and superior articular process.

• Approximately 1 cm from midline of spinous process

• The deepest portion lies between the ligamentum flavum and lamina.

• Most lateral part of ligamentum flavum

• The beveled-tip working channel can tightly insert into the V point (Fig. 8.7).

To achieve good results with targeted fragmentectomy, evocative chromodiskography can be performed to assess the degenerated or pathologic disk using indigo carmine dye. Fluoroscopic imaging is used to determine the placement of the needle tip, and the needle tip is advanced toward the more caudal and dorsal part of Kambin’s triangle. To reduce the occurrence of neural injury, the needle should be positioned on the ventral part of the facet joint (superior articular process) in the first step. After making contact with the safe bony structures of the superior articular process, the needle is repositioned in Kambin’s triangle (Fig. 8.8, Fig. 8.9).

After guide needle insertion, indigo carmine dye is injected into the disk space to identify the degenerated or pathologic disk (Video 8.2).

8.4.5 Skin Incision and Working Channel Insertion

After injection of indigo carmine into the operative area, a skin incision is made at the point estimated preoperatively. After skin incision, subdermal fascia should be dissected to allow insertion of the working channel. Then the obturator is inserted into the target point. The working channel is inserted through the obturator. After optimal positioning of the working channel on the target point, the percutaneous endoscope is inserted into the working channel. Insertion of a round-tip working channel is shown in Fig. 8.10, and insertion of a beveled-tip working channel is shown in Fig. 8.11. The anatomical approach point for PEILD is shown in Fig. 8.12 (Video 8.3a,b).

8.4.6 Ligamentum Flavum Approach

Ligamentum Flavum Resection Technique¹⁹

• Cut the ligamentum flavum using the punch.

• The procedure is similar to conventional microscopic lumbar diskectomy.

• This technique is especially indicated in the shoulder approach.

Indirect Ligamentum Flavum Splitting Technique^18,26

• Insert the 18 G needle into the axilla.

• Check the free axilla area after the dye injection.

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