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Combined Ventral-Dorsal Surgery
Summary of Key Points
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Cervical spine trauma, malignancy, ankylosing spondylitis, diffuse idiopathic skeletal hyperostosis, kyphotic deformity, and cervical spondylotic myelopathy are all pathologies for which a combined surgical approach may be biomechanically advantageous when both ventral and dorsal elements are involved.
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When circumferential surgery is necessary, it has been shown that performing both the dorsal and ventral portions in a single setting is beneficial. This is the result of reduced blood loss, operative time, length of hospital stay, and total cost.
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Factors to consider include preoperative cervical alignment, the number of segments involved, the presence of ventral and dorsal pathology, and patient factors that may decrease the likelihood of fusion with a ventral or dorsal approach alone.
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Circumferential surgery has been shown to be a powerful technique in correcting deformities such as postlaminectomy kyphosis or S-type curves. If there is uncertainty regarding the necessity for circumferential fusion for deformity, algorithmic strategies may help guide the surgeon’s choice.
Acknowledgment
The authors would like to thank Dr. Clayton L. Haldeman for his contributions to the previous edition of this chapter.
Combined ventral and dorsal surgery is indicated for a variety of cervical spine disorders. Traditionally, combined operations were most appropriate for trauma patients with three-column instability, much like that seen in the thoracolumbar model described by Denis. With anterior and posterior ligamentous and osseous disruption, combined ventral and dorsal surgery may provide short- and long-term stability and prevent late kyphotic deformity. , More recently, for deformity, algorithmic strategies have been devised to help guide less experienced surgeons in their choice of approach.
In addition to acute trauma, kyphotic deformity, symptomatic pseudarthrosis, rheumatoid arthritis, ankylosing spondylitis, diffuse idiopathic skeletal hyperostosis (DISH), neoplasms, and cervical spondylotic myelopathy may benefit from combined ventral and dorsal operations from a biomechanical and symptomatic relief standpoint. When considering a patient for combined ventral and dorsal operations, several factors must be taken into account. Patient age, comorbidities, bone quality (e.g., osteoporosis), degree of ligamentous and bony disruption, and the surgeon’s level of expertise can all influence the results of a combined versus ventral-only or dorsal-only approach. This chapter summarizes some indications for performing combined surgery, as well as the technical and complicating factors associated with such procedures.
Acute Cervical Spine Injury
Today, nearly any patient with suspected cervical spine injury will have computed tomography (CT) imaging performed. Whereas CT is excellent for determining osseous injury, ligamentous injury is not adequately depicted. In the authors’ opinion magnetic resonance imaging (MRI) should be considered in the patient who is stable and being considered for a ventral, dorsal, or combined procedure.
The three-column framework for managing spinal instability in the thoracolumbar spine can likewise be incorporated in acute cervical spine injury patients. Before the use of MRI, Cybulski and colleagues reviewed the factors that make three-column disruption more likely: (1) disruption of anterior and posterior longitudinal ligaments, (2) dislocation of facets, and (3) disruption of the posterior interspinous ligaments with sufficient force to cause shear dislocation of one vertebra on another.
Although posterior tension band stabilization procedures can be performed on most reduced cervical fracture-dislocations, Cybulski and colleagues have recommended consideration of circumferential surgery in cases of significant three-column instability. Distractive-flexion or compressive-flexion injuries corrected with posterior fusion were the most likely to need a ventral fusion. These injuries apply horizontal shearing forces that destabilize all three columns.
In defining the most optimal procedure, most shortcomings arise from the lack of a standardized nomenclature or scoring system. Vaccaro and associates proposed a scoring system (Subaxial Cervical Spine Injury Classification [SLIC]) based on three key features: (1) injury morphology as determined by mechanism of injury from existing imaging studies, (2) integrity of the discoligamentous soft tissue complex (DLC) based on anterior and posterior longitudinal ligamentous structures and the intervertebral disc, and (3) patient neurology ( Table 114.1 ). An ideal classification system would be based on fracture pattern, suspected mechanism of injury, spinal alignment, neurological injury, and prognosis of long-term stability. The Vaccaro classification was derived from a literature review and surveys performed by the Spine Trauma Study Group (STSG; founded in 2004, consisting of 50 surgeons from 12 countries dedicated to improving the interpretation and management of traumatic spine conditions). The results demonstrated that DLC is the most difficult to objectify on the basis of low interrater and intrarater intraclass correlation coefficients. There was a high degree of validity, with 93.3% of raters agreeing on a treatment plan based on the SLIC algorithm.
TABLE 114.1
Subaxial Injury Classification
From Vaccaro AR, Hulbert RJ, Patel AA, et al. The subaxial cervical spine injury classification system: a novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine (Phila Pa 1976). 2007;32(21):2365-2374.
| Points | |
|---|---|
| Morphology | |
| No abnormality | 0 |
| Compression | 1 |
| Burst | +1–2 |
| Distraction (e.g., facet perch, hyperexten-sion) | 3 |
| Rotation/translation (e.g., facet dislocation, unstable teardrop, advanced-stage flexion-compression injury) | 4 |
| Discoligamentous Complex | |
| Intact | 0 |
| Indeterminate (e.g., isolated interspinous widening, MRI signal change only) | 1 |
| Disrupted (e.g., widening of disc space, facet perch, dislocation) | 2 |
| Neurological Status | |
| Intact | 0 |
| Root injury | 1 |
| Complete cord injury | 2 |
| Incomplete cord injury | 3 |
| Continuous cord compression in setting of neurological deficit (neuromodifier) | +1 |
MRI , Magnetic resonance imaging.
Multiple algorithm-driven methods for choosing an approach have been proposed. , Dvorak and coworkers based their choice of surgical approach on a systematic review of the literature, as well as the opinions of 48 of the spine surgeons who make up the STSG. On the basis of the scoring system from the SLIC scale, algorithms were created by the STSG. Although many approaches described are for either ventral or dorsal approaches, some algorithms conclude with a combined approach. In distraction injuries with hyperextension injury with or without avulsion fractures, the fusion construct can be addressed ventrally. However, in cases of severe spondylosis, diffuse idiopathic skeletal hyperostosis, or ankylosing spondylitis, the adjacent level stiffness is best neutralized with an additional dorsal approach. For bilateral facet subluxations (perched facets without fracture) there is a higher incidence of kyphosis after posterior fusion alone. End plate compression fracture with facet fracture/dislocation almost always requires a combined approach. In those who have a ventral surgery alone, there may be early mechanical failure of the fusion. Severe ventral vertebral body fractures, including teardrop fractures and burst-fracture dislocations, have posterior element failure as a common feature ( Fig. 114.1 ). These patients are candidates for a combined approach. In unilateral or bilateral facet fracture dislocations (no vertebral body fracture), a posterior approach is often used. However, if prereduction MRI demonstrates a disc fragment displaced into the spinal canal, or if the patient declines neurologically after closed reduction, a concomitant anterior discectomy, reduction, and fusion approach is recommended.
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