12. Posterior Cervical Plating Techniques

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Contraindications

Facet joint incompetence.

Advantages

Can be used in combination with the Rogers technique to provide increased rotational stability.

Disadvantages

Technically demanding, especially in light of more recent advances in posterior lateral mass plating.

Procedure

The facet capsule and soft tissues covering the lateral masses that are to be stabilized are removed in a subperiosteal manner. The facet joint is opened

with a small elevator and the joint cartilage is removed using a high-speed

bur or a small curved curet. A Penfield dissector or small curved osteotome then is passed into the facet joint for protection of the superior articular process. A small drill is used to create a hole in the inferior articular process at a 90-degree angle to the articular surface. While the facets are distracted, a 20-gauge stainless steel wire is passed from posterior to ante-

rior through the drill hole, grasped within the facet joint, and pulled free of the joint. The wire is then passed through or beneath an intact spinous process one or two segments below the vertebral segment in which the inferior articulating process was wired. The wire ends are then tightened on itself to reduce and stabilize the motion segment. This procedure may be performed bilaterally. Additional stability may be obtained with the addition of Rogers‘ interspinous process wiring.

Following a laminectomy, a series of inferior articular process wires may be passed along an intended fusion segment and then passed through drill holes placed along a corticocancellous strut graft. This again is done

bilaterally.

Pitfalls

Care must be taken to obtain an adequate reduction at the time of wire tightening. Inferior facet wire pullout may be a problem if adequate bone stock is not available surrounding the inferior articular process drill path.

Complications

1. Facet wire pullout may occur, leading to loss of cervical alignment and

late deformity.

2. The most common complication associated with any wiring procedure

in the cervical spine is loss of fixation and subsequent recurrence of deformity. This complication is directly related to bone quality, the surgeon’s technique, and postoperative external support.

Postoperative Care

The patient is usually kept in a cervicothoracic orthosis or halo vest for approximately 2 to 3 months to allow for bony healing. Early after surgery the patient is encouraged to carry out general isometric neck muscle exercises.

Thoracolumbar Spine

Sublaminar Wire Passage (Fig. 11–9)

Indications

1. Segmental stabilization of multiple vertebral motion segments.

2. Used to secure rods or plates to the posterior thoracolumbar spinal ele-

ments.

Contraindications

1. Lack of competent posterior elements

2. Spinal stenosis

Advantages

1. Segmental stabilization of multiple vertebral elements

2. Technically easy

Disadvantages

1. Risk of spinal cord or cauda equina injury with sublaminar wire pas-

sage

2. Cables are much more user friendly due to their flexibility and ease of

handling

Procedure

The ligamentum flavum is removed in a subperiosteal manner from the upper and lower surfaces of the laminae. A Kerrison punch (2 or 3–0) is used to create a small opening in the interlamina space above and below

the lamina level to be instrumented. Over aggressive removal of lamina bone should be avoided so that the bone is not weakened.

A doubled 16-, 18-, or 20-gauge wire is contoured into a semilunar shape to conform to the undersurface of the lamina. The blunted doubledover end is then passed in a caudad to cephalad direction until the looped end is visualized at the superior lamina border. The looped end is hooked with a nerve hook or needle-nosed needle driver. With great care to prevent any wire migration into the spinal canal, the leading wire end is gently pulled along with a posterior manual force applied to both wire ends to ensure continued wire contact with the posterior lamina border. After the wires are pulled under the lamina, the inferior wire end is bent in a cephalad direction across the posterior lamina surface medial to the superior wire end, which is bent in a caudad direction over the posterior lamina border. This maneuver protects against wire migration into the spinal canal (Wilber et al, 1991).

Pitfalls

Risk of neurologic injury from direct posterior thecal sac compression.

Complications

1. Spanning multiple laminae during a single sublaminar wire passage

should be avoided due to the increased risk of neurologic injury.

2. If initial wire passage is met with any resistance, the procedure should

be stopped and the wire should be gently repositioned.

Postoperative Care

Segmental thoracolumbar sublaminar wire placement affords optimum spinal stability, often decreasing the need for a rigid thoracolumbar sacral orthosis (TLSO).

Scott Technique (Fig. 11–10)

Indications

Symptomatic spondylolysis of the lumbar spine unresponsive to conservative treatment.

Contraindications

1. Clinical evidence of symptomatic degenerative disc disease (Fig. 11–

10A)

2. Marked instability at the pars-interarticularis defect on lateral flexion-

extension plain radiographs

Advantages

Avoids immobilization (fusion) of a spinal motion segment.

Disadvantages

A semirigid method of stabilization.

Procedure

An 18-gauge wire is looped around the base of the spinous process and transverse process on the side of the pars-interarticularis defect. Autogenous bone graft is then placed within the decorticated surfaces of the pars defect followed by twist tightening of the free ends of the wire. The modified Scott technique utilizes the pedicle as an anchorage site instead of the transverse process (Fig. 11–10B). The pedicle screw is then secured to the spinous process of the same vertebral level with an 18-gauge wire tightened in a similar manner (Nicole and Scott, 1986) (Fig. 11–10C).

Pitfalls

On tightening of the wire, the transverse process may break, especially if atrophic or osteopenic.

Complications

Nonhealing due to the lack of rigidity.

Postoperative Care

Patients should be immobilized in lumbar-sacral orthosis (LSO) with a hip spica for at least 3 months.

Conclusion

Posterior spinal wiring is a safe, inexpensive, and versatile method of offering semirigid stabilization to the posterior spinal elements. Adjunctive external methods of immobilization are frequently necessary with this method of internal fixation in the perioperative period to improve the success of bony healing and maintenance of spinal alignment.

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SECTION I THE CERVICAL SPINE

Eurostile

Posterior Cervical Plating Techniques

Jeffrey J. Wise and Howard S. An

Goals of Surgical Treatment

1. To stabilize and reduce the cervical spine

2. To maintain sagittal alignment

3. To allow for early rehabilitation

4. To increase the rate of fusion

Diagnosis

1. Multilevel cervical laminectomy for myelopathy

2. Trauma

3. Deformity

4. Posttraumatic instability

5. Reconstruction after neoplasm excision

Indications for Surgery

1. Anterior column not capable of load bearing (e.g., burst fractures).

2. Stabilization of the cervical spine after total unilateral or partial bilateral facetectomy.

3. Stabilization of the cervical spine in the absence of posterior elements (spinous process, lamina, facet).

Contraindications

1. Incompetence of facets

2. Anterior spinal cord compression

3. Fixed kyphotic deformity

4. Osteoporosis

5. Infection

Advantages of Posterior Plating in the Cervical Spine

1. Immediate rigid stabilization of cervical spine.

2. Maintenance of sagittal alignment.

3. Diminished need for postoperative immobilization.

4. Increased rate of fusion.

5. Earlier return to function.

6. Titanium implants allow for postoperative imaging.

7. Can be used if spinous processes, lamina, or facets are injured or absent.

8. Can be used for multilevel fusions.

Disadvantages

1. Technically demanding procedure

2. Additional operative time

3. Cost

Patient Preparation and Positioning

Care must be taken to stabilize the neck during intubation and turning to the prone position. A Mayfield headrest is applied with one pin placed 1 inch above the pinna of the ear. The other side of the headrest has two pins that are placed 1 inch above the ear. The frame crosses in front of the forehead and attaches to the table. A horseshoe-shaped headrest may also be used, but no pressure may be placed on the eyes because retinal ischemia may result. The knees and elbows should be well padded. The reverse Trendelenburg position diminishes venous bleeding and lowers cere-

brospinal fluid pressure (Fig. 12–1). The shoulders may be taped to help with caudal retraction.

Incision

The incision is made in the midline of the neck over the spinous processes of the involved levels to be fused (Fig. 12–2A). The ligamentum nuchae is identified and incised in the midline. The C3-C6 spinous processes are

bifid. The C2 and C7 spinous processes are more prominent. Subperiosteal dissection of the paraspinal musculature is performed down the spinous process and over the lamina. Lateral dissection at C1 should be limited to

1.5 cm from the midline as the vertebral artery is in this region. The facet capsule is excised subperiosteally at the joints to be fused. Facet capsules should be preserved above and below the fusion.

Exposure Secrets

Limit dissection to the involved levels to prevent formation of a “creeping fusion.” The interlaminar spaces are wide in the cervical spine. Great caution must be exercised during dissection to avoid violating the dural sac and injuring the spinal cord.

Facet joint anatomy may be distorted by osteoarthritis. It is imperative to properly define the boundaries of the facet to correctly identify the starting point of the screw hole.

Procedures

Occipitocervical Fixation

Several systems are available including AO reconstruction plates, Y plates, and rod-screw constructs. The plates should be contoured to 105 degrees to approximate normal occipitocervical lordosis, although premolded plates are available (Fig. 12–2B). A 2.8-mm drill bit is used to drill the occiput after the plate is applied in the lower cervical spine (see below). Bicortical screw purchase is ideal, but may be risky at this level. The 3.5-mm-diameter unicortical screws that are 6 to 8 mm in length can usually be applied safely. Longer screws can be inserted in the midline due to the increased thickness of bone in the external occipital protuberance (Fig. 12–3).

Lateral Mass Plating

Plates are selected and contoured to maintain/correct cervical lordosis (Fig. 12–4). The plate should sit flush over all facets prior to screw placement. If the spinous processes and lamina are intact, these areas may be decorticated on the dorsal surface and bone graft applied after plating. If these bony areas are resected as in laminectomies, the facet joints are decorticated and bone chips packed prior to plating. Screw holes in the plate should be centered over the midpoint of the facet at each level to be fused. It is useful to drill the first hole without the plate since it inevitably rotates. The plate may then be applied with the screw, but the screw should not be fully seated. This prevents rotation and lifting of the plate. To place screws between C3 and C7, the center of the articular pillar is identified. The starting point will vary depending on technique or upon the holes in the plate (Fig. 12–5). Based on anatomic dissection, the technique of An is least likely to injure the nerve root. Using this preferred technique, an awl or small bur is used to create a starting hole 1 mm medial to the center of the lateral mass (Fig. 12–2A). This step is important in preventing the drill bit from sliding. The drill is used with a drill stop and directed 15 degrees cephalad and 30 degrees lateral (Fig. 12–5). Either unicortical or bicortical drilling is performed depending on the screw purchase. The hole is tapped with a 3.5-mm tap, and 3.5-mm cortical screws are placed. Four-millimeter screws may be reserved for hole salvage. The average screw length is 10 to 12 mm. If the starting hole is inferior and medial, then the Magerl technique is recommended (Fig. 12–5). If the starting hole is in the middle of the lateral mass, then the Roy-Camille technique is recommended.

Magerl screws may be placed through a lateral mass plate if the fusion extends to C1. The C2 facet is exposed as described above. The entry point is the inferior aspect of the C2 inferior facet 1 mm medial to the mediallateral midpoint (Fig. 12–2A). Drilling should be performed under biplanar fluoroscopy.The drilling point exits the posterior aspect of the upper articular process. It crosses the facet joint and enters the lateral mass of C1. The hole is tapped with a 3.5-mm tap and 3.5-mm screws are placed.

Pitfalls

The use of somatosensory evoked potential monitoring is helpful in identifying intraoperative nerve injury. Screw placement should be confirmed by radiograph intraoperatively. Either a postprocedure radiograph on the operating room table or fluoroscopy to place screws should be used.

Some instrumentation systems limit screw placement within the plate. Care must be taken to ensure that the plate can be aligned over the starting points of all levels to be instrumented prior to drilling screw holes. One method to avoid this problem is to use the technique of screw placement (An, Magerl, or Roy-Camille) that best fits the local anatomy of the level and orientation of the plate.

Complications of Instrumentation

1. Dural penetration from drill, tap, or screw-the diagnosis should be made at time of injury and repaired if amenable.

2. Nerve root injury due to screw impingement: axial computed tomography (CT) scanning should demonstrate the improperly placed screw. Screw removal is recommended.

3. Spinal cord injury due to screw or hook placement: magnetic resonance imaging (MRI) scanning may demonstrate signal changes within the spinal cord, but CT-myelography will show nerve compression by hardware. Again, hardware removal is recommended.

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SECTION I THE CERVICAL SPINE

Eurostile

Knees flexed

Head and neck in neutral position

Figure 12–1

Position for posterior cervical spine procedures. The Mayfield tongs are applied 1 cm above the external auditory meatus. The double tong side is centered over the ear. The

reverse Trendelenburg position allows venous drainage and

less intraoperative bleeding. The arms are well padded and tucked by the side. The knees are flexed to prevent the

patient from sliding.

C 2 Magerl screw entry point inferior facet 1 mm medial to medial - lateral midpoint

Lateral mass entry point, 30- degree lateral, 15- degree cephalad (1 mm medial to center of lateral mass)

Contoured reconstruction plate

Bone

chips

Screws

Lateral mass plates

Figure 12–2

(A) Posterior cervical fusion. Approach: midline skin incision over involved levels. Subperiosteal dissection over lamina and facet joints. Preserve capsules of unfused

levels and avoid unnecessary exposure. The Magerl screw entry point is the inferior aspect of the C2 inferior facet 1 mm medial to the medial-lateral midpoint. The lateral

mass screw drilling technique is demonstrated at the C3-C4 level. The drilling is started 1 mm medial to the midpoint of the lateral mass directed 30 degrees lateral and 15 degrees cephalad. (B) Instrumentation: anteroposterior (AP) view. At the occiput to C3, contoured AO reconstruction plates are demonstrated with Magerl screws at C2. At the C5-C6 level, lateral mass plates are applied. Bone graft is applied to the facet joints and over the decorticated spinous processes, lamina, and exposed lateral mass if no central decompression is performed.

Eurostile

12 POSTERIOR CERVICAL PLATING TECHNIQUES

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Figure 12–3

Postoperative lateral radiograph demonstrating occipitocervical plating for an occipitocervical dislocation.

Figure 12–4

Postoperative anteroposterior and lateral radiograph of the cervical spine demonstrating lateral mass plating following multilevel laminectomy.

(Roy-Camille)

Center position

(Magerl)

1 mm medial and

1–2 mm cephalad

10° 25° 30°

1 mm medial to cephalad

(An)

0°

30°

Figure 12–5

The techniques of An, Roy-Camille, and Magerl for the drill starting point for lateral mass screw placement.

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SECTION I THE CERVICAL SPINE

Eurostile

15°

4. Loss of fixation/screw loosening: most commonly at the most cephalad or caudal hole; replace screw with larger diameter screw or remove plate if fused.

5. Screw/plate breakage: remove if symptomatic.

6. Vertebral artery injury.

7. “Creeping” fusions: avoid unnecessary dissection of the spine beyond area of fusion.

8. Damage to facet joint.

9. Iatrogenic foraminal stenosis: lateral mass shifts dorsally due to a lag screw effect. Foraminal narrowing may be prevented by placing a corticocancellous bone graft between the plate and the lateral mass.

10. Infection.

11. Pseudarthrosis: may present as hardware loosening, breakage; rarely gross instability. Treatment is anterior fusion.

12. Adjacent segment degeneration.

13. Loss of reduction.

Postoperative Care

1. Anteroposterior (AP) and lateral radiographs in operating room.

2. A subfascial drain is left in place for 48 hours or until output is less than 30 cc per 8 hours.

3. Antibiotics administered preoperatively and for 48 hours postoperatively.

4. The patient may be out of bed night of surgery and ambulation is encouraged.

5. Postoperative immobilization depends on the surgeon’s satisfaction with fixation.

6. If rigid fixation with intact anterior column, only a soft cervical collar is required for comfort for 1 to 2 weeks.

7. For slightly more protection, a rigid cervical collar may be used.

8. If fixation is not rigid and facets or anterior column are incompetent, halo immobilization is recommended.

9. Activity is restricted until signs of fusion healing. Avoidance of heavy lifting, manual labor, bending, twisting, etc. Ambulation is encouraged.

10. Follow-up visits at 2 and at 6 weeks postoperatively, as well as 3 and 6 months.

Suggested Readings

An HS. Internal fixation of the cervical spine: current indications and tech-

niques. J Am Acad Orthop Surg 1995;3:194–206.

Heller JG, Silcox DH, Sutterlin CE. Complications of posterior cervical

plating. Spine 1995;20:2442–2448.

Montesano PX, Magerl F. Lower cervical spine arthrodesis: lateral mass

plating. In: Clark CR, Ducker TB, Dvorak J, et al, eds. The Cervical Spine. 3rd ed. Philadelphia: Lippincott-Raven; 1998:509–517.

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12 POSTERIOR CERVICAL PLATING TECHNIQUES

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Anterior Cervical Disc Surgery

Technical Challenges

William Dillin

Goals of Surgical Treatment

To alleviate cervical nerve root generated arm pain and/or weakness secondary to mechanical pressure from a disc herniation or osteophyte. To remove mechanical pressure on the spinal cord secondary to posterior osteophytes at the disc space level or a herniated disc.

Diagnosis

Cervical Radiculopathy

1. The diagnosis is made on the basis of the history and physical and diagnostic studies.

2. The most reliable history for cervical nerve root compression is the development of arm pain, arm weakness, or numbness in the distribution of a single nerve root.

3. The physical examination may reveal a specific motor deficit or sensory deficit.

4. The arm pain often is exacerbated with hyperextension of the neck and rotation to the involved sign. This arm pain may be relieved by shoulder abduction.

5. Imaging studies such as a magnetic resonance imaging (MRI) scan may reveal an unequivocal structural abnormality (disc herniation, osteophyte, foraminal stenosis) correlating with the patient’s clinical complaints and physical examination.

6. Other studies may be necessary, however, to confirm the presence of pathologic correlate and a symptomatic nerve root. This could include a cervical myelogram, combined with a contrast-enhanced computed axial tomography (CAT).

Cervical Myelopathy

1. The diagnosis is made on the basis of the history and physical and diagnostic studies.

2. The most reliable history for spinal cord compression is the development of a sense of balance loss, unsteadiness of gait, or unusual sensory disturbances in the lower extremities.

3. Upper extremity involvement may involve numb, clumsy hands or a radicular component.

4. The physical examination may reveal a hyperactive reflexes, nondermatomal sensory changes, and pathologic reflexes (Babinski, Hoffman’s). Myelopathy in its earlier stages, however, may not reveal symptoms on physical examination.

5. Neck motion may produce a shock-like feeling in the torso or extremities.

6. Imaging studies such as an MRI scan may reveal an unequivocal structural abnormality (disc herniation, osteophyte) with spinal cord compression.

Indications for Surgery

1. Cervical radiculopathy with compression at the interspace level

2. Cervical myelopathy with compression at the interspace level

3. Unacceptable arm pain

4. Progressive symptoms with a gait disorder

5. Progressive weakness in involved upper extremity

6. Progressive symptoms with numb, clumsy hands

7. Loss of control of bowel and bladder symptoms

8. Cord syndromes such as an anterior cord syndrome, central cord syndrome, Brown-SUquard syndrome

Contraindications

1. Posterior pathology as the compressive agent.

2. Patient is not a candidate for surgery because of medical reasons.

Advantages

1. Direct visualized decompression of the offending pathology, which is commonly located anteriorly.

2. Indirect decompression with restoration or amplification of disc space height, which may increase foraminal size, and canal size.

Disadvantages

1. The potential for further destabilization of a motion segment in the spine at an adjacent level, leading to pain and disability and possible further surgery.

2. The anterior approach involves structures that might be infringed upon: recurrent laryngeal nerve, the trachea, the sympathetic trunk, the vagus nerve, the carotid sheath, the internal jugular vein.

Procedure

Technical Goal

To decompress the cervical spinal nerve and/or spinal cord due to a disc herniation or osteophyte.

Technical Challenge

Precision surgery aided by magnification and illumination.

Technical Principles

1. Approach to establish safe and secured anatomic plane for decompression and fusion.

2. Maintain optimum access to provide adequate decompression and stabilization.

Decision Making

1. Is the pathology actually represented on the preoperative films discovered in the operation?

2. Is the patient adequately decompressed?

Position and Exposure

1. Supine position, chest roll under posterior upper back to facilitate a neck neutral to slightly extended position. Radiolucent table to facilitate use of fluoroscopy in surgery. Arms tucked in at side, Boger straps placed but not tightened to provide visualization of C7 when needed for intraoperative x-ray.

2. Hypotensive anesthesia to reduce bleeding.

3. Preincision x-ray with sterile paper clip used as marker if there is any doubt about landmarks.

4. Incision (transverse for single level, transverse and/or oblique incision along medial sternocleidomastoid border for more than one level). Landmarks include cricothyroid membrane for the C5-C6 level and then estimate distance if superior or inferior levels need the approach. X-ray verification if there is any question prior to incision (Fig. 13–1).

5. Skin incision with superficial hemostasis. Placement of skin retractors allows for dissection in subcutaneous plane. Avoid separating subcutaneous tissue from skin.

6. Platysma is identified and divided either longitudinally or transversely.

7. Identify the medial border of sternocleidomastoid muscle and palpate the vertebral bodies with a gloved finger.

8. Place a hand-held Cloward retractor against the bone surface, trapping the middle colic and deep colic fascia against the vertebral body.

9. Gently tease through the fascial layers with peanuts, utilizing the bony surface as a background for dissection. If the fascia is tough, a small aperture may need to be created to allow cephalad and caudad exposure. This may be done with a Metzenbaum scissors, and then the peanut for further blunt dissection.

10. Identify both side of the longus coli muscle and obtain hemostasis while still using the hand-held retractor.

11. Place a needle into the interspace that is the likely target (hills are the discs, valleys are the vertebral bodies). Either clamp the needle or bend it into a staircase configuration to prevent the needle from being inadvertently pushed through the disc space into the spinal canal. Once the fluoroscopic verification has taken place, inject indigo carmine into the disc space to preserve the identity after replacement of the handheld Cloward retractor.

12. The longus coli muscles are reidentified and the medial borders cauterized with the bipolar to prevent bleeding and allow mobilization.

13. The Trimline retractor blades are carefully inserted against and under the longus colli muscle and the external retractor placed onto the blades and gently opened until a satisfactory view is obtained (Fig. 13–2).

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SECTION I THE CERVICAL SPINE

Eurostile

Hyoid

Thyroid

Figure 13–1

Landmarks and levels of surgical incision to expose the cervical spine from C2C3 through C7-T1.

Cricoid

Figure 13–2

Exposure of cervical spine. A 5-mm burr is used to remove the

disc and prepare end plates.

Eurostile

13 ANTERIOR CERVICAL DISC SURGERY

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14. For a single-level procedure, the intravertebral pins are used with the Caspar set, and each pin is placed in the center of the vertebral body above and below the corresponding disc space parallel to the end plates. Once placed, the external distractor slides over the pins and is opened gently.

Discectomy and Osteophytectomy

1. An incision into the disc space identified by the indigo carmine allows further distraction. With the initial incision made, curets are used to scrape the disc material off the end plates and into the upper part of the disc space to facilitate removal with the micropituitary.

2. Further exposure may be obtained by using a small Schlesinger rongeur to remove any overhanging bone at each lip of the vertebral body.

3. Removal of disc material proceeds from the anterior aspect of the disc space to the posterior aspect of the disc space, maintaining the full width of the disc space in the disc removal. This prevents becoming tunneled with a deeper penetration to the posterior vertebral space without adequate side-to-side disc removal. At the posterior aspect, curets remove disc in a side-to-side sweep, or with gentle placement in the posterior aspect, a back-to-front sweep.

4. A high-speed drill (diamond tip is consideration) is now utilized in a side-to-side sweeping motion along the end plates to bur the plates to the bleeding surface and to rectangularize the space for future graft fit.

5. If the pathology consists of posterior spurring of the back of the vertebral disc space at the posterior aspect of each vertebral body, a trough (2 to 4 mm?) along this osteophyte can be created so that the osteophyte is exquisitely thin and can then be removed with microcurets or micro-Schleshingers. This effectively reduces uncinate spurring.

6. The central canal provides an excellent entry point unless the injection of indigo carmine has demonstrated a clear tract and defect through the posterior longitudinal ligament. The posterior annular fibers can be detached from bone and a position behind the vertical stripes of posterior longitudinal ligament obtained with a microcuret. It is possible to use the back of the vertebral body to advantage if the surgeon uses a thin micro-Schlesinger rongeur to facilitate removal of the posterior longitudinal ligament behind the disc space.

7. Once adequate visualization of the canal is obtained, the pathology can be assessed if not apparent. Further spur resection can be accomplished at the posterior vertebral margin and carried into the medial foramen as indicated utilizing microcurets or the micro-Schlesinger. The foraminal aperture sounded to assess the adequacy of decompression. The micronerve hook is used to search for disc fragments in the foraminal aperture in the sweep behind the vertebral body. The nerve hook is a valuable tool in finding and retrieving disc fragments.

Bone Graft Insertion

1. Once the pathology has been found and addressed, the disc space is reinspected to assess spatial symmetry, rectangularization, and adequate symmetrical width. The drill is helpful in any sculpturing to achieve these goals.

2. The measurement of depth and height of the graft to be inserted is determined off of precalibrated measuring sticks placed in the disc space.

3. A graft is cut from cadaver iliac crest bone graft on the back table to conform to the controllable measurements of height and depth. Width contouring involves the sacrifice of cortical bone on the rim of the horseshoe, and if this is necessary, we choose another graft.

4. The end plates have been previously decorticated. The graft is inserted with the cortical rim directed posteriorly in most cases and is countersunk behind the anterior vertebral margin. Any protuberant spur is removed to determine the anterior vertebral margin.

5. With the vertical retraction released, a fluoroscopic x-ray is taken to identify the placement of the graft and is inspected for graft fit in the interspace and graft placement depth.

6. If the x-ray shows good graft position, then the vertebral body pins and the companion external sleeve distractor are removed and vertical distraction no longer is possible.

7. Selection of the plate is based on the following criteria: a plate long enough to allow placement of the screws, preferably with variable angle, into the vertebral bodies adjacent to the disc space but short enough not to overhang an adjacent disc space.

8. With the vertical pins removed, any bony contouring of the anterior surface to allow the plate to sit down on the bone is accomplished. An option is to bend the plate for contouring if necessary, and then to place it where the surgeon anticipates placing the screws, and take a fluoroscopic x-ray to review this position and plate length.

9. If the plate length is satisfactory, the orientation of the plate to vertical is eyeballed.

10. One variable angled system allows placement of a holding pin so that the plate is fixed at one end to the bone and allows the placement of other screws controlling for vertical tilt.

11. The first screw into the four-hole plate is an anchor about which the plate becomes a small pivot.

12. The sequence of screw placement is drill, tap, and insert screws of variable length: 12, 13, and 14 mm.

13. Once the first screw is in place, but not fully tightened down, reassessing the plate position and placing a screw on the side opposite and inferior or superior to the initial screw fixes the plate in its final position. The remaining screws are placed with the standard technique described above. The holding pin would have been removed to facilitate one screw’s placement (if utilized).

14. An x-ray is taken to verify position of the screws. Ensure that they are not in the graft or in an adjacent disc space, but are anchored in the appropriate vertebral body. All screws are then tightened and the locking screws tightened. All retractors are removed and final x-rays in both the anteroposterior (AP) and lateral plane obtained so that they may be reviewed before the patient awakens.

Closure

The wound is irrigated with antibiotic solution, the hemostasis is reviewed, a Hemovac drain is placed, and then layered closure of the platysma muscle and the subcutaneous tissue and the skin is completed. The final x-rays are reviewed and the preoperative films correlated with the intraoperative x-rays.

Pitfalls

1. Assessment of cervical disc herniation a. The correct patient: ideal arm pain b. The nerve root may have intrinsic injury that is immeasurable and

therefore repeat surgery is not valuable? No pain-free interval means nerve root injury from index pathology, retained compressive pathology, wrong initial diagnosis, or surgery performed at the wrong level.

2. Diagnostic problems a. Physical examination is not as reliable as initial surgery. b. Enhanced imaging studies are frequently falsely positive in the

first 6 months after surgery.

Complications

Approach

Structures injured on approach and securing and maintaining an adequately exposed surgical field include the recurrent laryngeal nerve, the trachea, the esophagus, the sympathetic chain, the carotid artery, the jugular vein, and the vagus nerve.

Intraoperative

Nerve root injury, spinal cord injury, dural tear, vascular injury (vertebral artery), malplacement of screws.

Postoperative

Wound infection, wound dehiscence, discitis, graft dislodgment, plate or screw failure.

Postoperative Care

Soft collar or Philadelphia collar for a variable postoperative period (depending on the surgeon’s judgment of quality of fixation).