ANATOMY

 

 

Familiarity with the anterior cervical anatomy is a necessity, particularly in regard to muscular, fascial, vascular, aerodigestive, nervous, and bony structures (FIG 1).

 

Approach level can be estimated by overlying anatomy:

 

 

C3: hyoid bone

 

C4-C5: thyroid cartilage

 

 

C6: cricoid cartilage, carotid tubercle Muscular anatomy

 

The only muscle transected in the approach is the platysma, which lies superficially, just under the subcutaneous fat layer.

 

The sternocleidomastoid extends from the mastoid inferomedially to the sternomanubrial articulation and provides a lateral border for the exposure.

 

The omohyoid traverses the approach to the anterior cervical spine at approximately the C6 level and may be retracted or resected.

 

The longus colli muscles lie on the anterolateral surface of the cervical spine and are more widely spaced in the caudal direction than the cephalad. The position of the longus muscles is helpful in identifying the midline of the vertebral bodies.

 

Fascial planes

 

 

Superficial cervical fascia—lies just deep to the dermis and surrounds the platysma

 

Deep cervical fascia

 

Superficial layer: Also called the investing layer, this forms a collar around the neck and contains the sternocleidomastoid, among other structures, and blends with the lateral aspect of the carotid sheath.

 

Middle layer: Muscular part surrounds the strap muscles and great vessels, whereas the visceral part (also known as pretracheal fascia) encloses the anteromedial structures of the neck (aerodigestive tract and thyroid gland). It blends laterally with the carotid sheath.

 

 

 

FIG 1 • Cross-sectional view of the cervical spine with avenue of Smith-Robinson approach drawn.

 

 

Deep layer: The prevertebral part closely surrounds the vertebral column and prevertebral muscles. The alar part lies between the prevertebral and pretracheal fascia and defines the posterior border of the retropharyngeal space.

 

 

Vascular structures

 

 

The anterior and external jugular veins take variable courses superficial to the sternocleidomastoid and deep to the platysma.

 

The carotid artery and internal jugular vein are contained in the carotid sheath and help define the lateral margin of the deep exposure.

 

The vertebral arteries enter the transverse foramen at the C6 level in most (˜90%) of cases. The vertebral artery lies around 1.5 mm laterally to the uncovertebral joints in the middle cervical spine, although this is somewhat variable. The course of the vertebral artery takes is more medial, closer to the uncinate processes

 

more rostrally.43 Neural structures

 

The recurrent laryngeal nerve ascends from the thoracic cavity in the tracheoesophageal groove to innervate all the intrinsic muscles of larynx with the exception of the cricothyroid.

 

The right recurrent laryngeal nerve arises in anterior to the subclavian artery and takes a more anterior course in the neck than does the left nerve, which arises more distally near the arch of the aorta.

 

Superiorly, the superficial laryngeal nerve crosses lateral to medial at the level of the hyoid to pierce the thyrohyoid membrane, at the level of the C3-C4 interspace, and provides innervation to the cricothyroid muscle as well as sensory innervation to the posterior pharynx.38,52

 

The spinal radicular nerve exits the spinal canal through the neural foramen at approximately 45-degree angle to the cord in the axial plane.

 

Bony and ligamentous structures

 

 

The anterior longitudinal ligament (ALL) overlies the anterior aspect of the vertebral column and closely adheres to the intervertebral disc and endplate.

 

 

The disc underlies the ALL and is composed of a tough outer annulus fibrosus surrounding a soft gelatinous core, the nucleus pulposus.

 

The annular fibers are attached to the subchondral bone of the adjacent vertebral bodies.

 

The posterior longitudinal ligament (PLL) runs down the posterior aspect of the vertebral column and is more robust centrally.

 

The uncovertebral joints, or uncinate joints, are situated laterally in the intervertebral space and serve as a landmark for anterior cervical decompressions.

 

 

Foraminal stenosis is often caused by hypertrophic degeneration of the uncinate joints.

 

 

70

PATHOGENESIS

 

Arthritic degeneration can affect any mobile joint in the spine.

 

 

Facet joint: neck pain (not treated with arthroplasty)

 

 

Uncovertebral joints: foraminal stenosis causing radiculopathy Disc space

 

Osteophytic degeneration can cause central stenosis and myelopathy or radiculopathy.

 

Herniated disc fragments can be associated with significant inflammatory response and profound acute symptoms of radiculopathy or myelopathy.41

 

 

Risk factors for arthritic degeneration23,59

 

 

Genetic predisposition

 

 

Age Tobacco use

 

 

Activity/occupation (heavy manual labor) Obesity (body mass index [BMI] >30)

 

NATURAL HISTORY

 

The natural history of cervical radiculopathy is most often benign, with about 70% of patients having spontaneous improvement.24,31,48

 

 

Symptoms can recur or take on a waxing and waning course.

 

Between 6% and 35% matriculate to surgical intervention.

 

The natural history of myelopathy is controversial and appears to most often have a course of episodic or steady decline while improving with conservative treatment in only a minority of patients.32

HISTORY AND PHYSICAL FINDINGS

 

Radiculopathy

 

 

Patients often present with dermatomal pain, sensory changes (numbness, paresthesias), and weakness (Table 1).

 

May have dull ache in neck, shoulder, and scapula49

 

Often worse with extension; lateral rotation and bending toward symptomatic side; or when straining, sneezing, or coughing

 

Neurologic examination may be normal or reveal segmental weakness and reflex deficit.

 

Myelopathy

 

 

Over 50% of patients may present without significant painful complaints.13 Often presents as insidious decline of upper and lower extremity motor function:

 

Clumsiness of hands

 

Root

Motor Function

Sensory Distribution

Reflex

 

Table 1 Cervical Radicular Function

C3

Diaphragm

Upper neck

C4

Diaphragm

Neck, upper

shoulder, and chest

C5

Shoulder abduction (deltoid), elbow flexion

(biceps), external rotation of arm (supraspinatus/infraspinatus; diaphragm)

Shoulder, lateral

arm to anterior forearm

Biceps,

brachioradialis

C6

Wrist extension, elbow flexion, forearm

supination

Anterior arm and

forearm to thumb and index finger

Biceps,

brachioradialis

C7

Elbow extension, wrist flexors, finger extensors

Lateral arm, dorsal

forearm to middle three fingers

Triceps

C8

Intrinsic, thumb extension, wrist ulnar deviation

Back of arm to little

and index fingers

Pronator

 

 

 

Gait instability Sensory dysfunction

 

Physical examination can reveal the following:

 

Weakness, often greatest in hands

 

 

Muscle wasting, often greatest in hands Spasticity

 

Hyperreflexia with pathologic reflexes (Hoffman sign, Babinski sign)

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Plain x-rays may demonstrate arthritic changes such as disc space narrowing, subchondral sclerosis, osteophyte formation, and foraminal stenosis (with oblique views) as well as overall alignment of neck and evidence of instability.

 

Computed tomography (CT) clearly delineates bony changes and may demonstrate bony foraminal compression. CT may be useful in evaluating for suspected ossification of the PLL when considering arthroplasty. CT myelography is useful in evaluating for the presence of neural compression in patients who are

unable to undergo magnetic resonance imaging (MRI) and in those who have been previously instrumented.33

 

MRI is the imaging modality of choice for the evaluation of cervical radiculopathy or myelopathy and is sensitive in detecting disc herniations, osteophytes, spinal cord signal abnormalities, and central and foraminal stenosis.

 

Other modalities, including electrodiagnostic studies (electromyography [EMG]) and injections, may be used to clarify a diagnosis in difficult cases.

 

DIFFERENTIAL DIAGNOSIS

Cervical radiculopathy Cervical myelopathy Tumor (cranial or spinal) Stroke

Motor neuron disease Multiple sclerosis Syringomyelia Brachial plexopathy

Parsonage-Turner syndrome Thoracic outlet syndrome Radiation plexopathy

Peripheral nerve entrapment

71

Musculoskeletal

Shoulder disease (eg, rotator cuff) Myofascial pain syndrome Infection

Tumor Tendinitis

Inflammatory arthropathy

 

Cardiac ischemia

Chest pathology

Reflex sympathetic dystrophy

 

 

NONOPERATIVE MANAGEMENT

 

Nonoperative treatment should be attempted in most patients with radiculopathy.

 

Physical therapy or placement of a cervical collar have both been shown to be efficacious in acute (<1 month

duration) symptoms and nonefficacious in cases of long-standing (>3 months) radiculopathy.31,42,45 Medications

Anti-inflammatory medications

“Nerve medications”—gabapentin, amitriptyline, Lyrica Narcotics—limited role

Injections—epidural steroid injection and selective nerve root block can be therapeutic and predictive of surgical outcome.54,60

Cervical myelopathy can be treated conservatively with a collar in patients unable or unwilling to undergo surgical decompression.28,29

SURGICAL MANAGEMENT

Surgical intervention is indicated in cases of radiculopathy remittent to conservative care and in cases of progressive weakness.

Surgical intervention is indicated for cervical myelopathy in the presence of a compressive spinal cord lesion.

 

Indications

Treatment of symptomatic degenerative disease of the cervical spine, including disc degeneration, herniation, and osteophyte formation causing radiculopathy or myelopathy.

Symptoms resistant to conservative care for over 6 weeks or progressive neurologic deficit. Treatment of degeneration or disc disease in cervical levels C2-C3 and C6-C7.

The Mobi-C cervical disc was U.S. Food and Drug Administration (FDA) approved in 2013 for two-level cervical arthroplasty.

Cervical disc replacement remains controversial for the treatment of adjacent level disease.

 

 

Contraindications

Significant sagittal plane deformity (angulation >20 degrees) Instability (>3.5 mm of motion in flexion/extension or spondylolisthesis)

Severe disc space collapse with limited range of motion (<2 degrees of motion) Significant facet arthrosis

Ossification of the PLL

Treatment of fractures, infections, and tumors

 

Osteoporosis

 

 

Preoperative Planning

 

Films should be thoroughly examined for anomalous anatomy, such as an aberrant vertebral artery course, and for other possible causes of the patient's symptoms. The depth and height of the disc space can be measured to estimate the size of the potential implant. Preoperative measurements should always be confirmed intraoperatively as endplate preparation will alter dimensions.

 

Positioning

 

The patient is positioned supine with a small bump under the shoulders and the head in a doughnut in slight extension. A radiolucent table is used to allow for anteroposterior (AP) and lateral fluoroscopy.

 

The shoulders may need to be retracted inferiorly with tape to allow visualization of more caudal levels in large patients. Overly aggressive retraction should be avoided to reduce risk of brachial plexus injury.

 

Approach

 

A standard Smith-Robinson approach is used to access the anterior cervical spine.

 

On initial exposure, the level of interest is confirmed radiographically, and the midline of immediately adjacent cephalad and caudad levels are marked with Bovie electrocautery prior to elevation of the longus muscles (FIG 2). Using a marking pen over the cauterized bone can help to more clearly delineate and preserve midline markings.

 

After the midline is clearly marked, the medial border of the longus colli muscle is incised with the Bovie electrocautery, and a longus flap is elevated. The longus should be elevated over approximately one-half the height of the adjacent vertebral body with care taken to preserve the annular attachments of the adjacent level. A self-retaining retractor is placed underneath the flap.

 

 

 

FIG 2 • Illustration showing exposure of the anterior cervical spine. The longus colli are used to identify the midline, which is then marked with Bovie electrocautery and a marking pen.

 

 

72

TECHNIQUES

• Discectomy

The disc space is incised with a no. 15 blade scalpel, and a partial discectomy is performed with pituitary rongeurs.

A 3-0 curette is then used to separate the attachment of the annular fibers to vertebral endplate at the lateral margins of the disc space.

The separation with the curette proceeds from lateral to medial and superficial to deep, allowing for the lateral aspect of the disc to be removed en bloc.

This technique allows for rapid identification and exposure of the uncovertebral joints and thus the lateral margins of the exposure.

 

 

The disc is removed posteriorly to the PLL.

Use of Distraction: Pins, Tongs, Spreaders

 

Distraction posts may be placed before or after the discectomy, although placing posts after the discectomy allows better definition of the vertebral endplates and an improved understanding of their trajectory.

 

Although we place distraction posts in a mildly divergent trajectory when performing fusion, to reestablish cervical lordosis, we place them parallel in arthroplasty so as not to introduce hyperlordosis and for better fitment of the implant. The ProDisc system comes with unique distraction posts which should be placed parallel to the adjacent endplate as outlined in the following text.

 

The superior post should be placed high in the vertebral body so as not to interfere with endplate preparation, as the anteroinferior margin of the superior vertebral body often has an overhang which must be milled flush with the rest of the endplate to accommodate the implant.

 

Distraction about the endplate should be employed only to aid in visualization for neural decompression. Overdistraction during implant sizing and placement may lead the placement of an oversized implant which will have suboptimal mobility.

Endplate Preparation

 

The cartilaginous endplates are removed with care taken to preserve the integrity of the bony endplate as this will provide the structure to prevent subsidence. The cartilaginous endplates can often be removed with curettes. Alternatively, the high-speed drill can be used.

 

The inferior endplate of the superior level is most often concave, with an inferiorly protruding lip at the anteroinferior aspect. A high-speed drill is used to mill this flush with the posterior aspect of the endplate to create a broad, flat surface for implant apposition.

 

The superior endplate of the inferior level requires less preparation to create a flat surface. It is often slightly concave in the coronal plane, and the high-speed drill is used to mill down the proud lateral aspects and create a flat surface to accommodate the implant.

 

The final endplate preparation should be performed without distraction across the disc space to ensure flush and parallel endplates in the neutral position. A rasp can be used after burring to remove any small irregularities.

• Foraminotomy and Osteophytectomy

   

  An aggressive foraminotomy is needed with arthroplasty as motion will be preserved and incomplete decompression will result in recurrent symptoms. Furthermore, foraminal expansion by means of distraction is not used in arthroplasty as an oversized implant will result in reduced motion due to increased ligamentous tension.

   

  The PLL is left intact for the initial foraminotomy to protect the underlying neural elements.

   

  The high-speed burr is used to perform the majority of the foraminotomy. We use the burr with a horizontal back and forth motion to remove posteriorly protruding osteophytes off the uncinate process. The burr can also be used in circular motion at the foraminal opening to enlarge the foramen. The burr should be operated under continuous motion and with frequent irrigation to prevent thermal injury to the underlying nerve root.

   

  Final osteophytectomy can be accomplished with a small upgoing curette used in a rotational motion. The cutting edge of the curette can be angled in to bone for safe removal with minimal intrusion into the foraminal space.

   

  A small (2 mm) Kerrison rongeur can also be used to expand the foraminotomy. Care should be taken to angle the butt of the instrument directly against the thecal sac to minimize chances of injuring the

  underlying exiting nerve.

   

  Small instruments should be used when enlarging to foraminal opening to avoid traumatic damage to the exiting nerve.

   

  Adequate foraminal decompression is confirmed by placing a nerve hook out the neural foramen without resistance.

   

  The high-speed burr can also be used to remove posteriorly protruding osteophytes. The burr should be angled to attack the junction of the osteophyte and normal vertebral body, to reduce the chances of drilling out the endplate and more efficiently disconnect and remove the osteophyte. Final osteophytectomy can be accomplished with an upward angle curette used in a twisting motion.

   

  Resection of posterior osteophytes can be confirmed by placing a nerve hook or upgoing curette posterior to the vertebral bodies and taking a fluoroscopic image. The instrument should lie flush with the posterior aspect of the vertebral body (TECH FIG 1).

   

   

  Anterior osteophytes should also be removed, either with rongeurs or a high-speed burr, to ensure flush fitment of devices with anterior flanges (eg, Prestige ST).

  73

   

   

   

  TECH FIG 1 • A. Fluoroscopic image demonstrating residual posterior osteophyte underlying nerve hook. B. Image after osteophyte has been removed, showing flush apposition of the nerve hook to the posterior vertebral body.

• Posterior Longitudinal Ligament Resection

   

  The question of whether to resect the PLL in all cases of cervical arthroplasty is controversial.

   

  PLL resection results in increased segmental motion without instability, which may aid the goal of arthroplasty.36,50

   

  PLL resection may further aid in the adequate posterior positioning of the implant, especially in cases of significant arthritic degeneration, and may aid in restoration of a physiologic instantaneous axis of rotation.

   

  PLL resection should be performed in all cases of posterior disc extrusion in which a fragment may be situated dorsal to the ligament.

   

  The first step in resecting the PLL is the creation (or identification) of a rent in the ligament, allowing access to the epidural space. A rent may be present in cases of posteriorly herniated fragments, whereas one can otherwise be created with an upgoing curette.

   

  The curette can be used in a rotational cephalocaudal fashion to slip between the fibers of the PLL and enter the epidural space.

   

  Once the rent in identified or created, it can be expanded with an upgoing curette.

   

  A small (2 mm) Kerrison can then be used to resect the ligament. Using the Kerrison at the intersection of the ligament and vertebral body ensures efficient resection.

   

  Care must be taken to minimize dorsal pressure on herniated fragment behind the PLL with the butt end of the Kerrison rongeurs.

   

  Care is also taken when resecting the ligament laterally to avoid grasping the exiting nerve root with the Kerrison rongeur.

• Prestige ST

   

  The footprint size of the Prestige ST implant (TECH FIG 2) can be estimated preoperatively by measuring endplate depth and width on the preoperative MRI or CT.

   

  As large a footprint as possible should be chosen.

   

  The height of the device can more accurately be determined intraoperatively, as the height of the disc space, and thus that of the appropriate implant, will be altered by the endplate preparation.

  Sizing

   

   

  After the decompression is complete, a trial spacer is used to confirm implant size. The spacer should slide smoothly into the disc space without distraction applied.

   

  If distraction is needed to place the trial, a smaller trial should be placed or the endplates should be further milled.

   

  Care is taken to ensure midline placement of the trial, as marked previously.

   

  Final position is confirmed with biplanar fluoroscopy with AP views used to confirm midline position.

  Placement

   

  Anterior osteophytes are removed with rongeurs or the high-speed burr to ensure that the implant sits flush with anterior vertebral body.

   

  The profile trial, which is angled to slide into the prepared disc space, is then used to confirm adequate anterior osteophyte resection and flush fitment of the implant (TECH FIG 3A).

   

  Following preparation, the appropriate-size implant is loaded into the loading block and inserted into the disc space.

   

  The implant is directional, with a slight cranial inclination, and should slide easily into the disc space, although gentle tamping with a mallet is sometimes needed.

   

   

   

  TECH FIG 2 • The Prestige ST implant.

   

   

  74

   

   

   

  TECH FIG 3 • A. The profile trial spacer is used to confirm adequate milling of anterior osteophytes. Anterior (B) and lateral (C) views of the implant inserted into the disc space, mounted on the inserter with incorporated drill guide.

   

   

  Prospective screw tracts are then created using the drill placed through a guide in line with the holes in the insertion device. The 13-mm drill guide is typically used (TECH FIG 3B,C).

   

  The drill guide is removed and the screws are then partially placed through the inserter. All four screws are then sequentially tightened and the inserter is removed.

   

  Locking screws are placed over the screw heads to prevent back out.

  Confirmation

   

  Final position of the implant is confirmed with AP and lateral fluoroscopy. Motion can be confirmed by manipulating the patient's head through the drapes.

• ProDisc-C

  Sizing and Distraction

   

  The size of the ProDisc-C implant (TECH FIG 4) can be estimated on preoperative imaging studies.

   

  On initial exposure, the midline is marked using the fluoroscopy. A lasting mark is made by using the Bovie to burn down the bone and then using a marking pen over this mark.

   

  The distraction screws are then placed in the distal one-third of the adjacent vertebral bodies.

   

  An initial perforation of the anterior cortex is created, and the screws are placed parallel to the adjacent endplates. The screws are placed under fluoroscopic guidance as deeply as possible.

   

  It is important to place the screws distally enough to allow for the implant keels to be placed between them (TECH FIG 4B).

   

  The retainer is then placed over the screws, and a partial discectomy is performed.

   

  The vertebral distractor is placed in the disc space, and the distraction is applied across the operated level. The distraction is maintained in a parallel fashion with the retainer and the distractor is removed.

   

   

   

  TECH FIG 4 • A. The ProDisc-C implant. B. The distraction posts are placed parallel to the adjacent endplates.

  Trial Fitting

   

  The discectomy and decompression are completed.

   

  Trial implants are then placed into the disc space. The implant with the largest possible footprint is chosen. The trial should be inserted flush with the posterior aspect of the vertebral body in the midline.

   

  Distraction is released, and the trial handle is removed to leave the trial in the disc space. Care is taken not to over distract the interspace, which may compromise implant motion.

   

  A 5-mm implant is most commonly selected. AP and lateral fluoroscopy images are then taken to confirm adequate position (TECH FIG 5A).

   

  The milling guide is next placed over the shaft of the trial implant and secured with a locking nut. A retention pin is placed through the superior hole of the guide.

   

  A power drill is used to create the inferior hole under fluoroscopic guidance. The drill is sunk to the level of the stop and

   

  75

  then rotated to the limits of the stop in a cephalad and caudal angulation. The drill is removed, a retention pin is placed in its spot, and the process is repeated at the cephalad level (TECH FIG 5B,C).

   

   

   

  TECH FIG 5 • A. The trial is placed to be flushed with the posterior vertebral body line. The stops can be adjusted for optimal depth positioning. Anterior (B) and lateral (C) depictions of the milling guide placed over the trial. The guide sets the limits of bone removal to accommodate the implant keel.

   

   

  The box chisel is next placed over the shaft of the trial and advanced into the vertebral bodies with a mallet under fluoroscopic visualization. Prior to impaction, it is confirmed that the trial stop is seated securely against the anterior face of the vertebral bodies.

   

  The box-cutting chisel is next used over the implant. Prior to removal of the box-cutting chisel, a small amount of distraction is reintroduced around the operated level through the distraction pins.

   

  Excess bone is removed from the keel tracts with the keel cut cleaner. Symmetric depth of the superior and inferior keel cuts is also confirmed—the posterior edge of both keels should be identical when measured from the posterior vertebral body wall.

   

  A position gauge can be used to confirm adequacy of the final bone work to accept the implant.

  Placement

   

  The implant is prepared in the implant inserter with the appropriately sized spacer and keels with care taken to maintain the superior and inferior directionality of the keels.

   

  The implant is then advanced into the prepared disc space under fluoroscopic control.

   

  The inserter, retainer, and retainer screws are then removed and final position is confirmed with AP and lateral fluoroscopy (TECH FIG 6).

   

   

   

  TECH FIG 6 • A. The implant is tamped into the defect under fluoroscopic guidance with care taken to ensure that it is fully seated posteriorly. B. Anterior view of the final implant.

• Bryan Cervical Disc

Selection Criteria

 

There are strict criteria for a Bryan cervical disc prosthesis (TECH FIG 7A).

 

Patients are not eligible if they exhibit hypermobility, instability, degenerative disease, facet joint pathology, or severe osteoporosis.

 

The prosthesis is most appropriate for single-level radiculopathy or myelopathy from a herniated disc or uncovertebral osteophyte at C4-C5 or C5-C6, although C3-C4 and C6-C7 may be appropriate based on patient anatomy.58

 

The implant size and sagittal slope are determined based on preoperative imaging56,58 (TECH FIG 7B,C).

 

 

 

TECH FIG 7 • A. The Bryan disc implant is made of two porous convex shells over a central access port. There are two anterior stops that will sit on the vertebral endplate. (continued)

 

 

76

 

 

 

TECH FIG 7 • (continued) B. The Bryan disc in situ. C. Cross-section of the Bryan disc prosthetic. The void is around the center post between the endplates and the nucleus. The nucleus is convex at the center and concave at the border.

Positioning

 

The patient is placed supine with the neck in a neutral position, which can be achieved by placing a rolled towel under the neck55,58 (TECH FIG 8).

Exposure and Decompression

 

The initial exposure and discectomy is carried out using the usual Smith-Robinson approach.

 

A 0.5-mm sagittal cam distractor is then used to measure the disc space height and segment mobility.

 

At this point, if there is hypermobility, the case may be converted to a standard anterior cervical fusion.

 

The gravitational referencing system is then constructed and the extensions are attached to the operating table side rails.

 

The retractor frame is centered a few centimeters above the wound in parallel with the spine. This will be used to determine the intraoperative sagittal angle of the disc space (TECH FIG 9A).

 

The center of the disc is defined using the milling jig, which sits between the uncovertebral joints and finds the center.

 

A sagittal wedge is placed into the disc space under fluoroscopic guidance (TECH FIG 9B).

 

The milling fixture is set to the sagittal slope measurement and screwed into the vertebral body above and below the disc space.

 

The milling technique, drilling along the y-axis, creates concave surfaces to exactly match the convex porous-coated Bryan disc endplates.

 

 

 

TECH FIG 8 • Positioning for the Bryan disc.

 

 

The lateral dimension for the implant is then verified with fluoroscopy (TECH FIG 9C).

 

Final decompression of the neural foramen and canal can then be completed while preserving the uncovertebral joints.

 

 

 

TECH FIG 9 • A. The Bryan frame in its final position. A towel has been rolled behind the neck to support physiologic cervical lordosis. B. The milling disc moves along the x-axis to prepare the vertebral recess. There is a hook in the slit of this apparatus which prevents damage to the thecal sac. C,D. Intraoperative lateral fluoroscopy. C. Milling depth gauge at the anterior edge of the vertebra (white arrow), anchor screws (black arrows), retractor blades (white asterisk), and endotracheal anesthesia tube (black asterisk). D. Burring depth gauge at the posterior vertebral edge and the remainders of the PLL (white arrow). (A,C,D: From Wenger M, Markwalder TM. Bryan total disc arthroplasty: a replacement disc for cervical disc disease. Med Devices [Auckl] 2010;3:11-24.)

 

 

77

Sizing

 

The correct size of the Bryan disc is determined by preoperative review of imaging and intraoperative measurements using a milling depth gauge.

 

The trial prosthesis size burring block ring is attached to the frame and inserted to the level of the PLL using fluoroscopic guidance.

 

The anchor screws are left in place as the burr and assembly is removed.

Placement

 

The Bryan disc is then filled with sterile saline and attached to the introducer via the superior and inferior projections of the Bryan disc.

 

An intervertebral distractor is inserted and the disc is hammered into position under lateral fluoroscopy. Correct positioning is confirmed with AP imaging and ensures a low profile in the intervertebral space (TECH FIG 10).

 

The anchor screws are then removed and the wound is closed in the standard fashion.55

 

 

 

TECH FIG 10 • In situ Bryan disc with low profile in the intervertebral space at the end of the procedure.

• Mobi-C Disc

Selection

 

The Mobi-C disc (TECH FIG 11A) is approved for one- and two-level cervical arthroplasty from C3 to C7 for degenerative disease or herniated nucleus pulposus with radiculopathy or myelopathy.

 

Patients with severe osteoporosis, malignancy, prior cervical spine surgery, obesity, or heavy tobacco use are not candidates for this procedure.15

 

 

 

TECH FIG 11 • A. The Mobi-C disc endplates are made of components of cobalt-chromium alloy coated with plasmasprayed titanium and hydroxyapatite coating. The insert nucleus is polyethylene. The goal is to restore height while maintaining rotation of the segment. B. Range of motion in flexion-extension and lateral bending for the Mobi-C disc. (A: Courtesy of LDR, Austin, Texas; B: From Kim SH, Shin HC, Shin DA, et al. Early clinical experience with the Mobi-C disc prosthesis. Yonsei Med J 2007;48: 457-464.)

 

 

Preoperative measurements on CT and MRI are used to estimate the size of the implant(s) (TECH FIG 11B).

Positioning

 

The patient is positioned with a neutral neck in anatomic lordosis. A towel can be placed under the patient's head or neck to achieve this position. Halter traction may be used for positioning.

Exposure and Distraction

 

A standard Smith-Robinson anterior exposure is performed at the most diseased level first to obtain restoration of disc height as well as lordosis and sagittal balance.44

 

The Caspar retractor fixation pins are then inserted 5 mm from the superior and inferior vertebral body endplates (TECH FIG 12).

 

Resection of the PLL is at the discretion of the surgeon.

 

Osteophytes are removed and the uncovertebral joint identified bilaterally to ensure bilateral

decompression of the foramen.39,44

 

Minimal endplate milling is advised for this procedure.

Sizing

 

The width gauge is used to estimate the size of the implant. The implants are 15, 17, and 19 mm.

 

The depth of the disc space can be measured by a hook placed behind the posterior edge of the vertebral endplate. There are 13- or 15-mm depth implants (TECH FIG 13).

 

The available implant heights are 5, 6, and 7 mm. One should start with the shortest trial, and the implant should not exceed the height of healthy adjacent discs.

Placement

 

A trial implant is tamped into place using a self-retracting inserter under fluoroscopic guidance within 1 mm of the posterior vertebral body wall (TECH FIG 14A).

 

The self-retracting inserter has a stop which is set to 0 to 5 mm by the surgeon.

 

 

An implant holder is used to place the Mobi-C disc in alignment with the disc space and to keep contact with the anterior wall of

78

the vertebral body as the implant is hammered into place under fluoroscopy.

 

 

 

 

TECH FIG 12 • Caspar pin distraction. (Courtesy of LDR, Austin, Texas.)

 

 

The groove in the inserter should be at the midline of the disc space (TECH FIG 14B).

 

At this point, the universal implant inserter and disposable implant holder are released (TECH FIG 14C).

 

 

 

TECH FIG 13 • Measurement of trial depth. (Courtesy of LDR, Austin, Texas.)

 

 

The Caspar pins are compressed to seat the teeth of the implant into the vertebral bodies. The position of the implant is confirmed using AP and lateral fluoroscopy (TECH FIG 14D).

 

 

This technique is repeated for desired adjacent levels (TECH FIG 14E). Closure is undertaken in the standard fashion.15,39,44

 

 

 

TECH FIG 14 • A. Insertion of trial Mobi-C implant. B. Insertion of Mobi-C disc using universal inserter. C.

Removal of universal inserter. D. Removal of Caspar distractors. (continued)

 

 

79

 

 

 

TECH FIG 14 • (continued) E-G. Radiographic range of motion for Mobi-C implant. (A-D: Courtesy of LDR, Austin, Texas; E-G: From Kim SH, Shin HC, Shin DA, et al. Early clinical experience with the Mobi-C disc prosthesis. Yonsei Med J 2007;48:457-464.)

POSTOPERATIVE CARE

 

Bracing is not typically used postoperatively.

 

A drain may be placed depending on surgeon preference.

 

Most patients are admitted for a single hospital day, although some surgeons perform single and two-level arthroplasty on an outpatient basis.

 

Diet is advanced as tolerated. Dysphagia, when experienced, is usually transient and may mandate a slower advance of diet.

 

Nonsteroidal anti-inflammatory drugs (NSAIDs) may be given postoperatively and may have a role in decreasing the incidence of heterotopic ossification.37

 

Activity is restricted with no heavy lifting or high-impact activity for 6 weeks. After 6 weeks, patients are encouraged to slowly resume their activity to preoperative levels.

 

OUTCOMES

 

Recent reports from randomized trials of the four devices described here demonstrate significant improvements or trends toward improvements in Neck Disability Index (NDI), arm pain, neck pain, SF-36, Visual Analog Scale (VAS) neck pain score, and VAS arm pain score postoperatively.30,68 Reports also

show a reduced need for further surgery when compared to fusion at 4 and 5 years.7,18,40

 

Although not statistically significant, these reports demonstrate trends among the arthroplasty groups toward a greater improvement in quality of life and reported pain scores across all postoperative time frames from 6 weeks to 1 year.16,53,67

 

There does not appear to be a significant difference in operative time, length of hospital stay, or perioperative complications between the arthroplasty and fusion groups.2,12,20,21

 

A recent meta-analysis of prospective randomized studies showed no statistical difference between the fusion and arthroplasty groups' rate of adjacent segment disease requiring reoperation at 2 and 5 years postoperatively. However, the overall number of reoperations was lower in the arthroplasty group.6,27,61

 

In biomechanical models, cervical arthroplasty has been demonstrated to maintain segmental and global spinal range of motion similar to the native spine.17 This flexibility may reduce the physical demands on adjacent segments, which may lessen or slow the development of arthritic disease. However, longer follow-

up is needed.3,11

 

Adjacent level cervical range of motion has been shown to be maintained until 2 years postoperatively among patients who underwent arthroplasty.5 However, imaging has demonstrated a potential trend towards reduced range of motion and worsening alignment in arthroplasty constructs after 2 years.10,15,63 Of note, no clinical symptoms were reported by these patients.62

 

Studies have yet to show definitively whether cervical arthroplasty will have similar or reduced risk of aseptic loosening of hardware in comparison to large joint arthroplasty.25,64

 

Some groups have reported worsening cervical kyphosis after arthroplasty.19,57 However, more recent literature shows that cervical lordosis and sagittal balance can be restored by selecting appropriate patients, avoiding overmilling the endplates, and choosing appropriate insertion angles and depth.1,46,56

 

A hybrid technique using fusion and arthroplasty at alternate levels for multilevel disease has been

described with good results.4,8,66 This has been shown to reduce adjacentlevel hypermobility and

increasing moment loads.9,26,34

 

 

COMPLICATIONS

Approach related

Dysphagia is a frequent complication and often is selflimited. The incidence and severity of dysphagia may be lower after arthroplasty compared with fusion, potentially as a result of the lower profile of the constructs or the decreased need for esophageal retraction.35

Nerve palsies—recurrent laryngeal nerve, superior laryngeal nerve Nerve root injury

Spinal cord injury Cerebrospinal fluid (CSF) leak Hematoma

Prevertebral Epidural

Esophageal injury

80

Device related

Device failure: Loosening or migration is rare but has been reported more frequently in the perioperative period in devices not secured with screw fixation.22

Arthrosis of the facet at the operated level and heterotopic ossification have been reported to occur in up to 20% and 50% of patients, respectively, but neither have been shown to have a correlation with clinical outcome.51,65

The incidence of same-level facet arthrosis may be influenced by suboptimal positioning of the implant.

The incidence of heterotopic ossification may be reduced by thoroughly irrigating the wound to eliminate bone dust, coagulating exposed bone with electrocautery, and administering NSAIDs in the perioperative period.

Segmental kyphosis is likely attributable to improper endplate preparation and device insertion.47 Arthroplasty is not likely to correct preoperative segmental kyphosis and should be avoided in such cases.

Risk of subsidence is increased with osteoporosis and minimized by placing as large an endplate footprint as possible.

Continued neurologic deficit can be caused by the maintenance of motion in the setting of inadequate decompression.

Persistent radiculopathy may be treatable with a posterior foraminotomy. Persistent myelopathy or pain may require fusion.

Sagittal split fracture of the vertebral body is rare and may be predisposed by osteoporosis and the use of a keeled device.14

 

 

 

REFERENCES

1. Anakwenze OA, Auerbach JD, Milby AH, et al. Sagittal cervical alignment after cervical disc arthroplasty and anterior cervical discectomy and fusion: results of a prospective, randomized, controlled trial. Spine 2009;34(19):2001-2007.

    

    

2. Anderson PA, Sasso RC, Riew KD. Comparison of adverse events between the Bryan artificial cervical disc and anterior cervical arthrodesis. Spine 2008;33(12):1305-1312.

    

    

3. Auerbach JD, Anakwenze OA, Milby AH, et al. Segmental contribution toward total cervical range of motion: a comparison of cervical disc arthroplasty and fusion. Spine 2011;36(25):E1593-E1599.

    

    

4. Barrey C, Campana S, Persohn S, et al. Cervical disc prosthesis versus arthrodesis using one-level, hybrid and two-level constructs: an in vitro investigation. Eur Spine J 2012;21(3):432-442.

    

    

5. Barrey C, Champain S, Campana S, et al. Sagittal alignment and kinematics at instrumented and adjacent levels after total disc replacement in the cervical spine. Eur Spine J 2012;21(8):1648-1659.

    

    

6. Botelho RV, Moraes OJ, Fernandes GA, et al. A systematic review of randomized trials on the effect of cervical disc arthroplasty on reducing adjacent-level degeneration. Neurosurg Focus 2010;28(6):E5.

    

    

7. Burkus JR, Haid RW, Traynelis VC, et al. Long-term clinical and radiographic outcomes of cervical disc replacement with Prestige disc: results from a prospective randomized controlled clinical trial. J Neurosurg Spine 2010;13(3):308-318.

    

    

8. Cao JM, Zhang YZ, Shen Y, et al. Clinical and radiological outcomes of modified techniques in Bryan cervical disc arthroplasty. J Clin Neurosci 2011;18:1308-1312.

    

    

9. Cardoso MJ, Mendelsohn A, Rosner MK, et al. Cervical hybrid arthroplasty with 2 unique fusion techniques. J Neurosurg Spine 2011;15:48-54.

    

    

10. Cheng L, Nie L, Zhang L, et al. Fusion versus Bryan cervical disc in two-level cervical disc disease: a prospective, randomised study. Int Orthop 2009;33(5):1347-1351.

     

     

11. Coric D, Kim PK, Clemente JD, et al. Prospective randomized study of cervical arthroplasty and anterior cervical discectomy and fusion with long-term follow-up: results in 74 patients from a single site. J Neurosurg Spine 2013;18:36-42.

     

     

12. Coric D, Nunley PD, Guyer RD, et al. Prospective, randomized, multicenter study of cervical arthroplasty: 269 patients from the Kineflex-C artificial disc investigational device exemption study with a minimum 2-year follow-up: clinical article. J Neurosurg Spine 2011;15(4):348-358.

     

     

13. Crandall PH, Batzdorf U. Cervical spondylotic myelopathy. J Neurosurg 1966;25(1):57-66.

     

     

14. Datta JC, Janssen ME, Beckman R, et al. Sagittal split fractures in multilevel cervical arthroplasty using a keeled prosthesis. J Spinal Disord Tech 2007;20(1):89-92.

     

     

15. Davis RJ, Kim KD, Hisey MS, et al. Cervical total disc replacement with the Mobi-C cervical artificial disc compared with anterior discectomy and fusion for treatment of 2-level symptomatic degenerative disc disease: a prospective, randomized, controlled multicenter clinical trial. J Neurosurg Spine 2013;19(5):532-545.

     

     

16. Ding C, Hong Y, Liu H, et al. Comparison of cervical disc arthroplasty with anterior cervical discectomy and fusion for the treatment of cervical spondylotic myelopathy. Acta Orthop Belg 2013;79(3):338-346.

     

     

17. Duggal N, Pickett GE, Mitsis DK, et al. Early clinical and biomechanical results following cervical arthroplasty. Neurosurg Focus 2004;17(3):E9.

     

     

18. Fessler RG, Sasso R, Papadopoulos S, et al. Cervical disc replacement: four-year follow-up results from the United States prospective randomized Bryan clinical trial. Neurosurgery 2009;65(2):407-408.

     

     

19. Fong SY, DuPlessis SJ, Casha S, et al. Design limitations of Bryan disc arthroplasty. Spine J 2006;6(3):233-241.

     

     

20. Gao Y, Liu M, Li T, et al. A meta-analysis comparing the results of cervical disc arthroplasty with anterior cervical discectomy and fusion (ACDF) for the treatment of symptomatic cervical disc disease. J Bone Joint Surg Am 2013;95(6):555-561.

     

     

21. Garrido BJ, Taha TA, Sasso RC, et al. Clinical outcomes of Bryan cervical disc arthroplasty a prospective, randomized, controlled, single site trial with 48-month follow-up. J Spinal Disord Tech 2010;23:367-371.

     

     

22. Goffin J, Van Calenbergh F, van Loon J, et al. Intermediate followup after treatment of degenerative disc disease with the Bryan Cervical Disc Prosthesis: single-level and bi-level. Spine 2003;28(24): 2673-2678.

     

     

23. Hassett G, Hart DJ, Manek NJ, et al. Risk factors for progression of lumbar spine disc degeneration: the Chingford Study. Arthritis Rheum 2003;48(11):3112-3117.

     

     

24. Heckmann JG, Lang CJ, Zobelein I, et al. Herniated cervical intervertebral discs with radiculopathy: an outcome study of conservatively or surgically treated patients. J Spinal Disord 1999;12(5):396-401.

     

     

25. Hou Y, Liu Y, Yuan W, et al. Cervical kinematics and radiological changes after discover artificial disc replacement versus fusion. Spine J 2013;14:867-877.

     

     

26. Hyun Oh C, Hwan Yoon S. Past, present, and future of cervical arthroplasty. Keio J Med 2013;62(2):47-52.

     

     

27. Jawahar A, Cavanaugh DA, Kerr EJ III, et al. Total disc arthroplasty does not affect the incidence of adjacent segment degeneration in cervical spine: results of 93 patients in three prospective randomized clinical trials. Spine J 2010;10(12):1043-1048.

     

     

28. Kadanka Z, Mares M, Bednarik J, et al. Approaches to spondylotic cervical myelopathy: conservative

    versus surgical results in a 3-year follow-up study. Spine 2002;27(20):2205-2210; discussion 2210-2211.

     

     

29. Kadanka Z, Mares M, Bednarik J, et al. Predictive factors for spondylotic cervical myelopathy treated conservatively or surgically. Eur J Neurol 2005;12(1):55-63.

     

     

30. Kim SH, Shin HC, Shin DA, et al. Early clinical experience with the Mobi-C disc prosthesis. Yonsei Med J 2007;48(3):457-464.

     

     

31. Kuijper B, Tans JT, Beelen A, et al. Cervical collar or physiotherapy versus wait and see policy for recent onset cervical radiculopathy: randomised trial. BMJ 2009;339:b3883.

     

     

32. Lees F, Turner JW. Natural history and prognosis of cervical spondylosis. Br Med J 1963;2(5373):1607-1610.

     

     

33. Lehman RA Jr, Helgeson MD, Keeler KA, et al. Comparison of magnetic resonance imaging and computed tomography in predicting facet arthrosis in the cervical spine. Spine 2009;34(1):65-68.

     

     

    81

     

34. Martin S, Ghanayem AJ, Tzermiadianos MN, et al. Kinematics of cervical total disc replacement adjacent to a two-level, straight versus lordotic fusion. Spine 2011;36:1359-1366.

     

     

35. McAfee PC, Cappuccino A, Cunningham BW, et al. Lower incidence of dysphagia with cervical arthroplasty compared with ACDF in a prospective randomized clinical trial. J Spinal Disord Tech 2010;23(1):1-8.

     

     

36. McAfee PC, Cunningham B, Dmitriev A, et al. Cervical disc replacement-porous coated motion prosthesis: a comparative biomechanical analysis showing the key role of the posterior longitudinal ligament. Spine 2003;28(20):S176-S185.

     

     

37. Mehren C, Suchomel P, Grochulla F, et al. Heterotopic ossification in total cervical artificial disc replacement. Spine 2006;31(24): 2802-2806.

     

     

38. Melamed H, Harris MB, Awasthi D. Anatomic considerations of superior laryngeal nerve during anterior cervical spine procedures. Spine 2002;27(4):E83-E86.

     

     

39. Mobi-C® cervical disc: surgical technique. LDR. Available at: http://us.ldr.com/Portals/1/PDF/2LST.pdf. Accessed August 14, 2014.

     

     

40. Murrey D, Janssen ME, Delamarter RB, et al. Results of the prospective, randomized, controlled multicenter Food and Drug Administration investigational device exemption study of the ProDisc-C total disc replacement versus anterior discectomy and fusion for the treatment of 1-level symptomatic cervical disc disease. Spine J 2009;9:275-286.

     

     

41. Olmarker K, Blomquist J, Stromberg J, et al. Inflammatogenic properties of nucleus pulposus. Spine 1995;20(6):665-669.

     

     

42. Pain in the neck and arm: a multicentre trial of the effects of physiotherapy, arranged by the British

    Association of Physical Medicine. Br Med J 1966;1(5482):253-258.

     

     

43. Pait TG, Killefer JA, Arnautovic KA. Surgical anatomy of the anterior cervical spine: the disc space, vertebral artery, and associated bony structures. Neurosurgery 1996;39(4):769-776.

     

     

44. Park JH, Rhim SC, Roh SW. Midterm follow-up of clinical and radiologic outcomes in cervical total disc replacement (Mobi-C): incidence of heterotopic ossification and risk factors. J Spinal Disorders Tech 2013;26:141-145.

     

     

45. Persson LC, Carlsson CA, Carlsson JY. Long-lasting cervical radicular pain managed with surgery, physiotherapy, or a cervical collar. A prospective, randomized study. Spine 1997;22(7):751-758.

     

     

46. Pickett GE, Mitsis DK, Sekhon LH, et al. Effects of a cervical disc prosthesis on segmental and cervical spine alignment. Neurosurg Focus 2004;17:E5.

     

     

47. Pickett GE, Sekhon LH, Sears WR, et al. Complications with cervical arthroplasty. J Neurosurg Spine 2006;4(2):98-105.

     

     

48. Radhakrishnan K, Litchy WJ, O'Fallon WM, et al. Epidemiology of cervical radiculopathy. A population-based study from Rochester, Minnesota, 1976 through 1990. Brain 1994;117(pt 2):325-335.

     

     

49. Riina J, Anderson PA, Holly LT, et al. The effect of an anterior cervical operation for cervical radiculopathy or myelopathy on associated headaches. J Bone Joint Surg Am 200;91(8):1919-1923.

     

     

50. Roberto RF, McDonald T, Curtiss S, et al. Kinematics of progressive circumferential ligament resection (decompression) in conjunction with cervical disc arthroplasty in a spondylotic spine model. Spine 2010;35(18):1676-1683.

     

     

51. Ryu KS, Park CK, Jun SC, et al. Radiological changes of the operated and adjacent segments following cervical arthroplasty after a minimum 24-month follow-up: comparison between the Bryan and Prodisc-C devices. J Neurosurg Spine 2010;13(3):299-307.

     

     

52. Sant'Ambrogio G, Sant'Ambrogio FB. Role of laryngeal afferents in cough. Pulm Pharmacol 1996;9(5-6):309-314.

     

     

53. Sasso RC, Anderson PA, Riew KD, et al. Results of cervical arthroplasty compared with anterior discectomy and fusion: four-year clinical outcomes in a prospective, randomized controlled trial. Orthopedics 2011;34:889.

     

     

54. Sasso RC, Macadaeq K, Nordmann D, et al. Selective nerve root injections can predict surgical outcome for lumbar and cervical radiculopathy: comparison to magnetic resonance imaging. J Spinal Disord Tech 2005;18(6):471-478.

     

     

55. Sasso RC, Martin L. The Bryan® artificial disc. In: Yue JJ, Bertagnoli R, McAfee PC, et al, eds. Motion Preservation of the Spine: Advanced Techniques and Controversies. Philadelphia: WB Saunders, 2008: 193-198.

     

     

56. Sasso RC, Metcalf NH, Hipp JA, et al. Sagittal alignment after Bryan cervical arthroplasty. Spine 2011; 36:991-996.

     

     

57. Sears WR, Sekhon LH, Duggal N, et al. Segmental malalignment with the Bryan cervical disc prosthesis: does it occur? J Spinal Disord Tech 2007;20:1-6.

     

     

58. Sekhorn L. Bryan. Spine Universe. Available at: http://www.spine universe.com/treatments/emerging/artificial-discs/bryan. Accessed August 14, 2014.

     

     

59. Shiri R, Karppinen J, Leino-Arjas P, et al. Cardiovascular and lifestyle risk factors in lumbar radicular pain or clinically defined sciatica: a systematic review. Eur Spine J 2007;16(12):2043-2054.

     

     

60. Stav A, Ovadia L, Sternberg A, et al. Cervical epidural steroid injection for cervicobrachialgia. Acta Anaesthesiol Scand 1993;37(6):562-566.

     

     

61. Verma K, Gandhi S, Maltenfort M, et al. Rate of adjacent segment disease in cervical disc arthroplasty versus single-level fusion. Spine 2013;38(26):2253-2257.

     

     

62. Wenger M, Hoonacker PV, Zachee B, et al. Bryan cervical disc prostheses: preservation of function over time. J Clin Neurosci 2009;16(2):220-225.

     

     

63. Wenger M, Markwalder TW. Bryan total disc arthroplasty: a replacement disc for cervical disc disease. Med Devices (Auckl) 2010;3: 11-24.

     

     

64. Yang YC, Nie L, Cheng L, et al. Clinical and radiographic reports following cervical arthroplasty: a 24-month follow-up. Int Orthop 2009;33(4):1037-1042.

     

     

65. Yi S, Kim KN, Yang MS, et al. Difference in occurrence of heterotopic ossification according to prosthesis type in the cervical artificial disc replacement. Spine 2010;35(16):1556-1561.

     

     

66. Yi S, Shin HC, Kim KN, et al. Modified techniques to prevent sagittal imbalance after cervical arthroplasty. Spine 2007;32:1986-1991.

     

     

67. Yin S, Yu X, Zhou S, et al. Is cervical disc arthroplasty superior to fusion for treatment of symptomatic cervical disc disease? A metaanalysis. Clin Orthop Relat Res 2013;471(6):1904-1919.

     

     

68. Yoon DH, Yi S, Shin HC, et al. Clinical and radiological results following cervical arthroplasty. Acta Neurochir (Wien) 2006;148:943-950.