The endoscopes we use are rod-lens endoscopes that are 4 mm in diameter and 18 cm in length. One set consists of five endoscopes: a 0-degree-lens endoscope, 30-degree lens angled toward the light source, 30-degree lens angled away from the light source, 70-degree lens angled toward the light source, and 70-degree lens angled away from the light source (Fig. 152-1) The 0-degree-lens endoscope is the basic working configuration used for most applications. Because the endoscope provides a wide-angle view, the 0-degree-lens endoscope usually provides adequate views for exposure at the nerve root as well as the spinal cord. However, the 30-degree-lens endoscope angled toward the light source can be used when a more-angled view toward the spinal cord is desired, and a 30-degree-lens endoscope angled away from the light source can be used when a more-angled view toward the nerve root at the neural foramen is desired.

FIGURE 152-1 The endoscopes we use are rod-lens endoscopes that are 4 mm in diameter and 18 cm in length. One set consists of five endoscopes: a 0-degree lens, a 30-degree-lens angled toward the light source, a 30-degree lens angled away from the light source, a 70-degree lens angled toward the light source, and a 70-degree lens angled away from the light source. The 0-degree-lens endoscope is the basic working configuration used for most applications.

Endoscope Lens-Cleaner

An endoscopic lens-cleansing device is required to keep the lens clear so that the surgeon can continually operate without interruption (Fig. 152-2). The device consists of a disposable irrigation tube that passes through an electric-powered motor. The endoscope is placed through a rigid tubular irrigating sheath, which is connected to the irrigating tube. The irrigation tube is connected to a saline bag, which is hung on a pole. This motor-powered irrigation device is controlled by a foot pedal to flush saline forward. When the foot pedal is released, the motor reverses its rotary direction and draws the saline back from the tip of an endoscope for 1 to 2 seconds. The forward flow of irrigating saline cleans the lens, and the reverse flow clears away water bubbles at the tip of the endoscope. Although this device is not yet ideal, it helps the surgeon significantly in the task of keeping the endoscope lens clean without removing the endoscope from the surgical site.

FIGURE 152-2 An endoscopic lens-cleansing device is required to keep the lens clear so that the surgeon can continually operate without interruption. The device consists of a disposable irrigation tube that passes through an electric-powered motor. The endoscope is placed through a rigid tubular irrigating sheath, which is connected to the irrigating tube. The irrigation tube is connected to a saline bag, which is hung on a pole. This motor-powered irrigation device is controlled by a foot pedal to flush saline forward. When the foot pedal is released, the motor reverses its rotary direction and draws the saline back from the tip of an endoscope for 1 to 2 seconds. The forward flow of irrigating saline cleans the lens, and the reverse flow clears away water bubbles at the tip of the endoscope.

Endoscope Holder

An appropriate endoscope holder is another piece of essential equipment required to perform this operation bimanually. An endoscope holder is mounted to the operating table. It not only provides steady video imaging on a video monitor, but it also allows a surgeon to use both hands freely, similar to microscopic surgery. The holder must provide rigid fixation of the endoscope, and its holding terminal must be compact and slender to render adequate operating space around the endoscope shaft needed for the surgeon to maneuver surgical instruments.

Two different types of endoscope holders are available, but both are not yet ideal. One is a simple manual holder with multiple joints that can be tightened by hand, and the other is a holder with joints powered by nitrogen gas and controlled with a single button. Manual holders are inconvenient to maneuver with releasing, repositioning, and tightening; they also have limitations in flexibility for reaching certain positions. Nitrogen gas–powered devices are more expedient than manual types but are not as smooth as the operating microscope in releasing and locking at various positions. Currently, we use a Mitaka endoscope holder (distributed by Karl Stortz) for cranial applications and an Aesculap holder for spine applications (Fig. 152-3). The Mitaka holder is relatively bulky at the attachment shaft and has very narrow accessibility at the holding terminal; thus the endoscope holding terminal has to be appropriately positioned at the surgical area before tightening at the shaft joints. Because the holding terminal maneuverability of the Mitaka holder is superior to Aesculap, we like to use the Mitaka holder for cranial endoscopic surgery. The Aesculap holder has longer flexible arms compared to the Mitaka, but its holding terminal has a limited range of motion, even with custom modifications. We prefer to use the Aesculap holder for spine endoscopy, but holding terminals of both types of holders are not yet ideal for endoscopic spine surgery. Sagging of a few millimeters after release of the powerbutton is another suboptimal feature of the nitrogen-powered holders.

FIGURE 152-3 We use an Aesculap holder for spine applications. The Aesculap holder has a longer flexible arm compared to other products, but its holding terminal has a limited range of motion, even with custom modifications. Sagging of a few millimeters after release of the power-button is another suboptimal feature of nitrogen-powered holders.

Endoscopic Surgical Instruments

Because the region of bone removal in anterior cervical foraminotomy requires high precision, a fine drilling device is required. We use a Midas telescoping tubular drill with a 2-mm diamond bit. The drill bit tip can be progressively extended as the depth of drilling advances. Other commercial drill products are available that have comparable systems. Bipolar forceps are shaped to accommodate the endoscopic surgical environment, and the blades of the bipolar forceps are parallel to each other, similar to a single-bladed instrument, once the blades are approximated. Various surgical curettes and other endoscopic instruments were customized and developed in order to function efficiently within the uniquely curved endoscopic surgical trajectory.

Surgical Technique

Most of the equipment and instruments are similar to those used in conventional cervical spine surgery. The operation was performed under the operating microscope in earlier cases but evolved to pure endoscopic surgery. A thin-bladed cervical retractor system is used to keep the split longus colli muscle apart to expose the uncovertebral juncture.

Positioning

All operations were performed under general endotracheal anesthesia. In the past when SSEP was used, baseline SSEP waveforms were obtained before positioning the head and were continuously followed until the end of surgery. As experience grew, this evolved to using selective SSEP monitoring only for severe cases of myelopathy.

Patient positioning is similar to that for conventional anterior discectomy, keeping the head straight (without turning) and the neck neutral (without extension). Gentle neck extension with a small bolster under the shoulders may only be done if sufficient spinal canal is demonstrated on MRI to provide room for the spinal cord. Precaution during neck positioning is important to prevent position-induced injury to the cervical cord, especially if the patient experiences exaggerated symptoms by neck extension preoperatively or when severe spinal cord compression is noted in MRI scans. Cervical traction devices are not used. Significantly obese patients with short thick necks might require 2-inch adhesive tape for application of gentle skin traction at the chin superiorly and at the anterior chest wall inferiorly.

Surgical Exposure of the Uncovertebral Juncture

The skin incision site is assessed by finger palpation of the C6 transverse tubercle, which is typically palpable just medial to the sternocleidomastoid (SCM) muscle. Surgical target area related to the jaw and larynx are reviewed in reference to MRI scans of the cervical spine, along with the location of the vertebral arteries (being mindful of anatomic variants). The skin incision starts 1 to 2 cm lateral from the midline and extends laterally across the medial margin of the SCM muscle for approximately 3 to 5 cm in total length. Although the center of surgical exposure is usually 3 to 4 cm lateral from the midline, it must be adjusted to the size of the neck. A patient with a large neck requires a longer skin incision to maintain a 20-degree lateral-to-medial trajectory angle toward the surgical target.

At the anterior portion of the cervical spine column, the surgical target anatomy is the uncovertebral juncture that is covered by the longus colli muscle. Picturing in axial view, the surgical trajectory angle is determined by an extension line from the very medial margin of the inlet neural foramen to that of the outlet. When this line is extended toward the skin, it is the key exposure point of the skin. The platysma may be split longitudinally along the direction of the muscle fibers or alternatively may be cut parallel to the skin incision. The medial border of the SCM must then be defined, with clean dissection carried down to the prevertebral fascia just medial to the SCM.

The carotid artery on the working side is identified with finger palpation, and a self-retaining Meyerding retractor is placed just medial to the carotid artery. The tracheoesophageal structure is slightly and gently displaced medially and held with the Meyerding retractor, although not as much exposure of the anterior cervical column is needed as in conventional anterior cervical discectomy. The perimeter of exposure at the lateral portion of the cervical column is just over the longus colli muscle.

For upper cervical spine surgery, an intraoperative x-ray is obtained to corroborate the correct level of surgery. However, for lower cervical spine surgery, finger palpation of the surgical anatomy at the anterior column of the cervical spine and C6 transverse tubercle is often sufficient to identify the correct level of surgery (although confirmatory x-ray may still be made).

By palpating the transverse tubercles, the extent of the longus colli is identified. The longus colli is split just medial to the transverse tubercles rostral and caudal to the intervertebral disc level, being careful to avoid injury to the sympathetic trunk and fibers located laterally along the longus colli. A cervical retractor system is applied between the split longus colli muscle fibers to maintain exposure of the uncovertebral juncture. The original description mentioned sectioning of the medial part of the longus colli muscle, but this soon evolved to splitting the longus colli muscle, allowing its preservation.

At this point, an endoscope is brought in to the surgical site, and the vertebral artery is defined just lateral to the uncinate process under endoscopic visualization. The vertebral artery pulsation is easily visible lateral to the uncinate process. The proximal transverse processes of the rostral and caudal vertebrae are then defined. Because the surgical site is small, the close-up panoramic endoscopic view often improves surgical visualization compared to the operating microscope.

Original Description of Microsurgical Anterior Cervical Foraminotomy

The original technique for microsurgical anterior cervical foraminotomy was reported as a new approach for cervical disc herniation in 1996.¹ In the original description, the lateral 5- to 8-mm portion of the uncovertebral juncture was drilled and removed, which eventually evolved into less bone removal. The vertical dimensions of bone removal originally extended from the inferior margin of the rostral vertebra’s medial transverse process to the superior margin of the caudal vertebra’s medial transverse process, usually measuring 7 to 10 mm in total length. Bone removal is performed using a 2-mm cutting bit in a slender high-speed drill. The intervertebral disc is kept largely intact, and the posterior longitudinal ligament (PLL) is sometimes opened to confirm an adequate decompression from the lateral portion of the spinal cord to the nerve exit behind the vertebral artery. It is possible for venous bleeding to be cumbersome while the PLL is open. Once adequate decompression is accomplished, the platysma and subcutaneous tissue are closed with 3-0 absorbable sutures. The surgical incision site is infiltrated with a local anesthetic, and skin is closed with absorbable stitches or adhesive glue.

The original technique involved removing a few millimeters’ width of the most lateral portion of the uncovertebral juncture in a medial-to-lateral direction as a surgical conduit to the compressive pathology. However, this technique was soon modified because the end result of bony removal often became more superfluous than required since concern for potential vertebral artery injury often made the start of bone removal farther medial than truly necessary. In addition, bone opening at the uncovertebral juncture did not always produce optimal access to the target pathology, depending on the surgical trajectory from the skin incision. Thus, technical refinements into four major approach subtypes of anterior cervical foraminotomy followed.

Surgiologic Evolution of Anterior Cervical Foraminotomy

Transuncal Approach (Jho Procedure Type 1)

When the surgical trajectory from the skin incision to target pathology is perpendicular to the sagittal plane of the cervical spine, a bone opening at the anterolateral spine should be made along this trajectory line. Particularly for C4–5 or C5–6 operations, a routine skin incision at the upper or mid portion of the neck produces such a perpendicular surgical trajectory. In this case, the uncinate process lies directly along the perpendicular surgical trajectory (Fig. 152-4A). The skin incision to the point of bone exposure is similar to the general description of the anterior cervical foraminotomy approach. The most medial 1- to 2-mm portions of the transverse processes of both upper and lower vertebrae are removed to identify the proximal and distal extent of the vertebral artery in the region.

FIGURE 152-4 The schematic drawing illustrates the transuncal approach (Jho procedure type 1) from the left side. A, The surgical trajectory from the skin incision to the target pathology must be perpendicular to the longitudinal axis of the spine for this technique. The vertebral artery is defined just lateral to the uncinate process. B, The lateral uncinate process is dissected from the vertebral artery, and the lateral 2- to 3-mm portion of the uncinate process (dotted area) is drilled toward the posterior longitudinal ligament. The medial uncinate process has to be preserved to maintain the integrity of the intervertebral disc. C and D, Preoperative magnetic resonance imaging (MRI) scans, T2-weighed axial and sagittal views, show spondylotic stenosis at the C5–6 level. E and F, Postoperative MRI scans, T2-weighted axial and sagittal view, taken 6 weeks postoperatively, confirm good decompression at C5–6. G, Postoperative x-ray in an anteroposterior view shows the left-sided preserved C6 uncinate process (arrow).

The vertebral artery is dissected off laterally from the lateral portion of the uncinate process. Often the uncinate process protrudes laterally far beyond the line drawn between the medial margin of upper and lower transverse foramina. Thus, the most lateral extent of the uncinate has to be well defined in relation to the vertebral artery. Then, the most lateral 2- to 3-mm portion of the uncinate is drilled just medial to the vertebral artery toward the PLL (see Fig. 152-4B).

The compressing pathology is exposed rostrally from the normal margin of the rostral vertebra and caudally to the normal margin of the caudal vertebra. The caudal-to-rostral exposure must be performed in reference to the endplates of the caudal and rostral vertebrae along with the intervertebral disc space posteriorly. The vertical extent of bone removal is usually about 5 mm in length. Because of the natural lateral-to-medial incline of a surgical trajectory demanded by surgeon’s standing at the side of the patient, the surgical trajectory slightly inclines medially when bone drilling advances toward the spinal canal. Drilling must therefore be maintained laterally, initially leaving a very thin rim of cortical bone on the nerve root and vertebral artery.

Once the PLL is exposed posteriorly, the thin layer of uncinate cortical bone that was left attached at the nerve root is dissected and removed. Additional compressing pathologies such as herniated soft disc and/or bone spurs are then removed off the nerve root and lateral portion of the spinal cord (see Fig. 152-4C-F). Often the PLL is opened to expose the dura mater at the most lateral portion of the spinal cord and proximal nerve root to detect any hidden migrated disc fragments. When the PLL is opened, the ligament should be opened medially in front of the spinal cord because the epidural vein is located at the junction between the nerve root and the spinal cord. Copious epidural bleeding can occur when the PLL is opened laterally. Herniated disc fragments or bone spurs are removed with variously curved curettes. Awareness is necessary to avoid damaging the bony wall of the medial uncinate to maintain the integrity of the intervertebral disc (see Fig. 152-4G). When spinal cord decompression is required, a specially designed curette system is used to achieve further medial decompression by undercutting the compressive pathology posterior to the rostral and caudal vertebral bodies.

Surgical closure is made using the aforementioned techniques.

Upper-Vertebral Transcorporeal Approach (Jho Procedure Type 2)

The term upper-vertebral transcorporeal approach refers to the location of the bone opening at the lateral portion of the upper vertebra to the intervertebral disc. This technique involves creating a bone opening at the inferolateral portion of the upper vertebra when the anteroposterior surgical trajectory inclines caudally (Fig. 152-5A and B). This approach is most often used in C6–7 or C7–T1 surgery but is also commonly used with other levels when the skin incision is made purposefully cephalad. When the vertebral artery is shown to enter at the C6 transverse foramen on preoperative MRI scans, an intraoperative x-ray is not necessary for C6–7 or C7–T1 surgery because the vertebral artery entrance into the C6 transverse foramen is visible at the time of surgery. However, an intraoperative x-ray is still confirmatory.

FIGURE 152-5 A and B, Illustrative drawing and a T2-weighted sagittal magnetic resonance imaging (MRI) scan demonstrate surgical trajectory (A) and bone opening (B) in the upper-vertebral transcorporeal approach (Jho procedure type 2) from the left side. The medial 2-mm portion of the transverse process at the upper vertebra is removed, and the vertebral artery is defined. The lateral 3-mm portion of the inferolateral upper vertebra is drilled posteriorly (dotted area). C, Postoperative roentgenogram, anteroposterior view, shows a bone opening (arrow) at the right-sided C6–7. The anterior two thirds of the endplate should be avoided to prevent damage in this technique. Anteroposterior surgical trajectory from the skin incision to the target pathology inclines caudally in this technique. D and E, Preoperative MRI scans, T2-weighted axial (D) and sagittal view (E), demonstrate large disc herniation at C6-7. F and G, Postoperative MRI scan, T2-weighted axial (F) and sagittal view (G), taken 6 weeks postoperatively, show a trace of the surgical tract and good decompression.

The vertebral artery is exposed and a 2-mm medial portion of the transverse process is removed at the upper vertebra. Bone opening is then made at the inferolateral 2- to 3-mm portion of the upper vertebra with drilling toward the PLL (see Fig 152-5C). The surgical trajectory is directed toward the pathologic target through only the most posterior portion of the intervertebral endplate. Damage to the intervertebral endplate at the anterior two thirds portion of the intervertebral disc must be avoided (see Fig 152-5D to G). The rest of the procedure is the same as described for other approaches.

Lower-Vertebral Transcorporeal Approach (Jho Procedure Type 3)

The term lower-vertebral transcorporeal approach refers to the location of the bone opening at the lateral portion of the lower vertebra to the intervertebral disc. For a C3–4 operation or when a skin incision is made inadvertently more caudal than it should be at any cervical disc level, this technique is required (Fig. 152-6A).

FIGURE 152-6 The schematic drawing demonstrates the lower-vertebral transcorporeal approach (Jho procedure type 3) from the left side. This technique is used when a foraminotomy is performed at a high cervical disc such as C3–4. A, The anteroposterior surgical trajectory from the skin incision to the surgical target pathology makes a cephalad incline (arrow) as demonstrated in preoperative magnetic resonance imaging (MR) scan, a T2-weighted sagittal view, of a patient with left-sided C3–4 stenosis. B, A small bone opening is made at the superolateral aspect of the lower vertebra. The most medial 2-mm portion of the transverse process at the lower vertebra is removed, and the vertebral artery is exposed. The lateral 3-mm portion of the superolateral part of the lower vertebra or the base of the uncinate process (dotted area) is drilled toward the posterior longitudinal ligament. Thus, the bone opening has to be made at the lower vertebra to reach the target along the surgical trajectory. Similar techniques can be used if a skin incision is made inadvertently caudal for surgery at other cervical levels. C and D, Preoperative MR scans, axial (C3-4) and sagittal view of a patient with C3-4 and C4-5 stenosis. E and F, Postoperative MRI scans, T2-weighted axial (C3–4) (E) and sagittal view (F), taken 6 weeks after left-sided C3–4 and C4–5 Jho procedure type 3 anterior foraminotomy demonstrates good surgical decompression.

The medial portions of the transverse processes at the rostral and caudal vertebrae are identified. The superomedial 1- to 2-mm portion of the transverse process at the lower vertebra is removed, and the vertebral artery is identified. Just medial to the vertebral artery, the superolateral 2- to 3-mm width portion of the lower vertebra is drilled away posteriorly using a 2-mm cutting drill bit (see Fig. 152-6B). The total vertical dimension of bone removal is approximately 5 mm in length. A cephalad-directed surgical trajectory leads the drilling posteriorly toward the target. In other words, a superior-posterior surgical trajectory from a bone opening at the rostral lower vertebral body leads to the compressing pathology at the intervertebral disc while preserving the uncovertebral juncture at the ventral part of the cervical spine. Microdissectors and various up-curved curettes are used to remove compressing herniated soft disc or bone spurs. The nerve root and the most lateral portion of the spinal cord are released from compression.

The amount of bone removal posteriorly must be tailored depending on the extent of pathology. As drilling is advanced posteriorly, the surgical reference points include the endplate of the lower vertebra, followed by the intervertebral disc space, and the endplate of the upper vertebra at the area of target pathology. The PLL is first exposed at the uncompressed portion just caudal to the compressing pathology, then it is exposed rostral to the compressing pathology. Drilling must be done with caution at the lateral portion where the nerve root is located. The thin cortical bone covering the nerve root is dissected and removed, followed by lifting the compressing pathology away from the PLL and removing it. The PLL can be opened medially with a microdissector and excised laterally except when the MRI scans do not suggest soft disc herniation and the PLL fails to show any defect, in which case the PLL should not be removed. Removal of the PLL laterally can cause cumbersome epidural bleeding because the epidural veins run between the two layers of the PLL at the lateral spinal cord canal. When the PLL is opened longitudinally with a microdissector, the white glistening dura mater is visualized. After the spinal cord dura mater is identified, the PLL can be excised. When spinal cord decompression is required, the compressing pathology is removed farther medially along the posterior margin of the rostral and caudal vertebrae (see Fig. 152-6C-F).

Anterior Cervical Foraminoplasty (Jho Procedure Type 4)

Sometimes the compressive pathology continues along the entire medial wall of the narrowed neural foramen, such as when spondylotic bone spur formation extends from the inlet (where the nerve originates from the spinal cord) to the outlet (where the nerve exits posterior to the vertebral artery). In this case, the nerve foramen must be enlarged along its entire longitudinal axis, and the term foraminoplasty describes this procedure of remodeling the neural foramen to its larger normal shape by eliminating medial bone spurs along the longitudinal axis of the neural foramen. Because the compressive pathology usually exists at the medial wall of the neural foramen, an anterior approach toward the medial wall of the foramen is most suitable for effectively eliminating the compressive pathology.

The 2-mm medial portion of the transverse process at the vertebral artery foramen is removed at both the upper and lower vertebrae. Then the inferolateral portion of the upper vertebra, superolateral portion of the lower vertebra, and lateral 2-mm portion of the uncinate process are drilled toward the PLL (Fig. 152-7A). Drilling is directed along the nerve passage from pedicle to pedicle in order to have complete decompression in the vertical dimension. After the PLL is exposed, posterior bone spurs are excised in front of the lateral spinal cord. If spinal cord decompression is required, bone spurs anterior to the spinal cord are excised through a foraminoplasty hole (see Fig. 152-7B-E). The PLL is excised, and the dura mater is exposed from pedicle to pedicle. Sometimes it is necessary to shave the superior portion of the pedicle of the caudal vertebra when the vertical dimension of the neural foramen is excessively narrowed, which is relatively common in elderly patients.

FIGURE 152-7 The schematic drawing demonstrates anterior cervical foraminoplasty (Jho procedure type 4). The vertebral artery is defined by removal of a 2-mm portion of the transverse processes at the upper and lower vertebrae. This technique is used for spondylotic foraminal stenosis. A, The bone spurs along the medial wall of the neural foramen along the longitudinal axis of the neural foramen are trimmed with a high-speed drill. B and C, Preoperative magnetic resonance imaging (MRI) scans, T2-weighted axial view at C5–6 (B) and sagittal view (C), in a 65-year-old-woman with myelopathy reveal multiple-level stenosis with cord compression. She underwent right-sided foraminoplasty and cord decompression at C4–5, C5–6, and C6–7. E and E, Postoperative MRI scans, T2-weighted axial view at C5–6 (D) and sagittal view (E), demonstrate enlarged right C5–6 neural foramen in axial view and good cord decompression from C4 through C7.

Spinal Cord Decompression via an Anterior Cervical Foraminotomy

Originally, the anterior cervical foraminotomy was developed for decompressing the nerve root by removing either herniated soft disc material or spondylotic bone spurs. However, it naturally advanced to spinal cord decompression as well because compressive pathology often extends to the spinal cord canal in addition to nerve root compression, even if patients have only radicular symptoms. For those patients, spinal cord decompression is also performed in addition to nerve root decompression because the surgical access to the pathology was already made by the anterior foraminotomy.

Compressive pathology at the neural foramen is somewhat cephalad to that on the spinal cord. This has to be kept in mind when the spinal cord decompression is required through one of the anterior foraminotomy techniques. Although the foraminoplasty technique is often used when the spinal cord decompression is the main part of the operation, the aforementioned various anterior foraminotomy techniques can be used depending on the location of the surgical pathology. These techniques can also be used for spinal tumor surgery, such as a meningioma located anterior to the spinal cord or a neurofibroma located intradurally and/or extradurally as a dumbbell-shaped tumor. Multilevel spinal cord decompression for the ossification of the posterior longitudinal ligament (OPLL) or severe spondylotic stenosis is also performed with these anterior foraminotomy techniques (Fig. 152-8). In earlier cases, multilevel surgery was performed at as many levels as pathology extends. However, this approach has been refined to multiple smaller staged operations, generally to address two levels at a time with each stage of surgery.

FIGURE 152-8 A 53-year-old man with ossification of the posterior longitudinal ligament (OPLL) from C3 through C6 underwent cord decompression via left-sided C3–4, C4–5, C5–6 endoscopic foraminoplasty (Jho procedure type 4). Preoperative magnetic resonance imaging (MRI) scans, T2-weighted axial (C3–4) (A) and sagittal view (B), show severe spinal cord compression. Computed tomography (CT) scans, axial (C3–4) (C) and sagittal view (D), show calcified pathology with severe cord compression. Postoperative CT scans, axial (C3–4) (E) and sagittal view (F), and MRI scans, T2-weighted axial (C3–4) (E) and sagittal view (F), show good surgical decompression with preservation of motion segments.

Surgical closure is the same as previously described.

Postoperative Management

Postoperatively, all patients were kept overnight in the hospital as standard protocol except for the earliest described patients (who received outpatient surgery) and some patients who insisted on going home on the same day of surgery. Postoperative pain is relatively minor, and most patients are prescribed oral narcotic analgesics, although some decline to take them. Patients are allowed to resume normal routine activities immediately following surgery. Cervical collars are neither necessary nor used. The surgical wound is exposed to the air right after surgery, when adhesive glue is used to close the skin, or the following day when subcuticular sutures with bandage are applied.

Exercises or taking a shower are allowed the following day. Although light exercises are encouraged right after surgery, contact sports activities and heavy weight-lifting are delayed for 4 to 6 weeks. Return to office-type work is allowed within a few days, but return to physically laborious jobs is delayed for 4 to 6 weeks. Postoperative contrast-enhanced MRI scans and dynamic x-rays are obtained in all patients 6 weeks after surgery as a routine protocol.

Results

We previously reported our series of 104 patients who met the following study criteria: unilateral cervical radiculopathy that had not responded to conservative treatment after at least 6 weeks (or at least 4 weeks if patients exhibited profound motor weakness), imaging studies confirming pathoanatomic features corresponding to the clinical symptoms, no previous cervical spine surgery, and no significant spondylotic stenosis causing spinal cord compression. Forty-five patients were men, and 59 were women. Patient ages ranged from 26 to 74 years, with the median age being 46 years. Compressive pathology was spondylotic spurs in 44 patients (42.3%), soft disc herniation in 54 patients (51.9%), and a combination of the two in 6 patients (5.8%). The duration of symptoms ranged from 4 weeks to 156 months (mean, 17.6 months). Follow-up periods ranged from 12 to 86 months (median, 36 months). In addition to radiculopathy, preoperative symptoms included severe neck pain in 83 patients (79.8%) and significant occipital head pain in 11 patients (10.6%).

Surgical results were graded as follows: “excellent” meant that the patient exhibited complete resolution of all symptoms, “good” indicated that the patient experienced relief of radiculopathy but still experienced occasional minimal or mild residual nonradicular discomfort, “fair” meant that the patient exhibited mild residual radiculopathy with or without mild to moderate residual nonradicular discomfort, and “poor” meant that the patient continued to exhibit significant radicular symptoms with or without nonradicular discomfort (including those unchanged from or worse than at preoperative conditions). Among 104 patients, 83 patients (79.8%) demonstrated excellent results, 20 patients (19.2%) demonstrated good results, and one patient (1%) experienced a fair outcome. No patient had a poor outcome, and there were no results that were unchanged or worse. One patient developed discitis, which resulted in spontaneous fusion at the operated-on level following antibiotic treatment, although his radiculopathy resolved well. One patient developed transient position-related hemiparesis, which resolved in 6 weeks. Two patients developed transient Horner’s syndrome, which resolved 6 weeks postoperatively.⁴

Discussion

Although variations in surgical trajectories to the cervical spine such as lateral approaches have been reported, the notion of discectomy with bone fusion was retained.^5,⁶ Conventional anterior cervical disc surgery evolved over a half century into complete removal of the intervertebral disc with bone graft fusion and metal implant by adhering to this idea.⁷ The more-recent methods using arthroplasty with artificial discs attempt to reestablish the motion segment but still rely on complete discectomy. The superiority and validity of an artificial disc Implant over conventional spinal fusion surgery remain to be proved.

The original description of anterior cervical foraminotomy involved not only new surgical techniques using access via an anterolateral route through the uncovertebral juncture but also introduced the novel concept of functional spine surgery.¹ The goal of functional spine surgery entails preserving the motion unit while achieving direct removal of the compressive pathology. The original description involved removing the most lateral 5-mm portion of the uncovertebral juncture as a surgical access to the compressive pathology, followed by wide decompression of the nerve root from its origin at the spinal cord to its exit posterior to the vertebral artery. Then the subsequent evolution of our surgical techniques was reported.^2,^3,^4,⁸^–¹²

Generally, the intervertebral discs of the cervical spine in the sagittal plane incline cephalad from an anterior-to-posterior direction. Therefore, the surgical approach involved in the originally described foraminotomy usually arrives at the superior portion of the pedicle and inferior portion of the surgical target. To compensate for this, the surgical trajectory must be inclined cephalad while proceeding posteriorly. The skin opening also has to line up with the surgical trajectory of this foraminotomy. Thus, the skin incision has to be made more cephalad than in conventional anterior discectomy, and the anterior bone opening is also shifted cephalad to arrive at the surgical target efficiently. The anterior bone opening is made at the most lateral portion of the upper vertebral body to arrive naturally at the surgical target when the foraminotomy hole is advanced posteriorly perpendicular to the longitudinal axis of the spinal column. The posterior one third portion of the anteroposterior surgical trajectory involves the intervertebral juncture, which is the posterior portion of the uncovertebral juncture and usually comprises the actual compressive pathology. This technique consists of bone opening at the upper vertebrae; thus, the technique is termed the upper-vertebral transcorporeal approach. When an anteroposterior surgical trajectory is perpendicular to the longitudinal axis of the spine, the bone opening has to be made at the lateral portion of the uncinate; hence, the variant technique is called a transuncal approach. When the surgical trajectory inclines cephalad, a lower-vertebral transcorporeal approach has to be adopted, with a bone opening made at the lateral lower vertebrae. The medial 2-mm portion of the vertebral artery is exposed to minimize the amount of bone removal at the vertebral body. When a narrowed neural foramen requires reconstruction into a larger normal shape, anterior foraminoplasty is performed, with direct removal of the medial bone spurs along the longitudinal axis of the neural foramen. Since the introduction of these refined surgical techniques, others have also reported their own experiences with anterior cervical foraminotomy.¹³^–²¹

Biomechanical effects of various techniques of anterior cervical foraminotomy on the cervical spinal column still remain to be fully tested. However, clinical findings sometimes contrast with cadaveric biomechanical studies, which may be explained in part by the fact that live patients undergo healing at the surgical site while cadaver specimens lack this ability and also increase specimen fatigue with repeated testing. Kotani and colleagues.²² reported that the unilateral foraminotomy procedure reduced 30% of spinal stiffness in their cadaver study and raised the question of spinal instability. However, their specific technique of foraminotomy involved an annulotomy and partial discectomy, along with a medial-to-lateral removal of the uncinate process instead of a lateral-to-medial approach.

In live patients, one of the most common preoperative complaints is stiffness and limited range of motion in the cervical spine, particularly head tilt and rotation to the symptomatic side. Most patients experienced a significant improvement of these complaints postoperatively such that their head tilt and rotation to the operated side improves significantly. However, there is sometimes continued limitation in their range of motion opposite to the operative side related to degenerative spondylotic disease. When anterior cervical foraminotomy is performed correctly, there can be improvement of the stiff decreased range of motion associated with cervical spondylotic disease toward normal ranges. Thus, improved range of motion can be a beneficial effect observed in live patients with various techniques of anterior cervical foraminotomy, akin to some other types of operative treatment of arthritic joint disease in various parts of the body.²³ However, excessive or inadvertent removal of disc, ligament, or bone beyond the target range can theoretically result in spinal instability as in any type of spine surgery.^13,^24,²⁵

Although the surgical risks of anterior cervical foraminotomy have been minimal in our experience, permanent and serious complications theoretically exist as in any type of anterior cervical spine surgery. Major potential concerns include vertebral artery injury, Horner’s syndrome, recurrent disc herniation, infection, spinal cord injury, and spinal instability. Because the cervical sympathetic nerve and chain pass along the lateral margin of the longus colli, Horner’s syndrome can occur if sympathetic nerves are damaged by traction injury or complete section while dissecting the longus colli. Depending on the method and extent of injury, Horner’s syndrome may be temporary or permanent.

Vertebral artery injury is a risk in any situation but is a particular concern in anatomic variations in which the vertebral artery enters the transverse foramen through C4 or C5 instead of the common location at C6. When the lateral aspect of the cervical spine is exposed by splitting or dissecting the longus colli, one must be mindful if there is a vertebral artery course that passes through the muscle at the level of dissection. The level of vertebral artery entry into the transverse foramen should be foreseen on preoperative MRI scan to help avoid this injury. Because vertebral artery injury (especially for dominant or codominant vertebral arteries) can result in brain stem stroke immediately or in a delayed fashion, significant damage might need to be repaired surgically with the aid of extended proximal and distal exposure.

Recurrent disc herniation through the surgical defect in the annulus is a delayed complication that can occur when the intervertebral disc is violated substantially. To prevent recurrent disc herniation, the foraminotomy hole has to be minimal in size but large enough to provide adequate decompression. This recurrent disc herniation is extremely rare in our practice.

Spinal instability can occur if bone removal is substantial.¹³ When patients complain of significant neck pain postoperatively, spinal instability has to be considered. When patients have significant spinal instability, fusion may be necessary. In our experiences, we have not had any single case that required spinal fusion to address spinal instability after this operation.

Other possible complications associated with conventional anterior cervical spine surgery are also relevant, such as cerebrospinal fluid leakage, epidural bleeding or hematoma, nerve root or spinal cord damage, wrong-level operation, infection, or wound hematoma. Hoarseness can theoretically occur as it does after conventional anterior cervical spine surgery, but it is very unlikely because the anterior foraminotomy technique is farther lateral in approach. This minimally invasive form of surgery is not recommendable to an inexperienced surgeon because of these potential complications.