Cervicothoracic Deformity: The Role of Anterior Surgery

Clinical Evaluation of Cervicothoracic Junction Deformity Patients

The preoperative evaluation of CTJ deformity requires a detailed history, physical examination, and imaging. Key considerations throughout the evaluation of a CTJ deformity include determining the patient’s ability to safely undergo surgical intervention, the presence of compensatory mechanisms, the flexibility of the deformity, the presence of ankylosis, and signs or symptoms of neural compression.

The initial history of a patient with CTJ deformity should evaluate for (1) the degree of deformity and its functional impact on the patient, (2) symptoms of neural compression including radiculopathy and/or myelopathy, and (3) the specific loss of compensatory mechanisms. Regarding the functional impact of the deformity, the presence and character of any neck and back pain, progressive dysphagia, difficulty maintaining a horizontal gaze, and/or significant limitations in daily activities should all be evaluated. In addition, the history taken should focus on symptoms of neural compression, including radiculopathy, gait imbalance, and difficulties with fine motor movements. Finally, it is important to document loss of deformity compensation including recent progression of symptoms, especially the development of increasing neck or back pain when upright.

The physical examination should not only corroborate these symptoms, but additionally begin to quantify the degree of the deformity. Gait, motor strength, reflexes, and sensory changes in particular can provide objective signs of neural compression. If a deformity is present, the clinical apex should be ascertained, as it can differ from the radiographic apex; the clinical apex of a deformity is defined as the vertebral level of the area of maximum deformity using surface-based landmarks. The chin-brow vertical angle (CBVA) can similarly be measured as the angle between a line subtending the chin to the brow and a vertical line, with worsening deformity as the angle increases. Compensatory mechanisms can also be determined through observation of the patient during a clinic visit. Common compensatory mechanisms used by patients include retroversion of the pelvis, bending at the knees, extending at the craniocervical junction, and compensating at the CTJ.

Following patient assessment through a physical examination, the deformity should be further characterized through the use of standing scoliosis films. First, the radiographic apex of the deformity can be determined using the films. Cervicothoracic radiographic parameters can then be used to further characterize the deformity. One of the most valuable radiographic parameters is the cervical sagittal vertical axis (SVA), which is measured as the horizontal distance between the plumb line from the center of the C2 body to the posterior, superior end plate of C7. The cervical SVA has been directly related to quality-of-life metrics, with larger cervical SVAs (>40 mm) associated with worse quality of life. The CBVA is the angle formed by a line parallel to the vertical axis of the patient and a line drawn from the brow to the chin. Normal values are between ‒10 degrees and +10 degrees, and this parameter is used to measure loss of horizontal gaze. Related to this, the occipital to C2 angle has been shown to be a point of compensation for malalignment in the CTJ ( Fig. 144.1 ).

The thoracic inlet angle (TIA) has been proposed by Lee et al. as a predictor of physiological sagittal cervical alignment. The TIA is the sum of the T1 slope and neck tilt angles (see Fig. 144.1 ). The T1 slope is the angle of the T1 end plate to the horizontal plane, and the neck tilt is the angle formed between a vertical line to the sternum and the line connecting the sternum to the midpoint of the T1 end plate. Spinopelvic measures such as lumbar lordosis, pelvic tilt, and pelvic incidence can also be evaluated, as the pelvis can be an important site of compensation for patients with cervicothoracic deformity.

After evaluating radiographic measures of cervical alignment, the flexibility of the deformity should be assessed through the use of dynamic flexion-extension x-rays of the cervical spine. The flexibility of the deformity can have a significant impact in determining the appropriate surgical intervention. If a fixed deformity is present, a computed tomography (CT) scan can be obtained to evaluate the presence of bony fusion, which can also help inform subsequent surgical intervention. The importance of rigid vs. flexible deformity must be emphasized. Just as in the thoracolumbar spine, rigid deformities drastically change the surgical approach. If a rigid deformity is present, as determined by irreducibility on dynamic flexion-extension x-rays, then an anterior-posterior approach (or even a posterior-anterior-posterior approach) is needed to release the deformity and instrument the spine in the reduced position. Flexibility of the deformity can be inferred from several radiographic features, including mobility on flexion/extension radiographs, the “vacuum disc sign” on CT studies indicating degeneration and motion of the intervertebral space, variability of cervical and thoracic alignment on supine vs. standing x-rays, and even dynamic magnetic resonance imaging (MRI; when indicated).

Anatomical Considerations

Anatomy of Anterior Access

The CTJ classically spans from C7 to T2; thus, the manubrium, clavicle, and ribs all pose bony obstructions to the cervicothoracic spine. The vascular anatomy involved in anterior approaches to the cervicothoracic spine is complex, and includes the left and right brachiocephalic veins, right brachiocephalic artery, left common carotid artery, aortic arch, esophagus, trachea, and thoracic duct. Low cervical approaches, described below, are usually sufficient to access T1 and T2; however, the manubrium and sternum prevent access to lower levels. The manubrium corresponds to the T2‒T3 level at the suprasternal notch and the T4‒T5 level at the sternal angle.

Preoperative MRI is often used to identity the anatomy of the brachiocephalic vein and the aortic arch to determine whether or not an anterior approach can be taken. Division of the left brachiocephalic vein is required to access T3‒T4, but this is associated with a risk of postoperative venous congestion and swelling of the left upper extremity. The recurrent laryngeal nerve is also vulnerable in anterior approaches. The left-sided recurrent laryngeal nerve is usually found in the tracheoesophageal groove. It is longer than the right-sided nerve and less likely to have anatomical variants. The recurrent laryngeal nerve loops under the arch of the aorta on the left and under the subclavian artery on the right and is prone to injury during anterior approaches. Recurrent laryngeal nerve palsy can result in hoarseness, aspiration, or dysphagia. There can be direct injury to the nerve attributed to exposure, traction injury, or (in 11.2% of cases) entrapment of nerve between the endotracheal tube cuff and retractor blades. An additional anatomic consideration is the location of the thoracic duct, which can be injured on left-sided approaches. The thoracic duct drains into the left subclavian vein, although there are several variants of its course that make it prone to injury and chylous leakage postoperatively. The esophagus is also encountered on anterior approaches and can be at risk for injury as well ( Fig. 144.2 ).

Surgical Management of Cervicothoracic Junction Deformity

In cases of metastatic, infectious, or traumatic lesions to the CTJ, the main indications for surgical intervention are the onset of a neurological deficit and/or the development of instability leading to mechanical pain or deformity. When indicated, the surgical approach used is determined based on the involved levels, the tumor/infection location, and the patient’s preoperative health status. Anterior-only approaches are indicated for anteriorly-located cervical lesions confined to one or two levels, and should be avoided in patients who have posterior ring disruption or a pedicle lesion. A combined approach can be considered in patients who have circumferential pathology, disease involving multiple levels, or compromised bone quality.

In patients with CTJ deformity as a result of degenerative changes, without an infectious, traumatic, or metastatic lesion, decision-making surrounding surgical management can differ, reflecting the lack of an acute process. In these patients, surgical management is indicated with symptomatic myelopathy or radiculopathy that is progressive or unresponsive to conservative care. In the pediatric population there is literature advocating for a combined anterior-posterior approach for severe kyphotic deformities, using a sternal split for resection of the apical vertebral bodies. In this young population, the additional posterior fusion becomes necessary to resist curve progression as the child grows.

Regardless of the etiology of the CTJ deformity, when the decision to proceed with surgical management has been made, careful consideration should be given to which levels need to be accessed and how best to access them. C7 to T1 can be accessed with a low cervical approach, whereas more direct anterior approaches, involving sternotomies or manubriotomies, are indicated for accessing the T1/T2 vertebral body when the patient has kyphosis ( Fig. 144.3 ).

In addition, the limited exposure and kyphotic shape of the thoracic spine make anterior screw placement difficult and predispose the surgeon to screw misplacement. Falavigna et al. studied various approaches to cervicothoracic spinal tuberculosis and found that lesions above the sternal notch could be managed with a single-stage anterior debridement and instrumentation. However, patients with lesions lower than the sternal notch or patients requiring internal fixation below the sternal notch should be managed with combined anterior and posterior approaches.