11.3.6\ Anterior Cervical Fusion

11.3.6.1\ Discussion

Anterior cervical plates are commonly used for fusion to treat degenerative conditions, as well as fractures, infections, and tumors. The hardware most commonly spans two or three vertebral body levels, but can be as many as five vertebral bodies. The plates are affixed to the vertebral bodies via screws (Fig. 11.39). The screws should not transgress the adjacent disc space. The plates and screws are most often metallic, although some biodegradable devices have been developed. Another technique for anterior cervical fusion is the use of interbody devices without the use of plate (stand-alone). These devices are typically composed of polyether ether ketone (PEEK) and are fixed to the vertebral body either with two or three screws or fins (Fig. 11.40). For example, Zero P is a Synthes device used as a stand-alone implant in cervical interbody fusion and incorporates both the interbody cage and fixation plate. The device has a low profile anteriorly, resulting in decreased soft tissue and esophageal irritation. Zero P and all similar devices are designed to reduce adjacent level ossification, since the plate does not irritate the adjacent disc.

a

Complications of anterior cervical fusion include hardware infection, dysphagia, hematoma, esophageal perforation, subsidence, spinal cord injury in the cervical spine, and bowel, or vascular injury in the lumbar spine. A fluid collection and foci of gas can be identified in the prevertebral space on CT with hardware infection (Fig. 11.41). MRI is used to evaluate for an associated epidural abscess.

Subsidence of the hardware or graft material is a chronic process in which the materials penetrate into the adjacent vertebral bodies or disc spaces. This can lead to postoperative deformity and sclerosis, which can be assessed on CT (Fig. 11.42).

Cervical spinal cord injury can rarely occur during screw placement, potentially creating a transecting spinal cord injury (Fig. 11.43). Dysphagia and dysphonia are common following anterior cervical fusion due to injury to the pharyngeal plexus and recurrent laryngeal nerve. CT can be used to assess the neck soft tissue in such cases, which may reveal supraglottic edema (Fig. 11.44). Otolaryngology consultation should be obtained for patients with postoperative dysphagia or dysphonia, particularly if that persists longer than 1–2 months.

b

Fig. 11.39  Anterior cervical discectomy and fusion (ACDF). Axial (a), sagittal (b), and 3D (c) CT images show an anterior cervical plate secured flush against the

vertebral bodies via screws. Anterior discectomy and placement of intervertebral allografts was also performed (arrows)

Fig. 11.41  Infection. Axial CT image (a) demonstrates a fluid collection containing foci of gas anterior to the anterior cervical spine hardware (arrow). Axial fat-suppressed

post-contrast T1-weighted MRI (b) shows extensive enhancement in the prevertebral space as well as extension into the anterior epidural space (arrow)

Fig. 11.42  Bone graft subsidence and retropulsion. Sagittal CT image shows the bone graft dowel (arrow) protruding into the spinal canal and adjacent vertebral bodies

Fig. 11.44  Supraglottic swelling after anterior cervical fusion. The patient experiences difficulty breathing after cervical spine surgery. Sagittal CT image shows multiple level cervical anterior fusion with surgical hardware and swelling of the supraglottic soft tissues (arrow)

11.3.7\ Anterior Approach

Thoracolumbar Spine

Stabilization Devices

11.3.7.1\ Discussion

Anterior surgical approach short-segment stabilization systems, such as the Kaneda device (DePuy Spine, Raynham, Mass) and the Vantage plate (Medtronic, Sofamor Danek, Memphis TN), are adjustable devices that can provide rigid fixation

a

of the thoracolumbar vertebral column in the setting of burst fracture stabilization or corpectomy via anterior approaches. The Kaneda device consists of a rod and screws with additional staples, which reinforce the purchase of the screws in the vertebrae, resulting in robust fixation (Fig. 11.45). The Vantage plate features several slots for selecting the optimal level of the screws that are secured to adjacent vertebral bodies (Fig. 11.46). The device is inserted by using an anterior approach.

b