Degenerative cervical spondylosis is a common cause of multilevel cervical stenosis that can result in symptomatic radiculopathy or myelopathy depending on the location of compression. The indications for surgical management include persistent or worsening symptoms despite a trial of appropriate nonoperative treatment options. The primary goal of surgical treatment is physical decompression of the neurologic elements. This can be accomplished posteriorly using laminectomy or laminoplasty techniques, or anteriorly through corpectomy or diskectomy approaches.
The decision to decompress anteriorly or posteriorly depends not only on surgeon preference, but also on several key factors, including location of the stenosis, alignment of the cervical spine, and number of levels involved. One of the primary settings in which a surgeon will choose an anterior approach is a case in which anterior compressive structures are present in a patient with a kyphotic cervical spine. In this scenario an anterior approach allows for direct decompression as well as restoration of spinal alignment.
Once the decision has been made to proceed with anterior decompression for multilevel cervical stenosis, the surgeon must choose between multilevel diskectomies and vertebral corpectomy. Although no consensus exists with regard to which option is appropriate in which circumstance, it is the feeling of many that in most cases the same degree of decompression can be achieved through multilevel diskectomy as through vertebral corpectomy. In addition, one of the advantages of multilevel cervical diskectomy is that it provides multiple distraction points, which can permit more effective restoration of lordosis than a long, straight corpectomy graft such as a fibula.
Although decompression of the neurologic elements is the primary goal in the treatment of radiculopathy and myelopathy, successful fusion and maintenance of normal cervical spinal alignment are critical to the long-term success of most operative treatment options for multilevel cervical stenosis. The reported rates of fusion for single-level anterior cervical diskectomy and fusion (ACDF) procedures are extremely high, reaching 97% in some studies. Unfortunately, as the number of operative levels increases, the fusion rates for ACDF decrease. Studies that have compared multilevel cervical diskectomy and fusion to cervical corpectomy and fusion have found that although there are higher fusion rates in patients undergoing corpectomy, there are also higher rates of graft extrusion resulting in loss of spinal alignment. The addition of an anterior cervical plate not only can improve stability, but also has been shown to enhance fusion rates in multilevel ACDF operations.
The ultimate goal of multilevel ACDF surgery is decompression of the neurologic elements, restoration of spinal alignment, and achievement of fusion. Often, the ability to achieve fusion is the most difficult part, with rates of pseudoarthrosis ranging from 2.5% to 44%. Although there are several factors that can contribute to pseudoarthrosis (nicotine usage, inadequate end-plate preparation, excessive distraction, improper graft positioning, etc.), the type of graft used is an important variable. This chapter presents the different bone-grafting options available when performing multilevel ACDF and reviews the indications for inclusion of posterior fusion.
Case Presentation
A 39-year-old right-hand-dominant woman came for treatment after 4 months of severe neck pain radiating into both upper extremities. Her condition had failed to improve after several months of physical therapy and management with multiple medications. At the time of presentation she reported severe paresthesias throughout her left upper extremity and worsening left arm weakness. The patient reported no problems with balance or fine motor control and did not suggest any changes in bowel or bladder habits.
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PMH: Unremarkable
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PSH: Unremarkable
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Exam: On physical examination, the patient was quite tender to palpation along the posterior cervical spine. She had limited range of motion of the cervical spine due to pain. She had 4/5 weakness in the left upper extremity in the deltoid, biceps, triceps, and hand intrinsics. Her reflexes were diminished in the biceps, brachioradialis, and triceps in the left upper extremity. No abnormal reflexes were present. Her gait pattern was normal.
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Imaging: Preoperative imaging evaluation revealed a neutral to slightly kyphotic alignment of the cervical spine. Magnetic resonance imaging (MRI) of the cervical spine showed multilevel cervical spinal cord compression secondary to ventral compression at C3-4, C4-5, C5-6, and C6-7 ( Figures 2-1 and 2-2 ). Computed tomographic (CT) scanning was ordered, and the findings confirmed that the compressive elements were soft herniations.
FIGURE 2-1
Preoperative sagittal T2-weighted MRI scan showing multilevel disk herniations causing spinal cord compression.
FIGURE 2-2
Preoperative axial T2-weighted MRI scan showing central and left posterolateral herniations with multilevel cervical stenosis at C3-4 ( A ), C4-5 ( B ), C5-6 ( C ), and C6-7 ( D ).
Surgical Options
Interbody grafts in multilevel ACDF serve several purposes. Perhaps the two most important goals for the graft are to provide structural support and to allow solid fusion to be achieved. The most commonly used interbody options are autogenous bone grafts, allogeneic bone grafts, and anterior cervical cages. When the surgeon is deciding on what type of graft to use, important considerations include the number of levels being fused, the quality of the host bone, medical comorbidities, and the smoking status of the patient.
After discussion of management options, a decision was made to proceed with multilevel ACDF given the lack of cervical lordosis and the ventral nature of compression, which was all at the level of the disk spaces.
The patient underwent successful multilevel ACDF from C3 to C7 using freeze-dried machined allograft with recombinant human bone morphogenetic protein-2 and an anterior cervical plate.
Postoperatively the patient experienced complete resolution of her neck and arm symptoms and her strength normalized. Successful fusion was achieved both clinically and radiographically ( Figure 2-3 ).
Fundamental Technique
When a multilevel ACDF operation is performed the patient is positioned supine on a radiolucent operating table with a roll placed between the shoulder blades to allow for neck extension ( Tips from the Masters 2-1 and 2-2 ). Gardner-Wells tongs can be applied to allow controlled distraction. The amount of distraction can be increased at the discretion of the surgeon. Distal traction through the shoulders is applied using wide tape to help with fluoroscopic visualization.
Make sure the majority of neurologic compression is occurring ventral to the thecal sac and is at the level of the disk space.
Always make sure the patient is positioned so that cervical lordosis is restored and all disk spaces can be visualized fluoroscopically.
The preference is to use a left-sided approach to the anterior cervical spine. However, a right-sided approach can also be used if the surgeon is more comfortable with this. Placement of a longitudinal incision along the medial border of the sternocleidomastoid can allow for easier visualization proximally and distally. However, a horizontal incision centered over the center vertebra or disk space is more cosmetically pleasing.
After confirming the appropriate disk levels, many surgeons tend to work from distal to proximal in performing the diskectomies. Distraction pins are used sequentially at each disk level to help in opening the disk space and performing a complete diskectomy ( Figure 2-4 ). It is common practice to resect the posterior longitudinal ligament in all cases ( Tips from the Masters 2-3 ).
A thorough decompression is critical to the relief of neurologic symptoms.
Prepare the end plates to reveal points of bleeding cancellous bone, which can be created with a small angled currette punched through the end plates at multiple points.
After each diskectomy is completed the end plates are prepared using a high-speed bur to reach bleeding cancellous bone ( Tips from the Masters 2-5 ). The disk space is then sized and packed with a hemostatic agent such as surgical foam ( Figure 2-5 ). Attention is then turned to the next proximal disk space and the steps are repeated until all diskectomies are performed, end plates prepared, and disk spaces sized ( Tips from the Masters 2-6 ).
A graft that is at least 2 mm larger, but not more than 4 mm larger, than the resting disk height should be placed to allow for restoration of foraminal height without risking nonunion or overdistraction of the facet joints.
Interbody grafts should be slightly recessed and all anterior vertebral osteophytes removed for appropriate plate placement.
Related posts:
Asymptomatic Intradural Schwannoma: Surgery Versus Radiosurgery Versus Observation
Cervical Spondylosis–Spinal Stenosis: Laminoplasty Versus Laminectomy and Fusion
Lumbar Degenerative Disk Disease: Fusion Versus Artificial Disk
Degenerative Scoliosis: Anterior and Posterior Fusion Versus Posterior Fusion
Laminectomy Across the Cervicothoracic Junction: Fusion Versus Nonfusion
C1-C2 Fusion: Transarticular Screws Versus Harms/Melcher Procedure
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