Chapman’s Orthopaedic Surgery
3rd Edition

CHAPTER 148
FAILED AND REVISION CERVICAL SPINE SURGERY
Eeric Truumees
Robert F. McLain
E. Truumees: Department of Spinal Surgery, William Beaumont Hospital, Royal Oak, Michigan, 48073.
R. F. McLain: Department of Orthopaedics, The Cleveland Clinic Foundation, Cleveland, Ohio, 44195.
Cervical spine surgery is usually successful. The population of chronic, failed cervical spine surgery patients is smaller than for the lumbar spine. However, cervical spine surgery is becoming more common. Fusion procedures increased 70% between the periods of 1979–1981 and 1988–1990 (11). With this increase, more complications will be encountered and the need for revisions will rise. This chapter will focus on pseudarthrosis, residual compression, postlaminectomy kyphosis, hardware failure, and progressive or adjacent segment degeneration.
CAUSE OF FAILURE
PATIENT-RELATED FACTORS
Patients with active medicolegal issues or complex, unresolved psychosocial problems are less likely to achieve a satisfactory outcome from primary cervical spine surgery. Unrealistic expectations and poor compliance with postoperative care also reduce the chances for successful post-surgical outcome. Nutrition, smoking, diabetes, and steroid use all have implications in wound healing, bony fusion, and recovery.
Poor patient selection will predispose to failure of primary cervical surgery and will make revision surgery even more difficult. When failure is the result of, or compounded by, any of these factors, the issues must be addressed before surgical revision is likely to succeed.
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SURGEON-RELATED FACTORS
Preoperative factors leading to poor outcome include errors in diagnosis, surgical timing, and intended procedure. Common errors of surgical judgment include choosing the wrong approach, selecting improper fusion levels, or recommending improper postoperative care. These errors will be considered in terms of their outcome: deformity, pseudarthrosis, or inadequate decompression. Perioperative events, including infection, dural leak and pseudomeningocele, and hematoma are not uncommon causes of clinical failure and must be evaluated before planning a revision procedure.
Pseudarthrosis
Pseudarthrosis complicates both anterior and posterior fusion procedures, but it is not always the cause of postoperative neck pain. Anterior cervical discectomy (ACD), without fusion, relieves radicular and axial neck pain in many patients. The success of ACD highlights the fact that nonunion is not always painful (26). Nonetheless, the most common cause of axial pain or radicular symptoms after anterior cervical discectomy and fusion (ACDF) is still pseudarthrosis (36,41). Published reviews of ACDF outcomes report pseudarthrosis in up to 26% of patients (13,22,32,36). Patients at increased risk for pseudarthrosis after ACDF include those undergoing multilevel, individual fusions and those fused with allograft (20,48).
In their analysis of anterior cervical fusion, Lowery et al. (22) defined pseudarthrosis as having the following components:
  • Continued or worsening axial pain 6 months after the index procedure
  • Complete radiolucency at the host–graft interface
  • Vertebral body motion of >2 mm on flexion–extension films
Symptomatic pseudarthroses were seen mainly at the interface between the graft and the vertebral body below. Only 9% of patients with pseudarthrosis felt better after their initial surgery; 27% felt the same, and 64% felt worse.
The literature regarding pseudarthrosis after posterior cervical fusion is relatively sparse. Posterior fusions do not enjoy the biological advantage of grafting under compression, but overall, fusion rates are felt to be high. Reported pseudarthrosis rates following traditional wiring techniques range from 0% to 50% (16), but it can be expected in 10% of patients. Outcomes after rigid posterior plating are reported with rates of 0% to 1.4% pseudarthrosis (16).
Residual Compression
Residual compression of the neural elements is a common cause of failure in both anterior and posterior cervical spine procedures (29). The diffuse nature of degenerative changes in the cervical spine sometimes requires more global or comprehensive procedures than the surgeon is initially willing to entertain. Residual compression after an index spine procedure may result from any of the following:
  • Failure to perform a complete decompression at the injured/involved level
  • Failure to decompress adjacent involved levels
  • Migration of graft or fixation materials into the canal or foramen
  • Wrong-level surgery
After ACDF, posterior osteophytes in the region of the posterior longitudinal ligament (PLL) may be a significant source of residual compression (44). Some surgeons feel that posterior osteophytes will resorb after successful fusion. Therefore, they avoid PLL resection and the dangers of operating near the spinal cord. However, the extent of osteophyte resorption is controversial. Recent studies have noted little remodeling or resorption after solid ACDF (32,38). Some authors have advocated more complete decompression in this area through PLL resection and direct visualization with an operating microscope or loupes (19).
Similarly, persistent neural compression following fracture may impair neurologic recovery. While stabilization alone affords some protection of neurologic tissues, adequate decompression of bony and soft-tissue elements increases neurologic recovery (31).
Postlaminectomy Kyphosis
Postlaminectomy kyphosis is a focal and often dramatic angulation of the cervical spine occurring after posterior decompression (21). Wide decompression necessarily sacrifices all or part of the facet and eliminates the attachments for the posterior spinal musculature. Bilateral facetectomy of more than 25% of the facet increases cervical motion in all planes and should prompt posterior fusion to prevent deformity (27,28). After extensive laminectomy, glacial progression toward scoliosis or kyphosis occurs in 30% to 50% of younger patients, and fusion is indicated (39).
Risk factors for postoperative kyphosis include (21) the following:
  • Young age (into third decade)
  • Preoperative deformity [particularly S-shaped or kyphotic deformities (25)]
  • Removal of more than four laminae
  • Destruction of facets
  • Tumors
  • Removal of C-2 posterior elements (major semispinalis insertion)
  • Paralysis with paraspinal muscle weakness
  • Anterior instability following fracture
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Hardware Failure
If due consideration is given to the biomechanical status of the cervical spine and its relationship to the construct employed, the likelihood of failure of most modern instrumentation is small. Fixation failure reflects the types of failure already described:
  • Persistent pseudarthrosis results in fatigue failure or failure at the host–hardware interface.
  • Underestimated or unrecognized biomechanical loads cause acute failure.
  • Aggressive postoperative mobilization, particularly in osteopenic bone, causes acute or progressive hardware loosening.
  • Noncompliant patients can accelerate all these processes, particularly when smoking retards the healing process.
  • Progressive destruction by tumor or infection further destabilizes the spine.
Progressive or Adjacent-Segment Degeneration
Cervical spine fusion may accelerate degeneration of neighboring, unfused levels (3). These changes may reflect local biomechanical alterations that result from an existing fusion (adjacent segment degeneration) or may simply reflect the natural history of that patient’s cervical spondylosis. As such, this degeneration may take the form of recurrent stenosis, recurrent disc herniation, or degenerative disc disease. Up to 89% of ACDF patients report symptomatic degeneration at long-term follow-up (17,43). Anecdotal evidence suggests that fusions ending at C-5 or C-6 are particularly associated with recurrent axial neck pain, perhaps because of the increased segmental motion at these levels (40).
In patients with continued pain despite a solid arthrodesis, rule out inadequate decompression first. Then evaluate radicular or myelopathic symptoms for evidence of foraminal or canal stenosis or recurrent disc herniation. In patients with predominantly axial pain, assessment of the cervical discs above and below the fusion mass remains controversial. Some authors recommend cervical discography with anterior fusion for concordant pain (33).
PREOPERATIVE ASSESSMENT AND PLANNING
PRESENTATION
Failed Cervical Spine Surgery
Patients with failed cervical spine surgery present with the following:
  • Residual axial pain
  • Recurrent or residual myelopathy
  • Recurrent or residual radiculopathy
  • Development or progression of deformity
Evaluation algorithms are presented in Figure 148.1, Figure 148.2, Figure 148.3.
Figure 148.1. Evaluation algorithm for patients with failed cervical spine surgery
Figure 148.2. Evaluation algorithm for radiculopathy and myelopathy.
Figure 148.3. Evaluation algorithm for postsurgical deformity.
Pseudarthrosis
Patients with pseudarthrosis typically present with the following:
  • Axial neck pain
  • Recurrent radiculopathy or myelopathy from regrowth of posterior osteophytes
  • Deformity from failure of intended fusion after wide posterior decompression
Inadequate Decompression or Adjacent-level Degenerative Disc Disease
Patients with inadequate decompression or progressive or adjacent-level degenerative disc disease present with the following:
  • Neural compression after cervical spine surgery, most commonly related to inadequate decompression, recurrent disc herniation, or recurrent stenosis
  • Radicular pain (radiculitis), one of the earliest symptoms of neural compression; often relieved by distraction and increased with axial loading
  • Weakness and sensory changes, presenting in a radicular pattern (radiculopathy) with increasing compression
  • In advanced cases, lower motor neuron findings, including weakness and diminished reflexes, at the level of compression; below the compression, upper motor neuron signs, including hyperreflexia and spasticity
  • Ataxia, clumsiness, diffuse lower extremity weakness, and bowel and bladder problems (i.e., myelopathy) after cervical spine surgery, often related to the following:
    Large central disc (less common)
    Severe, unaddressed osteophytosis (with normal or stenotic canal)
    Hardware displacement
    Postoperative deformity
Postlaminectomy Kyphosis
Patients with postlaminectomy kyphosis present with a history of prior posterior cervical spine surgery and an often subtle, progressive pattern of pain and neurologic change (18):
  • Neck pain (75%)
  • Severe neck deformity (30%)
  • Progressive myelopathy (90%)
  • Radiculopathy (50%)
Hardware Failure
Hardware failure may result in any of the symptoms described in this section. In dramatic cases, patients complain
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of tracheal or esophageal impingement. Sudden changes in alignment, neurologic status, or pain often indicate failure of hardware. Patients may be aware of a “pop” or acute onset of instability. However, slow pull-out of lateral mass plates, for example, can present with slowly increasing deformity, such as is seen in postlaminectomy kyphosis.
HISTORY AND PHYSICAL EXAMINATION
Understand the patient’s spine thoroughly before making treatment decisions. First, obtain complete records of previous procedures and determine the following:
  • What types of postoperative immobilization were employed?
  • What was the condition of the bone?
  • Was allograft or autograft employed?
  • Was the PLL resected?
A complete motor and sensory examination is critical. Patients with prior cervical spine surgery are likely to demonstrate complex abnormalities. Perform a detailed and stepwise assessment of sensory, motor, and reflex abnormalities, as well as a careful search for evidence of myelopathy to define new or residual neurologic deficits. Note bowel or bladder changes, gait disturbance, and the unilaterality or bilaterality of symptoms. The following may be a useful checklist:
  • Recognize possible aberrant innervation patterns (23).
  • Map complex sensory deficits on the skin with a skin marker.
  • Chart complex motor and reflex changes.
  • Distinguish cervical problems from those of shoulder, cardiac, cranial, or peripheral origin.
  • Assess the location and healing of the prior incision(s).
  • Assess cervical range of motion (ROM) and neck and body posture.
  • Note areas of tenderness and spasticity of paravertebral and anterior strap muscles.
IMAGING STUDIES
Compare plain anteroposterior (AP), lateral, and oblique views with prior studies to assess progression of spondylosis, fusion, deformity, or hardware migration. New degeneration most often presents with narrowing of adjacent disc heights and increase in osteophyte formation. Space available for the cord, from the posterior vertebral body to its lamina, is normally over 17 mm; an AP diameter of less than 13 mm suggests spinal cord compression (12). Oblique views assess the fusion mass, intervertebral foramina, pedicles, and facets, and they show persistent compression due to uncovertebral joint spurring.
If postoperative instability or pseudarthrosis is suspected, flexion–extension lateral films are useful. Dynamic x-rays are also helpful in evaluating new instability secondary to adjacent-level degenerative disc disease. In a patient with postoperative deformity, 5 pounds of axial traction may be used to determine reducibility (15).
Correlate radiographic findings with presenting complaints and physical exam. For example, pseudarthrosis is often difficult to identify. As in the lumbar spine, shingling of the bone mass may obscure the fusion defect (5). Therefore, clinical criteria (intractable neck pain with or without radicular symptoms) must be correlated with radiographic criteria (6). Radiographic signs of pseudarthrosis include the following (6):
  • Gross motion at previous fusion site on dynamic radiographs
  • Persistence of disc-space lucency
  • Graft displacement or failure to incorporate
  • No dissolution of endplates
  • Hardware failure
Advanced imaging modalities may also prove useful.
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Single photon emission computed tomography (SPECT) scanning employs a tomographic camera to remove three-dimensional superimposition from scintigraphic images, thereby improving image contrast and offering more complete spatial information than conventional bone scans. It is increasingly being used to demonstrate increased focal uptake at sites of pseudarthrosis (37).
Computed tomographic myelography demonstrates neural compression indirectly through contour of the dural sac. While myelography is invasive, it is helpful in the presence of spinal deformity. Further, it offers information on conjoint nerve roots and other pathologies not readily appreciated with magnetic resonance imaging (MRI) (23). When spinal instrumentation is in place, myelography may be the only way to visualize neural structures.
Magnetic resonance imaging elucidates disc degeneration and intrinsic changes in the cord. However, major abnormalities are commonly encountered in asymptomatic patients (1). In postoperative patients, gadolinium enhancement reveals recurrent discs as nonenhancing space-occupying lesions, which scar enhances.
Some authors advocate cervical discography for patients with undetermined axial pain, reporting 70% good to excellent results with anterior fusion after concordant discography (41). However, others cite higher failure rates, including one report of 54% fair to poor results (8). These authors cite a 13% complication rate with cervical discography, including one case of acute epidural abscess resulting in quadriplegia. Discography is likely to remain controversial for some time.
Finally, root injections are occasionally used to determine painful levels. Resolution or mitigation of pain indicates specific root-level pathology and the likelihood of surgical relief of symptoms following surgery.
TREATMENT
Principles and operative indications are the same as for patients requiring primary treatment. Early operative treatment should be considered in any patient demonstrating the following:
  • Progressive motor or gait impairment
  • Persistent disabling pain and weakness (3 months)
  • Progressive deformity
  • Instability
  • Static neurologic deficits with significant axial or radicular pain
Surgery should not be contemplated in patients without consistent findings in both clinical examination and imaging studies. Pseudarthrosis alone, for example, is not an indication for revision surgery. Nonoperative treatment should be fully explored in the majority of “failed neck” patients.
NONOPERATIVE TREATMENT
A trial of nonoperative treatment (Fig. 148.4) is useful even in those patients for whom later surgery is felt to be unavoidable. During this period, develop rapport with the patient, document compliance with prescribed treatment, maximize medical status, and optimize nutritional and smoking status. In certain patients, urine nicotine levels may be obtained.
Figure 148.4. Algorithm for treatment of patients with failed anterior surgery.
OPERATIVE PLANNING AND TREATMENT
The operated neck is different in many ways from the “untouched” spine:
  • Prior decompression may have rendered the spine unstable.
  • Prior fusions create significant lever arms that must be considered in any subsequent construct.
  • Surgical soft-tissue injury from the prior surgery interferes with blood supply, healing potential, and local biomechanics.
While many authors report acceptable results with allograft use in both index and revision cervical spine procedures, the decreased vascularity and altered biomechanics of the revision situation are an indication for autograft bone (14).
Anterior Pseudarthrosis
Posterior Repair of Cervical Pseudarthrosis
Posterior fusion for symptomatic anterior pseudarthrosis was proposed by Riley and Robinson (30). The additional stabilization offered by posterior wiring encourages the anterior fusion mass to consolidate. This approach remains the gold standard today, with 94% to 100% union rates reported (4,13,20,34) (Fig. 148.5).
Figure 148.5. Treatment algorithm for failed anterior surgery.
Several randomized, prospective series have been undertaken to compare anterior and posterior treatment of anterior pseudarthrosis (4,22,29). Interestingly, while over 80% of patients treated posteriorly felt better than before surgery, only 70% of those treated circumferentially reported symptomatic improvement. These results argue for a posterior approach unless specific hardware concerns require an anterior approach.
  • Use a standard, midline approach to the involved level.
  • Several wiring methods may be employed. If the spinous processes are intact, a triple wire technique provides good resistance to torsional and flexion forces (Fig. 148.6).
    Figure 148.6. Posterior stabilization for failed anterior cervical discectomy and fusion. A: Graft collapse and pseudarthrosis result in focal kyphosis, fragmentation, and instability. B: Posterior instrumentation and fusion are carried out without disturbing the anterior graft. The simplest approach is a triple wire technique using autograft bone. Approximate the spinous processes using an 18-gauge interspinous wire applied in a modified Rodger’s technique. Apply the split autograft to either side of the intact spinous processes and compress the “sandwich” with a pair of 22-gauge wires. C: Posterior wiring will most often cause the anterior graft to consolidate at the same time the posterior fusion is healing.
  • If the posterior elements are absent or inadequate, lateral
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    mass plates provide greater resistance to torsional and extension forces.
  • Use lateral mass plates for multisegmental fusions as well.
  • Postoperative immobilization includes a Philadelphia collar for 6–12 weeks.
Anterior Repair of Cervical Pseudarthrosis
An anterior approach to failed anterior cervical fusion is often required in cases of residual radiculopathy, or failed or migrated hardware. Although repeat anterior surgery was felt to have lower success rates than posterior surgery, recent authors, citing modern anterior osteosynthesis techniques, report increased fusion rates with excellent and good results in 83% (9).
Proponents of the repeat anterior approach cite lower rates of wound problems, the biomechanical advantages of anterior column grafting, and the ability to explore the decompression site and to remove any remaining osteophytes. Anterior repair is being increasingly recommended for patients with collapse of a previous anterior graft in conjunction with pseudarthrosis.
Some authors recommend using a contralateral approach to avoid operating through the scarring on the previously approached side. Contralateral exposure should not be carried out until laryngoscopic evaluation of the vocal cords has confirmed that both cords are functioning normally. This approach limits the risk of sequential injury to both recurrent laryngeal nerves.
  • Use a transverse incision to approach the cervical spine in the standard fashion (see Chapter 138).
  • Locate the failed fusion intraoperatively by x-ray.
  • Next, place distraction pins into the superior and inferior vertebral bodies.
  • Once slight distraction is applied, excise residual graft, scar, and fibrous tissue with curets, rongeurs, and a high-speed burr.
  • Carefully contour the superior and inferior endplates with the burr.
For revision surgery, a tricortical block iliac crest autograft is preferred to dowel techniques.
  • Carefully measure the disc space for height, depth, and width.
  • Fashion the graft to fit the distracted disc space by cutting it 2–4 mm longer than the interspace is high.
  • The graft should be at least 5 mm thick to prevent resorption and restore disc space height.
  • To prevent microfracture, cut the iliac crest with a saw rather than osteotomes.
  • Carefully remeasure the graft depth. In smaller patients, a graft depth of 12–14 mm may cause cord impingement. Contour the graft so that it can be countersunk 2 mm below the anterior cortex without impinging on the back rim of the vertebral body.
Revision ACDF is a strong indication for anterior plate osteosynthesis. We use a unicortical fixation system with screws that lock to the plate.
  • Measure the sagittal depth of the vertebral body and preset the drill depth.
  • When drilling, be aware of the endplate angle to avoid penetrating the intervertebral disc space above or below the intended body.
  • Immediately mobilize the patient in a Philadelphia collar (usually worn for 6–12 weeks).
  • When plate fixation is impractical or bony purchase is tenuous, longer postoperative immobilization in a rigid
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    collar or a four-poster brace is advocated. In some circumstances, adjuvant posterior fixation may be employed as well, as mentioned.
Inadequate Decompression
The principles of treatment of residual compression are fairly straightforward. If significant compression remains anteriorly, the approach must be anterior. If significant compression remains posteriorly, the approach must be posterior. Similarly, posterior hardware problems are addressed posteriorly, and so on.
Anterior decompression of residual or recurrent cervical spine disease is indicated in patients with less than three levels of disease. Occasionally, large central osteophytes will militate against posterior decompression in even multilevel spondylosis.
In patients with prior posterior procedures, an anterior procedure for recurrent or residual radiculopathy or myelopathy most often involves anterior corpectomy with strut graft fusion (Fig. 148.7). The likelihood of posterior instability represents a strong indication for anterior plate osteosynthesis in conjunction with well-fashioned struts. In patients with single-level and radicular findings, standard ACDF is recommended. Plate fixation may be helpful in these patients as well (7). Preoperative flexion–extension radiographs will better define the stability of the cervical spine.
Figure 148.7. Treatment of residual cord compression after inadequate decompression. A: In patients who have undergone previous but inadequate surgical treatment, the original compressive lesion is densely consolidated, and access may be hindered by surgical scarring, old hardware, and, often, a well-integrated strut graft. B: Remove the strut graft with rongeurs and a high-speed burr, back to the posterior vertebral cortex. Study the preoperative CT scan to determine whether there is a distinct interval between the back of the graft and the residual vertebral body. C: Use a burr and microcurets to thin the posterior cortex in the lateral recess of the side with least compression. D: Enter the canal with a small curet or elevator directed toward the neural foramen and away from the cord. Thin the compressive mass with the burr, and use a diamond tip burr to thin the lateral recess to eggshell thickness. E: Use a small elevator or curet to reflect the residual bone fragments directly away from the canal and spinal cord. Dural adhesions may be divided with a fine Penfield elevator or microcuret.
Anterior Decompression
Techniques for ACDF are discussed in Chapter 143. Anterior cervical corpectomy in the revision situation is discussed in the context of postlaminectomy kyphosis later. Key elements of the anterior decompression procedure include the following:
  • Incise the annulus and remove adjacent discs with a pituitary rongeur and a small, angled curet.
  • Remove the anterior portion of the vertebral body with rongeurs.
  • Carefully thin the posterior cortices with a burr.
  • Use a micro-Kerrison rongeur or curets to decompress the cord.
  • Fashion a strut graft with iliac crest (two or fewer levels) or use allograft or autograft fibula.
  • Contour and apply a plate.
  • Use standard closure and postoperative immobilization (as described previously).
Postlaminectomy Kyphosis
Several approaches to postlaminectomy kyphosis have been described. They include anterior corpectomy and fusion, posterior fusion with lateral mass plates, and circumferential procedures (Fig. 148.8).
Figure 148.8. Algorithm for treatment of failed posterior cervical spine surgery.
Correction of postlaminectomy kyphosis begins with preoperative traction. In most cases, moderate correction of the deformity is achieved and fusion is planned to the next normal level above and below the deformity (24,35).
A repeat posterior approach is often limited by inadequate bone stock, and corrective osteotomy through this approach is generally ineffective (2). Anterior cervical corpectomy with strut graft fusion and plating has become the favored approach in all cases without new posterior pathology (35,42,47).
A circumferential approach includes anterior corpectomy with posterior osteotomy and internal fixation (Fig. 148.9). This approach is particularly beneficial in patients with significant anterior instability as well. Generally, the circumferential approach allows for greater correction of the sagittal plane deformity. While reasoning of this surgical approach is sound, the added risks of a second operation make its use less compelling in the majority of postlaminectomy kyphosis patients (10,35).
Figure 148.9. Postlaminectomy kyphosis. A: This patient presented with progressive pain and deformity 3 months after multilevel cervical laminectomy. The deformity was passively correctable, to a degree, and the patient was neurologically intact. B: After 48 hours in halo traction, significant correction was obtained and surgical treatment was initiated. C: A staged anteroposterior reconstruction was planned. A five-level anterior vertebrectomy was performed initially, reconstructed with an autograft fibular strut. D,E: Five days later, we performed a posterior instrumentation and fusion using lateral mass plates. The slight increase in cervical lordosis produced by the plates caused the anterior strut to loosen and shift. During the same surgical procedure, the graft was repositioned and a short anterior plate placed to buttress the distal pole of the graft. Fusion was successful and the excellent sagittal correction was fully maintained. Figures D & E show anteroposterior and lateral views 1 year after surgery.
Herman and Sonntag (18) found that anterior corpectomy and plate yielded a mean correction of only 16° of kyphosis, but that 95% of these patients reported improvement of their presenting complaints. The authors report
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limited correction of the deformity due to fusions of the remaining levels at the facet and posterior element levels. Moreover, the goals of stabilization and prevention of further progression having been met, 10% reported complete relief of their symptoms and 55% noted substantial improvement.
Combined Approach for Postlaminectomy Kyphosis
  • Begin the anterior approach with the patient supine. Tape the shoulders caudally and turn the head slightly away from the operative side. Place a bolster between the shoulders to provide mild hyperextension. A bolster may not be useful in patients with a fixed-flexion deformity due to the wedging of the vertebral bodies.
  • A transverse incision may be used in most cases up to five levels. In longer procedures, an extensile incision along the anterior border of the sternocleidomastoid muscle can be used instead. A standard, left-sided approach is recommended.
  • Use blunt, finger dissection to dissect the platysma from overlying and underlying tissues.
  • Carefully develop the intervals between the tissue planes. This will increase the extensibility of the incision.
  • The omohyoid may cross the surgical field, depending on the level of dissection. Division for increased exposure is rarely required.
A variable amount of scar may be seen anteriorly at the apex of the kyphosis (15). This scar may exert a tethering effect. Debridement of the scar will allow increased exposure of the anterior bodies. Overly aggressive lateral dissection threatens the sympathetic chain.
  • To achieve correction of the deformity, completely excise the intercalary discs to the level of the PLL.
  • Use a rongeur to remove large portions of the intervening bodies.
  • Next, use a dental burr to remove bone laterally and posteriorly to the posterior cortex of the body.
  • Use fine Kerrisons to remove the cortical wafer from the PLL.
  • Once adequate decompression and visualization have been achieved, obtain radiographs to assess correction. Adjust the alignment and traction to achieve lordosis.
  • Next, fashion an allograft or autograft fibular strut in the Whitecloud-LaRocca method with an H-shape. For less than two or three levels, iliac crest struts may be used. While crest graft offers a faster incorporation time, fibular graft is stronger in compression.
  • Prior to insertion, undercut the endplates of the cranial and caudal vertebra with the burr. This allows the graft to be pushed into position cranially and, with a concurrent extension force on the neck, impacted into the caudal vertebra.
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  • Release the extension moment provided by traction to lock the graft into place.
  • Anterior plate osteosynthesis is recommended. In long constructs, a short anterior plate can be applied at the caudal vertebra to buttress the inferior pole of the graft.
  • Screws are not placed into the graft because of the risk of graft fracture. A heavy suture may be passed around the graft and the plate to keep the graft from shifting posteriorly.
Once the anterior reconstruction is completed, the patient is turned and prepared for posterior instrumentation and fusion. While this procedure is not necessary in two- or three-level fusions, we routinely add posterior fusion to reconstructions of four or more levels, and to those with poor bone quality, translational instability, or risk factors for pseudarthrosis.
  • Expose the posterior cervical spine in the usual fashion, taking care to document levels and protect levels not instrumented anteriorly.
  • Use a burr to decorticate the laminae and facets, and remove articular cartilage from the facets with a small curet.
  • Use a 2.0 mm drill to prepare pilot holes for lateral mass plating.
  • Contour the lateral mass plate to neutralize the alignment obtained during the anterior procedure. Increasing lordosis at this point will tend to loosen the anterior construct.
  • Graft the facet joints and apply the plates over the graft.
  • Close in layers and apply a sterile dressing.
A hard cervical collar is used for 8–12 weeks. Halo immobilization for 12 weeks may be useful in patients with poor bone, previous failures, or multiple-level procedures. These patients may also benefit from a posterior stabilization procedure, often with lateral mass plates.
Hardware Failure
As in pseudarthrosis, not all failed hardware requires surgical intervention. In some cases, external immobilization can be used until fusion occurs. However, when failed hardware results in neurologic or soft-tissue compression, instability, or progressive deformity, surgical treatment is offered.
Anterior hardware impinging on anterior structures must be approached anteriorly. Failed posterior hardware may be approached posteriorly. However, in cases of poor bone quality, deformity, or three-column destabilization, circumferential stabilization procedures are recommended.
Take care when approaching displaced anterior hardware. The inflammation and tissue reaction around the old hardware will make the exposure difficult and will distort tissue planes. Inadvertent entry into the carotid sheath, esophagus, or thoracic duct can result in potentially lethal complications.
After hardware removal, spinal instability must be addressed. In some cases, postoperative halo immobilization suffices. Typically, however, revision internal fixation is employed in conjunction with postoperative immobilization (7).
Failed spinous process wires are easily removed and replaced with lateral mass plates. Sublaminar wires are more problematic, and they may be retained or removed. In cases where dense scar makes dissection difficult, the broken wire may be retightened around the intact lamina and left in place. If monofilament wire must be removed, contour the end to be pulled through the canal so that it can be pulled out smoothly. Place a Woodson or Penfield elevator between the wire and the thecal sack and extract the wire by winding the free end up with a needle-holder. Cut braided wires close to the lamina to remove as much of the frayed portion as possible before trying to remove them.
Adjacent-Level Degeneration and Recurrent Stenosis or Disc Herniation
Adjacent-level degeneration in the cervical spine is related to recurrent compression. Recurrence of stenosis or disc herniation often reflects the same global nature of cervical spondylosis seen in patients with recurrent axial symptoms. Whether or not surgical intervention accelerates degenerative changes at neighboring levels, principles regarding their treatment remain the same.
Treatment options for recurrent disc herniation include ACDF of the new level or posterior keyhole foraminotomy. There are proponents of each approach. In the patient with a previously operated neck, the same principles apply, with the caveat that repeat anterior surgery requires special attention to the status of the recurrent laryngeal nerves and vulnerable soft-tissue structures of the neck (as previously discussed).
When recurrent or residual root compression is the result of soft disc pathology at one or two levels, keyhole foraminotomy may be indicated. Most often, this is seen in patients with a prior ACDF and an incompletely excised disc, or with recurrent soft disc pathology at a neighboring level.
The advantages of keyhole foraminotomy include the avoidance of fusion-related problems and the need for only minimal laminar resection to expose the lateral edge of the dura. Disadvantages include its failure to decompress the cord and stabilize the spine. Laminoforaminotomy is contraindicated in patients with cervical kyphosis or major anterior cord compression (17).
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As in primary cervical spine procedures, debate continues as to the best method to treat multilevel recurrent or residual stenosis. Laminaplasty is recommended for recurrent stenosis above and below a previously, anteriorly fused level, or in the case of disease affecting more than three levels (28). Others report success with vertebrectomy and strut graft fusion techniques (42).
Laminaplasty preserves the cervical facets and decreases the incidence of instability associated with multiple-level laminectomies. However, decompression may be incomplete if foraminal stenosis is not addressed. Contraindications include cervical deformity (especially kyphosis) and major anterior cord compression.
Anterior vertebrectomy and strut graft fusion is recommended for patients with recurrent or residual stenosis after laminectomy and in those patients who are not candidates for posterior decompressive laminaplasty.
In patients with no evidence of stenosis and predominantly axial pain, the possibility of adjacent-segment disc degeneration must be considered. Advocates of cervical discography recommend anterior fusion for concordant pain (41).
Keyhole Foraminotomy for Recurrent or Residual Disc Herniation
  • With the patient prone, obtain precise radiographic localization prior to skin incision. Employ a standard midline approach with careful, unilateral exposure to the lateral aspect of the facet capsule.
  • Thin the lateral portion of the lamina and the medial portion of the facet with a burr.
  • Carefully develop the interval between the medial facet capsule and the ligamentum flavum with a fine curved curet or Penfield.
  • Remove the medial 25% of the facet with Kerrison rongeurs. Remove the volar facet capsule to visualize the root and the lateral margin of the thecal sack.
  • Expand the laminotomy over the junction of the root and dura taking care to preserve over 50% of the facet.
  • If a contained herniation is found, incise the PLL to retrieve the fragment.
  • Apply a collar for comfort for the first 2–3 weeks after surgery. If more than 50% of both facets, or more than 75% of one facet, is removed, consider fusion with lateral mass plates.
Laminaplasty for Multilevel Residual or Recurrent Stenosis
Open-book laminoplasty requires a wide exposure of the posterior elements and lateral masses of the involved cervical spine, as well as exposure of at least one normal level above and below the compression. The surgeon must elevate laminae at the margins of stenosis as well as those directly over the narrowed segment.
  • Through a standard, midline approach, carefully elevate the paraspinal musculature to the lateral edges of the facets.
  • Use a high-speed burr to cut longitudinal bone troughs through the lamina–facet junction.
  • Use a fine Kerrison punch to complete the trough on the side of primary compression (i.e., at the greatest narrowing or most significant radiculopathy).
  • Excise the ligamentum flavum and interspinous ligaments at the proximal and distal junctions of the laminaplasty segment with the normal spine.
  • Apply gentle, sustained pressure on the spinous processes and upward on the open laminotomy to elevate the laminar flap on its intact cortical “hinge.” Allow the intact lamina to deform plastically, being careful not to snap it off by applying too much force.
  • Release dural adhesions to the lamina with a Penfield elevator.
  • The lamina flap is then hinged wide open on the intact lamina in a staged fashion, moving cranially from the inferiormost hinged lamina. An elevation of 10–15 mm on the open side increases the sagittal diameter of the canal by 4–5 mm.
There are a number of techniques to keep the laminar flap open (Fig. 148.10). The laminae may be open with cadaver rib graft, as follows.
Figure 148.10. Trap-door laminoplasty for extensive stenosis or adjacent-level degeneration. A: Cut longitudinal troughs through the involved laminae using a high-speed burr. Troughs should be centered over the medial edge of the facet so that penetration exposes the lateral recess and not the cord. Complete the defect on the side of most compression using a small Kerrison. B: Thin the opposite lamina down to the volar cortex, then gradually elevate the opened side up and away from the facet, allowing time for the intact hinge to deform plastically. If the hinge is too stiff, thin it further. C: Use the spinous processes or an allograft bone strut to hold the laminoplasty open. Groove both ends of the graft to capture the cut edges of the lamina and the lateral mass. Use a small drill to make holes at the margins of both, and pass a heavy suture through the drill holes and lengthwise through the graft. D: Position the strut and allow the lamina to close down slightly to capture the strut. Tie the heavy suture over the outside of the graft to prevent it from migrating into the canal or dislodging and allowing the laminaplasty to close.
  • Cut three grafts to length (12–14 mm).
  • Cut a trough into each end of the graft.
  • One graft is inserted between the lamina and lateral mass at C-3, C-5, and C-7.
  • To avoid inadvertent fusion, care must be taken to avoid bone graft touching another level.
Often, the cervical spinous processes can be used for this purpose as well, as follows.
  • To keep the graft from displacing, pass a heavy suture longitudinally through the cancellous bone of each spinous process or rib allograft. Pass the suture through a small drill hole in the laminar margin and through the medial edge of the facet, and tie it tightly to compress the graft strut between the lamina and the facet margin. The secured strut will keep the flap from closing.
  • Supplemental foraminotomies may then be carried out to treat radiculopathy, as needed.
  • Close the posterior wound over drains. Reattach the deep layer to the spinous processes at the margins of the laminaplasty. Immobilize in a Philadelphia collar for 6–12 weeks. Some authors recommend a CT scan at 8 weeks to check healing on the hinge side and ensure canal patency. Once healing is complete, physical therapy emphasizing cervical extension exercises is recommended.
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GENERAL REHABILITATION AND POSTOPERATIVE PRINCIPLES
Most patients have already been immobilized from their prior cervical spine procedure. Significant deficits in extensor muscle strength and flexibility are common. Therefore, a supervised isometric strengthening and ROM program is indicated prior to returning to unlimited activity. At 12 weeks, or when x-rays demonstrate adequate bony union, prescribe a twice-daily regimen of 10 minutes of neck muscle ROM and isometric strengthening. Weekly physical therapy supervision to monitor progress and add incremental exercises until functional strength and ROM are regained may be recommended.
PITFALLS AND COMPLICATIONS
Prior surgery increases the likelihood of complications (Table 148.1). The hypovascular scar bed predisposes to infection or failure of healing. Some authors have reported complication rates for anterior surgery following failed posterior procedures similar to those reported in index anterior procedures (42,46,47). However, hardware problems are more likely in osteopenic bone and when normal anatomic landmarks are distorted.
Table 148.1. Complications of Revision Anterior Surgery
Repeated dissection through anterior soft tissues increases the possibility of transient sore throat or swallowing difficulty. Further, dissection through scar requires meticulous attention to detail and great caution. Perforation of the esophagus is a life-threatening injury, and only one third are recognized at the time of surgery. Mortality for injuries recognized early is 15%. If recognized late, mortality rises to 30% (30,36).
The literature regarding incidence of vocal cord paralysis after revision anterior cervical spine surgery is varied (9,22). Although the ipsilateral operative approach requires dissection through scar, the contralateral approach should not be undertaken without confirming the function of both vocal cords through laryngoscopy.
Other problems related to anterior surgery could be increased in the revision situation as well. Horner’s syndrome from injury to the sympathetic chain and overretraction of the longus colli is ostensibly more likely if the longus muscles are encased in scar, or the dissection difficult.
The most common complications of revision posterior cervical spine surgery are wound infection (1.2%) and failure of healing. Correction of identifiable nutritional deficiencies may decrease these problems. The incidence of dural tear also rises when dissecting through posterior scar (16).
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+ 24. Mikawa Y, Shikata J, Yamamuro T. Spinal Deformity and Instability after Multilevel Cervical Laminectomy. Spine 1987;12:6.
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! 27. Nolan JP, Sherk HH. Biomechanical Evaluation of the Extensor Musculature of the Cervical Spine. Spine 1988;13:9.
+ 28. Nowinski GP, Visarius H, Nolte LP, Herkowitz HN. A Biomechanical Comparison of Cervical Laminaplasty and Cervical Laminectomy with Progressive Facetectomy. Spine 1993;18:1995.
+ 29. Raynor R. Anterior or Posterior Approach to the Cervical Spine. An Anatomical and Radiographic Evaluation and Comparison. Neurosurgery 1983;12:7.
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+ 31. Robertson PA, Ryan MD. Neurologic Deterioration after Reduction of Cervical Subluxation. Mechanical Compression by Disc Tissue. J Bone Joint Surg Br 1992;74:224.
+ 32. Robinson RA, Walker AE, Ferlic DC, et al. The Results of an Anterior Interbody Fusion of the Cervical Spine. J Bone Joint Surg Am 1962;44:1569.
+ 33. Schellhaus KP, Smith MD, Gundry CR, Pollei SR. Cervical Discogenic Pain. Prospective Correlation of Magnetic Resonance Imaging and Discography in Asymptomatic Subjects and Pain Sufferers. Spine 1994;21:300.
+ 34. Shinomiya K, Okamoto A, Kamikozuru M, et al. An Analysis of Failures in Primary Cervical Anterior Spinal Cord Decompression and Fusion. J Spinal Disord 1993;6:277.
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+ 35. Sim FH, Svien HJ, Bickel WH, et al. Swan-neck Deformity following Extensive Cervical Laminectomy. A Review of Twenty-one Cases. J Bone Joint Surg Am 1974;56:564.
+ 36. Simmons EN, Bhalla SK. Anterior Cervical Discectomy and Fusion. J Bone Joint Surg Br 1969;51:225.
+ 37. Slizofski WJ, Collier BD, Flatley TJ, et al. Painful Pseudarthrosis following Lumbar Spinal Fusion. Detection by Combined SPECT and Planar Bone Scintigraphy. Skeletal Radiol 1987;16:136.
+ 38. Stevens JM, Clifton AG, Whitiar P. Appearance of Posterior Osteophyte After Sound Anterior Interbody Fusion in the Cervical Spine. A High Definition CT Study. Neuroradiology 1993;35:227.
+ 39. Tachdjian MO, Matson DD. Orthopaedic Aspects of Intraspinal Tumors in Infants and Children. J Bone Joint Surg Am 1965;47:243.
# 40. White AA, Panjabi MM. Clinical Biomechanics of the Spine, 2nd ed. Philadelphia: JB Lippincott, 1990.
+ 41. Whitecloud TS, Seago RA. Cervical Discogenic Syndrome: Results of Operative Intervention in Patients with Positive Discography. Spine 1987;12:313.
+ 42. Whitecloud TS III. Anterior Surgery for Cervical Spondylotic Myelopathy. Smith-Robinson, Cloward and Vertebrectomy. Spine 1988;13:861.
+ 43. Winter CY, Brannstein EM, Bailey WR. Radiographic Changes following Anterior Cervical Fusion. Spine 1980;5:399.
+ 44. Wu W, Thuomas KA, Hedlund R, et al. Degenerative Changes following Anterior Cervical Discectomy and Fusion Evaluated by Fast Spin-echo MR Imaging. Acta Radiol 1996;37:614.
+ 45. Yonenobu K, Okada K, Fuji T, et al. Causes of Neurologic Deterioration following Surgical Treatment of Cervical Myelopathy. Spine 1986;11:818.
+ 46. Zdeblick TA, Bohlman HH. Cervical Kyphosis and Myelopathy. Treatment by Anterior Corpectomy and Strut-grafting. J Bone Joint Surg Am 1989;71:170.
+ 47. Zdeblick TA, Ducker TB. The Use of Freeze-dried Allograft Bone for Anterior Cervical Fusions. Spine 1991;16:726.