Spine 2023, Jan, 11 | 12:00 am

Posterior Cervical Foraminotomy

DEFINITION

Cervical radiculopathy is a clinical diagnosis defined by the presence of motor or sensory changes or complaints in a specific dermatomal distribution.

ANATOMY

Cervical radiculopathy is largely due to mechanical compression of the exiting cervical nerve roots. The intervertebral foramen is bounded by the following structures (FIG 1):

The disc and uncovertebral joint ventrally

The borders of the pedicles cranially and caudally

The superior articular facet of the caudal segment (eg, the superior articular facet of C6 at the C5-C6 foramen) dorsally

In the subaxial cervical spine, the foramen averages 9 to 12 mm in height and 4 to 6 mm in width, and in a young person, the cervical nerve root occupies approximately onethird of the available space in the foramen.

With increasing age, degenerative changes (osteophyte formation), disc protrusion, or cervical instability, this proportion may increase and signs of radiculopathy may develop.

PATHOGENESIS

Any process that causes impingement of the exiting cervical nerve roots can lead to cervical radiculopathy.

Potential etiologies of cervical radiculopathy include cervical spondylosis leading to foraminal stenosis due to uncinate or facet hypertrophy, disc herniation, instability, and anterolisthesis or retrolisthesis.

FIG 1 • Model and illustration showing the posterior element anatomy and boundaries of the foramen.

NATURAL HISTORY

The natural history of cervical radiculopathy is not well studied, but about half of the adult population will have neck and radicular symptoms at some point during their lifetime.

In patients treated nonoperatively, up to 66% will have persistent symptoms and up to 23% of patients with persistent neck or radicular pain will be unable to return to their original occupation.

PATIENT HISTORY AND PHYSICAL FINDINGS

When a patient presents with radiculopathy, a complete history and physical examination is of paramount importance.

Questions about the duration of the symptoms, location and nature of the pain, distribution of altered sensation and numbness (axial or radicular), presence of weakness, and any associated manifestations must be asked to understand the underlying pathology and target the offending level of cervical pathology.

Because radiculopathy can be associated with myelopathy, the presence or absence of balance difficulties, loss of bowel or bladder control, presence of constitutional symptoms, trauma, signs of dysdiadochokinesia, or change in neurologic status must be elucidated.

The physical examination should include motor and sensory evaluation (both gross and pinprick), reflex testing, upper and lower motor neuron signs, and cerebellar functional testing.

IMAGING AND OTHER DIAGNOSTIC STUDIES

Plain radiographs of the cervical spine, including anteroposterior (AP), lateral, odontoid, oblique, and lateral flexion/extension

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views, are used initially to evaluate for the presence of cervical pathology.

If symptoms have been present for at least 6 weeks, additional imaging is indicated and usually includes cervical spine magnetic resonance imaging (MRI).

If MRI is contraindicated, a cervical computed tomography (CT) myelogram may be beneficial.

A CT scan with coronal and sagittal reconstructions may be helpful in operative planning.

DIFFERENTIAL DIAGNOSIS

Cervical radiculopathy Myelopathy Myeloradiculopathy

Entrapment syndromes (eg, pronator syndrome, carpal tunnel syndrome, cubital tunnel syndrome) Thoracic outlet syndrome

NONOPERATIVE MANAGEMENT

Although cervical radiculopathy is common, only a few patients require surgical intervention, and despite a heightened clinical acumen for the diagnosis and treatment of cervical spondylosis, the mainstay of treatment remains nonsurgical.

Nonsurgical modalities that are initiated first include physical therapy, nonsteroidal anti-inflammatory drugs, and activity modification.

If these methods fail, a selective nerve root injection at a designated level can be attempted with a high degree of safety and efficacy.

The purpose of the nerve root injection is twofold: to provide pain relief by decreasing inflammation through the use of a corticosteroid and to serve as a diagnostic tool to localize the offending pathology.

SURGICAL MANAGEMENT

Posterior cervical foraminotomy is indicated for foraminal stenosis or a foraminal disc herniation resulting in a neurologic deficit such as a sensory deficit, motor weakness, and/or progressive symptoms that fail to respond to an appropriate course of nonsurgical treatment.

As with any surgical intervention, a thorough discussion with the patient and family about the desired outcomes and risks and benefits of the procedure must be undertaken before surgery.

Preoperative Planning

To perform an adequate foraminotomy, one must first understand the anatomy of the foramen.

The basic principle of the procedure is to unroof the foramen, which then allows the nerve root to displace dorsally away from the compressive pathology, which is anterior in most cases.

Less commonly, a portion of the superior facet may itself be a source of compression, which can then be directly removed by the posterior foraminotomy.

Because the superior articular facet of the caudal cervical segment forms the roof of the foramen, resection of the medial portion of the superior articular facet is necessary to adequately decompress the neuroforamen.

Similarly, because the pedicles form the cranial and caudal borders of the neuroforamen, adequate decompression requires resection of the superior articular facet to the lateral margin of the pedicles, as any overhang of the superior articular facet over the caudal pedicle can lead to persistent compression.

In contrast, because resection of more than 50% of the facet joint can lead to facet instability, resection of the superior facet lateral to the pedicle is unnecessary.

Positioning

Proper patient positioning is critical when performing posterior cervical foraminotomy to reduce blood loss and improve visualization of the operative field.

Although there are a variety of ways to position a patient, we routinely place the patient in bivector Gardner-Wells tongs traction and position the patient prone on an open Jackson frame (Mizuho Osi, Orthopaedic Systems, Inc., Union City, CA).

This table is quite versatile and allows for intraoperative alterations in patient positioning throughout the operation.

Typically, the table is tilted into reverse Trendelenburg to distribute blood into the abdomen and legs, thereby creating a more physiologic state for the patient and providing better visualization in the operative field.

To facilitate this position, the head of the table is placed on the top rung, and the foot of the bed is placed on the bottom rung.

The chest and abdomen are supported on bolsters that allow the abdomen to hang free, and the legs are supported in a sling with pillow support.

The shoulders are taped down on both sides to provide traction, thereby allowing better radiographic visualization of the lower cervical spine during intraoperative imaging.

Bivector traction is used with the aid of two separate ropes so that the neck is maintained in proper alignment, depending on the procedure being performed (FIG 2).

One of the ropes is placed in line and horizontal to the table through a pulley system, and the other is placed over a crossbar on the Jackson frame to facilitate placement of the head into extension.

It is imperative to maintain good coordination and communication with the anesthesia providers during change of positioning of the head, as the endotracheal tube may become dislodged if not secured properly.

Foraminotomies are best accomplished with the neck in maximal flexion. This position unshingles the facets and exposes the underlying superior articular facet.

If the neck is not adequately flexed during a foraminotomy, one must resect a large amount of the overhanging inferior articular facet to expose the underlying superior facet.

This may weaken the lateral mass and lead to a fracture, or more commonly, it makes placement of the lateral mass screw more difficult if a fusion is being performed in addition to a foraminotomy.

Approach

A posterior cervical foraminotomy can be performed using open, endoscopic, or microscopically assisted approaches.

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FIG 2 • Bivector traction technique using the open Jackson frame. Two separate ropes are used so that the neck is maintained in proper alignment, depending on the procedure being performed: one of the ropes is placed in line and horizontal to the table through a pulley system, and the other is placed over a cross-bar on the Jackson frame to facilitate placement of the head into extension. Although not necessary, a horseshoe may be used ventral to the face to catch the head if the tongs slip.

TECHNIQUES

Exposure

For bilateral foraminotomies, typically, a midline incision is used, whereas for a unilateral foraminotomy, an incision approximately 2 cm lateral to the midline can be made (TECH FIG 1A-C).

With either approach, the lamina, the junction between the lamina and the facet joint, and the facet joint itself have to be exposed while preserving the facet capsule.

TECH FIG 1 • A. Dissection of the posterior cervical spine along the midline in the avascular plane. B. Continued dissection, showing midline splitting of the muscles. C. The posterior cervical spine after meticulous dissection of the posterior elements with lateral extension over the facet capsules. Bovie marks illustrate the lateral mass-laminar border. (continued)

After exposure, the intralaminar V is identified, and the decompression is performed (TECH FIG 1D,E).

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TECH FIG 1 • (continued) D. Model of the cervical spine showing the C5-C6 interspace with the intralaminar V (black lines). This is the key anatomic landmark that must be recognized to perform an adequate foraminotomy. E. An intraoperative image showing the C5-C6 interspace with the intralaminar V (yellow lines).

Resection of Inferior Articular Facet

A high-speed, 2-mm, acorn-shaped, carbide-tip cutting burr is used to resect the overlying inferior articular facet and then the medial superior articular facet with the neck in neutral or flexed position (TECH FIG 2).

TECH FIG 2 • A. Model of the cervical spine showing the C5-C6 interspace with resection of the inferior facet, which must be resected to the lateral margin of the pedicles to expose the underlying superior articular facet. To determine whether enough of the inferior facet has been resected, a small angled microcurette can be used to palpate the pedicle. B. An intraoperative image showing the C5-C6 interspace with resection of the inferior facet. The probe illustrates the cranial extent of the C6 superior articular facet.

Although the inferior articular facet does not cause impingement of the nerve root (the inferior articular facet lies dorsal to the superior articular facet), the overlying inferior articular facet must be resected to the lateral margin of the pedicles to expose the underlying superior articular facet.
Resection of Superior Articular Facet

Once the inferior articular facet is resected, the superior articular facet underneath is resected out to the lateral border of the pedicles, completing the decompression (TECH FIG 3).

During the decompression, copious irrigation (20-mL syringe with a 2-inch long 18-gauge angiocatheter) must be used to prevent thermal damage to the surrounding tissues. It also aids in visualization.

Typically, we recommend the use of a burr over Kerrison rongeurs because inserting instruments (such as Kerrison rongeur, which may have a relatively thick footplate) into the already stenotic canal and foramen can cause neurologic damage. However, once most of the roof of the foramen has been removed, it is usually safe to use a 1-mm Kerrison rongeur to clean up any overhanging bone.

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TECH FIG 3 • A. An intraoperative image showing that once the inferior articular facet is resected, the superior articular facet underneath can be identified. B. The superior articular facet is resected out to the lateral border of the pedicles; this is best performed using an L-shaped resection, as shown in the intraoperative image, to ensure there is no iatrogenic impingement on the nerve root, which can occur if a keyhole or a C-shaped resection of the superior articular facet is performed (see E). C. An intraoperative image showing the complete resection of the superior articular facet. The remaining small ledge of bone can be removed using a small angled microcurette or 1-mm Kerrison rongeur. D. An intraoperative image showing the completed foraminotomy. E. Model of the cervical spine showing the C5-C6 interspace showing C- or sickle-shaped decompression, which can lead to iatrogenic impingement on the nerve root.
Discectomy

If the patient has an intraforaminal disc herniation, then the nerve root must be manipulated to expose the herniated disc fragment that is ventral to the nerve root.

If there is little room for the root to migrate cranially, the cranial 2 to 3 mm of the caudal pedicle may have to be burred down, and a microscopic right angle probe can then be placed into this space and rotated ventrally to the root to sweep any herniated disc fragment out from under the root, and micropituitary rongeurs can be used to remove the disc fragment.
Confirmation of Adequate Decompression

After completing the decompression, a hemostatic agent such as FloSeal or Surgiflo is used to control any bleeding surfaces.

Once the foraminotomy is completed, the lateral walls of the cranial and caudal pedicles should be readily palpable, and there should be no bone overhanging the medial and superior aspect of the caudal pedicle (TECH FIG 4).

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TECH FIG 4 • A. Model showing completion of the foraminotomy with complete decompression of the foramen. The microprobe shows the medial pedicle border. B. An intraoperative image showing palpation of the medial pedicle border after completion of the foraminotomy.

Wound Closure

The posterior wound is closed in multiple layers.

If meticulous midline exposure was performed, the preserved interspinous ligaments with the muscular attachments are used as the first layer of closure. The amount of muscle incorporated into the suture is minimized because all such muscle will necrose.

With a well-exposed spine, one can find a thin fascial layer enveloping the muscle that can be used to close the layers.

The closure progresses from deep to superficial with the placement of deep, middle, and superficial drains.

The multiple drains prevent isolated pockets of hematoma, which can act as a nidus for infection.

PEARLS AND PITFALLS

Positioning ▪ Bivector traction with the neck placed in flexion when the foraminotomy is being performed is crucial, as neck flexion unshingles the facets and exposes the underlying superior articular facet.

Reverse Trendelenburg position helps to decrease blood loss.
Good coordination and communication with the anesthesia providers during change of positioning of the head is critical.

Exposure ▪ Meticulous midline dissection through avascular raphe decreases blood loss and allows better closure.
Care must be taken not to detach the semispinalis cervicis from the spinous process of C2 if a C2-C3 foraminotomy is required.
Care must be taken to remain superficial to the facet capsules during dissection to preserve them, as they provide some protection against postoperative kyphosis.

Decompression ▪ Adequate decompression requires resection of the superior articular facet (the

roof of the foramen) to the lateral margin of the pedicles.

About 50% (mediolateral) of the overlying inferior articular facet must be resected to expose the underlying superior articular facet.
Any overhang of the superior facet over the caudal pedicle can result in persistent nerve root compression.

Closure ▪ The posterior wound is closed in multiple layers to more closely reapproximate the normal anatomy.

Postoperative ▪ Postoperatively, patients do not have any range-of-motion restrictions nor are course they required to wear a brace.

POSTOPERATIVE CARE

Postoperative pain regimen includes patient-controlled analgesia and ketorolac (Toradol) for 36 to 48 hours in patients younger than age 65 years who have normal renal function and no history of congestive heart failure.

Patients typically remain in the hospital for 24 to 48 hours, depending on drain output. Patients are discharged on oral pain medication and are instructed to return to the clinic for routine follow-up at 6 weeks postoperatively.

Although a soft collar is given for comfort, patients are encouraged to discontinue using the collar as soon as they can.

There are no range-of-motion restrictions, and therapy with immediate motion can begin. Rapid return to normal activities and aerobic exercise is encouraged.

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OUTCOMES

Results of posterior cervical foraminotomy are encouraging, with good or excellent outcomes reported in about 90% to 95% of patients.

COMPLICATIONS

Neurologic injury or worsening radiculopathy Infection

Inadequate decompression or failure to relieve symptoms

Instability and deformity secondary to overly aggressive decompression Air embolism if the procedure is done in a sitting position

Posterior Cervical Foraminotomy

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Posterior Cervical Foraminotomy

DEFINITION

ANATOMY

PATHOGENESIS

FIG 1 • Model and illustration showing the posterior element anatomy and boundaries of the foramen.

NATURAL HISTORY

PATIENT HISTORY AND PHYSICAL FINDINGS

IMAGING AND OTHER DIAGNOSTIC STUDIES

DIFFERENTIAL DIAGNOSIS

NONOPERATIVE MANAGEMENT

SURGICAL MANAGEMENT

Preoperative Planning

Positioning

Approach

TECHNIQUES

Exposure

Resection of Inferior Articular Facet

Resection of Superior Articular Facet

Discectomy

Confirmation of Adequate Decompression

TECH FIG 4 • A. Model showing completion of the foraminotomy with complete decompression of the foramen. The microprobe shows the medial pedicle border. B. An intraoperative image showing palpation of the medial pedicle border after completion of the foraminotomy.

Wound Closure

POSTOPERATIVE CARE

OUTCOMES

COMPLICATIONS

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