Percutaneous Full-Endoscopic Interlaminar Approach for Lumbar Pathologies: Disc Herniation and Lumbar Spinal Stenosis

34 Percutaneous Full-Endoscopic Interlaminar Approach for Lumbar Pathologies: Disc Herniation and Lumbar Spinal Stenosis

Javier Quillo-Olvera and Jin-Sung Luke Kim

Summary

Recently, full-endoscopic techniques have emerged as a minimally invasive option for treating several spine diseases, demonstrating safety and effectiveness. The development of new endoscopic devices has allowed overcoming the anatomical barriers that prevented to reach the pathology. Among full-endoscopic procedures, the percutaneous endoscopic interlaminar approach for treating disc herniations and central or lateral recess stenosis is a very effective option. The procedure-related advantages include less iatrogenic impact for paravertebral soft tissue and facet joints. This chapter describes the technique for discectomy and lumbar decompression by using the aforementioned approach. Technical advice to avoid complications and tips for getting encouraging outcomes are also included in this chapter.

Keywords: central stenosis endoscopic decompression interlaminar approach lateral recess stenosis lumbar spinal stenosis lumbar disc herniations minimally invasive spine surgery percutaneous endoscopy

34.1 Introduction

For the past two decades, full-endoscopic techniques have proven to be highly accurate and effective for lumbar disc herniations, achieving at least the same result as conventional surgery.1^,²^,³^,⁴ The interlaminar endoscopic approach is preferred for axillary type and migrated disc fragments,⁵ especially in L5–S1, where transforaminal endoscopic technique can be technically demanding because of the high iliac crest, a large L5 transverse process, a large facet joint, or a narrowed disc space and foramen.⁶ This approach allows focal neurologic decompression. More recently, the interlaminar endoscopic approach has been used to treat lumbar spinal stenosis (LSS).¹^,⁷^,⁸ The percutaneous endoscopic interlaminar approach has allowed the expansion of endoscopic surgical indications. LSS is one of the most common indications for lumbar spine surgery. In 2007, more than 37,500 surgeries for spinal stenosis were performed in Medicare patients in the United States alone, and the total cost was almost $1.65 billion.⁹ The prevalence of LSS increases with age, and is estimated to be 9% in the general population and up to 47% in people over the age of 60.¹⁰ Surgical decompression is the most common spine procedure performed in patients older than 65 years of age.¹¹^,¹² The hypertrophy of the ligamentum flavum, facet joints degeneration, and bulging disc lead to central or lateral narrowing of the spinal canal. The reduced space available for neural and vascular elements in the lumbar spine produces a clinical syndrome characterized by radiated leg pain with or without low back pain, which is exacerbated while standing/walking (claudication). The pain is absent when seated and improves when bending forward or with a wide-based gait.¹³^,¹⁴ The North American Spine Society defines LSS as “a clinical syndrome of the buttock or lower extremity pain, which may occur with or without back pain, associated with diminished space available for the neural and vascular elements in the lumbar spine.”¹² The surgery is recommended after all conservative means fail.¹⁵ The so-called decompressive lumbar laminectomy introduced by Henk Verbiest in 1954 was adopted as an alternative treatment for LSS.¹⁶ However, the complications rate reported with open laminectomy in patients older than 75 years was 18%,¹⁷^,¹⁸ including a high prevalence of iatrogenic instability,¹⁹^,²⁰ and mortality increased fourfold in patients older than 80 years.²¹ The efficient decompression of neural structures while preserving most of the stabilizing components of the spine such as muscles, ligaments, facet joints, and bone is an advantage associated with the endoscopic interlaminar approach.² Moreover, a smaller skin incision with no need of muscular and neural retraction, the use of epidural anesthesia leading a complete communication between the surgeon and the patient to prevent a neural injury during whole procedure, a lower incidence of intraoperative complications and postoperative epidural fibrosis, shorter hospital stay, and faster return to normal daily activities are some of the advantages associated with this approach.¹^,⁷^,²² The abovementioned is especially important in elderly patients with several comorbidities and LSS; hence, the endoscopic interlaminar approach is a safe and feasible alternative to treat LSS. The development of new surgical tools, such as the endoscopic bone drill, flexible forceps, and new optic devices, has allowed overcoming the anatomical barriers to decompress the lumbar spinal canal. In this chapter, we present the percutaneous endoscopic interlaminar technique for discectomy and LSS.

34.2 Indications

The use of percutaneous endoscopic interlaminar approach is adequate in the following situations:

•Sequestered or nonsequestered disc herniation within the spinal canal.¹^,³^,⁶ The axillary type is more suitable for this approach.²³^,²⁴

•Calcified disc herniations.⁶^,²⁵

•Upward and downward migrated disc herniations of up to 8 mm can be removed. This will depend on the vertical distance between the lower border of the L5 lamina and the upper border of the S1 lamina. In these cases, an endoscopic drill to enlarge the interlaminar window is necessary.⁶^,²³^,²⁶

•Recurrent disc herniation.³

•Intracanal L4–L5 disc herniations can be approached.²⁷^,²⁸

•LSS can be classified into three categories according to the narrowing zone as follows: Central stenosis, lateral recess stenosis, and foraminal stenosis.²⁹^,³⁰ The percutaneous endoscopic interlaminar approach for spinal decompression is more suitable for central and lateral recess stenosis. In our institution, the clinical criteria are neurogenic intermittent claudication and radiculopathy, which are refractory to conservative treatment for at least 12 weeks. The radiological criteria are monosegmental central or lateral recess stenosis on computed tomography (CT) and magnetic resonance imaging (MRI).⁸

34.3 Contraindications

Extraforaminal nerve entrapment is an absolute contraindication. However, foraminal stenosis is a relative contraindication. It depends on the surgeon’s skills. Undercutting the inferior and superior articular process can release the traversing and exiting nerves through a highly addressed interlaminar contralateral endoscopic approach. segmental instability; degenerative spondylolisthesis of more than Meyerding Grade I; multidirectional rotation slide; scoliosis of more than 20 degrees; and coexisting pathological conditions such as neoplasms or infections.8^,³¹

34.4 Preoperative Planning

The general workout consists of dynamic radiographs (flexion and extension) to exclude segmental instability.³²^,³³ The North American Spine Society suggests MRI as the best noninvasive imaging modality to evaluate the spinal canal anatomy in patients with radicular symptoms.³⁴

For patients in whom there is a contraindication for MRI, the use of Myelo-CT or conventional myelography has been proposed for the diagnosis of LSS.³⁵ Information obtained from imaging studies are as follow: location of the herniated disc regarding traversing nerve root (axillary or shoulder type), interlaminar window area, diagnosis of central LSS or lateral recess stenosis, and the type of surgical target (bony element, soft tissue, or both).³⁶^,³⁷ The patient’s symptoms will determine the side of decompression or if it will be unilateral or bilateral.

34.5 Patient Positioning

The procedure is performed under either general or regional anesthesia. Others like epidural or regional anesthesia could be used depending on the case complexity. The patient is positioned prone on a Jackson table with a Wilson frame. The operation table is adjustable to enable a kyphotic positioning for maximizing the interlaminar space³^,⁸^,³³ (Fig. 34.1a).

Fig. 34.1 (a) Patient positioning. (b) Operating room setup.

34.6 Surgical Steps

34.6.1 Operating Room Setup

The optimal operating room setup is as follow: The patient is located at the center of the operating room (placed in prone position), and the surgeon should make the approach ipsilateral to the patient’s symptoms side. If the patient does not have a dominant side of symptoms, the surgeon should stand on the left side of the patient to use his right hand (dominant hand) for working. Scrub nurse should stand along with the surgeon on the left side, and the assistant on the right side to the surgeon. The endoscopy and C-arm monitors are positioned in front of the surgeon. Next to the surgeon’s right foot, the radiofrequency (RF) pedal is placed. Lastly, anesthesiology team is located cephalic to the patient (Fig. 34.1b).

34.6.2 Surgical Tools

All surgical procedures for lumbar stenosis are performed with a complete endoscopic instrument set: Vertebris stenosis (RIWOspine GmbH, Knittlingen, Germany) (Fig. 34.2) and Ilessys Delta® (Joimax GmbH, Raumfabrik 33A, Amalienbadstraße, 76227 Karlsruhe, Germany) (Fig. 34.3). In the case of lumbar disc herniation, the endoscopic instrument set of Vertebris Lumbar is used. The characteristics of each system are summarized in Table 34.1. Two different endoscopic drill systems with different burrs are used to enlarge the interlaminar window, and remove bony structures or osteophytes: ART1 (RIWOspine GmbH, Knittlingen, Germany) and Shrill® (Joimax GmbH, Raumfabrik 33A, Amalienbadstraße, 76227 Karlsruhe, Germany). An endoscopic bipolar RF coagulator (Elliquence LLC, Baldwin, New York, USA) is useful for hemostasis and soft-tissue clearance in the surgical field, which is continuously irrigated with antibiotic-containing saline solution during whole procedure.

Fig. 34.2 Wolf® spinal endoscopic system: (a) 20-degree endoscope; (b) obturator and working cannulas; (c, f) endoscopic drill; (d, e) different types of rongeurs and nerve hook.

Fig. 34.3 Joimax® spinal endoscopic system: (a) 15-degree endoscope; (b) should change for the proper shrill system. (c) Kerrison rongeur with different types of tips; (d) obturator and working cannulas.

Table 34.1 Characteristics of two different endoscopes used for percutaneous endoscopic interlaminar approach

	RIWOspine system	Joimax® system
Length (mm)	177	125
Total length (mm)	255	205
Out diameter (mm)	9.3	10
Working channel diameter (mm)	5.6	6
Operative angle (°)	20	15
Weight (g)	240	300

34.6.3 Surgical Approach

True anteroposterior (AP) and lateral intraoperative C-arm images should be used to mark the index level. The radiological landmarks recognized are the following: the inferior margin of the upper lamina and the spinous process. The entry point is planned on the midpoint between the spinous process and the lateral extension of the interlaminar window at the level of the caudal margin of the upper lamina. Then the skin is infiltrated with approximately 2 or 3 mL of 1% lidocaine, and a paramedian skin incision of approximately 10 mm long is made; cutting the thick muscle fascia may facilitate the next step. Blunt insertion of serial dilator toward the target point is done under lateral projection of the C-arm. The working cannula is inserted through the final dilator with the beveled opening directed medially toward the ligamentum flavum, and the endoscope is passed through it (Fig. 34.4).

Fig. 34.4 Interlaminar endoscopic approach. (a) Paramedian skin incision located at the level of inferior margin of upper lamina. (b) Sequential dilation of paravertebral soft tissue. (c) Docked of working channel in the interlaminar space. (d) Intraoperative C-arm image on lateral view showing the proper location of working channel.

34.6.4 Endoscopic Interlaminar Approach for Discectomy

After general considerations such as operating room setup, patient positioning, and anesthesia, the use of prophylactic antibiotics for infection is recommended. An intraoperative C-arm AP and lateral views are useful for planning the entry point, which is made usually close to the midline for reaching the spinal canal with the least possible bone resection and the least disruption of the facet joint (Video 34.1, Time 00:17). A 10-mm skin incision is made, and the fascia is also opened to facilitate the entrance of working instruments. The tissue is sequentially dilated and the beveled working cannula is inserted through the last dilator. The endoscopic system is inserted into the working cannula to perform discectomy under direct endoscopic vision (Video 34.1, Time 00:25). Continuous irrigation with saline solution starts now. The tissue adjacent to the outer layer of the ligamentum flavum is cleared by the use of RF probe and endoscopic forceps (Video 34.1, Time 00:29). The bone landmarks need to be recognized (upper and lower edge of the caudal and cephalic laminae, and the medial facet). When the interlaminar space is not very wide or the working cannula does not advance through this, the bone can be drilled enough to access the spinal canal using an endoscopic drill (Video 34.1, Time 00:55). The ligamentum flavum is removed with a micropunch until the epidural space is observed (Video 34.1, Time 01:40). The positive pressure of the continuous irrigation displaces the neural elements below the ligamentum flavum, which decreases the risk of neural element injury during flavectomy. The inner layer of the ligamentum flavum is removed to allow the passage of the endoscopic system. Afterwards, the traversing nerve root is observed, and the axillary space is reached (Video 34.1, Time 02:10). When this space is enough to mobilize and remove the herniated disc, the surgeon can use the endoscopic forceps; otherwise when the space is limited in an axillary disk herniation, the beveled working cannula can be advanced to the spinal canal and rotated to retract with the bevel the dural sac medially and remove the axillary disc herniation (Video 34.1, Time 02:09). In the case the herniated disc is located in the shoulder, a medial facetectomy should be done using the endoscopic drill to reach the fragment. The endoscopic nerve hook is used to explore the ventral epidural space and confirm that there is no residual disc (Video 34.1, Time 02:33). Finally, the annular defect is sealed using an RF probe to reduce the risk of recurrence. The use of a drain after the surgery is not usually necessary for discectomies due to the minimal bleeding. When adequate hemostasis has been confirmed, the endoscope can be removed and the skin incision can be closed with a single suture Fig. 34.5. Table 34.2 summarizes the 10 steps of the technique.