Chapter 48 Combined Ventral-Dorsal Surgery
Disorders of the cervical spine can be considered for combined ventral and dorsal surgery in one setting. The indications for these cases may be small in number but when necessary can be technically demanding with associated significant morbidity.1,2 Traditionally, such operations were most appropriate for trauma patients having three-column instability, much like that seen in the thoracolumbar model described by Denis.3 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.4,5
It is clear that a combined operation under a single anesthetic offers savings in blood loss, incidence of wound infections, hospital stay, and total cost.1,2 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
Patients who suffer traumatic cervical spine injury will have plain radiographs taken or CT imaging performed. Although these methods can demonstrate osseous injury, ligamentous injury is not accurately depicted. Advanced imaging such as MRI should be considered in the patient who is stable and is being considered for a ventral, dorsal, or combined procedure.6
The three-column framework for managing spinal instability in the thoracolumbar spine can likewise be incorporated in acute cervical spine injury patients.3 Before the use of MRI, Cybulski et al. 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.6
Although posterior tension band stabilization procedures can be performed on most reduced cervical fracture-dislocations, Cybulski et al. recommend 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.6
In defining the most optimal procedure, most shortcomings arise from a lack of standardized nomenclature or a scoring system.7 Vaccaro et al. proposed a scoring system (subaxial 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 48-1).8 An ideal classification system would be based on fracture pattern, suspected mechanism of injury, spinal alignment, neurologic injury, and prognosis of long-term stability.8 The Vaccaro classification was derived from literature review and surveys done with the Spine Trauma Study Group (STSG, founded in 2004, consisting of 50 surgeons from 12 countries dedicated to improving 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 coefficient (ICC). There was a high degree of validity, with 93.3% of raters agreeing on a treatment plan based on the SLIC algorithm.8
| Points | |
|---|---|
| Morphology | |
| No abnormality | 0 |
| Compression | 1 |
| Burst | +1–2 |
| Distraction (e.g., facet perch, hyperextension) | 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 |
| Neurologic Status | |
| Intact | 0 |
| Root injury | 1 |
| Complete cord injury | 2 |
| Incomplete cord injury | 3 |
| Continuous cord compression in setting of neurologic deficit (neuromodifier) | +1 |
Data from Vaccaro AR, Hurlbert RJ, Fisher CG, et al: The sub-axial cervical spine injury classification system (SLIC): a novel approach to recognize the importance of morphology, neurology and integrity of the disco-ligamentous complex. Spine (Phila Pa 1976) 32(23):2365–2374, 2007.
Dvorak et al.7 described an algorithm for deciding the choice of surgical approach on the basis of a systematic review of the literature, as well as opinions of 48 spine surgeons comprising 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 (perches facets without fracture) there is a higher incidence of kyphosis after posterior fusion alone speculating progressive disc space collapse as a cause for failure. 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. 48-1). 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 the patient declines neurologically after closed reduction, a concomitant anterior discectomy, reduction, and fusion approach is recommended.7
Kyphotic Deformity
Cervical kyphosis can occur because of several conditions, including trauma, malignancy, inflammatory disease, infection, spondylosis, and iatrogenic processes. Postlaminectomy kyphosis, or “swan neck” deformity, occurs in approximately 20% of adult patients after multiple cervical laminectomy.9 Risk factors associated with postoperative kyphosis include preoperative loss of cervical lordosis, extent of laminectomy, facet capsule destruction, tumor, and radiation.9 In postlaminectomy kyphosis, a ventral decompression and fusion are associated with significant graft complications and instability. Graft complications can include dislodgement, pseudarthrosis, and acceleration of adjacent level degeneration.10 In advanced disease, further degeneration resulting in foraminal stenosis and subsequent radiculopathy; progressive spinal cord shift to the anterior portion of the spinal canal, resulting in myelopathy; as well as swallowing, breathing, and forward gaze difficulties can be present and are reasons for surgical intervention.11
