DEFINITION

Cervical radiculopathy is a neurologic condition characterized by dysfunction of a cervical spinal nerve, the roots of the nerve, or both.

It usually presents with unilateral pain that radiates from the neck to the arm and/or the hand.

There can be a combination of sensory loss, loss of motor function, and reflex changes in the affected nerve root distribution.

This chapter focuses on minimally invasive posterior cervical laminoforaminotomy as a surgical treatment option for patients with cervical radiculopathy.

 

 

ANATOMY

 

The external occipital protuberance (EOP) can be palpated in the midline of the skull. The superior nuchal line is the thickened ridge that extends laterally from the EOP (FIG 1A).

 

Beneath the skin and subcutaneous fat of the posterior cervical spine is located the superficial fascia (FIG 1B).

 

Deep to the superficial fascia, structures are anatomically compartmentalized by an organized deep fascia and several interfascial planes (FIG 2).

 

There are three principal deep fascial layers: a superficial, middle, and deep layer.

 

 

One layer is attached to the EOP, the superior nuchal line, the ligamentum nuchae, and the spinous processes of the cervical vertebrae.

 

It divides to surround the trapezius.

 

The deep layer of the deep cervical fascia is attached to the ligamentum nuchae in the midline.

 

The most superficial muscle on the posterior aspect of the neck is the trapezius, which arises from the EOP and the medial part of the superior nuchal line of the occipital bone, the spinous processes of C7-T1 through T12, the supraspinal ligament, and the ligamentum nuchae (FIG 3).

 

The next muscle is the splenius capitis and arises from the ligamentum nuchae and spinous processes of C7 through T3 and inserts on the lateral portion of the superior nuchal line (see FIG 1B).

 

The erector spinae lie deep in the cervical region and include the iliocostalis cervicis, longissimus cervicis, the splenius cervicis, and the splenius capitis.

 

The deep layer of the deep cervical musculature includes the semispinalis cervicis and the semispinalis capitis (see FIG 1B).

 

The spinous process projects posteriorly from the junction of the laminae.

 

The lateral mass forms at the junction of the lamina and pedicle and gives rise to the superior and inferior

articular processes or facets (FIG 4).

 

The superior facet at each level faces upward and posteriorly; the inferior facet faces downward and anteriorly.

 

A superior facet articulates with the corresponding inferior facet of the vertebral body cephalad to form the osseous elements of the zygapophyseal joints.

 

A vertebral notch is located on the superior and inferior aspect of each pedicle, such that adjacent notches contribute to the intervertebral foramen, through which the spinal nerve exits the spinal canal.

 

The foramen is bound superiorly and inferiorly by the pedicle; posteriorly by the facets; and anteriorly by the intervertebral discs, uncovertebral joints, and vertebral bodies (FIG 5).

 

The vertical diameter of the foramen is approximately 9 mm, the horizontal diameter is 4 mm, and the length ranges from 4 to 6 mm.

 

Foramina exit at an angle of 45 degrees from the midsagittal plane.

 

The spinal cord is cylindrical and slightly flattened in the anteroposterior (AP) direction, and thus usually has a larger transverse than AP diameter.

 

The spinal cord enlarges from C3 to C6 where it usually attains a maximal transverse diameter of 13 to 14 mm (FIG 6).

 

In the lower cervical spine, the anterior and posterior root entry zones are located approximately one disc level higher than the corresponding intervertebral foramen through which will pass the nerve root formed from its rootlets.

 

The rootlets pass obliquely laterally and caudally within the canal, entering the root sleeve where the sensory and motor roots are separated by the interradicular septum, a lateral extension of the dura mater.

 

Each dorsal root presents an oval enlargement, the spinal ganglion, as it approaches or enters the intervertebral foramen.

 

Just distal to this ganglion, the dorsal and ventral roots combine to form a spinal nerve.

 

The cervical nerve root occupies one-third of the foraminal space in a normal spine, usually the inferior aspect, with the superior aspect being filled with fat and associated veins.

 

The ventral (motor) roots emerge from the dura mater more caudally than the dorsal (sensory) roots, and the ventral roots course along the caudal border of the dorsal roots within the intervertebral foramina.

 

Thus, compression of the ventral roots, dorsal roots, or both depends on the anatomic structures around the nerve roots, such as a prolapsed disc (ventral root compression) or osteophytes from the facet joint (dorsal root compression).

 

 

 

The most likely site of compression of the radicular nerve is at the entrance zone of the intervertebral foramen because the medial entrance zone of the foramen is smaller in diameter than the lateral exit zone, whereas the nerve roots

 

 

are widest at their takeoff from the central thecal sac and become more narrow laterally.

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FIG 1 • A. Superficial anatomic landmarks of the posterior cervical spine. B. Cross-sectional anatomy of posterior cervical spine: superficial fascial layer (blue) and the muscles underneath.

 

 

 

FIG 2 • Cross-sectional anatomy of posterior cervical spine: deep fascial layer (blue) and the muscles underneath.

 

 

 

FIG 3 • Trapezius muscle anatomy and its insertion points.

 

 

 

FIG 4 • Bone anatomy of the posterior cervical spine demonstrating the relationships of the superior and inferior facets, the lamina, and the exiting nerve roots.

 

 

 

FIG 5 • Lateral view of cervical spine depicting exiting nerve roots and vertebral artery within the region of the neural foramen.

 

 

 

FIG 6 • Cross-sectional anatomy of the cervical spine.

 

 

Nerves C2-C7 exit above the correspondingly numbered vertebrae.

 

The C8 nerve root exits the intervertebral foramen formed between C7 and T1.

 

The dorsal root ganglion is usually located between the vertebral artery and the superior articular process.

 

In the sagittal plane, cervical nerve roots C3-C8 in the intervertebral foramina lie midway between the posterior midpoints of the lateral masses situated an average of 5.5 mm above or below each lateral mass point.

 

Thus, cervical nerve roots enter their intervertebral foramina and leave the spinal canal at the level of the disc and above the pedicle of the same numbered level, except for C8, which exits above the T1 pedicle.

 

 

 

 

FIG 7 • A. Cross-sectional anatomy of the cervical spine depicting several pathologic states: hypertrophy of

the uncovertebral joints, hypertrophy of zygapophyseal joints, and herniation of the nucleus pulposus. B. Sagittal T2-weighted image of a patient with a right C7 radiculopathy due to a C6-C7 lateral disc herniation. (continued)

 

 

The vertebral artery enters the transverse foramen of C6 and ascends through the transverse foramen to the level of the atlas.

 

In this region, it lies just in front of (ventral) to the ventral rami of cervical nerves C2-C6 and is surrounded by a venous plexus and sympathetic nerve fibers.

 

The transverse interforaminal distance and thus the transverse distance between vertebral arteries at the same cervical level increases slightly from C3 to C6.

 

PATHOGENESIS

 

The most common cause of cervical radiculopathy is foraminal compression of the spinal nerve.

 

Contributing factors include disc herniations and bulges, decreased disc height, degenerative changes of the uncovertebral joints anteriorly, and the zygapophyseal joints posteriorly (FIG 7A-D).

 

 

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FIG 7 • (continued) C,D. Axial T2-weighted image of the same patient with a right C7 radiculopathy due to a C6-C7 lateral disc herniation. E. Axial T1-weighted MRI with contrast showing a left C5-C6 nerve sheath tumor. F. Axial T1-weighted MRI with contrast showing a disc space infection with left foraminal epidural abscess.

 

 

Other rare causes include tumor and spinal infections (FIG 7E,F).

 

Normal disc itself does not contain nociceptive nerve fibers and is insensitive to pain.

 

When the nucleus pulposus ruptures through the annulus fibrosus, there is little or no localized pain until nociceptive fibers of the sinuvertebral nerves in the lateral posterior ligament and the dura of the nerve root sleeves are stimulated.

 

This stimulation generates localized back and neck pain.

 

In cases of cervical spondylosis, vertebral bodies subside and lose height, the ligamentum flavum and facet joint capsule tend to fold, which further decreases foraminal dimensions.

 

Some have postulated that nerve root compression by itself does not always lead to pain and note that the dorsal root ganglion must also be compressed.7

 

Mechanical distortion of the nerve root leads to a cascade of events in the microenvironment of the nerve.

 

Hypoxia of the nerve root and dorsal ganglion can aggravate the effect of compression.

 

Evidence indicates that inflammatory mediators—including matrix metalloproteinases, prostaglandin E, interleukin-6, substance P, and nitric oxide—are released by herniated cervical intervertebral discs.

 

 

These observations underlie the reason that anti-inflammatory agents often suffice to treat the radicular pain.

 

NATURAL HISTORY

 

Cervical radiculopathy occurs annually in 85 out of 100,000 people.

 

It is estimated that 75% to 90% of patients with acute cervical radiculopathy due to disc herniation will improve without surgery.

 

In a 1994 population-based study from Rochester, Minnesota, 26% of patients with cervical radiculopathy underwent surgery within 3 months of the diagnosis (typically for the combination of radicular pain, sensory loss, and muscle weakness), whereas the remainder were treated medically.

 

 

Recurrence, defined as the reappearance of symptoms of radiculopathy after a symptom-free interval of at least 6 months, occurred in 32% of patients during a median follow-up of 4.9 years. At the last follow-up, 90% of the nonoperated patients had normal findings or were only mildly incapacitated owing to cervical radiculopathy.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Patients with cervical radiculopathy exhibit the hallmark symptoms of unilateral neck and/or arm pain, sensory disturbances, and possibly motor deficits (Table 1).

 

Central to the patient's history are descriptors that include location, onset, duration, severity, associated symptoms, and triggers.

 

 

 

Table 1 Distribution of Cervical Disc Herniations and Anatomic Correlates

 

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Level

Percentage of Cervical Discs

Compressed Root

Muscles Affected

Sensory Region

Reflex

 

C4- C5	2%-5%	C5	Deltoid	Shoulder	Deltoid and pectoralis
C5-C6	15%-20%	C6	Forearm flexion	Upper arm, thumb, radial forearm	Biceps and brachioradialis
C6-C7	65%-70%	C7	Triceps and forearm extenders	2nd and 3rd fingers	Triceps

C7-

T1

10%

C8

Hand

intrinsics

4th and 5th

fingers

Finger jerk

 

 

Pain is most prominent in acute cervical radiculopathy and it may be described as sharp, electric, achy, or burning.

 

 

It can be located in the neck, shoulder, arm, or chest, depending on the nerve root involved. Classically, an acute radiculopathy presents with pain radiating in a myotomal distribution.

 

Sensory symptoms, predominantly paresthesias and numbness, are more common than motor loss and diminished reflexes.

 

The clinician should keep in mind that the sensory symptoms frequently do not follow classic dermatomal patterns as there is normal anatomic variation from individual to individual (FIG 8).

 

For patients with acute cervical radiculopathy, arm pain is present in nearly 100%, sensory deficits in 85%, neck pain in 79%, reflex deficits in 71%, motor deficits in 68%, scapular pain in 52%, anterior chest pain in 17%, headaches in 9%, anterior chest and arm pain in 5%, and left-sided chest and arm pain in 1%.

 

Radicular pain is often accentuated by maneuvers that stretch the involved nerve root, such as coughing, sneezing, Valsalva, and certain cervical movements and positions.

 

 

 

 

FIG 8 • Cervical dermatomes and sites of sensory symptoms.

 

 

The Spurling test is performed by maximally extending and rotating the neck toward the involved side (FIG 9).

 

When positive, this test is particularly useful in differentiating cervical radiculopathy from other etiologies of upper extremity pain, such as peripheral nerve entrapment disorders, because the maneuver stresses only the

structures within the cervical spine.

 

It is important to note that the physical examination can be normal.

 

The presence of “red flags” in the patient's history (including fever, chills, unexplained weight loss, unremitting night pain, previous cancer, immunosuppression, or intravenous drug use) should alert clinicians to the possibility of more serious disease such as tumor or infection.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

Plain Films

 

Plain films offer the advantage of showing the spinal column in a weight-bearing state.

 

 

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FIG 9 • Spurling maneuver.

 

 

Degenerative changes on plain radiographs become more prevalent as individuals age.

 

However, it has been shown that degenerative changes are present in both symptomatic and asymptomatic individuals.

 

They are inexpensive, readily available, and provide information regarding sagittal balance, congenital abnormalities, fractures, deformity, and instability.

 

Flexion-extension lateral cervical spine radiographs can reveal instability that may be the cause of intermittent or positional symptoms.

 

Myelography

 

 

Changes in the contrast-filled spinal canal can serve as indirect measure of neural compression. The major disadvantage of plain myelography is its invasive nature.

 

Accuracy rates for cervical myelography in the diagnosis of clinical nerve root compression ranges between 67% and 92% when compared with intraoperative findings.

 

Myelography is associated with few false-positive results, a 15% false-negative rate, and an overall accuracy rate of 85% in a study of 53 patients who had surgical confirmation of the cervical spine pathology.

 

See the Exam Table at the back of the book for methods for examining the cervical spine for nerve root syndromes.

 

Computed Tomography

 

Computed tomography (CT) allows for the direct visualization of pathology causing compression of neural structures.

 

CT also has a high-spatial resolution and is especially helpful in visualizing the foraminal region.

 

Another important advantage of CT is that it can distinguish neural compression caused by soft tissue from compression related to bony structures such as facet hypertrophy.

 

The main disadvantage of CT is the partial volume averaging effect and streak artifacts.

 

 

These can cause distortion of images, particularly at the lower cervical levels, or in individuals with wide shoulders.

 

The reported accuracy of CT of the cervical spine ranges from 72% to 91%.

 

By combining myelography with CT scan, the diagnostic accuracy approaches 96%.

 

Magnetic Resonance Imaging

 

Magnetic resonance imaging (MRI) can detect neural structures directly and noninvasively.

 

The accurate assessment of disc herniations and spinal stenosis is due to the intrinsic contrast and good spatial resolution.

 

MRI correctly predicts 88% of the lesions as opposed to 81% for CT myelography, 57% for plain myelography, and 50% for CT.

 

Disc herniations are commonly observed with MRI scans of asymptomatic individuals.

 

They may be observed in 10% of asymptomatic people younger than 40 years of age and 5% of those older than 40 years of age.

 

Degenerative disc disease may be observed in 25% of asymptomatic people younger than 40 years of age

and 60% of those older than 40 years of age.

 

Therefore, the imaging findings should be carefully correlated with the neurologic examination.

 

Electrodiagnostic Studies

 

Electrophysiologically, identify physiologic abnormalities of the nerve root and rule out other neurologic causes of the patient's symptoms.

 

However, in patients with well-defined radiculopathy and good imaging correlation, the pain and added expense of electrodiagnostic studies are usually not justified.

 

The electrodiagnostic study has two parts: the nerve conduction velocities (NCV) and the needle electrode examination (electromyography [EMG]).

 

NCV are performed to exclude peripheral nerve pathology.

 

The EMG is performed by analyzing multiple muscles within the same myotome and in adjacent myotomes.

 

The presence of fibrillation potentials and positive sharp waves at rest is indicative of denervation, but these changes may not occur until 3 weeks after the onset of neural injury.

 

They are noted in the paraspinal musculature before they become apparent in the appendicular muscles.

 

EMG may be normal in the presence of mild radiculopathy or a predominantly sensory radiculopathy and are less likely to be positive in patients with no demonstrable weakness.

 

Nerve conduction studies and EMG have been shown to be useful in diagnosing nerve root dysfunction and distinguishing cervical radiculopathy from other lesions that are unclear on physical examination.

 

They have also been found to correlate well with findings on myelography and surgery.

DIFFERENTIAL DIAGNOSIS

Carpal tunnel syndrome Cubital tunnel syndrome

Anterior interosseous syndrome

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Posterior interosseous syndrome Suprascapular nerve entrapment

Infection (discitis, osteomyelitis, epidural abscess) Primary bone neoplasm

Nerve sheath tumor

Metastatic disease (epidural and/or bony element) Inflammatory arthropathy

Cervical facet syndrome

Peripheral brachial plexus nerve tumor

Acute brachial neuritis (Parsonage-Turner syndrome) Cervical sprain/strain injuries

Disorders of rotator cuff and shoulder Thoracic outlet syndrome

 

Herpes zoster Pancoast tumor

Sympathetically mediated syndromes Myocardial infarction/angina

 

 

NONOPERATIVE MANAGEMENT

 

Activity modification

 

 

Patients should be educated regarding the cause of their pain and basic activity modifications that may improve it.

 

Simple activity modifications to keep the head and neck in a midline and unflexed position may minimize stress on the cervical spine and thereby relieve pain and reduce root compression.

 

The effectiveness of these measures, however, is unproved.10 Cervical orthoses (or collars) sometimes are recommended for this same purpose but should be used for less than 1 to 2 weeks, given the counterproductive effects of prolonged immobilization.

 

Lifting objects greater than 5 to 10 pounds is generally advised to be avoided during an acute stage of cervical radiculopathy.

 

Physical therapy

 

 

 

Core strengthening of neck musculature Arm and hand exercises

 

 

Cervical traction Medications

 

Nonsteroidal anti-inflammatory drugs (NSAIDs) and acetaminophen generally are the medications recommended most frequently early in the course of radiculopathy.

 

These agents are believed to reduce the inflammatory response that may underlie the pain in these conditions. NSAIDs have the potential for renal and gastric toxicity.

 

This is important to remember in high-risk patients (eg, the elderly or those treated with anticoagulants).

 

 

Coadministration of gastric protective agents, such as proton pump inhibitors, may be needed.

 

Steroids often are used in the acute period of radiculopathy as a pulse treatment.

 

Many regimens are described, but generally, an initial oral dose (approximately 1 mg/kg of ideal body weight daily) is followed by a tapered reduction over 2 to 3 weeks.

 

 

Steroids are associated with side effects, such as impaired glycemic control, worsening hypertension, and gastritis, but short-term use generally results in few long-term complications.

 

 

Epidural injections

 

 

Few randomized clinical trials are available and those available generally do not provide assessment with validated outcome measures.

 

Multiple studies suggest that these injections may be beneficial, with decreased pain reported in up to 60%

of patients.

 

 

These procedures may have significant complications, although the current use of fluoroscopic guidance may minimize the risk.

 

SURGICAL MANAGEMENT

 

The primary indication for a posterior cervical foraminotomy is cervical radiculopathy that can be correlated to radiographic findings of a lateral herniated cervical disc or cervical foraminal stenosis.

 

Open posterior cervical foraminotomy was historically the treatment for foraminal stenosis.

 

Advances in the anterior approach to cervical disease made the anterior cervical discectomy and fusion (ACDF) the preferred method for spine surgeons.

 

Anterior cervical approach is allowed for decreased muscle injury, decreased postoperative pain, and decreased length of stay as compared to the classic open posterior foraminotomy.1,5,11

 

 

Many studies have shown that posterior cervical foraminotomy is still a highly effective treatment option.2,4,5,8 Posterior cervical laminoforaminotomy has been shown to provide symptomatic relief in 92% to 97% of these patients.5

 

Other indications for cervical foraminotomy include multilevel foraminal narrowing without central stenosis, persistent radicular symptoms after ACDF, and patients with relative contraindications for anterior cervical surgery (infection, prior radiation, multiple anterior surgeries).

 

However, there are several major drawbacks to the posterior open procedure. These included the need for extensive subperiosteal stripping of the paraspinal musculature. This approach-related morbidity leads to significant postoperative pains and muscle spasms. This pain and dysfunction can be debilitating in 18% to

60% of patients.3,6,10

 

Compared with an ACDF, there remain several key advantages to the posterior approach, including the direct visualization of the lateral cervical spinal cord and exiting cervical nerve root. The nerve root can be followed out into the neuroforamen and the source of compression can be directly visualized and addressed.

 

The other significant advantage of the posterior approach is the preservation of motion segments in the cervical spine. This is especially important in young patients and athletes. In the elderly population, by avoiding a fusion, the risk of accelerated degenerative changes at the levels above and below the pathologic

segment can be avoided as well.3,13

 

The posterior cervical microendoscopic foraminotomy (CMEF) and posterior cervical microendoscopic discectomy (CMED) are minimally invasive approaches that were developed to exploit the advantages of a posterior cervical decompression while minimizing the approach-related morbidity.

 

The major contraindication for CMEF/D is the presence of a large central herniated disc causing symptoms of radiculopathy.

 

 

Using a posterior approach, the cervical cord cannot be retracted to adequately address a central pathology. Other contraindications include cervical instability or a kyphotic cervical deformity.

 

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FIG 10 • The METRx system of endoscopic retractors, camera, and instruments for our MEF procedures.

 

Preoperative Planning

 

A complete history and physical examination identifies patients with probable cervical pathology.

 

Acute onset of symptoms, report of pain or paresthesias in a dermatomal distribution, and weakness are good historical clues that nerve root compression may exist.

 

If this is corroborated on examination by findings of weakness, decreased sensation, presence of the Spurling sign, or diminished reflexes in a specific nerve root distribution, there is high clinical suspicion of root compression.

 

It is paramount to exclude the presence of myelopathy (hyperreflexia, ataxia, presence of upper motor signs), which would suggest spinal stenosis and not root pathology.

 

Plain cervical spine radiographs with flexion and extension views are essential for beginning the evaluation process.

 

Oblique views are sometimes helpful in correlating foraminal stenosis with clinical symptoms.

 

These studies reveal areas of foraminal stenosis, significant osteophytes, and the presence of spinal instability.

 

A cervical spine MRI is next used to look for any disc herniations or foraminal stenosis and to exclude the presence of central stenosis.

 

In patients with previous cervical surgery in whom hardware was implanted or in patients whose clinical history and examination findings do not correlate with MRI findings, a CT myelogram of the cervical spine is warranted.

 

 

 

FIG 11 • A. Intraoperative picture of the patient in the Mayfield three-point fixation device and the sitting position. B. Intraoperative picture of the operating room setup. (continued)

 

 

MRI is notorious for inadequately showing the degree of compression from osteophytes—these can be clearly seen on CT myelograms.

 

We employ the METRx system (Medtronic Sofamor-Danek, Memphis, TN) of endoscopic retractors, camera, and instruments for our microendoscopic foraminotomy (MEF) procedures (FIG 10).

 

Positioning

 

The patient is placed under general endotracheal anesthesia in the standard fashion. Throughout the procedure, somatosensory evoked potentials and myotomal EMG monitoring are used to monitor the spinal cord. An arterial line and a precordial Doppler may be used as well.

 

The patient's head is secured in the three-point Mayfield head clamp.

 

The patient is positioned in a semisitting position with the head slightly flexed. This position significantly reduces the blood loss and allows for better visualization of the affected stenosis and disc pathology. All extremities are carefully padded and the neck is once again examined to ensure adequate venous drainage (FIG 11A).

 

The organization of the operating room is as follows: The anesthesiologist is located to the left of the operating table; the scrub table, fluoroscopic monitor, and video cart are on the right side (FIG 11B).

 

 

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FIG 11 • (continued) C. Intraoperative picture showing the operative field with the sterile drape over the C-arm and the surgeon's operating screen in view. D. Example of this operative arrangement with a close-up view of the endoscopic apparatus in place as it would appear during the procedure.

 

 

The fluoroscopy unit is brought in from the right side as well.

 

 

The C-arm is brought either over or under the patient's head, according to the surgeon's preference. Suction canisters and a Bovie unit are generally located at the patient's feet.

 

The Midas drill is placed on a sterile Mayo stand on the left side behind the patient.

 

We use a standard blue sterile drape, similar to the one used for routine hip surgery, to create our surgical field (FIG 11C,D).

 

 

A single dose of antibiotics (either cefazolin or vancomycin) is routinely given before skin incision. Intravenous steroids are not routinely administered.

 

A Foley catheter is generally not needed.

 

A C-arm fluoroscopic image is taken to identify the correct operative level.

 

 

 

FIG 12 • Sample picture of traditional “open” posterior approach to the cervical spine.

 

Approach

 

Traditionally, the posterior cervical laminoforaminotomy is performed via a midline incision in the region of interest.

 

This approach, typically referred to as an open technique, requires an incision long enough such that the exposure can be carried laterally to the facet complex.

 

The paraspinal muscles are then stripped from the spinous process, which requires violation of their ligamentous attachments to the midline. The muscular attachments are also stripped from their position on the bony elements of the facet capsule, spinous process, and lamina.

 

To achieve this amount of muscular retraction, it is necessary to mobilize muscles above and below the targeted region (FIG 12).

 

 

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TECHNIQUES

• Minimally Invasive Cervical Laminoforaminotomy

Localization and Exposure

An 18-mm longitudinal incision is made 1.5 cm off the midline at the appropriate level.

The muscle is spread and the fascia is incised under direct vision to the length of the incision. After the fascia is opened, a Metz scissors is used to carefully dissect down to the facet.

The smallest dilator is introduced slowly in a perpendicular trajectory with no medial angulation.

 

 

Fluoroscopy is used to visualize the dilator docking onto the inferomedial edge of the rostral lateral mass of the appropriate level (TECH FIG 1A). The tubular muscle dilators are placed in a sequential fashion to the width of the retractor and endoscopic system that is used (TECH FIG 1B,C).

 

A 25-degree angled endoscope is then affixed to the retractor system.

 

 

 

TECH FIG 1 • A. First dilator in position at C6-C7. B. Intraoperative x-ray of final tube docked on facet complex. C. Drawing of final tube docked on facet complex. D. Intraoperative x-ray of tube secured at the C6-C7 level. E. Schematic drawing of the area on the facet used to dock the dilators and working channel.

 

 

Radiography reveals a tubular retractor docked at the C6-C7 interspace (TECH FIG 1D,E).

Initial Dissection

 

Monopolar cautery and pituitary rongeurs are used to identify the lateral mass and lamina.

 

It is best to begin this dissection laterally where the bone is clearly felt. The dissection can then be continued medially to expose the laminofacet junction, with attention paid to not slip into the interlaminar space at this point.

 

The possibility exists that there is a large interlaminar space medially and care must be used to remain

over bony landmarks during this dissection.

 

For a CMEF/D procedure, it is important to visualize the medial one-third of the rostral and caudal lateral mass and lateral onethird of the rostral and caudal lamina of interest (TECH FIG 2A).

 

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TECH FIG 2 • A. Illustration of the area of desired bone resection with the exiting nerve root and lateral thecal sac in view. B. Frequent dissection of the soft tissue off the bone with an angled curette facilitates safe use of the Kerrison rongeur. C. After the work rongeur.

 

 

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A small-angled curette is used to detach the ligamentum flavum from the undersurface of the inferior edge of the rostral lamina (TECH FIG 2B).

 

Proper placement of the curettes can be confirmed under fluoroscopy to double check that it is indeed under the lamina of the correct level. Good dissection of the underlying flavum and dura from the bone defines the relevant anatomy and helps to prevent incidental dural tears.

 

Bleeding from epidural veins and the edge of the flavum is controlled via a long-tipped endoscopic bipolar

cautery. For bleeding underneath the edge of the lamina, angled bipolar forceps with a 45-degree angle are often useful.

Bone Decompression

 

A 1- or 2-mm Kerrison rongeur is then used to create a small laminotomy to visualize the lateral border of the cervical dura and the proximal exiting cervical nerve root.

 

 

The Kerrison is used to begin the medial facetectomy over the exit of the cervical root (TECH FIG 3A). Periosteal and bone bleeding is addressed with bone wax and cautery.

 

Often, the lamina can be oriented in quite a vertical fashion, making it difficult to bite it with a Kerrison punch.

 

In such instances, it is best to use a drill to simultaneously thin and flatten the lamina down.

 

Frequent dissection of the soft tissue off the bone with an angled curette facilitates safe use of the Kerrison rongeur.

 

 

 

TECH FIG 3 • A. Kerrison punch with joint synovium in view. B. A drill with a long endoscopic bit (eg, AM-8 bit with Midas Rex or TAC bit with MedNext drill) can be used to further thin the medial facet and lateral mass. C. Drill bit with safety shield.

 

 

The drill with a fine cutting bit is often useful to finish the medial facetectomy and guarantee an adequate foraminal decompression (TECH FIG 3B).

 

We prefer a drill bit with a safety shield on one side to prevent inadvertent injury to the thecal sac (TECH FIG 3C).

Nerve Root Exposure

 

After the bony decompression of the dorsal cervical foramen is complete, bipolar coagulation is used to dissect the venous plexus that surround the nerve root.

 

The nerve root can then be mobilized in a superior or inferior direction to visualize and palpate the ventral

foramen and to identify the osteophytes or cervical disc fragments.

 

To increase exposure to this ventral space without over distraction of the nerve root, the superomedial quadrant of the caudal pedicle can be drilled.

 

Disc fragments can be teased out with the use of a nerve hook and micropituitary (TECH FIG 4A). Osteophyte fragments can be manipulated and fractured through the use of angled curettes or tamped down with down-angled curettes.

 

The foramen should be inspected one final time to assure no ventral or dorsal compression of the exiting nerve root (TECH FIG 4B-D).

 

After hemostasis is achieved and the wound is irrigated with antibiotic irrigation, the tubular retractor is removed and the wound is closed in layers and Dermabond (Ethicon, Somerville, NJ) is applied over the incision.

 

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TECH FIG 4 • A. The adequacy of the decompression should be confirmed by palpating the root along its course with a small nerve hook. B. Intraoperative photograph showing that the foraminotomy is probed with

a blunt nerve hook for tactile feedback on the completeness of decompression. C. Intraoperative x-ray

demonstrating that the foraminotomy is probed with a blunt nerve hook for tactile feedback on the completeness of decompression. D. Intraoperative photograph at completion of the laminoforaminotomy. The lateral edge of the thecal sac can be seen as well as the exiting nerve root.

 

 

 

PEARLS AND PITFALLS

 

Positioning ▪ Care should be directed to ensuring that the cervical spine and neck musculature are not kinked or held in an unfavorable position. The neck, chin, and chest must be allowed to remain loose and free of compression. Precordial Doppler monitoring can be used to detect air emboli within the atrium.

 

Localization ▪ The incision should be 1.5 cm from the midline to ensure that the surgical exposure is not too medial. The incision length and the tubular retractor width should be the same to ensure adequate stability of the final tube.

 

Incision and tube dilation

• A mini-open approach is used to avoid the need for K-wire insertion, and potential spinal cord injury, in the cervical spine. The first dilator is docked directly on the bony lamina. As sequential dilators are placed, care is taken to not apply too much pressure, which could result in an inadvertent plunge through the interlaminar space.

   

  Surgical approach

  • After the initial induction of anesthesia, we have refrained from the use of neuromuscular paralytics to allow for improved feedback from the nerve root during the operation. It is best to begin this dissection laterally where the bone is clearly felt. The dissection can then be continued medially to expose the laminofacet junction with attention paid to not slip into the interlaminar space at this point.

     

    Bone exposure

  • Good dissection of the underlying flavum and dura from the bone defines the relevant anatomy and helps to prevent incidental dural tears. For bleeding underneath the edge of the lamina, angled bipolar forceps with a 45-degree angle are often useful.

 

Foraminotomy ▪ Often, the lamina can be oriented in quite a vertical fashion, making it difficult to bite it with a Kerrison punch. In such instances, it is best to use a drill to simultaneously thin and flatten the lamina down. Frequent dissection of the soft tissue off the bone with an angled curette facilitates safe use of the Kerrison rongeur. The adequacy of the decompression should be confirmed by palpating the root along its course with a small nerve hook.

 

 

 

POSTOPERATIVE CARE

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Most of our patients can be safely discharged home the same day of surgery.

 

Patients are counseled to expect neck/muscle and incisional pain for the first week or two after surgery.

 

They are given prescriptions for a narcotic pain medication and a muscle relaxant; we typically prescribe hydrocodone/acetaminophen and baclofen.

 

Patients are also placed on a bowel regimen consisting of daily stool softeners to avoid constipation from the narcotic medication.

 

 

They are encouraged to walk as tolerated and discouraged from lifting more than 10 pounds. Most patients can return to light work duties by 4 weeks.

 

All patients begin a short course of physical therapy 4 to 6 weeks after surgery to improve neck strength and mobility.

 

 

 

Most patients return to work, are able to drive, and have discontinued narcotic pain medication by 6 to 8 weeks following surgery.

 

OUTCOMES

Good to excellent outcomes are reported in up to 96% of patients following laminoforaminotomy performed for radiculopathy.13

Poor prognostic factors include long-term preoperative complaints and long-standing preoperative neurologic deficits.12

 

FIG 13 • A. Postoperative CT scan demonstrating the typical foraminotomy defect that is obtained after MEF with good preservation of the lateral mass integrity. B. Postoperative MRI.

Posterior CMEF and CMED have been demonstrated to be safe and effective procedures with improvement in patients' neck disability index and visual analog scale for both the neck and arm after 1-

and 2-year follow-up.9

Additionally, patients appear to exhibit continued good long-term outcomes in which 86% of patients were still doing well 15 years later (FIG 13).12

 

COMPLICATIONS

 

Potential complications following either a minimally invasive cervical decompression include injury to the cervical spinal cord or nerves, cerebrospinal fluid leak, and infections.

 

The treatment of an unintended durotomy include direct repair of a visible tear or placement of muscle, fat, or Gelfoam (Pfizer, New York, NY) over the tear and the application of a dural sealant such as DuraSeal (Confluent Surgical, Waltham, MA).

 

The limited volume of dead space created with the minimally invasive approach has led to a decreased incidence of postoperative pseudomeningocele.

 

The potential exists for injury to the cervical cord or the cervical nerve root. By careful dilation technique through the direct visual incision of the cervical fascia and placement of the first dilator tube directly perpendicular to the spine without any medial angulation, the risk of direct injury to the spinal cord can be minimized.

 

To minimize injury to the cervical nerve root, adequate bony decompression must be achieved prior to manipulation of the nerve root.

 

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Venous bleeding from the plexus surrounding the cervical nerve root must be carefully monitored and controlled with bipolar coagulation and Gelfoam packing. The use of the semisitting position helps decrease the amount of this venous blood loss. The potential exists for a symptomatic air embolus in this semisitting position, although this has not been observed in the authors' series to date. The use of a precordial Doppler can help in identifying an air embolus and the appropriate treatment can be performed.

 

The vertebral artery runs immediately anterior to the cervical nerve root. When manipulating the cervical nerve root and osteophytes that may exist in this space, the surgeon should carefully monitor for an increase in venous bleeding. Because the vertebral artery is surrounded by a rich venous plexus, this venous bleeding is a good indicator of the proximity to the artery itself.

 

Cervical instability following surgery can be avoided by preserving at least 50% of the facet complex during the bony decompression. When drilling the superomedial quadrant of the pedicle, careful attention must be paid to drill only the volume necessary to allow a nerve hook access behind the cervical nerve root.

 

REFERENCES

1. Bailey RW, Badgley CE. Stabilization of the cervical spine by anterior fusion. J Bone Joint Surg Am 1960;42-A:565-594.

    

    

2. Bohlman HH, Emery SE, Goodfellow DB, et al. Robinson anterior cervical discectomy and arthrodesis for cervical radiculopathy. Long-term follow-up of one hundred and twenty-two patients. J Bone Joint Surg Am 1993;75(9):1298-1307.

    

    

3. Fessler RG, Khoo LT. Minimally invasive cervical microendoscopic foraminotomy: an initial clinical experience. Neurosurgery 2002;51 (5 suppl):S37-S45.

    

    

4. Grieve JP, Kitchen ND, Moore AJ, et al. Results of posterior cervical foraminotomy for treatment of cervical spondylitic radiculopathy. Br J Neurosurg 2000;14(1):40-43.

    

    

5. Henderson CM, Hennessy RG, Shuey HM Jr, et al. Posterior-lateral foraminotomy as an exclusive operative technique for cervical radiculopathy: a review of 846 consecutively operated cases. Neurosurgery 1983;13(5):504-512.

    

    

6. Hosono N, Yonenobu K, Ono K. Neck and shoulder pain after laminoplasty: a noticeable complication. Spine 1996;21(17):1969-1973.

    

    

7. Howe JF, Loeser JD, Calvin WH. Mechanosensitivity of dorsal root ganglia and chronically injured axons: a physiological basis for the radicular pain of nerve root compression. Pain 1977;3(1):25-41.

    

    

8. Klein GR, Vaccaro AR, Albert TJ. Health outcome assessment before and after anterior cervical discectomy and fusion for radiculopathy: a prospective analysis. Spine 2000;25(7):801-803.

    

    

9. Lawton CD, Smith ZA, Lam SK, et al. Clinical outcomes of microendoscopic foraminotomy and decompression in the cervical spine. World Neurosurg 2014;81(2):422-427.

    

    

10. Ratliff JK, Cooper PR. Cervical laminoplasty: a critical review. J Neurosurg 2003;98(3 suppl):230-238.

     

     

11. Smith GW, Robinson RA. The treatment of certain cervical-spine disorders by anterior removal of the intervertebral disc and interbody fusion. J Bone Joint Surg Am 1958;40-A(3):607-624.

     

     

12. Woertgen C, Holzschuh M, Rothoerl RD, et al. Prognostic factors of posterior cervical disc surgery: a prospective, consecutive study of 54 patients. Neurosurgery 1997;40(4):724-728.

     

     

13. Zeidman SM, Ducker TB. Posterior cervical laminoforaminotomy for radiculopathy: review of 172 cases. Neurosurgery 1993;33(3):356-362