Percutaneous Endoscopic Cervical Diskectomy
Gun Choi
Alfonso Garcia
Bhushan Khedkar
REBUTTAL ▪ The Case against MIS Cervical Diskectomy
Alan S. Hilibrand
First described by Robinson and Cloward, anterior cervical diskectomy and fusion (ACDF) has become an established, commonly performed operation for subaxial cervical disk prolapse.1,2 Even though ACDF remains the mainstay of the surgical approach to cervical disk prolapse, it still requires entrance into the spinal canal with accompanying risks such as epidural bleeding, perineural fibrosis, graft-related problems, dysphasia, and hoarseness. Indirect decompression using minimally invasive laminoforaminotomy fails to address the anterior pathology. The successful use of percutaneous endoscopic cervical diskectomy (PECD) has been reported by several authors.3, 4, 5, 6 From the long-term outcome study by Lee JH and Lee SH, the reduction of disk height and progression of disk degeneration did not affect clinical symptoms.7 Also in 2014, Kim et al. stated that cervical curvature did not worsen after posterior PECD.8 These findings suggest that PECD can be a good alternative for treating various cervical disk problems assuming proper selection of patients.9 The indications for PECD are soft cervical disk prolapse without cervical instability and evidence of central canal or foraminal stenosis. PECD and thermodiscoplasty can effectively treat discogenic cervical headaches due to soft disk herniation.10 It is not advisable for approaching the C3-C4 levels and above because of the broader hypopharynx and carotid artery bifurcation. It is also not recommended for patients with previous anterior surgery, axial neck pain, and cervical infection or tumor. Relative contraindications of PECD include bilateral cervical radiculopathy.11 The advantage of PECD is that it can accomplish both a decompressive surgery and thermal neurotomy/denaturation with the use of radio frequency energy.
INDICATIONS
Indications for surgery include (a) low cervical (C3-C7) soft disk herniations without segmental instability and (b) cervicogenic headaches.
Contraindications
PECD is not recommended in the following cases:
Patients with previous anterior cervical surgery
Patients with dominant axial neck pain
Cervical instability
Cervical infection or tumor
High cervical level pathology (C3-C4 and above)
Relative Contraindications
Patients with the following conditions are relatively contraindicated for PECD: (1) Bilateral cervical radiculopathy; (2) Calcified disk and/or foraminal stenosis; (3) Cervical stenosis not related to soft disk herniation.
TECHNIQUE
Anatomic Considerations
When performing anterior cervical disk puncture, one must consider and pay careful attention to the carotid artery, which is localized medial to the sternocleidomastoid muscle laterally to the entry point and both the trachea and esophagus medially. The pretracheal fascia is fused on either side with the prevertebral fascia completing a compartment composed of the larynx, trachea, thyroid, and pharynx-esophagus. When moved together all of these structures displace as one piece, increasing the safety zone for initial disk puncture. The carotid artery runs medially at the C3-C4 level and more laterally at the C6-C7 level. The safest entry point is between the airway and the pulsating carotid artery.
Anatomic Structures Related to Levels of PECD
C3-C4 Inferior Border of Hyoid Bone
Between the hyoid bone and the thyroid cartilage, there is a narrow safety zone at this level. The hypopharynx is broader and the carotid artery is bifurcated medially. The superior thyroid artery is located in the trajectory of C3-C4 puncture. Translational movement of the pretracheal fascia enclosing the thyroid gland may change the course of superior thyroid artery more horizontally.
C4-C5 Middle of Thyroid Cartilage
The hypopharynx is placed more medially to the lateral margin of the thyroid cartilage, protecting it from injury.
C5-C6 (between the Thyroid Cartilage and Cricoid Ring) and C6-C7 (Inferior to Cricoid Ring)
The safety zone is larger at these levels. With correct retraction of the carotid artery and pharynx-esophagus, there is minimal risk to the vital structures.
SURGICAL TECHNIQUE
Settings for PECD include the following:
Laser settings: Energy of 1 to 1.5 J (Joules), 10 to 15 Hz (pulse/second)
Radio frequency cautery: 35 for ablation and 30 for coagulation
Irrigation pump: Flow at 100% and pressure of 30 mm Hg
Step One: Anesthesia
This is performed under conscious sedation using propofol and remifentanil intravenously with target-controlled infusion pump (Fig. 12.1). This is the preferred form of anesthesia since it is ideal for having intraoperative feedback directly from the patient, which makes the procedure safer by informing the surgeon if neural structures are being stimulated.
Step Two: Patient Position
The patient is made to lie supine on radiolucent table. The neck is slightly extended by placing a towel roll under the neck. Head can be stabilized by applying plaster tape across forehead. A plastic tent is placed over the patient’s face in order to prevent the feeling of suffocation after draping and to facilitate intraoperative communication during the procedure (Fig. 12.2A and B). Neck and shoulder padding is done to keep cervical spine in slight extension (Fig. 12.3A). The shoulders are pulled down and the arms are fixed to the sides of the table by using plaster tape for better visualization under fluoroscopic lateral view (Fig. 12.3B).
Step Three: Procedure
The level and midline are marked with the help of C-arm fluoroscope (Fig. 12.4A and B). For lower cervical levels, the C-arm may have to be tilted obliquely to avoid shoulder girdles. The anterior cervical skin is prepared and draped. Lidocaine (1%) is infiltrated into the skin and subcutaneous tissue at the entry point (Fig. 12.5). In the case of a foraminal disk herniation, approach from contralateral side is preferred. For a midline herniation, an entry point from the right side is preferred for a right-handed surgeon. The carotid pulse is palpated with the left hand and tracheoesophageal complex is gently pushed away while applying soft pressure and alternating movements with the fingertips of either index and middle fingers or middle and ring fingers, until the anterior portion of the cervical vertebral body is felt. The anatomic relationship of tracheoesophageal complex makes it possible to retract both esophagus and trachea as a single structure (Fig. 12.6). When displacing the tracheoesophageal complex medially and carotid sheath laterally, it is important to maintain this hand position while holding the guide needle between the third and fourth fingers before insertion. Confirmation of needle position and minor adjustments are made with the aid of a C-arm fluoroscope, ensuring that
the needle is aimed at the target disk space (Fig. 12.7A and B). Keeping the fingers in place, a 90 mm 18G needle is inserted into the interval between the carotid sheath and the tracheoesophageal complex to the anterior margin of the targeted disk space under fluoroscopic guidance in anteroposterior (AP) and lateral views (Fig. 12.7C). The disk is accessed between the longus coli muscles. This helps to prevent bleeding or injury to the sympathetic chain. Remember that the sympathetic chain is located more medially in the lower cervical vertebrae in comparison to the upper cervical vertebrae. Discography (Indigo carmine solution mixed with normal saline and contrast media in 1:2:2 ratio) is done to stain the pathologic disk fragment and for confirmation of needle position (Fig. 12.8A to C). A guide wire is then passed through the needle and the needle is withdrawn. When withdrawing the needle, the guide wire should be firmly secured to prevent it from slipping out of the disk space (Fig. 12.9). A 5-mm skin incision is then made in a transverse direction following the skin creases of the neck (Fig. 12.10). Serial dilators are passed over the guide wire starting from 1 mm. This maneuver is done with the right hand while the left hand is firmly guarding the carotid artery laterally and one finger is displacing the tracheoesophageal complex medially. C-arm verification of the correct positioning of guide wire is mandatory while inserting the dilators. A second dilator is lightly tapped until its tip is in close proximity and in line with the posterior vertebral wall on lateral C-arm view (Fig. 12.11A to F).
the needle is aimed at the target disk space (Fig. 12.7A and B). Keeping the fingers in place, a 90 mm 18G needle is inserted into the interval between the carotid sheath and the tracheoesophageal complex to the anterior margin of the targeted disk space under fluoroscopic guidance in anteroposterior (AP) and lateral views (Fig. 12.7C). The disk is accessed between the longus coli muscles. This helps to prevent bleeding or injury to the sympathetic chain. Remember that the sympathetic chain is located more medially in the lower cervical vertebrae in comparison to the upper cervical vertebrae. Discography (Indigo carmine solution mixed with normal saline and contrast media in 1:2:2 ratio) is done to stain the pathologic disk fragment and for confirmation of needle position (Fig. 12.8A to C). A guide wire is then passed through the needle and the needle is withdrawn. When withdrawing the needle, the guide wire should be firmly secured to prevent it from slipping out of the disk space (Fig. 12.9). A 5-mm skin incision is then made in a transverse direction following the skin creases of the neck (Fig. 12.10). Serial dilators are passed over the guide wire starting from 1 mm. This maneuver is done with the right hand while the left hand is firmly guarding the carotid artery laterally and one finger is displacing the tracheoesophageal complex medially. C-arm verification of the correct positioning of guide wire is mandatory while inserting the dilators. A second dilator is lightly tapped until its tip is in close proximity and in line with the posterior vertebral wall on lateral C-arm view (Fig. 12.11A to F).