Posterior Tubular Endoscopic Cervical Diskectomy

49 Posterior Tubular Endoscopic Cervical Diskectomy

Alejandro J. Lopez, Zachary A. Smith, Richard G. Fessler, and Nader S. Dahdaleh

49.1 Introduction

While less commonly performed than anterior cervical diskectomy, posterior approaches to the cervical spine reduce the approach-related risks of esophageal injury, vascular injury, recurrent laryngeal nerve injury, or dysphagia.1 Before the introduction of the endoscopic technique, a posterior approach involved extensive disruption of the paraspinal musculature that contributed to increased complications, pain, and disability.^2,3 Modern application of blunt tubular retractors has proven as effective as open procedures while preserving the musculature, achieving symptom relief in 87 to 97% of patients while decreasing blood loss, length of stay, and use of postoperative pain medication.^1,4 The application of endoscopic technology enhances visualization and has been increasingly applied during minimally invasive spinal surgery. This chapter focuses on endoscopic posterior cervical decompression and diskectomy (Video 49.1).

49.2 Patient Selection

49.2.1 Indications

• Cervical lateral disk herniation (Fig. 49.1) or foraminal stenosis causing radiculopathy⁵

• Persistent nerve root symptoms after anterior cervical diskectomy and fusion

• Cervical disk disease in patients for whom anterior approaches are contraindicated (e.g., those with anterior neck infection, tracheostomy, prior irradiation, previous radical neck surgery for neoplasm)

49.2.2 Contraindications

• Pain without neurologic symptoms

• Gross cervical instability

• Central disk herniation

• Excessive burden of ventral compression (diffuse ossification of the posterior longitudinal ligament)

• Kyphotic deformity that would render posterior decompression ineffective or destabilize the cervical spine

49.3 Preparation

49.3.1 Essential Surgical Instruments

• Head fixation device

• Tubular retractor system

• Endoscopic camera system

• Endoscopic spinal instruments, including microcurets and 1- to 2-mm rongeurs

• High-speed drill

49.3.2 Positioning

After induction of anesthesia with the patient in the supine position, the patient is placed in a three-point head fixation device and elevated to a sitting position (Fig. 49.2). The head is then flexed until the cervical spine is perpendicular to the floor, ensuring sufficient jugular venous return while preventing airway compromise. This position also accommodates fluoroscopic imagery by allowing the shoulders to fall inferiorly with gravity and decreases the accumulation of blood within the surgical field. Physician fatigue may also be decreased. Air emboli have not been reported as a complication of this position.^1,4

Fig. 49.1 A 30-year-old man presented with neck pain and right upper extremity radiation. On exam his right triceps motor strength was 4/5. MRI of the cervical spine showed a right-sided soft lateral disk herniation at C6–C7 causing impingement of the foraminal nerve at C7 noted on his right parasagittal T2 view (a, arrow) and axial T2 view (b, arrow).

Fig. 49.2 The intraoperative setup. Note that the patient is placed in the sitting position. The monitor is placed facing the surgeon.

Alternatively, the patient may be placed in the prone position with the head secured in three-point pin fixation. The neck is then flexed to better expose the interlaminar window. Continuous irrigation of the surgical corridor with normal saline may be employed to improve visualization of the surgical field.6,7,8

49.4 Surgical Technique

49.4.1 Preparation

Approach and visualization of the correct operative level should be confirmed with fluoroscopy before beginning sterilization of the site. The neck is then shaved, cleansed, and draped in sterile fashion.

49.4.2 Incision

After again confirming the operative level by fluoroscopy, the incision is planned. For single-level procedures, an 8- to 18-mm vertical incision offset 1.5 cm from the midline (toward the side to be operated) is sufficient, depending on the final width of the dilator system chosen. The length of the incision should be approximately equal to or slightly greater than the diameter of the final tubular retractor. When operating at two levels, the incision should straddle the affected levels. If bilateral access is planned, the incision can be made directly on the midline. The planned incision site is injected with local anesthesia, and an initial blade-length incision is made at the midpoint of the marked area.

49.4.3 Dilation

Under fluoroscopy, a Kirschner wire (K-wire), guidewire over needle, or obturator is introduced and guided toward the inferomedial edge of the superior lateral mass of the affected level and is docked. Bone must be identified by palpation to ensure that the interlaminar space has not been violated. The cervical fascia is then opened to allow for less forceful introduction of the muscle dilators.

Under fluoroscopy, the initial dilator is placed (Fig. 49.3). The instrument may be placed over a K-wire, or guidewire if preferred; however, extra care is needed to ensure that the K-wire does not violate the interlaminar space. To avoid this potential complication, we introduce the smallest dilator and dock it perpendicular to the facet/lateral mass, after which serial dilation then proceeds according to the dilator system chosen until the final tubular retractor overlies the laminofacet junction (Fig. 49.4, Fig. 49.5). Operative windows from 7.9 to 18 mm have been described.^5,9 The retractor arm is then fixed and the inner dilators are removed, allowing for introduction and attachment of the endoscope to the final retractor (Fig. 49.6).

Fig. 49.3 Initial dilation is performed following exposure of the laminofacet junction. Care should be taken to avoid violation of the interlaminar space by the K-wire or the smallest dilator.

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