Chapter 23 Percutaneous Endoscopic Cervical Discectomy and Stabilization

Percutaneous endoscopic cervical discectomy (PECD) is a relatively new surgical method for treating soft cervical disc herniations [1–7]. The goal of the procedure is decompression of the spinal nerve root by percutaneous removal of the herniated mass under local anesthesia. A holmium:yttrium-aluminum-garnet (Ho:YAG) laser is generally used to ablate and shrink the herniated disc [1–7].

The WSH cervical endoscopy set (Karl Storz, Tuttlingen, Germany) consists of a high-resolution endoscope, illumination, and two irrigation channels [7]. The working channel allows passage of a side-firing Ho:YAG laser and microforceps. The excellent visualization via the endoscope permits the surgeon to selectively remove a portion of the herniated nucleus pulposus. After the anular anchorage has been loosened by the side-firing laser, the herniated fragment can be removed easily with the microforceps. With circumferential rotation of the working cannula and the endoscope, the side-firing laser can also ablate the thickened ligamentum flavum, remnant bone fragment, and shoulder osteophyte.

Although PECD is effective and can be an alternative to open anterior cervical discectomy and fusion, it has limitations. For example, it is ineffective in patients with segmental instability or cervical discogenic pain syndromes. However, the specially designed WSH Cervical B-Twin expandable holder (Disc-O-Tech Medical Technologies Ltd., Herzliya, Israel), which is made of titanium, can be used as an interbody spacer to achieve stability without open discectomy and fusion.

The major advantages of PECD and PECD stabilization (PECDS) with the B-Twin spacer are as follows [8–12]:

Minimal insult to anterior anulus, anterior longitudinal ligament, longus colli muscle, and anterior vertebral body

Provision of cervical stability

Prevention of postoperative kyphosis

Avoidance of complications of open surgery

Rapid functional recovery

Excellent cosmetic effect

In cases of failure, this minimally invasive procedure does not preclude further conventional surgical approaches. It also offers numerous other advantages, such as the absence of risk of epidural bleeding and periradicular fibrosis, maintenance of stability of the intervertebral mobile segment, and reduced risk for recurrence after creating an anterior discal window. PECD or PECDS provides an excellent cosmetic effect, and the shorter operation time and hospital stay allow the patient to recover to normal daily activity more rapidly.

Indications and contraindications

The indication for PECD or PECDS (Box 23.1) is a soft cervical disc herniation that shows no response to conservative treatment for 6 weeks.

BOX 23.1 Indications for Percutaneous Endoscopic Cervical Discectomy With and Without Stabilization

Percutaneous Endoscopic Cervical Discectomy

Noncontained disc herniation

Radiculopathy

Percutaneous Endoscopic Cervical Discectomy and Stabilization

Disc herniation with vertical instability

Axial neck pain with or without radiculopathy

Spondylotic radiculopathy

Discogenic neck pain

Contraindications to these procedures are as follows:

Cervical spondylotic myelopathy

Hard disc or sequestrated disc fragment

Definite segmental instability

Advanced spondylosis with disc space narrowing

Central canal stenosis or severe osteophytosis

Neurologic or vascular diseases mimicking herniated disc

Preoperative preparation

The primary patient complaint is cervical radiculopathy or neck pain.

Imaging diagnosis consists of the following modalities and findings:

Magnetic resonance imaging (MRI) findings correspond with the physical findings.

Computed tomography (CT) must depict a soft disc herniation.

Plain films are used to confirm segmental instability and intervertebral space measurement preoperatively.

Discography can be performed during the preoperative or intraoperative period to check for the provocation of pain; the surgeon must note the disc shape, degree of resistance upon media injection, and volume of media injected.

Instrumentation

Equipment

The following instruments and modalities are required in the operating room for PECD/PECDS:

WSH cervical endoscopy set (Karl Storz) (Fig. 23-1)

Side-firing Ho:YAG laser (Fig. 23-2)

WSH cervical B-Twin expandable spacer (Disc-O-Tech Medical Technologies Ltd.) (Fig. 23-3)

Fluoroscope (Fig. 23-4)

Figure 23–1 A set of percutaneous endoscopic cervical discectomy (PECD) instruments. (Karl Storz, Germany)

Figure 23–2 An Ho:YAG laser (VeraPulse PowerSuite, Lumenis, Germany). A main computer body of powersuite (A) and side-firing delivery device (B).

Figure 23–3 (A) The single-use delivery system of the WSH cervical B-Twin expandable holder (Disc-O-Tech Medical Technologies Ltd., Herzliya, Israel). (B) Unexpanded end. (C) Expanded end.

(From Choi WC, Lee SH, Ahn Y, et al. Percutaneous cervical stabilization using the WSH cervical B-Twin. Joint Dis Relat Surg 2005;16:82-87.)

Figure 23–4 Fluoroscopic (A) and endoscopic (B) monitors used during percutaneous endoscopic cervical discectomy.

Anesthesia and Other Medications

To decrease the risk of infection, preoperative antibiotics (usually 1.0 g of cefazolin) should be given the day before operation. Preoperative sedatives are recommended.

Sterile preparation of the anterior neck skin and a shower with iodized antiseptics are usual. PECD must be performed in the operating room under strict asepsis.

A solution of 1% lidocaine is usually used to infiltrate the skin and subcutaneous tissue.

Procedure

Patient Preparation

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

2. The patient is placed supine on a radiolucent table. The neck is kept slightly extended by keeping a towel roll under the shoulder blades, and the head is stabilized by application of a plaster tape across the forehead that is then secured to the table. Both the patient’s arms are fixed to the table by application of plaster tape after the shoulders have been pulled down for better viewing of the lower cervical spine via the fluoroscope (Fig. 23-5).

3. Anterior cervical skin is aseptically prepared and draped. A C-arm (fluoroscope) is brought in, and with the help of a metallic needle, skin markings are made with a marking pen to indicate the midline and the correct surgical level with anteroposterior and lateral fluoroscopic views. The surgeon marks lesion by counting the cervical vertebrae downward, then up from the bottom. For better visualization of the C6–C7 level, a slight slope of the fluoroscope may be necessary.

4. The felt pen marks the internal edge of the sternocleidomastoid muscle, the median axis of the neck, and the upper edge of the sternum. The skin is prepared with an antiseptic. The fluoroscope is covered with a sterile field, and then the patient’s face is surrounded with a plastic drape that is held up over the patient’s head so that the anesthesiologist can observe and speak with the patient. Communication between the operator and the patient is necessary during the procedure.

The operation is typically conducted with the use of local anesthesia and analgesia by neuroleptics, so that the surgeon may know immediately of any changes in symptoms and signs from the patient. General anesthesia may be used in a few patients who want it or cannot tolerate the position. If the cervical discography or other procedures aggravate the spinal cord compression, patients can recognize and comment on the development of extremity weakness only if local anesthesia is used. When general anesthesia is used, the urgent need for conversion to open surgery may not be detected early.

5. Local anesthetic is used to infiltrate the skin. To minimize the thickening of underlying tissues and to allow a minute palpation of the spinal axis, we prefer to not infiltrate more deeply with lidocaine. The patient should be kept conscious throughout the operation so that his or her pain could be monitored.

Figure 23–5 Patient position: The patient is placed supine (A) and the face is surrounded by a plastic field to enable the patient to communicate with the anesthesiologist during the procedure (B).

Discectomy

The foraminal cervical disc herniation is better approached from the opposite side—that is, for a left foraminal herniation, a right-sided skin entry is more suitable, and vice versa (Fig. 23-6). The midline herniation can be better approached from the right side by a right-handed surgeon, and from the left side by a left-handed surgeon.

1. The surgeon palpates the carotid pulse with the left hand. By keeping the left thumb on the carotid pulsation, the surgeon pushes the tracheoesophagus complex toward the midline with the middle and index fingers while trying to feel the anterior surface of the cervical vertebrae with the fingertips. This maneuver is aided by the anatomical feature of a common layer of the deep cervical fascia that invests the trachea and esophagus; when pushed, the two structures move together. The medial displacement of tracheoesophagus complex is confirmed by checking of the tracheal air shadow on fluoroscopic image.

2. An 18-gauge spinal needle is inserted in the path to the intervertebral disc developed by the surgeon’s thumb on the lateral side and the middle and index fingers on the medial side (Fig. 23-7). After the needle pierces the skin and subcutaneous fascia, its path is checked with fluoroscopy, and then it is advanced toward the anterior surface of the affected disc.

3. The disc is penetrated in the midline between the longus colli muscles. This maneuver helps minimize pain during the procedure and also avoids the risk of sympathetic chain injury, especially in the lower cervical spine.

4. Once inside the center of the disc, the stylet is withdrawn, and discography is performed through injection of 1 mL of a mixture (5:1 ratio) of radiopaque dye (Telebrix, Guerbert, France) and indigo carmine (Carmine, Korea United Pharmaceutical, Seoul, South Korea) (Fig. 23-8).

Figure 23–6 The foraminal cervical disc herniation is better approached from the side opposite the side of the herniation.

Figure 23–8 Discography. For patients with multiple levels of disc disease, provocative discography is performed to determine the disc level to be treated. (A) Injection of a mixture of radiopaque dye (Telebrix, Guerbert, France) and indigo carmine (Carmine, Korea United Pharmaceutical, Seoul, South Korea) (B) proper disc level is confirmed by fluoroscopic lateral view.

Discography serves the following three purposes: (1) it may evoke concordant pain and thus confirm the level of origin of pain; (2) it provides information about whether the disc herniation is contained or noncontained; (3) indigo carmine, being a base, selectively stains the degenerated acidic nucleus pulposus, which in turn helps easier and better identification of the herniated fragments in the spinal canal during surgery. In the case of a lateral disc herniation, the contralateral approach to the hernia side is undertaken; this approach offers a better visual field for the foraminal portion and allows for easier removal of fragments.

5. A thin guidewire is passed through the needle, and the needle is withdrawn (Fig. 23-9).

6. A 5-mm skin incision is made, and serial dilators from 1 to 4 mm are passed sequentially over the guidewire under fluoroscopic guidance (Fig. 23-9).

7. After the tip of the 4 mm dilator is confirmed to be over the anterior surface of the disc, an anular window is cut with the help of an anular trephine (Fig. 23-10).

8. A blunt-tipped obturator is passed through the dilator and introduced into the disc space.

9. A 5-mm round-tip working cannula is inserted over the obturator and is pushed inside the disc to lie in the posterior third of the disc space (Fig. 23-11).

10. The obturator is withdrawn, and the position of the working cannula is readjusted according to the site of the pathologic lesion, as follows:

In the anteroposterior fluoroscopic view, the tip of the cannula should lie in the midline for a midline disc herniation, and the cannula tip should be facing the affected foramen for a foraminal disc herniation.

In the lateral fluoroscopic view, the cannula tip should lie in the posterior one fourth of the disc space.

Figure 23–9 Serial dilation. A thin guidewire is passed through the needle, and the needle is withdrawn. A 5-mm skin incision is made, and serial dilators from 1 to 4 mm are passed sequentially over the guidewire under fluoroscopic guidance.

Figure 23–10 Anulus trephination. A trephine is inserted through the cannula and cuts the anulus in a circular fashion.

Figure 23–11 Insertion of the working cannula. After trephination of the anterior anulus, a working cannula (5 mm in diameter) is inserted over the obturator and adjusted according to the site of the pathologic lesion. Under fluoroscopic guidance, a small amount of disc tissue is removed from the posterior one fourth of the disc with a microforceps to provide better subsequent endoscopic visualization.

Figure 23–12 Manual discectomy. Under C-arm guidance, the posterior part of the disc is widely decompressed with a microforceps; the anterior part is preserved as shown in an intraoperative photograph (A). The final placement of the tip of microforceps is at the end of the posterior margin as shown in fluoroscopic view (B).

Figure 23–7 Needle insertion. The surgeon pushes the trachea or larynx toward the opposite side with the index finger and then slips a finger inside toward the front of the vertebral body until the prominence of the anterior edge of the disc to be treated is perceived as shown in an intraoperative photograph (A) and a schematic drawing (B). The surgeon’s thumb palpates the beats of the carotid artery. The tracheoesophageal complex was displaced medially and the carotid artery laterally. An 18-gauge spinal needle is then inserted into the disc space.

11. A small amount of disc tissue is removed from the posterior one fourth of the disc with a forceps under fluoroscopic guidance to provide better subsequent endoscopic visualization (Fig. 23-12).

12. The working channel endoscope is introduced through the working cannula.

13. Continuous irrigation is performed with cold normal saline mixed with epinephrine and cefazolin to help with hemostasis and to prevent infection.

14. After the position of the tip of the endoscope is confirmed fluoroscopically, the herniated disc fragment is carefully identified with the endoscopic view.

15. It is often difficult to clearly localize the herniated fragment because it lies inside the spinal canal, behind the anular and posterior longitudinal ligament layers. In such cases, the fragment can be mobilized with the use of the side-firing Ho:YAG laser, which is used to release the adhesions between the herniated mass and surrounding anular and fibrotic tissue. Once mobilized, the herniated fragment can be removed easily with the help of a grasping forceps. The side-firing laser can also be used to ablate small osteophytes lying in the foraminal area as well as the painful anular nociceptors and some of the fragile remnant disc tissue. Using the side-firing laser probe at a 90-degree angle under continuous saline irrigation provides additional safety in terms of protection of neural tissue.

16. Any bleeding from the epidural venous system is controlled through alteration of the speed of irrigation with the epinephrine–cold saline mixture.

17. Adequacy of decompression is checked through visualization of the free course of the nerve root/cervical dural pulsation with the endoscope (Fig. 23-13). At this stage, the patient can also be asked about the status of preoperative symptoms, which usually are improved or have disappeared.

18. The endoscope and the working cannula are withdrawn.

19. A few minutes of manual pressure over the wound helps achieve hemostasis; the small skin wound is sutured with one subcutaneous suture, and antiseptic dressing is applied (Fig. 23-14).

Figure 23–13 Introduction of working channel scope. (A) WSH working channel endoscope is introduced through the working cannula and discectomy is done. (B) Adequate discectomy is confirmed by fluoroscopic lateral view.

Figure 23–14 Skin closure. After the instrument is removed, slight finger compression can be applied on the surgical area for a short time to prevent hematoma formation. Only one stitch is required to close the puncture site, and the wound is covered with a bandage.

Figure 23–15 The stages of the B-Twin implant (Disc-O-Tech Medical Technologies Ltd., Herzliya, Israel) from unexpanded to full expanded cage which is detached at last.

Percutaneous Cervical Stabilization Using the Cervical B-Twin Expandable Holder

1. After completion of the PECD, under fluoroscopic guidance, the reduced implant is introduced into the intervertebral disc space with the single-use delivery system.

2. The implant is expanded to its final form segment by segment through rotation of the expander rotational handle (Fig. 23-15).

3. Once in position, the implant is released from the delivery system.

4. The implant is fixed to the disc space and maintains the disc height. Bone chips are not needed to ensure fusion.

Figure 23–16 Case Study 23.1: (A) Preoperative sagittal magnetic resonance (MR) image shows noncontained disc herniation at C4-C5. (B) Sagittal MR image obtained 5 weeks after the procedure showed no instability. (C) Preoperative axial computed tomography (CT) demonstrates soft disc herniation. (D) Postoperative axial CT scan demonstrates complete removal of the disc herniation.

Postprocedural management

The patient is observed for 3 hours and permitted to go home within 24 hours unless there is a complication. The patient does not need bed rest for more than 1 night.

Oral postoperative antibiotics and analgesics are recommended for 3 to 10 days.

Use of a cervical collar is recommended for 3 to 14 days, depending on the patient’s condition.

Mild physical therapy may be helpful for fast recovery within 2 weeks postoperatively if cervicobrachialgia does not disappear completely.

If pain and discomfort remain, complementary epidural injection of steroids with lidocaine may be performed so that no further open procedure is necessary. The logic is to complement the therapeutic approaches of mechanical decompression and PECD with the reduction of inflammatory components by steroids.

Rehabilitation exercises for neck muscle strengthening and improvement of range of motion are recommended twice a week for 3 months after 4 to 6 weeks postoperatively.

CASE STUDY 23.1

A 61-year-old man suffered from cervical myelopathy. Preoperative magnetic resonance imaging showed noncontained disc herniation at the C4-C5 level, and computed tomography demonstrated soft disc herniation. Because the patient was concerned about the risks of general anesthesia, he underwent percutaneous endoscopic cervical discectomy. Five weeks after the procedure, magnetic resonance imaging showed no instability, and computed tomography demonstrated complete removal of the disc herniation (Fig. 23-16).

CASE STUDY 23.2

A 43-year-old man with C5-C6 instability suffered from neck pain and right shoulder pain. Preoperative magnetic resonance imaging showed C5-C6 instability with disc herniation, and computed tomography confirmed soft disc herniation. Percutaneous endoscopic cervical discectomy and stabilization were performed and immediate stability was obtained (Fig. 23-17)

Figure 23–17 Case Study 23.2: (A) Preoperative magnetic resonance image shows C5-C6 instability with disc herniation. (B) Preoperative computed tomography scan demonstrates soft disc herniation at right side. Postoperative lateral radiographs in extension (C) and flexion views (D) show proper position of cage and immediate stability.

Caveats

The surgical anatomy of the neck is quite suitable for an anterior percutaneous approach. Because the prevertebral content is very mobile owing to compartmentalization of the neck by the deep fascia, the visceral axis (thyroid, trachea, pharynx, larynx, and esophagus) can easily be displaced to the opposite side with one or two fingers.

The surgeon should recognize and manually feel the pulsation of the carotid artery so as to insert the needle and cannula away from the carotid artery. The surgeon should confirm the position of a needle or a cannula on the anteroposterior fluoroscopic view to prevent penetration of the vertebral artery. The fingertips of the operator or the assistant should touch the anterior surface of the vertebral body to avoid perforating the trachea or esophagus.

The surgeon should confirm the tip of the guidewire, the anular trephine, the pituitary forceps, and the laser fiber on the lateral fluoroscopic view, so that the ends of the instruments do not pass more than 2 mm beyond the posterior vertebral body line, in order to protect the spinal cord.

The disc space should be irrigated frequently with 1000 mL saline mixed with antibiotics to reduce the chance of discitis or epidural abscess.