Anterior Cervical Foraminotomy (Jho Procedure): Microscopic or Endoscopic

Chapter 152 Anterior Cervical Foraminotomy (Jho Procedure)


Microscopic or Endoscopic



David H. Jho, Diana H. Jho, Hae-Dong Jho


The optimal surgical treatment of degenerative cervical spine disease that involves radiculopathy and/or myelopathy is the direct surgical removal of compressive pathology while preserving segmental motion. Historically, current cervical spine surgical techniques were introduced more than a half century ago as anterior approach (anterior cervical discectomy) and posterior approach decompression procedures. Although anterior cervical discectomy directly targets the compressive pathology, which usually consists of soft disc herniation or spondylotic stenosis, the approach also involves removing structural elements important for segmental motion—such as the anterior longitudinal ligament and nonherniated portions of the disc—for the sake of surgical exposure. In comparison, some posterior decompression techniques can preserve segmental motion, but in many cases they do not target the compressive pathology directly. To optimize the two surgical goals of directly removing compressive pathology while maximizing the preservation of segmental motion, anterior cervical foraminotomy techniques were developed and previously reported by the senior author as the “Jho procedure.”1,2


The classic anterior cervical approach has been that of surgical decompression by disc removal, often followed by bone graft fusion. Minor technical modifications have been made over the years, such as removing various amounts of the vertebral column and using various sources of bone substitutes, fusion-enhancing materials, and metal implants. Although anterior cervical discectomy achieves one goal of directly removing compressive pathology, there is loss of segmental motion due to complete disc removal at the intervertebral space performed to access the pathology. Bone graft fusion is done to fill the vacant intervertebral space, resulting in the loss of segmental motion and sometimes exacerbating degenerative disease at adjacent levels. Reconstruction with spinal fusion and metal implant is done to compensate for the removal of anatomic structures related to the surgical approach pathway of exposure and not due to the focal removal of compressive pathology itself. In attempts to maintain segmental motion, disc arthroplasty has been introduced to reconstruction after anterior cervical discectomy. However, the value of installing a foreign device in maintaining motion remains to be established.


A classic posterior approach emerged from traditional posterior laminectomy techniques in the 1960s. It involves cervical laminectomy or laminoplasty, with or without posterior foraminotomies. It has been further refined into endoscopic or microscopic posterior foraminotomies. However, posterior approaches often provide indirect compensatory decompression and fail to achieve direct removal of compressive pathology that is commonly located ventral to the compressed nerve root or spinal cord. There may also be reduction or loss of segmental motion with some posterior approaches, especially when spinal fusion is used in conjunction with laminectomies to eliminate potential exacerbating dynamic factors or delayed kyphotic deformities, or both.


The Jho procedure was developed to overcome the deficits of classic anterior and posterior cervical procedures in selected patients to optimize the achievement of surgical goals. Microsurgical anterior cervical foraminotomy was first reported by H.D. Jho in 1996 under the minimally invasive concept of functional spine surgery, in which compressive pathology is directly removed via an anterior approach while the remaining disc and functioning motion unit is preserved without the use of implants or bone fusion.1 The originally reported technique for anterior cervical foraminotomy involved removing the uncovertebral juncture (the most lateral part of the intervertebral disc) to access the compressive pathology. Once the surgical access is made, the soft disc and/or bone spurs that compose the compressive pathology are excised. This surgical approach directly addresses the compressive pathology with access via the lateral portion of the spinal column and effective preservation of the anatomic structures so that segmental motion remains intact and bony fusion is not necessary.


Originally, the Jho procedure was performed under the operating microscope; hence the surgery was also called anterior cervical microforaminotomy.2 Several variations of the surgical technique gradually evolved to achieve surgical goals more efficiently while minimizing surgical impact to the spinal column and functioning motion unit. Because no precise terminology currently prevails to describe the evolution of surgical techniques, the term surgiology was coined to represent the progressive pursuit of scientific or artistic knowledge to improve a particular operative treatment. The loose derivation of this term is from roots defined by the Webster’s dictionary with “surgery” being “a) the treatment of disease, injury, or deformity by manual or instrumental operations, as the removal of diseased parts or tissue by cutting, b) an operation of this kind, c) the branch of medicine dealing with this” and the suffix “-ology” as “the science, doctrine, or theory of” something. Surgiology has historically been an inherent process with the tendency to result in the eventual elimination of ineffective surgeries and the improvement of effective techniques. The Jho procedure involving anterior cervical foraminotomy therefore underwent surgiologic refinement to result in four basic variations and use of the endoscope.


In our original report, the approach to the nerve root was made through a surgical entry hole at the lateral portion of the uncovertebral juncture. To minimize the risk of injury to the vertebral artery, this approach began by making a small hole at the medial portion of the uncovertebral juncture. Then the anterior foraminotomy hole was enlarged toward the lateral portion of the uncovertebral juncture up to the medial margin of the vertebral artery. The technique of medial-to-lateral bone removal soon evolved to a lateral-to-medial approach, with bone removal starting just medial to the vertebral artery. Because the surgical approach pathway is made at the very lateral aspect of the spinal column, the stability of the spinal column is still preserved.


Further variations on this technique evolved from the concept that the trajectory from the skin incision to the surgical target in the sagittal plane of the cervical spine directs where a bone opening should be made to access the target pathology efficiently and effectively. Thus, surgical technique became tailored depending on the trajectory, as determined by the nature of the pathology and cervical anatomy. The surgiologic result was the progressive development of the following variations: 1) transuncal approach; 2) upper-vertebral transcorporeal approach; 3) lower-vertebral transcorporeal approach; and 4) anterior cervical foraminoplasty.3


In addition, the use of the operating microscope in anterior cervical microforaminotomy evolved into the use of a purely endoscopic technique in endoscopic anterior cervical foraminotomy. Microscopic visualization has a limited view through the small bony opening owing to its straight tubular viewing access with an inwardly coning configuration. Even if the operating microscope is tilted to visualize the medial inner aspect of the spinal canal, the view at the surgical target can be limited despite providing a three-dimensional image. An endoscope was adopted to overcome this limitation in surgical view and can provide an outwardly coning viewing configuration with a flask-shaped view that allows wide enhanced visualization at the surgical target region although the image is two-dimensional. In this chapter, technical aspects of anterior cervical foraminotomy are described, with the term rostral-caudal being used interchangeably with upper-lower or superior-inferior when referencing the vertebral bodies bordering the level of target pathology.



Surgical Indications and Preparation


Surgical indications are the same as those for conventional anterior cervical discectomy or corpectomy, with patients often presenting for an alternative surgical option after hearing a recommendation of conventional anterior fusion surgery or posterior approaches. Conservative treatment for a minimum of 6 weeks was first attempted unless profound motor weakness or significant myelopathy was evident. Initial use of anterior cervical foraminotomy was limited to cervical radiculopathy caused by soft disc herniation or stenosis with bone spur formation. Application of the technique and its evolved variations were expanded to decompression of the spinal cord for spondylotic stenosis or ossification of the posterior longitudinal ligament (OPLL), removal of spinal tumors (extradural or intradural), placement of a syringosubarachnoid shunt, or treatment for any other pathology that required an anterior approach.


All patients had preoperative magnetic resonance imaging (MRI) scans. Occasional patients required myelo-computed tomography (CT) scans, particularly when MRI scans showed surgical artifact from their previous surgery with anterior fusion and metal implant. Intraoperative somatosensory evoked potential (SSEP) monitoring was used in all patients in the early surgiologic evolution, but as experience grew, SSEP was used more selectively. All patients were kept one night in the hospital as a standard protocol, except for the earliest patients, who received surgery on an outpatient basis, and those who insisted on going home on the same day of surgery. All patients obtained follow-up MRI scans and dynamic cervical spine roentgenograms 6 weeks after surgery.



Surgical Tools and Techniques



Surgical Instruments


When microscopic surgery was performed, a slender power drill with a 2-mm diamond drill bit and various curettes were used. Once pure endoscopic surgery was adopted, endoscopic equipment and instruments were used. The required surgical instruments include endoscopes with 0-, 30-, and 70-degree lenses and associated appendages such as the light source plus video-imaging system, an endoscope lens-cleansing device, a rigid endoscope holder, and specifically designed endoscopic surgical instruments.



Endoscopes


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.


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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.


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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.


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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.

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Jul 16, 2016 | Posted by in NEUROSURGERY | Comments Off on Anterior Cervical Foraminotomy (Jho Procedure): Microscopic or Endoscopic

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