DEFINITION

In recent years, the number of patients undergoing cervical spine surgery has risen dramatically. Cervical spine surgery is used to treat a number of common spinal pathologies including the following:

Cervical spinal stenosis Deformity

Disc herniation Myelopathy Trauma

Pathologic conditions such as neoplasia, infection, and metabolic and inflammatory disease

The surgical procedures used to treat these conditions are generally successful but occasionally result in complications that require revision cervical spine surgery. Unexpected life events after spine surgery such as trauma and cancer can cause instability or neurocompression leading to the need for surgical decompression and/or stabilization at the site of previous operative intervention. The more common complications and conditions are defined here.

Pseudarthrosis: The term suggests a “false joint.” Pseudarthrosis is a failure of bone fusion or nonunion at the site of attempted arthrodesis. Diagnosis is made after 6 months to 1 year following the index surgery. Pseudarthrosis may occur following anterior or posterior cervical procedures.

Adjacent segment degeneration (ASD) occurs when there are degenerative changes at unfused levels adjacent to prior cervical fusion. ASD is believed to result from excessive motion at the level adjacent to an arthrodesis as it compensates for the fused segment. Some controversy exists whether the degeneration occurs as a result of prior arthrodesis or as a result of natural progression in an individual already prone to degenerative disc disease.

Postlaminectomy kyphosis (PLK) is a kyphotic deformity of the cervical spine that develops as a result of previous surgery in which the posterior elements of the spine, including the spinous process and lamina, were removed. Removal of the posterior tethering structures, including the spinous processes and the associated supraspinous and interspinous ligaments, predisposes individuals to this condition.

Hardware/construct failure: Plates, screws, and rods may loosen or break if bone healing is prolonged or inhibited. Allograft and autograft bone used for structural support of the spine are subject to loading forces that can cause the graft to collapse. Poor bone quality in the patient may allow hardware to migrate or bone graft to subside.

Same segment disease/residual compression is persistent or recurrent pain is present at the level of previous decompression. Same segment disease results from failed stabilization or inadequate decompression at the site of the initial cervical surgical procedure.

Pathologic conditions may be the inciting event for the index surgical procedure or may result in the need for revision surgery. Tumor, infection, trauma, and inflammatory conditions such as rheumatoid arthritis and ankylosis spondylitis may lead to instability, deformity, or neurocompression after an index cervical procedure.

 

 

ANATOMY

 

Vertebrae

 

 

The cervical spine consists of seven specialized vertebrae.

 

Transverse foramina are present bilaterally for the passage of the vertebral artery.

 

The vertebral artery generally enters the cervical spine at C6. Occasionally, it will enter at C7 or C5. The artery may also enter the spine at different levels on either side of the cervical spine in the same patient. Magnetic resonance imaging (MRI) should be obtained prior to surgical intervention to ascertain the site of vertebral artery entry and any anomalies present along its excursion (FIG 1).

 

The spinous processes of C6-C2 are bifid. C7 does not possess a bifid spinous process but is more prominent than the other cervical vertebrae. C7 is often referred to as vertebra prominens.

 

Discs

 

 

An intervertebral disc is present between each of the cervical vertebrae from C2 through T1.

 

The occiput to C1 and the C1-C2 articulation do not have intervertebral discs and articulate through true synovial joints.

 

Each disc consists of an outer annulus fibrosus and inner nucleus pulposus.

 

Between the annulus fibrosus/nucleus pulposus complex and the vertebral body, a cartilaginous endplate is present. The removal of this cartilaginous endplate is pivotal to a successful interbody arthrodesis. Failure to remove the cartilaginous endplate increases the likelihood of pseudarthrosis.

 

Ligaments

 

 

A supraspinous ligament runs dorsally over the top of the spinous processes.

 

Then, an interspinous ligament is present between two spinous processes at each level.

 

An anterior longitudinal ligament runs along the front of the spine adherent to the ventral aspect of the vertebral body.

 

A posterior longitudinal ligament (PLL) runs along the dorsal aspect of the vertebral body and intervertebral discs. It forms a barrier between the discs and the dura/spinal cord.

 

 

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FIG 1 • A. Axial T2-weighted image through the C6 vertebral body. Note in this patient that the vertebral artery is anomalous and only the right-sided artery enters the spine at this level. B. Axial T2-weighted image through the C5 vertebral body in the same patient as FIG 1A. At this level, both right and left vertebral arteries have entered the cervical spine.

 

 

Normal lordosis of the cervical spine averages 14.4 degree.27

 

Weight-bearing axis of the cervical spine passes through the posterior column.18

 

Loss of the posterior tension band after resection of the lamina and spinous processes may lead to kyphosis and a shift in the weight-bearing axis of the spine to the anterior column.

 

PATHOGENESIS

 

Pseudarthrosis

 

 

Pseudarthrosis occurs when bone fails to form at the site of attempted arthrodesis. Multiple factors may play a role in the formation of pseudarthrosis.

 

Risk factors include the following28:

 

 

 

 

Multilevel fusions Metabolic abnormalities Smoking

 

 

Infection Excessive motion

 

Smoking is associated with lower fusion rates in cervical and lumbar fusion. Hilibrand et al9 found a higher rate of fusion in nonsmokers (81%) than in smokers (62%). In contrast to the effect of smoking on anterior cervical fusion, some studies found smoking did not decrease posterior cervical fusion with lateral mass instrumentation and iliac crest bone grafting.

 

Excessive motion at the site of an anterior cervical discectomy and fusion (ACDF) is associated with increased rates of pseudarthrosis. Use of anterior cervical plating has been shown in multiple studies to decrease the rate of pseudarthrosis.4,23

 

Corpectomy with the use of autogenous strut grafting should be considered when a multilevel anterior cervical decompression and fusion is performed in patients who are unable or unwilling to stop smoking

 

prior to surgical treatment.9 ASD

 

As previously noted, some controversy exists whether the degeneration of adjacent segments occurs as a result of prior arthrodesis, which may place increased demands on a level above or below a fusion, or whether the degeneration is a result of natural progression in an individual already prone to degenerative disc disease.

 

Deformity (PLK)

 

 

Causes of PLK include the following:

 

 

Removal of the posterior restraints of the cervical spine, namely posterior bony arch and the supraspinous and interspinous ligaments. Resection of greater than 50% of the facet has been shown to lead to instability.17

 

 

Attenuation or failure of the restraints secondary to radiation Neglect of deformity during index procedure

 

Removal of the posterior arch/facets leads to instability, which causes the weight-bearing axis of the spine to shift anteriorly.

 

 

Once the axis shifts anteriorly, the posterior cervical musculature fatigues and the kyphosis progresses.1 The load is then transferred to the anterior vertebral bodies and discs.

 

Hardware/construct failure15,16

 

 

The likelihood of hardware failure of current cervical instrumentation is small.

 

Anterior cervical hardware or construct failure is an infrequent occurrence; however, complication associated with hardware placement occurs in approximately 22% to 36% of cases.2

 

Screw breakage or loosening is often the result of a nonunion or pseudarthrosis, and evaluation of the fusion with flexion-extension views or computed tomography (CT) scan is warranted.

 

Infection, osteoporosis, tumor, and trauma can also lead to hardware failure or graft subsidence after cervical fusion with or without instrumentation.

 

The use of multilevel interbody fusion versus corpectomies with strut grafting has been shown to decrease the risk of graft extrusion.

 

Aggressive mobilization and smoking are other potential causes for prolonged healing and hardware failure.

 

Same segment disease/residual compression

 

 

A result of failed or inadequate initial surgical decompression

 

 

Truumees and McLain24 outlines four general causes for residual compression after cervical surgery. These are the following:

 

 

 

Failure to perform a complete decompression at the injured/involved level Failure to decompress adjacent involved levels

 

Migration of graft or fixation materials into the canal or foramen

 

Wrong-level surgery (initial surgery performed at a level that was not responsible for the patient's symptoms;

 

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this can occur as a failure to diagnose the offending level correctly or as a result of wrong-site surgery)

 

 

Pathologic conditions

 

 

The pathogenesis of tumor, infection, and inflammatory conditions such as rheumatoid arthritis and ankylosis spondylitis is beyond the scope of the current text. Failure of the cervical spine as it relates to these conditions is a progressive deterioration of the structural integrity of the bones or erosion of the ligamentous support of the spine. Loss of these structures leads to instability, deformity, or compression of the neural elements.

 

NATURAL HISTORY

 

Pseudarthrosis

 

 

 

The most common cause of pain or radiculopathy after ACDF is pseudarthrosis.21,25 Outcome studies of ACDF show up to 26% pseudarthrosis.6,16,20,21

 

Lowery et al16 defined pseudarthrosis as follows:

 

 

 

Continued or worsening axial pain 6 months after the initial procedure Complete radiolucency at the host/graft interface

 

 

Vertebral body motion greater than 2 mm on flexion and extension films Phillips et al18 followed 48 patients with radiographic pseudarthrosis:

 

Thirty-two patients (67%) developed symptoms.

 

Sixteen patients remained asymptomatic for 5.1 years.

 

Nine of the 32 symptomatic patients were pain free for 2 years before trauma caused development of symptoms.

 

 

Eighty-two percent of patients developed pseudarthrosis at the most caudal level after multilevel fusion. Revision surgery led to good or excellent results in all cases (anterior or posterior).

 

Allograft and multilevel fusion increases the risk of pseudarthrosis.13

 

Posterior fusion with lateral mass screws leads to high rate of fusion from 0% to 1.4%; less rigid posterior fixation (wiring) has a less reliable outcome.

 

ASD

 

 

Occurs at a rate of 2.9% per year, with 25% of patients developing ASD within 10 years8

 

Patients with degenerative changes at C5-C6 or C6-C7 at time of initial procedure are at greatest risk for development of ASD.

 

Eck et al5 measured disc pressures at C4-C5 and C6-C7 before and after simulated fusion at C5-C6 and found a 73% increase in cranial and 45% in caudal disc pressures during flexion.

 

Deformity (PLK)

 

Lonstein14 described PLK as a focal, dramatic angulation of the cervical spine after posterior decompression.

 

Kyphosis is the most common cervical deformity and the most frequent cause is iatrogenic postlaminectomy instability.

 

Patients with PLK generally have a pain-free period following the index surgical procedure followed by the development of persistent pain.

 

Risks of PLK as described by Lonstein14:

 

 

 

Age younger than 30 years Aggressive facetectomy

 

 

Removal of more than four laminae Preoperative deformity

 

Tumors

 

 

Removal of C2 posterior elements (major semispinalis insertion) Paraspinal muscle weakness

 

Anterior instability following fracture

 

 

Nowinski et al17 studied the effects of progressive facetectomy and recommend posterior fusion when over 25% of the facets are sacrificed for decompression. Some studies found a 25% incidence of kyphosis in patients with bilateral facet resection.

 

 

Facet capsular resection of greater than 50% increases the risk of progressive deformity.27 Hardware/construct failure

 

Hardware complications following ACDF have been characterized in 22% to 36% of cases.12

 

Graft extrusion and malalignment have been described in up to 6% of cases following anterior cervical fusions.12

 

When failure occurs, the risk of injury to the tracheoesophageal structures is minimal.15

 

Immediate removal of failed hardware is rarely necessary and should only be considered if there is evidence of dysphagia or risk to the spinal cord or nerve roots.

 

Careful and long-term follow-up in patient with loose or broken hardware assures that significant progression of the failure does not occur.

 

Same segment disease/residual compression

 

 

Results from failed or inadequate initial surgical procedure

 

 

 

ACDF, posterior cervical fusion, posterior foraminotomy, and micro-ACD ranged from 5% to 36%.12 Hardware complications following ACDF have been characterized in 22% to 36% of cases.

 

Residual compression after an index spine procedure may result from the following24:

 

 

Failure to perform a complete decompression at the injured/involved level

 

Failure to decompress adjacent involved levels

 

 

Migration of graft or fixation materials into the canal or foramen Wrong-level surgery

 

Posterior osteophytes may be a significant source of residual compression.26

 

 

Studies have noted limited remodeling or resorption of posterior osteophytes after solid ACDF.22,24 Kozak et al11 has advocated PLL resection to achieve a more complete decompression.

 

Decompression of the neural elements may be needed at the time of surgery for cervical trauma to

 

decrease the potential for compression at the level of the procedure.19 Pathologic conditions: tumor, infection, and inflammatory arthropathies

 

Only 17% of spinal tumors occur in the cervical spine.

 

The most common malignant tumors are chordoma and plasmacytoma, which occur most often in the anterior cervical spine leading to kyphosis.

 

Osteoid osteoma and osteoblastoma are the most common benign tumors of the cervical spine occurring most commonly in the posterior elements.

 

Benign lesion of the spine, and specifically osteoid osteoma, can lead to painful scoliosis, which often improves once the lesion is excised.

 

Three percent to 14% of spinal infections are cervical.

 

 

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Infection of the cervical spine typically begins as a spondylodiscitis causing destruction of the intervertebral disc, which can then spread to the vertebral bodies causing collapse and kyphosis.

 

Metastatic lesions of the cervical spine typically start in the subaxial anterior spine. Progressive destruction of the vertebral body leads to axial instability first followed by translational and rotational instability.

 

The natural history of inflammatory arthropathies is a progressive deformity leading to kyphosis.

 

In the case of rheumatoid arthritis, the cervical spine is affected by one of three potential deforming etiologies: atlantoaxial subluxation, cranial settling, and subaxial subluxation.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Patients with prior cervical surgery typically present with complaints of axial pain, radiculopathy, myelopathy, or progressive deformity. They may also have a combination of these symptoms.

 

It is helpful to know whether the current symptoms are similar or different from the symptoms experienced before the initial surgery.

 

The evaluation must begin with a complete review of all prior cervical procedures, pain-free periods, and trauma.2,24

 

If possible, obtain preoperative imaging and medical records to fully understand the nature and indication for the primary surgery.

 

Knowing if the original symptoms resolved or persisted after the initial procedure will help ascertain the etiology of the current symptoms.

 

 

Ask about any complications following surgery. Physical examination

 

 

A complete motor and sensory examination is essential for correct diagnosis of the offending cervical level. A map of the sensory disturbance can be drawn on the arm with a skin marker.

 

Evaluate the reflexes; include the biceps (C5), brachioradialis (C6), and triceps (C7). Note that normal reflexes diminish with age and an elderly patient with normal reflexes may be a manifestation of hyperreflexia.

 

Evaluate for signs of myelopathy; include Hoffman test, dysdiadochokinesia, inverted radial reflex, and the ulnar escape test. In the lower extremities, signs of myelopathy include clonus, an upgoing Babinski reflex, or a widebased gait.

 

Note whether the symptoms are unilateral or bilateral and if bowel or bladder dysfunctions are present.

 

Finally, rule out other potential causes of upper extremity dysfunction, including thoracic outlet syndrome, shoulder impingement/rotator cuff pathology, and/or peripheral nerve compression (cubital tunnel, radial tunnel, carpal tunnel syndromes).

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Plain radiographs, including anteroposterior, lateral, flexion, and extension views of the cervical spine should be obtained as part of the initial evaluation.

 

 

Evaluation of plain radiographs allows for comparison with prior studies to determine if there is deformity, hardware failure, graft subsidence, or spondylosis.

 

Flexion/extension view allows for evaluation of motion at a level suspected of pseudarthrosis or ASD.

 

In the case of spinal deformity, flexion/extension views provide information with respect to the reducibility of the cervical deformity to return to normal lordosis.

 

Oblique views of the cervical spine allow evaluation of the neural foramina, uncovertebral joint spurring, facet joints, and fusion mass.

 

CT scans

 

 

CT scans provide the best overall evaluation of the bony architecture of the cervical spine.

 

CT is the modality of choice for the evaluation of a fusion mass and to rule out pseudarthrosis.

 

Myelography of the cervical spine can be used in cases where an MRI scan is contraindicated. It is also useful in revision cervical surgery as instrumentation often obscures MRI imaging.

 

MRI

 

 

MRI is the modality of choice for evaluation of the soft tissues and neural elements.

 

The intervertebral disc and spinal cord are best visualized with MRI, which also has the ability to show intramedullary edema of the cord in cases of myelopathy.

 

MRI is noninvasive and does not require intradural contrast medium.

 

In cases of revision surgery, intravenous (IV) contrast medium is used to distinguish between scar tissue, which enhances on gadolinium MRI and recurrent disc herniation, which does not enhance with IV contrast medium as it lacks a blood supply.

 

MRI may be contraindicated in patients with pacemakers, spinal cord stimulators, and some cardiac stents.

 

Others modalities: nerve conduction studies/electromyography (EMG), bone scans, and pain blocks

 

 

Nerve conduction studies and EMG can be used to rule out peripheral nerve compression in cases where a peripheral cause is suspected. EMG can also assist with determination of the offending cervical level in cases where physical examination findings are confounding.

 

Nuclear tests including bone scans and, more specifically, a single photon emission computed tomography (SPECT) scan can assist in the diagnosis of pseudarthrosis. Both show increased uptake at the site of stress fracture or pseudarthrosis. The SPECT scan provides a better spatial representation of the cervical spine.

 

Selective nerve root blocks can provide therapeutic relief of pain symptoms and are often incorporated into the nonoperative management for recurrent cervical pain and radiculopathy. In addition, selective root blocks can provide diagnostic data in cases with complex pain or sensory distributions.

 

Laboratory workups including blood counts, chemistries, and the inflammatory markers erythrocyte sedimentation rate and C-reactive protein should be obtained prior to revision surgery to rule out infection as a potential cause of pain or dysfunction.

 

Physical examination (see Exam Table at back of volume for details)

 

 

Spurling test

 

 

 

Lhermitte phenomenon Hoffman reflex

 

 

Inverted radial reflex

 

 

Finger escape sign (ulnar escape sign) Impingement sign

 

Hawkins modified impingement sign

 

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Adson test

DIFFERENTIAL DIAGNOSIS

Discogenic, myofasciocutaneous, and cervical facet joint pain ASD

Deformity (PLK) Hardware/construct failure Pseudarthrosis

Recurrent pain from inadequate decompression during initial surgical procedure Peripheral neuropathies and pain syndromes that may mimic cervical pathology:

Thoracic outlet syndrome Parsonage-Turner syndrome Carpal tunnel syndrome

Cubital tunnel syndrome

 

Radial tunnel syndrome Wartenberg syndrome Ulnar tunnel syndrome

Shoulder impingement/rotator cuff disease

 

 

NONOPERATIVE MANAGEMENT

 

Surgical indications for revision cervical surgery are the same as those for primary surgery: radiculopathy, myelopathy, instability, progressive deformity, and tumor. Surgical outcomes for revision cervical surgery are much less predictable than for primary procedures. Every effort should be made to relieve the patient's symptoms with nonoperative measures prior to consideration of revision cervical surgery. Exceptions to this rule include progressive motor or gait impairment, persistent disabling pain and weakness (3 months),

 

progressive deformity, instability, and neurologic deficits with significant axial or radicular pain.24 Nonoperative modalities

 

 

 

Nonsteroidal anti-inflammatory drugs (NSAIDs) Isometric cervical strengthening/physical therapy Selective cervical root injections

 

 

 

Epidural steroid injections Pain management clinic Psychological evaluation

SURGICAL MANAGEMENT

 

A thorough understanding of the cause of the patient's symptoms is essential for appropriate surgical planning and management.

 

Surgical intervention should be considered in patients who have failed a trial of nonoperative intervention and who meet the indication for surgery—these being radiculopathy, myelopathy, instability, progressive deformity, and tumor.

 

The goals of surgical intervention are the following:

 

 

Stabilization of unstable segments

 

Decompression of the spinal cord or nerve roots in cases of myelopathy or radiculopathy

 

Correction of spinal deformity: This can be accomplished through an anterior, posterior, or combined approach and must be tailored specifically for each case.

 

Pseudarthrosis

 

 

In cases of pseudarthrosis, the goal is fusion of the failed segment. This can be accomplished through an anterior or posterior approach.

 

Posterior fusion augments stability, enhances the potential for eventual anterior fusion, avoids the risks of an additional anterior procedure, and is an excellent therapeutic alternative to a second anterior attempt at

stabilization.13

 

Posterior revision for pseudarthrosis has a 94% to 100% fusion rate.

 

Anterior revision for pseudarthrosis has less blood loss and shorter hospital stays. However, need for second revision is 44% in some series.3

 

Zdeblick et al29 and Coric et al4 support use of anterior revision with excellent result and solid fusion obtained by all treated.

 

ASD, residual compression

 

 

ASD is managed with ACDF at the adjacent level.

 

Management of residual compression or recurrent disc herniation is determined by the site of neurologic compromise. A revision ACDF or corpectomy may be required for significant anterior compression. A posterior keyhole foraminotomy can be made to decompress a soft disc herniation.

 

For extension of an anterior fusion to an adjacent level, previous hardware must be removed to allow for extension of the instrumentation. Knowing the manufacturer and required tools for removal is essential. Recently, stand-alone interbody devices have been introduced on the market that allow instrumentation at an adjacent level without removal of previous hardware.

 

Hardware/construct failure

 

 

Not all hardware failure requires revision surgery. Close follow-up with routine radiographs should be obtained in patients with asymptomatic hardware failure.

 

Surgical intervention is indicated in patients with neurologic compression or soft tissue compromise, instability, or progressive deformity.

 

Anterior failure is approached anteriorly. Posterior failure is approached from the back.

 

Hardware failure is often associated with significant inflammatory reaction and care should be taken as this can obscure the surgical approach.

 

In general, revision instrumentation can be replaced at the site of previous failure. If significant instability is present, a combined anterior/posterior stabilization should be performed.

 

Kyphosis

 

 

The general principles of cervical deformity correction are shortening of the posterior column, lengthening of the anterior column, and use of the PLL as a hinge to facilitate correction.

 

Three general approaches are used to address PLK:

 

 

Anterior-only approach: This approach corrects kyphosis through corpectomy and strut grafting or multilevel ACDF. The potential for lengthening of the anterior column through placement of interbody biomechanical devices or strut grafting is much greater than the potential of posterior osteotomies to shorten the posterior column. For this reason, an anterior procedure with or without a posterior approach

has become the preferred method of deformity correction.28

 

 

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Posterior-only approach: This approach uses lateral mass instrumentation with or without posterior osteotomy of the cervical spine to correct the deformity. This approach is limited to deformities that correct passively with flexion/extension views or deformities without significant anterior wedging.

 

Posterior fixation may be limited by poor bone stock following previous laminectomy. Anterior/posterior combined approach: This approach is useful for cases with significant anterior

instability and longer fusions over four segments. The combined approach allows for greater correction of sagittal plane deformity. Although potential for correction is greater with the combined approach, the added risk of a second procedure makes it less appealing to surgeons and patients. Of special note, in some patients with significant deformity with posterior arthrosis or fusions, a three-stage procedure may be required. The first stage performed is a posterior osteotomy of autofusion or levels of arthrosis with placement of instrumentation. The second stage is performed anteriorly with corpectomy and strut grafting or multilevel ACDF. The final stage is performed to secure the posterior fixation.

 

Posterior osteotomies for correction of kyphosis

 

 

Smith-Petersen osteotomy (SPO): This is an osteotomy through the posterior elements only. The lateral masses between two pedicles are resected at the levels of kyphosis, allowing extension of the spine.

SPOs can be performed at any level between C3 and C7.

 

Pedicle subtraction osteotomy (PSO): This is a threecolumn osteotomy involving resection of the posterior elements, pedicles, and a wedge-shaped resection of the vertebral body. A PSO allows for approximately 30 degrees of cervical extension. As the osteotomy passes through all three columns, acceptable levels for PSO are limited to C7 and T1. The vertebral artery passing through the foramen transversarium at C1-C6 makes PSO at these levels impossible.

 

 

 

 

FIG 2 • A. Patient in the supine position with a bolster between the scapulae, the head slightly extended. The shoulders are taped caudally to allow for visualization of the lower cervical levels. Ask the anesthesiologist to place the tube in the side of the mouth opposite the side anticipated for the approach. B. Patient in the prone position using the Mayfield headrest. The patient may also be placed in a prone view or soft face holder during the procedure. The arms are padded and tucked to the sides. The shoulders are taped caudally to allow for visualization of the lower cervical levels. For upper cervical surgery, the hairline must be trimmed prior to predraping.

 

Preoperative Planning

 

In most cases, an approach through a previously unexploited plane is the safest.

 

If the initial procedure was performed through a right-sided approach, then revision should be performed through a leftsided approach.

 

In cases of anterior surgery, consultation with an otolaryngologist for inspection of the vocal cords confirms that no injury has occurred to the recurrent laryngeal nerve. If vocal fold mobility is abnormal, the approach should be performed through the abnormal side to prevent injury to the healthy fold.

 

Consider neuromonitoring

 

Identify all implants prior to revision surgery.

 

Positioning

 

Modern neuromonitoring has decreased the need for surgeries performed under local anesthetic. This also allows for routine positioning in the prone and supine positions for almost all procedures.

 

Supine positioning: anterior cervical procedures (FIG 2A)

 

 

Patient is supine on a flat Jackson table or standard operating room (OR) table.

 

A bump or towel role is placed between the scapulae to promote cervical extension.

 

 

Tape is used to draw the shoulders down allowing for visualization of the cervicothoracic junction. Arms are tucked at the sides with foam around the wrists and elbows to prevent neurapraxia.

 

Padding is placed behind the knees and heels.

 

If using a standard OR table, the head rest can be extended to allow further lordosis. Flexion of head rest after placement of interbody grafts provides some compression prior to anterior plating.

 

Baseline neuromonitoring parameters should be established prior to draping.

 

Prone positioning: posterior cervical approaches (FIG 2B)

 

 

If a Mayfield headholder is to be used, this is placed with the patient in the supine position prior to flipping to the prone position.

 

 

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During placement of the Mayfield tongs, the adjustment arm should be in the forward position directly over the patient's nose. This allows the surgeon to confirm the tongs will not impinge on the nose during intraoperative adjustment of the tongs.

 

 

For most cases, we use a prone view headholder or a padded face rest. Neuromonitoring is attached prior to prone positioning.

 

 

 

The patient is gently turned to the prone position with the torso on bolsters or a four-point frame. If Mayfield tongs are used, attachment to the operating frame is the first priority following the flip. All bony prominences are padded to prevent neurapraxia.

 

Elbows and hands are padded and the arms tucked to the sides.

 

 

Tape is used to draw the shoulders down, allowing for visualization of the cervicothoracic junction. Fluoroscopy is used to confirm cervical alignment.

 

Baseline neuromonitoring parameters should be established prior to draping.

 

Deep vein thrombosis prophylaxis with thromboembolic deterrent hose and sequential compression devices should be initiated. A warming blanket should be placed prior to draping.

 

Approach

 

Anterior approach

 

 

A transverse incision is made at the level of pathology.

 

In general, the incision is made on the left side of the neck as the course of the recurrent laryngeal nerve is more predictable on the left side.

 

Superficial landmarks are used to determine the level of the incision. These landmarks are the following:

 

 

Hard palate: arch of the atlas

 

 

Lower border of the mandible: C2-C3 Hyoid bone: C3

 

 

 

Thyroid cartilage: C4-C5 Cricoid cartilage: C6 Carotid tubercle: C6

 

 

For longer exposures, a longitudinal incision is made just medial to the sternocleidomastoid (SCM) muscle. The platysma is split in line with the incision.

 

An interval is then developed between the SCM and carotid sheath laterally and the strap muscles with the tracheoesophageal structures medially.

 

The prevertebral fascia, a loose connective tissue layer, will be encountered over the anterior longitudinal ligament. The fascia is incised and stripped from the spine, exposing the anterior longitudinal ligament and longus colli muscles.

 

The level of pathology is marked with a spinal needle or disc marker and an x-ray obtained to confirm the correct level of pathology.

 

Tips for finding the correct level include palpation of the carotid tubercle and careful evaluation of preoperative x-ray for anterior osteophytes and their relation to the level of interest.

 

Once the level is confirmed, the longus colli are elevated bilaterally, and soft tissue retractors are placed below the muscle belly to expose the anterior body and uncinate processes bilaterally.

 

Posterior approach

 

 

The bony prominences of the posterior spine are palpated. C2 has a prominent spinous process as does C7 and T1.

 

 

A longitudinal incision is made in line with the spinous processes at the levels of pathology. Electrocautery is used to maintain hemostasis throughout the case.

 

The nuchal ligament is followed and divided as it courses down to the spinous processes. The paraspinal muscles in the cervical region often cross midline. The nuchal ligament appears as a lightly colored pale streak that follows the course of the paraspinal muscles. Following this streak will avoid cutting through muscle fibers and will ultimately lead to the spinous process.

 

X-rays are obtained with marker on spinous process to confirm correct-level surgery.

 

The deep layer of muscle is stripped from the spinous process and lamina close to the bone with the aid of electrocautery.

 

 

Subperiosteal dissection is carried laterally to the border of the lateral masses. Soft tissue retractors are placed for optimal visualization.

TECHNIQUES

• Anterior Revision Fusion for Pseudarthrosis or Recurrent Stenosis

   

   

  After anterior approach, previous anterior instrumentation is removed from the spine. Distraction pins are placed in the levels above and below the pseudarthrosis.

   

  Distraction is placed across the level of pathology, and the residual graft and fibrous tissue are removed with a curette or pituitary rongeur.

   

  In cases of severe collapse, the pseudarthrosis may literally be bone on bone. In this case, a high-speed burr is used to follow the “scar” or cleft left by the pseudarthrosis. This can be less than 1 mm wide.

   

  Periodically, stop and check the scar to confirm you are still in the correct plane. Opening and closing the distraction pins while looking at the pseudarthrosis will show micromotion in the plane of the nonunion.

   

  As the posterior cortex is thinned, a small forward-angled curette or micro-Kerrison can be passed through the cortex, and the posterior cortex can be removed.

   

  In cases of radiculopathy, the removal of the posterior cortex can be carried out laterally toward the foramen until a nerve hook can be passed out the foramen without impingement.

   

  In primary anterior surgery, resection of the PLL has been advocated for complete decompression. However, this should not be attempted in cases of previous PLL resection as there will be no true plane between the scarred PLL and the dura, increasing the risk of dural injury and cerebrospinal fluid leak. If previous operative notes suggest the PLL was undisturbed, it can be resected at the time of revision.

   

  97

   

  Following decompression, the interbody space is shaped to accommodate an interbody graft. The graft can be tricortical autograft or cortical strut allograft. Some controversy exists as to which grafting technique is most appropriate. All techniques mentioned here have found some supported literature.

   

   

   

  The graft is fashioned using a clamp and high-speed burr (TECH FIG 1). Following graft preparation, the block is inserted into the interbody space. Anterior plating is recommended in all cases of pseudarthrosis.

   

   

  X-rays are obtained to confirm appropriate placement of the graft and anterior plate. The incision is closed over a drain.

   

  Cervical collar is placed for immobilization.

   

   

   

  TECH FIG 1 • Graft preparation.

• Posterior Spinal Fusion for Anterior Pseudarthrosis

   

  After posterior exposure at the levels of anterior pseudarthrosis, all soft tissue is stripped from the lateral masses bilaterally.

   

  If radiculopathy is present, a laminoforaminotomy is performed. This technique is described in later text.

   

  Several methods of posterior instrumentation exist. At our institution, posterior fixation with lateral mass screws and rods is most frequently performed.

   

  A 2-mm high-speed burr is used to make a starting hole 1 mm medial to the center point on the lateral mass.

   

   

  A 2.4-mm drill bit is used to create a pilot hole for the 3.5-mm lateral mass screw. The direction of the drill hole is 15 degrees cephalad and 30 degrees lateral.

   

   

  Drilling begins with a 12-mm depth sleeve and can be increased by 2-mm increments. After drilling, a depth gauge is used to confirm appropriate screw length.

   

  The hole is tapped with a slightly undersized tap.

   

   

   

  The screw is inserted in the same trajectory as the drill and tap. These steps are repeated until all lateral mass screws are placed. The lateral masses and lamina are then decorticated.

   

  Appropriate length rods are contoured and then inserted into the heads of the screws bilaterally. Set screws are placed and tightened to appropriate torque.

   

  Bone graft is then placed over the decorticated lateral masses.

   

  Closure of the wound in layers.

   

  Cervical collar is placed for immobilization (typically for longer segmental reconstruction).

• Anterior Treatment of Postlaminectomy Kyphosis

   

  After anterior exposure, scar may be found over the apex of the deformity. Resection of the scar will allow for increased exposure and mobility of the spine.

   

  At each level of deformity, the intervertebral discs are excised using a pituitary rongeur, curettes, and a micro-Kerrison when needed. The discectomy should be carried down to the level of the PLL.

   

  Care should be taken to completely remove the cartilaginous endplate to prevent pseudarthrosis.

   

  In cases of associated radiculopathy, the foramen is decompressed. A nerve hook passed laterally into the foramen confirms the decompression is adequate.

   

  If multiple interbody grafts are to be used, trial spacers are inserted into the interbody spaces and appropriate grafts are selected for each level.

   

  The interbody grafts are contoured and inserted into the interbody spaces.

   

  If strut grafting is desired or required for adequate decompression, a corpectomy is performed by removing the anterior vertebral body with a rongeur.

   

  A trough is created 16 mm wide in the vertebral body.

   

   

  The trough is widened at the lateral uncovertebral joints and deepened to the level of the PLL. As the posterior cortex is approached, a high-speed burr is used to thin the bone.

   

  A small angled curette or micro-Kerrison can be introduced below the posterior cortex and this is resected.

   

  The superior and inferior vertebral endplates are prepared with the high-speed burr, creating decorticated bleeding cancellous beds with posterior lips to prevent displacement of the graft.

   

  A cortical strut is then fashioned from allograft fibula.

   

  Twenty pounds of traction is placed on the skull with an extension moment to allow for insertion of the contoured graft.

   

  The graft is inserted and tapped into place with extreme caution to avoid injury to the spinal cord or nerves.

   

   

  Anterior cervical plating is recommended in all cases. In multilevel ACDF, there are several sites for screw fixation. For strut grafting, screws are placed above and below the strut. Screws should not be placed through the graft as risk of graft fracture is substantial. If concerned about graft displacement, a nonabsorbable suture can be used to tie the graft to the plate.

   

• Posterior Approaches for Postlaminectomy Kyphosis

98

 

This approach is limited to minor deformities and those that passively correct to normal lordosis on flexion/extension views.

 

Prior to the procedure, the Mayfield headholder is positioned on the patient.

 

After prone positioning, the Mayfield is secured, and the head and neck are adjusted until appropriate lordosis is obtained. (Note: Neuromonitoring should be established and ongoing during any manipulation of the cervical spine with the patient under anesthesia.)

 

If lordosis is appropriate, lateral mass instrumentation can be placed as outlined previously in the technique for posterior fusion for pseudarthrosis.

 

If residual kyphosis is present, posterior osteotomies must be performed prior to lateral mass fixation.

 

Once the spine is exposed, the levels of kyphosis undergo posterior osteotomy. This often renders the posterior bone inadequate for isolated posterior fixation and anterior fusion becomes necessary.

 

If adequate bone stock is present after osteotomy, then posterior instrumentation with lateral mass screws and fusion is performed as outlined previously.

Combined Anterior Posterior for Postlaminectomy Kyphosis

 

Unless significant posterior fusions or arthrosis are present, the combined approach begins with anterior discectomy or corpectomy as outlined under the discussion of isolated anterior treatment of cervical kyphosis.

 

Once the anterior instrumentation is complete, the patient is turned to the prone position for lateral mass fixation with or without an osteotomy.

 

In general, short anterior procedures of three levels or less do not require posterior stabilization. In cases of four or more levels of reconstruction, posterior instrumentation should be considered.

 

 

Posterior fixation should also be considered in patients with poor bone stock or risks for pseudarthrosis. Posterior instrumentation is discussed in detail in the previous section.

 

Following combined anterior posterior fusion and instrumentation, the patient should be immobilized in a cervical collar for a minimum of 6 weeks.

Revision for Adjacent Segment Degeneration (Revision Anterior Cervical Discectomy and Fusion)

 

Revision surgery for ASD is similar in many ways to primary ACDF.

 

A major difference is the need for approach from a previously unexploited plane. Ear, nose, and throat (ENT) consultation should be obtained and, if vocal cords function normally, the anterior spine is approached from the side opposite that is used during the primary procedure.

 

A second difference is the potential need for hardware removal at the site of previous fusion. Every effort should be made to identify the hardware prior to revision surgery.

 

With these two exceptions, anterior treatment for ASD is ACDF as outlined under treatment of cervical disc herniation.

Laminoforaminotomy

 

Posterior laminoforaminotomy is useful for treatment of nerve root compression in cases of pseudarthrosis, adjacent level degeneration, or recurrent disc herniation at the site of previous anterior fusion.

 

 

After posterior approach at the level of nerve compression, the lamina and lateral mass are identified. A burr is used to thin the lateral lamina and medial facet.

 

A curved curette is used to create a plane between the medial facet and the ligamentum flavum.

 

The anterior facet capsule and additional bone are resected to visualize the exiting nerve root. (Care should be taken to avoid excessive resection of the facet; greater than 50% of this may cause iatrogenic instability to the cervical spine.)

 

The ligamentum is resected and the laminotomy is widened to expose the junction of the thecal sac and nerve root.

 

The foramen is probed with a Woodson or nerve hook to confirm decompression; if disc herniation is found, the PLL is incised and the disc fragment is removed.

 

The spine is closed in layers.

 

Soft cervical collar is provided for comfort.

 

 

Patient

selection

• Appropriate patient selection is the single most important step to reducing the

number of patients requiring revision cervical surgery.

Implants

• Identify all previously placed implants prior to revision surgery. Have specific

removal equipment available at the time of cervical revision surgery.

Nonoperative ▪ Nonoperative interventions including NSAIDs, physical therapy, and epidural

management injections should be attempted prior to surgical intervention.

Imaging

• Correlate patient symptoms with positive imaging findings to optimize patient

outcomes.

PEARLS AND PITFALLS

 

 

 

 

POSTOPERATIVE CARE

99

 

Immediate postoperative care after revision cervical surgery involves immobilization of the spine for 2 to 12 weeks, depending on the number of levels addressed during the surgery and the likelihood of instability or nonunion.

 

Short fixation over one to two segments is generally immobilized in a cervical collar for 2 weeks. At that time, the patient is allowed to gradually return to activities of daily living. Formal physical therapy evaluation for range of motion (ROM) and strengthening of the cervical spine is typically reserved until fusion mass is seen on plain radiographs.

 

Patients with longer fusion and those at risk for poor wound healing and pseudarthrosis are treated in a rigid cervical collar for a minimum of 6 weeks. Formal therapy is started once the fusion is visualized on plain x-rays.

 

Physical therapy following revision cervical surgery involves isometric strengthening and ROM prior to returning to unlimited activity.

 

OUTCOMES

Overall, revision surgery has less favorable outcomes when compared with primary surgical procedures.

Outcomes for revision for pseudarthrosis vary with the approach used for revision. Anterior revision surgery is associated with a 57% fusion rate. Several studies reported fusion rates of 94% following posterior revision for pseudarthrosis.

Zdeblick et al29 and Coric et al4 reported 100% fusion rates with anterior revision of interbody pseudarthrosis. Both autograft and anterior plating were advocated to increase fusion rates.

The rate of arthrodesis following surgery for ASD is lower in patients treated with interbody grafting (63%) versus those treated with corpectomy and strut grafting (100%). No statistical significance was found in the clinical outcomes between those treated with interbody fusion and corpectomy with strut

 

grafting.10

 

 

COMPLICATIONS

The risk of complications after revision cervical surgery is significantly higher than the risk associated with primary surgery. The overall risk of complication is reported at 27%.7

For each approach, the risk of complication associated with the primary surgery remains with the addition of risks associated with revision circumstances.

Anterior complications include the following:

Esophageal injury: a life-threatening injury; one-third recognized at time of surgery. Early recognition associated with 15% mortality; late recognition associated with 30% mortality.

Vocal cord paralysis: 15% of cases7 Dysphagia: 10% of cases

Neurologic injury/monoradiculopathy: 7% of cases Durotomy

Graft site complication

Posterior complications include the following: Neurologic injury

Durotomy

Significant wound complications/infection occurs at a rate of 1.2%.

 

 

REFERENCES

1. Albert TJ, Vacarro A. Postlaminectomy kyphosis. Spine 1998;23(24): 2738-2745.

    

    

2. Boden SD, Bohlman H. The Failed Spine. Philadelphia: Lippincott Williams & Wilkins, 2003.

    

    

3. Carreon L, Glassman SD, Campbell MJ. Treatment of anterior cervical pseudoarthrosis: posterior fusion versus anterior revision. Spine J 2006;6(2):154-156.

    

    

4. Coric D, Branch CL Jr, Jenkins JD. Revision of anterior cervical pseudoarthrosis with anterior allograft fusion and plating. J Neurosurg 1997;86(6):969-974.

    

    

5. Eck JC, Humphreys SC, Lim TH, et al. Biomechanical study on the effect of cervical spine fusion on adjacent-level intradiscal pressure and segmental motion. Spine 2002;27(22):2431-2434.

    

    

6. Farey ID, McAfee PC, Davis RF, et al. Pseudarthrosis of the cervical spine after anterior arthrodesis. Treatment by posterior nerve-root decompression, stabilization, and arthrodesis. J Bone Joint Surg Am 1990;72(8):1171-1177.

    

    

7. Gok B, Sciubba DM, McLoughlin GS, et al. Revision surgery for cervical spondylotic myelopathy: surgical

   results and outcome. Neurosurgery 2008;63(2):292-298.

    

    

8. Hilibrand AS, Carlson GD, Palumbo MA, et al. Radiculopathy and myelopathy at segments adjacent to the site of a previous anterior cervical arthrodesis. J Bone Joint Surg Am 1999;81(4):519-528.

    

    

9. Hilibrand AS, Fye MA, Emery SE, et al. Impact of smoking on the outcome of anterior cervical arthrodesis with interbody or strut-grafting. J Bone Joint Surg Am 2001;83-A(5):668-673.

    

    

10. Hilibrand AS, Yoo JU, Carlson GD, et al. The success of anterior cervical arthrodesis adjacent to a previous fusion. Spine 1997;22(14): 1574-1579.

     

     

11. Kozak JA, Hanson GW, Rose JR, et al. Anterior discectomy, microscopic decompression, and fusion: a treatment for cervical spondylotic radiculopathy. J Spinal Disord 1989;2(1):43-46.

     

     

12. Lawrence J, White A, Hilibrand A. Same segment disease after cervical spine surgery. Spine J 2007;7(5):55S.

     

     

13. Lindsey RW, Newhouse KE, Leach J, et al. Nonunion following twolevel anterior cervical discectomy and fusion. Clin Orthop Relat Res 1987;(223):155-163.

     

     

14. Lonstein JE. Post-laminectomy kyphosis. Clin Orthop Relat Res 1977;(128):93-100.

     

     

15. Lowery GL, McDonough RF. The significance of hardware failure in anterior cervical plate fixation. Patients with 2- to 7-year follow-up. Spine 1998;23(2):181-186.

     

     

16. Lowery GL, Swank ML, McDonough RF. Surgical revision for failed anterior cervical fusions. Articular pillar plating or anterior revision? Spine 1995;20(22):2436-2441.

     

     

17. Nowinski GP, Visarius H, Nolte LP, et al. A biomechanical comparison of cervical laminaplasty and cervical laminectomy with progressive facetectomy. Spine 1993;18(14):1995-2004.

     

     

18. Phillips FM, Carlson G, Emery SE, et al. Anterior cervical pseudarthrosis. Natural history and treatment. Spine 1997;22(14):1585-1589.

     

     

19. Robertson PA, Ryan MD. Neurological deterioration after reduction of cervical subluxation. Mechanical compression by disc tissue. J Bone Joint Surg Br 1992;74(2):224-227.

     

     

20. Robinson RA, Walker AE, Ferlic DC, et al. The results of anterior interbody fusion of the cervical spine. J Bone Joint Surg 1962;44(8): 1569-1587.

     

     

21. Simmons EH, Bhalla SK. Anterior cervical discectomy and fusion. A clinical and biomechanical study with eight-year follow-up. J Bone Joint Surg Br 1969;51(2):225-237.

     

     

22. Stevens JM, Clifton AG, Whitear P. Appearances of posterior osteophytes after sound anterior interbody fusion in the cervical spine: a high-definition computed myelographic study. Neuroradiology 1993;35(3):227-

    228.

     

     

23. Tribus CB, Corteen DP, Zdeblick TA. The efficacy of anterior cervical plating in the management of symptomatic pseudoarthrosis of the cervical spine. Spine 1999;24(9):860-864.

     

     

    00

     

24. Truumees E, McLain R. Failed and revision cervical spine surgery. In: Chapman MW, ed. Chapman's Orthopaedic Surgery, ed 3. Philadelphia: Lippincott Williams & Wilkins, 2001: 3846-3860.

     

     

25. Whitecloud TS III, Seago RA. Cervical discogenic syndrome. Results of operative intervention in patients with positive discography. Spine 1987;12(4):313-316.

     

     

26. Wu W, Thuomas KA, Hedlund R, et al. Degenerative changes following anterior cervical discectomy and fusion evaluated by fast spin-echo MR imaging. Acta Radiol 1996;37(5):614-617.

     

     

27. Zdeblick TA, Abitbol JJ, Kunz DN, et al. Cervical stability after sequential capsule resection. Spine 1993;18(14):2005-2008.

     

     

28. Zdeblick TA, Ducker TB. The use of freeze-dried allograft bone for anterior cervical fusions. Spine 1991;16(7):726-729.

     

     

29. Zdeblick TA, Hughes SS, Riew KD, et al. Failed anterior cervical discectomy and arthrodesis. Analysis and treatment of thirty-five patients. J Bone Joint Surg Am 1997;79(4):523-532.