Anterior Cervical Discectomy

Volker K.H. Sonntag, M.D., Patrick P. Han, M.D.,A. Giancarlo Vishteh, M.D.

Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospitaland Medical Center, Phoenix, Arizona

Anterior cervical discectomy is performed for a varietyof reasons. The most common is a degenerative diseasethat induces an osteophyte or a herniated nucleus pul-

posus that then causes radiculopathy or myelopathy (1, 3).The operation is usually straightforward but has multiplepitfalls and nuances (2). This article presents the senior au-thor’s (VKHS’s) surgical technique for anterior cervical disc-ectomy. Once conservative treatment for cervical radiculopa-thy, myelopathy, or both, has failed, surgical intervention isindicated. Depending on the location of the compression, theamount of axial pain, and the lordosis of the cervical spine, ananterior or posterior approach is used. The anterior approachfor a single-level discectomy is described below.

In the operating room, the patient must not be hyperex-tended during intubation. Somatosensory evoked potentialsare routinely monitored. The patient is placed supine with theneck slightly hyperextended. The head is not turned. TheCaspar operating table attachment is used to help visualizethe lower cervical spine on either plain radiographs or fluo-roscopy. The Caspar table attachment also allows slight hy-perextension of the neck. The neck bar is placed under thelower cervical and upper thoracic areas to avoid undue pres-sure on the cervical spine (Fig. 1).

SURGICAL APPROACH (see video at website article)

Superficial landmarks serve as the reference points to de-termine the level of the skin incision, but intraoperative ra-diographs or fluoroscopic studies are obtained to verify thelevel. The cervical spine is approached from the right sideunless the patient has undergone a prior approach from theleft side. If so, the original incision line is used. If a patient hassubclinical vocal cord paralysis on the side of the incision,proceeding with an incision on the opposite side is risky. Thepotential for recurrent laryngeal nerve palsy is highest on theright side, although the risk has not been documented inrecent reports. The thoracic duct, however, can be injuredwhen the approach is from the left side.

A transverse incision is made for a one- or two-level ante-rior cervical discectomy. A carotid incision, parallel and just

anterior to the sternocleidomastoid muscle, is made if three ormore interspaces are involved. The angle of the mandibletends to correspond to the level of C2, the hyoid bone corre-sponds to the level of C2–C3, and the inferior border of thethyroid cartilage is estimated to be at C4–C5 (Fig. 2). The skin

FIGURE 1. Patient positioning with the Caspar headholder.The patient’s head is maintained in a neutral position with anelastic chin strap. The cervical spine is maintained in either aneutral or a minimally extended posture to recreate the cer-vical lordosis. Adhesive tape is run along the lateral marginof the shoulder joint and arm and is affixed to the foot of thebed to assist with intraoperative fluoroscopic visualization ofthe distal cervical spine. To avoid a pressure injury to thebrachial plexus, the tape should not be run directly over theclavicle. An intrascapular roll is placed to facilitate operativeaccess by allowing the shoulders to fall below the coronalplane of the cervical spine. The neck bar is placed under theupper thoracic spine. Both the scalp leads for evoked poten-tial monitoring and the endotracheal tube (not shown) wouldbe rostral in the operative field. (Courtesy, Barrow Neurolog-ical Institute.)

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is incised sharply to the level of the platysma, which also isdivided sharply. When more than one level is exposed, rostraland caudal subplatysmal dissection is mandatory.

The plane between the carotid sheath laterally and theesophagus and trachea medially is dissected sharply andbluntly (Fig. 3). The omohyoid muscle can be divided if ex-tensive exposure is required or if it is directly in the route ofthe approach. The prevertebral tissues are dissected, initiallywith a “peanut” and then with low-power monopolar cauter-ization. The longus colli muscles are visible overlying theanterior longitudinal ligaments and vertebral bodies. With themonopolar cautery device set on low and its tip slightly bent,the longus colli muscle is dissected gently from the vertebralbody approximately 2 to 3 mm laterally. The teeth of theself-retaining retractor blades, which are placed beneath thedissected longus colli muscles, often get caught on an osteo-phyte. It is best to remove such osteophytes, usually with

large pituitary rongeurs, so that the blades can be hookedunder the longus colli muscles (Fig. 4).

A Caspar post is placed in what is thought to be one of theappropriate vertebrae, and a lateral radiograph or fluoro-scopic study is obtained. A post is preferred to a needlebecause it provides a more fixed landmark. If the post is in anincorrect vertebral body, it easily can be moved and placed inthe correct vertebral body. After the correct level is identified,a second vertebral post is placed. The post spreaders arepositioned over the post, and no distraction is performed untilthe anterior anulus is incised (Fig. 5). Then vertical traction isplaced on the vertebral bodies using the post spreaders.

Removal of the disc begins after the anulus has been cut(Fig. 6A). The anterior two-thirds of the disc is removed withangled curettes and pituitary rongeurs of various sizes (Fig.6B). An osseous lip, which is usually present on the superiorvertebral body, is removed with a No. 2 Kerrison rongeur(Codman/Johnson & Johnson, Raynham, MA) or with a Mi-das Rex AM-8 drill (Midas Rex Institute, Fort Worth, TX). Thesuperoanterior lip of the inferior vertebral body is drilled untilit is flush with the endplate. The microscope is brought intothe surgical field, and the rest of the disc is removed.

The posterior ligament becomes visible. It is wise to coag-ulate the posterior ligament to help identify its fibers and to

FIGURE 2. Orientation to the vertebral column may be esti-mated by palpating superficial anatomic structures. Thehyoid bone sits approximately at the level of the C2–C3 discspace. The top of the thyroid cartilage can be estimated asthe C3–C4 disc space. The inferior border of the thyroid car-tilage (dotted line) can be estimated as the C4–C5 level. TheC7–T1 disc space sits approximately one finger’s breadthabove the clavicle. The carotid-type incision (solid line) ismade if three or more interspaces are involved. (Courtesy,Barrow Neurological Institute © 1993.)

FIGURE 3. Axial view of the plane of dissection and expo-sure of the prevertebral space. The carotid sheath and thejugular vein are retracted laterally, and the trachea andesophagus are retracted medially. (Courtesy, Barrow Neuro-logical Institute.)

FIGURE 4. Once the tips ofthe self-retaining retractorsare positioned beneath thedissected longus colli mus-cles, the cervical vertebralbodies are exposed anteri-orly. (Courtesy, Barrow Neu-rological Institute.)

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coagulate the veins running through it. Coagulation alsoseems to make entering the ligament easier with the micro-curette. The posterior ligament is incised with the curette orwith the No. 1 Kerrison rongeur.

The symptomatic site is decompressed first. That is, if thepatient has a left radiculopathy, the patient is turned 10 to 20degrees away from the surgeon, who is on the right side sothat the left foramen is easily seen. With microcurettes and amicro-Kerrison rongeur, the foraminotomy is performed byremoving the osteophytes and disc material. Often the herni-ated disc is posterior to the ligament and is identified at thistime. It is often difficult to determine how far lateral to carrythe dissection. Helpful landmarks are the origin of the nerveroot, fat in the axilla, the curvature of the uncovertebral joint,or extensive venous bleeding from the laterally positionedveins. Bipolar coagulation and Avitene (Davol, Inc., Cranston,RI) are used to control these epidural veins. The uncovertebraljoint is best identified at the beginning of the curvature of theendplate. When the osteophyte is removed, the surgeon al-ways must bite bone with the Kerrison rongeur, an angledcurette, or both. The surgeon should never bite into “air” forfear of injuring the vertebral artery.

Once decompression of the symptomatic side is completed,if no fusion is contemplated, the nonsymptomatic side istreated just as diligently to prevent postoperative radiculop-athy related to settling (Fig. 7). If fusion is planned, the Smith-Robinson fusion technique is preferred. Endplates are rough-ened with the drill, and bone chips and shavings from thedrilling are saved to place into the middle of the fibula au-tograft. A posterior shelf of bone (1–1.5 mm) is formed bydrilling the inferior vertebral bodies where the shelf is almostpreformed by the curvature of the vertebral body (Fig. 8). Ifplating is not planned, a 1-mm anterior shelf is drilled as well(Fig. 9). Again, the cortical endplate must not be denudedcompletely. At this time, a graft is fashioned to fit the in-terspace. Distraction of the interspace spreader is increased,and the fibula graft filled with cancellous bone shavings istapped gently into the interspace (Fig. 10).

Alternatively, an autograft can be obtained from the iliaccrest. An incision is made 2 cm posterior to the anterior iliacspine. Soft tissue is dissected down to the iliac crest, and theperiosteum is dissected sharply with a knife or a monopolarcauterization device. An appropriate-sized tricortical piece ofiliac crest is obtained to fit the interspace. In a patient with alarge iliac crest, a bicortical autograft can be obtained. Afterthe autograft or allograft is placed, the distracting posts areremoved. If no plating is pursued, the graft should be placedjust below the formed anterior lip. If plating is considered, theanterior lip is unnecessary, and the graft is tapped flush withthe vertebral bodies. The microscope is then removed fromthe surgical field.

When an anterior plate is placed, an appropriate-sized plateis chosen. The vertebral bodies must be void of osteophytesand soft tissue before the plate is applied. The two superiorscrews should be placed just above the interspace 6 degreesmedially and 12 degrees rostrally, and the inferior screws areplaced 12 degrees caudally and 6 degrees medially. Thescrews are fastened to the plate with the appropriate lockingmechanisms.

After copious irrigation, the wound is closed. It is inspectedonce more by placing two self-retaining Cloward retractors inthe wound, keeping one self-retaining retractor deep in thewound. The walls of the wound are checked for any bleeding,which is then controlled, and the opposite retractor is re-moved slowly. The same maneuver is performed on the otherside. The platysma layer is closed with interrupted 3-0 Vicrylsuture (Ethicon, Inc., Somerville, NJ), and the skin is closedwith a running subcuticular 4-0 Vicryl suture. The suture line

FIGURE 5. Interbody posts and spreader in position. Two-headed arrow, direction of movement of the posts. (Courte-sy, Barrow Neurological Institute.)

FIGURE 6. A, the discec-tomy is initiated by incisingthe anulus with a No. 11blade. B, after the anulusfibrosus has been openedinitially, a small amount ofdistraction is applied acrossthe vertebral bodies by usingthe post spreaders. A curetteis used to “scrape” the carti-laginous endplate to removeadditional disc material.(Courtesy, Barrow Neurolog-ical Institute.)

FIGURE 7. Axial view of theoperative site after discec-tomy. The disc space has akeystone configuration afterthe disc and the posteriorlongitudinal ligaments havebeen resected and theforamina have been decom-pressed. (Courtesy, BarrowNeurological Institute.)

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is reinforced with Steri-Strips (3M Healthcare, St. Paul, MN)or Dermabond (Closure Medical Corp., Raleigh, NC).

For patients who undergo a fusion procedure, anterior andlateral radiographs are obtained in the recovery room to ver-ify the position of the graft, the plate, and the screws. Patientswithout an internal fixation device wear a rigid collar for 4 to6 weeks. In patients who receive internal fixation and in thosewho undergo no fusion, external orthosis is not applied rou-tinely, except to control pain. Patients are discharged the dayafter surgery. A problem with swallowing is the usual reasonwhy patients are kept longer in the hospital. Within 7 to 10

days of discharge, patients are seen in the office for a “woundcheck.” Flexion-extension radiographs are obtained 6 weeksafter the operation in patients with a fusion construct. Ifevidence of fusion is present and there are no signs ofpseudarthrosis, patients are started on exercise therapy at thattime. Patients who do not undergo a fusion procedure canstart exercise 2 to 3 weeks after surgery.

Received, January 24, 2001.Accepted, April 20, 2001.Reprint requests: Volker K.H. Sonntag, M.D., c/o Neuroscience Pub-lications, Barrow Neurological Institute, 350 W. Thomas Road, Phoe-nix, AZ 85013-4496. Email: neuropub@chw.edu

REFERENCES

1. Cloward RB: The anterior approach for removal of ruptured cer-vical disks. J Neurosurg 15:602–617, 1958.

2. Golfinos JG, Dickman CA, Zabramski JM, Sonntag VKH, SpetzlerRF: Repair of vertebral artery injury during anterior cervical de-compression. Spine 19:2552–2556, 1994.

3. Robinson RA, Smith GW: Anterolateral cervical disc removal andinterbody fusion for cervical disc syndrome. Bull John HopkinsHosp 96:223–224, 1955.

FIGURE 8. A shelf drilledalong the superior aspect ofthe inferior vertebral bodyprevents retromigration ofthe bone graft. (Courtesy,Barrow NeurologicalInstitute.)

FIGURE 9. Sagittal view ofthe anterior and posteriorvertebral body shelves. Dot-ted line defines posteriorvertebral body shelf. (Cour-tesy, Barrow NeurologicalInstitute.)

FIGURE 10. Sagittal view ofthe operative site after disc-ectomy or osteophytectomyand spinal canal decompres-sion with fusion. (Courtesy,the Barrow NeurologicalInstitute.)

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