Posterior stabilization of the cervicothoracic junction presents unique challenges to the spinal surgeon. This region of the spine is an area of transition. Anatomical characteristics of the spinal cord and vertebral segments and the biomechanical properties of the spine markedly alter over a relatively short anatomical distance. Cervicothoracic spinal surgery is demanding because of the anatomical nuances, the infrequent need for surgery at this region, and the relatively high rates of complications. Recent advancements in posterior spinal implants enable spinal surgeons to better cope with the problems encountered when stabilizing the cervicothoracic junction.
The strategic goals of any spinal surgery are to decompress neural structures, prevent, or correct deformities and ensure stability of the spine. How these strategic goals are achieved are the tactical details of the surgery. What is required for decompression or deformity release will determine the direction of attack. Reconstruction of the spine will be based on how the spine was dismantled, what collateral damage occurred to the spine and the surrounding anatomical structures, and what structures are available for attachment of spinal implants. The surgeon must keep in mind the biology of fusion, sagittal and coronal spinal alignment, and how the spine will respond to both the surgical and the normal alterations in anatomy over time.
The cervicothoracic junction as a surgically relevant unit is considered to be from C5 through T5.
Five specific challenges must be addressed and overcome for successful posterior stabilization of the cervicothoracic junction:
Variation in size and morphology between the cervical and thoracic spinal segments.
Reversal of the cervical lordotic curve to the thoracic kyphotic curve.
Variation in the degree of mobility between the flexible cervical spine and the less mobile thoracic spine.
Surrounding anterior thoracic anatomical structures.
Spinal implants required to transition between the variances in morphology of spinal segments.
Overcoming each of these challenges has driven improvements in posterior cervicothoracic implant technology. Posterior instrumentation techniques for the cervical spine differ significantly from techniques required in the thoracic spine. Excellent solutions have long been available to stabilize the cervical and thoracic regions separately. Successful cervicothoracic stabilization requires that both regions’ unique characteristics be addressed and then the differing segments securely linked. Current implant technology has risen to meet the challenges of posterior stabilization of the cervicothoracic junction, making it a much less daunting task than it was in the 20th century.
23.2 Patient Selection
Selection of surgical approach is dependent on what decompression, resection, or tissue release is required to achieve the strategic goal of the surgery. Current implant technology provides reasonable reconstruction and stabilization solutions for whatever is required. The spinal surgeon must be able to tailor the approach and subsequent stabilization to the specific pathology presented and thus should be familiar with all approaches and devices available. Posterior instrumentation alone will not adequately address all the pathology encountered at the cervicothoracic junction. In many cases, posterior instrumentation is just one of the tactics used to achieve the overall strategic surgical objective.
23.2.1 Posterior Only (Back)
Many situations at the cervicothoracic junction will need only secure posterior stabilization. No fixed deformity should be present, and the cervical lordosis is sufficient or easily obtained in extension. Posterior-only fixation can provide restoration of the tension band or prevent progressive deformity in cases of multilevel cervicothoracic decompression for spondylotic myelopathy. The implants used will be determined by the anatomy available for attachment. If laminectomies have been done, then the only option is lateral mass and pedicle screws.
23.2.2 Anterior Only (Front)
At the cervicothoracic junction, the indication for front-only fixation is limited. Certainly, single-level anterior diskectomy and fusion at the C7–T1 level has a long and successful track record. Because of the biomechanical forces mentioned earlier, anterior plating is strongly recommended at this level. Likewise, single-level corpectomies at either C7 or T1 are successfully managed with an anterior locking plate and strut graft or cage, provided no posterior pathology or instability is present. When two or more levels of corpectomy are done at the cervicothoracic level, or if there is significant posterior pathology, supplemental posterior instrumentation is also recommended.
23.2.3 Anterior and Posterior (Front–Back)
The front-back approach is used when there is both anterior and posterior pathology or when more than two levels of corpectomy are required for either decompression or release. The first stage of the procedure is usually the anterior decompression or release followed by the reconstruction. Anterior reconstruction can be done with a strut graft, titanium mesh cage, or telescoping cage in addition to an anterior locking plate. Deformity correction, if needed, must be done in the first stage because the posterior implants and bone of the cervical spine cannot be relied on to handle forces necessary to achieve correction. Changes in head position and use of vertebral body distraction pins are effective means of restoring cervical lordosis after releasing diskectomies or corpectomies. The second stage, either during the same anesthesia or staged, is the addition of the posterior stabilization. All the methods described in the posterior only approach can be used. If posterior decompression is needed, the choice is limited to lateral mass and pedicle systems.
23.2.4 Posterior–Lateral (Extracavitary)
The extracavitary approach is an anterior and posterior approach through one posterior incision. Multilevel vertebral resections and complete spondylectomies can be accomplished in this manner. The extracavitary approach is an excellent option in tumor, infection, and deformities when both anterior and posterior portions of the vertebral segment are involved. Anterior reconstruction can be accomplished with strut grafts, titanium mesh cages, or telescoping cages. Great care must be taken in positioning the anterior cage or graft because the important nerve roots at the cervicothoracic junction can be easily injured. Placing an anterior plate or rod device is exceedingly difficult through the extracavitary approach but is usually not needed if there is adequate compression of the posterior instrumentation over the anterior load-sharing device. Although the extracavitary approach has a steep learning curve, once mastered, it becomes a less invasive means of addressing anterior and posterior pathology.
23.2.5 Posterior–Anterior-Posterior (Back–Front–Back)
This aggressive approach is reserved for those patients with fixed sagittal plane deformities across the cervicothoracic junction. The deformities tend to be either congenital or longstanding. Both anterior and posterior osteotomies are required to achieve the desired correction. The initial stage is the posterior release with facet osteotomies or laminectomies. Frequently the posterior implants are placed in this stage, when the spine is still relatively stiff and there is no danger of dislodging anterior grafts or cages. The connecting rods are not secured until later, after the anterior correction has been achieved. Facetectomies may be performed to allow mobilization of the spine and restoration of lordosis. Multiaxial screw and rod systems are the best option when some of the posterior bone has been removed. The second stage is in the supine position, in which the anterior diskectomies, osteotomies, or corpectomies are done. The approach used depends on the level to be addressed. Usually the modified low anterior cervical or suprasternal approach is used for C7–T2, and a transsternal approach is used for access below T2. Anterior reconstruction is accomplished with multiple tricortical grafts, strut grafts, titanium mesh cages, or telescoping cages. An anterior locking plate secures the anterior load-sharing member. For the third and final stage, the patient is returned to the prone position, and the posterior instrumentation is locked onto the rod. Fine adjustments can be made with compression and gentle in situ bending of the rod, keeping in mind not to use too much force on the more delicate cervical bone anatomy.
23.3 Preoperative Preparation
Imaging of the spine should include magnetic resonance imaging (MRI) to evaluate the neural structures and the soft tissue surrounding the spine. MRI will also image tumors, infection, or disk pathology. Computed tomography (CT) will better delineate the morphology of the bone anatomy to include the size of the lateral masses, the pedicles, and the position of the transverse foramen that encases the vertebral artery. CT will identify bone destruction that frequently occurs in tumors or infection and thus will assist in the planning of implant placement. Plain radiographs in the neutral position will assess the degree of lordosis in the cervical spine and kyphosis in the thoracic spine. Attention must be paid to the location of the native thoracic kyphosis because it will help determine how many thoracic levels the construct will include. When a deformity is present, flexion and extension plain radiographs will help determine whether osteotomies or tissue releases will be required. In deformity cases, scoliosis views that include the entire spine in the standing position will assist in obtaining neutral global sagittal balance for the final construct position. Abnormalities in the lumbar spine, if not taken into account, will result in sagittal or coronal imbalance.
23.4 Operative Procedure
23.4.1 Anesthesia Considerations
The surgery should be done with the patient under general anesthesia. Care should be taken with intubation to avoid worsening of neurological status. Excessive extension or flexion of the neck should be avoided. Fiberoptic intubation should be considered in cases of greater stenosis. The anesthesia team should be cautious to maintain the patient’s normal blood pressure because hypotension could result in insufficient perfusion of the spinal cord. Consider arterial line for instantaneous monitoring of the systemic blood pressure for the period of position and throughout the procedure. In larger patients and tumor cases, blood loss may be considerable. Large-bore intravenous line, autologous blood donation, use of cell salvage, and cross-matched blood all should be available. In selected tumor cases, preoperative embolization has been very helpful in reducing intraoperative blood loss and should be strongly considered. Intraoperative neurophysiological monitoring through somatosensory evoked potentials and motor evoked potentials is becoming more commonplace and is recommended in the more severe cases. A Foley catheter should be placed. Antibiotics should be given before skin incision and repeat doses given as needed for time and blood loss.
23.4.2 Positioning
Correct positioning of the neck and cervicothoracic junction in neutral sagittal alignment (when possible) is arguably the most important part of the procedure. Failure to pay close attention to this detail will result in the patient being fused out of sagittal alignment into an iatrogenic deformity. Even if the patient is in sagittal balance before surgery, it is imperative that meticulous positioning be done so that the spine is not fused in a position of inadvertent deformity. Painful compensatory changes in the nonfused portions of the spine can result. Head fixation with a three-point skull fixation allows for the greatest control of the anatomy, although nonrigid fixation is reasonable in some cases. Before skin preparation, a radiograph should be taken with either fluoroscopy or plain films to verify a neutral position. Independent verification of an external neutral position can be done by the anesthesia or nursing staff. When deformity correction is part of the procedure, the ability to reposition the head and spine beneath the drapes must be ensured. The sitting position makes intraoperative position adjustments more difficult.
Intraoperative spinal cord monitoring is an excellent aid at the time of positioning and may help decrease intraoperative and perioperative neurological deficits in cervical spine surgery. Signals should be checked once final positioning has been completed and before the incision is made.
The arms should be tucked at the side of the patient, which enables the surgeon to be closer to the patient at both the cervical and the thoracic levels. This arm position also keeps the rhomboid muscle groups from being on stretch ( ▶ Fig. 23.1).
Fig. 23.1 Position of patient before draping. Neutral position of the head in the sagittal and coronal plane is verified by fluoroscopy. Neurophysiological monitoring is checked once the final position is achieved and before the incision is made.
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