Radiographic Evaluation

Radiologic evaluation begins with anteroposterior and lateral plain radiographs, and evidence of pathology includes malalignment, vertebral collapse, and widening of the pedicles. These radiographs can demonstrate traumatic or pathologic vertebral fractures, infections, tumors, and deformities.

Infections such as osteomyelitis or discitis have a variety of characteristics on plain radiographs. The earliest and most consistent finding of infection is narrowing of the disc space, which is present in 74% of patients.²¹ After 3 to 6 weeks, destructive changes in the body can be noted, which usually begin as lytic areas in the anterior aspect of the body adjacent to the disc and end plate. Active bone formation and sclerosis is also present in 11% of patients.

Metastatic disease of the bone has several classic signs including unilateral erosion of a pedicle, fishmouthing (cephalad and caudad end plate concavity within the vertebral body), osteoblastic changes, and vertebral body collapse. These findings can occur late in the disease process because 30% to 70% of the bone must be destroyed before changes are visible on plain radiographs.²²

Radionucleotide bone scintigraphy is a sensitive but not specific method for detecting metastatic disease and infections.^23,24 However, false negatives have been reported with lung cancer, renal cell carcinoma, myeloproliferative diseases, and regional ischemia, and in patients with leukopenia.^25–27

Myelography is primarily used to evaluate the patency of the subarachnoid space. Thus, myelography can demonstrate the level of a metastatic lesion by indentation or complete blockage of the myelographic dye column as it flows through the spinal canal. Additionally, myelography can demonstrate the presence of intradural extramedullary or intramedullary tumors, disc herniations, retropulsed vertebral fragments from pathologic or traumatic fractures, and vascular malformations.

Computed tomography (CT) also aids in the evaluation of diseases of the thoracic spine. These pathologies include metastatic disease, intradural tumors, disc herniations, and vascular malformations. Additionally, CT aids in defining the extent of paraspinal soft-tissue involvement for tumor staging and surgical planning, and also helps determine the extent of bone destruction. In addition, CT scans can help distinguish between osteoporosis and tumor as a cause of vertebral body collapse.

Magnetic resonance imaging (MRI) is the most important diagnostic tool for evaluating diseases of the thoracic spine. MRI permits early diagnosis of infection and recognition of paravertebral or intraspinal abscesses without the risk associated with myelography.²⁸ MRI is also effective in demonstrating the extent of metastatic disease, primary tumors of bone, primary lymphoma, intradural tumors, thoracic disc herniations, and vertebral fractures. Additionally, this modality may be helpful in spinal vascular malformations, and when assessing metastatic disease, MRI has been found to be at least as sensitive and accurate as gallium and bone scanning combined.²⁹ Finally, MRI provides anatomic detail, especially of soft tissue and nervous structures, not available with any other imaging studies.

Metabolic Evaluation

Metabolic evaluation of cervicothoracic junction pathology should include complete blood count, kidney profile (electrolytes, blood urea nitrogen, and creatinine), liver profile, and erythrocyte sedimentation rate. Other helpful metabolic evaluations include calcium, phosphorus, alkaline phosphatase, serum protein electrophoresis, and serum transferrin analysis. Antinuclear antibody and rheumatoid factor analysis assist in the evaluation for rheumatoid arthritis. Additionally, bone marrow aspiration may be helpful in the diagnosis of blood-borne dyscrasias, and antigenic markers for specific tumors include carcinoembryonic antigen, serum acid phosphatase, and prostate-specific antigen.

Lateral Parascapular Extrapleural Approach and Anterolateral Thoracotomy Approach

The lateral parascapular extrapleural approach is a posterolateral surgery that allows nearly lateral access to the cervicothoracic junction vertebral bodies. The anterolateral thoracotomy is a transthoracic approach through the third rib that allows access to the anterior and lateral aspects of the vertebrae and for control of the mediastinal vasculature. The relevant anatomy may be summarized in three major areas: scapula and parascapular anatomy, posterior thoracic cage, and retromediastinal space and spinal anatomy.

Scapular and Parascapular Anatomy

Posterolateral access to the thoracic cage and vertebral elements is hindered by the scapular and the parascapular shoulder musculature (Fig. 191-1). Mobilization of the scapula anterolaterally is necessary and requires the disruption of the posteromedial shoulder musculature.

FIGURE 191-1 Relationship of the scapula to the incision, as well as the surgical approach to the cervicothoracic junction, via the lateral parascapular extrapleural approach.

The first muscle encountered after skin incision is the trapezius muscle, which inserts medially at the superior nuchal line and external occipital protuberance and at the spinous processes of C1 through T12. This muscle extends laterally as the upper, intermediate, and lower divisions to the lateral third of the clavicle, the acromion, and the scapular spine. The trapezius muscle stabilizes and abducts the shoulder by the insertion of the lower fiber aponeurosis to the tubercle of the lower lip of the scapular spine. The trapezius muscle is innervated by the ventral rami of C3 and C4 of the spinal accessory nerve, which lies deep to the trapezius muscle and superficial to the levator scapulae. The arterial supply is from branches of the dorsal scapular artery.

The rhomboid major, rhomboid minor, and levator scapulae muscles are deep to the trapezius muscle. The ligamentum nuchae of the spinous processes provides the insertion site for the rhomboid major (T1 to T4) and the rhomboid minor (C6 to C7). Similarly, both of these muscles insert along the vertebral edge of the scapula: the rhomboid minor above and the rhomboid major below the scapular spine. The dorsal scapular artery supplies all three muscles, and the dorsal scapular nerve innervates the rhomboids. The levator scapulae muscle is innervated via branches from C3, C4, and C5. Both the artery and nerve lie deep to the muscle bodies, are located medially under the scapula, and are rarely seen during a routine exposure. The serratus posterior superior muscle lies deep to the trapezius muscle from C6 through T2, and the splenius arises ventral to this muscle at the ligamentum nuchae and upper thoracic spine, dividing into the splenius capitis and splenius cervicis. The splenius capitis inserts on the superior nuchal line and mastoid process, and the splenius cervicis joins the levator scapulae to insert on the transverse processes of C1 through C4. These muscles stabilize and rotate the skull.

During exposure of the cervicothoracic junction, the spinous process insertions of the trapezius, rhomboid, serratus posterior superior, splenius capitis, and splenius cervicis are laterally retracted as a single group. As these muscles are taken down, the scapula can be rotated anterolaterally out of the operative field. This maneuver exposes the posterior and posterolateral rib cage.

Posterior Thoracic Cage

The deep or intrinsic muscles including the erector spinae and transversospinalis muscles are next encountered (Fig. 191-2). The erector spinae muscles originate from the sacrum as a dense aponeurotic band and divide into three columns below the last rib as they proceed superiorly. The iliocostalis muscle is located laterally and inserts from the angles of the ribs and into the cervical transverse processes from C4 through C6 as series of related muscular bundles. Each bundle extends over approximately six segments, with the more medial bundles extending more cephalad.

FIGURE 191-2 Cross-sectional anatomy of the deep or intrinsic muscle layer of the upper thoracic spine. M., muscle.

The longissimus muscles (thoracis, cervicis, and capitis) insert into the lumbar and thoracic transverse processes and ribs between T2 and T12. Medially, the muscle bundles extend from T1 through T4 to the transverse processes of C2 through C6. Medial to the cervical insertions, other bundles extend superiorly to the mastoid process deep to the splenius capitis and sternocleidomastoid muscles. Thus, the longissimus is the only erector spinae muscle to reach the skull. Finally, the aponeurotic spinalis muscle extends from the upper lumbar to the lower cervical spinous processes.

The transversospinalis muscle group passes cephalad from the transverse processes to the spinous processes immediately deep to the erector spinae muscles in three layers. The most superficial layer, the semispinalis, arises from the tips of the transverse processes and inserts at the tips of the spinous processes approximately five vertebral levels cephalad. At the cervicothoracic junction, this muscle is primarily composed of the semispinalis capitis. This muscle passes from the upper thoracic transverse processes and lower cervical articular processes (C4 to T4) to the occipital bone between the superior and inferior nuchal lines. The muscle fibers run vertically and attach to the ligamentum nuchae. The intermediate layer, the multifidus, originates from the erector spinae aponeurosis and from the transverse processes up to C4 and extends to the lower border of each spinous process. This muscle spans approximately three levels. The deepest muscles of this group, the rotatores, are muscles that bridge one interspace. They pass from one transverse process root to the spinous process root immediately above.

These muscle groups extend the vertebral column or can bend and rotate the vertebrae. The erector spinae and transversospinalis muscles are typically dissected off the spinous processes, laminae, facets, and transverse processes as a single muscular mass. This dissection exposes all the vertebral elements from the spinous processes to the transverse processes, as well as the costotransverse ligaments, joints, and ribs.

Each rib articulates with its own vertebral body and transverse process, the vertebra above, and the intervertebral disc between them (Fig. 191-3), but the first rib articulates only with its own vertebral body. Each of these articulations forms separate synovial joints, and the joints of the posterolateral vertebral body surface are separated by an intra-articular ligament that attaches to the intervertebral disc. An articular capsule surrounds the joints and attaches to the vertebral body anteriorly via the radiate ligament.

FIGURE 191-3 Relationship of each rib and rib head with the transverse process, vertebral bodies, and intervertebral disc. Note that each rib articulates not only with its own transverse process and vertebral body but also with the vertebral body immediately above it. Ant., anterior; Lig., ligament; Sup., superior.

The costotransverse joint is surrounded by an articular capsule and is strengthened laterally by the lateral costotransverse ligament and the costotransverse ligament. The superior costotransverse ligament joins the neck of the rib to the transverse process immediately above. The canal formed between this ligament and the vertebral column contains the dorsal ramus of the spinal nerve and the dorsal branch of the intercostal artery. Finally, the ribs are attached to one another through the intercostal musculature, which originates medially on the superior rib and inserts laterally on the inferior rib.

The intercostal musculature contains the intercostal nerve, artery, and vein as they pass between the internal intercostal membrane and the pleura and between the internal and innermost intercostal muscles. Most commonly, the intercostal vein is cephalad and the intercostal artery is more caudad. The intercostal nerve may be separate from these structures and is located most caudad. The pleura lies ventral to the intercostal bundle and the intercostal muscles.

Transmanubrial Approach

The transmanubrial approach is an anterior approach that allows direct access to the vertebral bodies and associated pathologies. This approach consists of three major steps: the thoracic inlet, the visceral and vascular compartments of the superior mediastinum, and the retromediastinal space.

Lateral Parascapular Extrapleural Approach

The posterior neck and back from the nuchal line to the sacrum is prepared and draped in standard fashion. The incision begins in the midline three spinous processes above the intended surgical area and continues to three spinous processes below before curving gently to the surgical side of approach. The skin, trapezius muscle, and rhomboid muscles are reflected as a myocutaneous flap toward the medial border of the scapula by developing a plane between these muscles and the paraspinal muscles at the spinous processes (Fig. 191-4). The inferior trapezius fibers are transected to reflect this flap, and an identifiable muscle cuff is left for reapproximation.

FIGURE 191-4 Reflection of the trapezius and rhomboid muscles laterally and paraspinal muscle mass medially to expose the dorsal and lateral spinal elements and ribs.

At the cervical level, dissection of the levator scapulae muscles also improves exposure of the cervicothoracic junction. This added visualization is achieved by mobilization of the myocutaneous flap and the scapula laterally to expose the lower cervical region, upper dorsal rib cage region, and dorsal vertebral elements.

The deep cervical fascia and thoracolumbar fascia cover the splenius and erector spinae muscles. These muscles may be retracted medially to the contralateral side by dissecting from the spinous processes and dorsal spinal elements, allowing visualization of the dorsal rib cage and vertebral elements from the tip of the spinous process to the transverse process.

The neurovascular bundles and intercostal muscles are freed from the ribs via subperiosteal dissection, and subsequently the costotransverse and costovertebral ligaments are incised to facilitate the removal of the costovertebral tip to the posterior bend of each rib. This resection contrasts with the 3 cm removal in the standard costotransversectomy approach or the 5 cm removal in the lateral extracavitary approach. Following this dissection, the intercostal neurovascular bundles are dissected from the intercostal muscles, and the intercostal arteries are ligated and transected. The intercostal nerves are retracted to expose the intervertebral disc, but these nerves must be sacrificed proximal to the dorsal root ganglia to resect the vertebral body. As described previously, nerve roots cephalad to T2 should be preserved to maintain hand function.

The intercostal nerve can be followed to the vertebral foramen, and the sympathetic chain can then be identified on the lateral vertebral surface. The rami communicantes are then transected, and the sympathetic chain is displaced anterolaterally to expose the vertebral body, pedicle, and foramen. At the level of the intercostal nerve, the transverse process, lamina, and pedicles are removed with a high-speed drill or Kerrison punch to expose the lateral thecal sac. A corpectomy can then be performed using either a high-speed drill or curet with preservation of the anterior and posterior longitudinal ligament to protect the thecal sac and superior mediastinal structures (Fig. 191-5). Vertebral reconstruction is performed using a rib graft or fibular allograft strut. If the pathologic process is malignant, Steinmann pins and methyl methacrylate are used. Alternatively, a metal cage with autologous bone may be used for vertebral body reconstruction. Appropriate posterior spinal fixation is then performed.

FIGURE 191-5 Operative field after a corpectomy and neural decompression.

Before wound closure, the operative field is filled with saline to check for evidence of an air leak. If an air leak is present, a small (22 or 24 Fr) chest tube is placed into the wound and brought out through a separate stab incision below the primary incision. Two Hemovac drains are then placed, and a layered wound closure is performed.

Anterolateral Transthoracic Approach

For the anterolateral transthoracic approach, the patient is placed in the lateral decubitus position. The skin is incised from the paraspinous area of T1 to the seventh rib along the medial border of the scapula. This incision is continued laterally, anteriorly, and then medially to the costal cartilage of the third rib (Fig. 191-6). The trapezius, latissimus dorsi, rhomboid major, and serratus posterior muscles are divided to identify the third rib. This identification is aided by locating the attachment of the scalenus anterior or medius muscles on the second rib. The scapula is retracted cephalad and medially using a scapular retractor, and the third rib is resected from its angle to the costal cartilage. The chest spreader can be inserted and opened, exposing the pleura and underlying lungs, aorta, and spine.

FIGURE 191-6 Patient position and skin incision for right anterolateral transthoracic approach to the upper thoracic spine.

The parietal pleura is incised from the costochondral cartilage to the midvertebral body. The lung is deflated and retracted to expose the spine (Fig. 191-7). The pleura is incised cephalad and caudad to expose the pathologic vertebrae and the intervertebral discs, as well as the intercostal arteries and veins that lie over the midvertebral body. The appropriate intercostal arteries and veins are dissected, ligated, and cut prior to vertebrectomy.

FIGURE 191-7 Operative exposure of the upper thoracic spine through a T3 anterolateral transthoracic approach.

After vertebrectomy and reconstruction, a chest tube on water seal is placed. The pleura is then sutured closed, and the ribs are reapproximated with wire. Each muscle layer is independently reapproximated using 0 polyglycolic acid (Vicryl) sutures. Subcutaneous 2-0 polyglycolic sutures and skin staples are then used to close the wound.

Transmanubrial and Transclavicular Approach

The patient is positioned supine with the head turned slightly to the side contralateral to the approach. An incision is made 2 cm above the clavicle from the contralateral sternocleidomastoid to 2 to 3 cm lateral to the ipsilateral sternocleidomastoid (Fig. 191-8). A T incision is then created in the midline, extending to the midpoint of the sternal body. This incision may also be modified depending on the patient’s specific anatomy and pathology (Fig. 191-9). The platysma muscle is divided and mobilized cephalad and caudad, and the external jugular vein is divided. The supraclavicular nerves should be identified and protected as much as possible, but the medial branches are often sacrificed.

FIGURE 191-8 Patient position and skin incision for a transmanubrial/transclavicular approach to the cervicothoracic junction.

FIGURE 191-9 Transmanubrial/transclavicular incision on a patient with previous tracheostomy.

The sternocleidomastoid muscle is identified and dissected from the deeper structures. The pectoralis major muscle is also identified and separated from the medial half of the clavicle and the manubrium. The superficial and middle layers of the deep cervical fascia are dissected to allow the reflection of the sternocleidomastoid, sternohyoid, and sternothyroid muscles from the manubrium and clavicle without damaging their neurovascular supply.

The suprasternal space of Burns (a suprasternal midline space created by a leaflet split in the superficial layer of deep fascia) is opened while leaving the periosteum and anterior transthoracic fascia for protection of the brachiocephalic veins. Next, the omohyoid muscle is marked and divided prior to identifying the internal jugular vein and common carotid artery.

A high-speed drill is used to cut the ipsilateral two thirds of the manubrium, and the first costal cartilage is divided while leaving the clavicular manubrial joint intact. The clavicle is divided after drilling holes for the eventual application of a fixation plate. The manubrium, sternoclavicular joint, and medial half of the clavicle are elevated on the pedicle of the sternocleidomastoid muscle. This elevation exposes the infrahyoid muscles, trachea, brachiocephalic veins and tributaries, brachiocephalic artery and branches, subclavian and common carotid arteries, scalenus anterior muscle, phrenic nerve, brachial plexus, and first rib.

The alar and mediastinal fascia are exposed via blunt dissection medial to the carotid sheath, and incision of these fasciae exposes the retromediastinal space and the prevertebral fascia covering the vertebral bodies and longus colli muscles (Fig. 191-10). Retractors are placed, and the pathologic process can be removed via curettage and suction or via a high-speed drill and Kerrison punch.

FIGURE 191-10 Operative exposure of the cervicothoracic junction via transmanubrial/transclavicular approach. M., muscle.

Following decompression of the spinal cord, reconstruction is begun using either autologous or allograft bone (tricortical iliac crest or fibula) or by synthetic implant (Fig. 191-11). After bony reconstruction, stabilization is achieved by an anterior plate screwed to the intact vertebrae above and below the pathologic levels or by placement in a halo brace.

FIGURE 191-11 Intraoperative photograph of the cervicothoracic junction after corpectomy and placement of implant.

The wound is then closed in layers over vacuum drainage. If the pleura is opened, a chest tube is inserted through a separate stab incision and connected to an underwater seal. The osteomuscular flap is then returned to its appropriate position. The manubrium is reattached using wires, and the clavicle is reattached using a plate and screws.

Variations have been reported in an attempt to reduce the sternal and clavicular dissection. Liu and colleagues reported the “trans–upper sternal approach,” which involves splitting the sternum to a point 2 cm distal to the sternal angle followed by cutting the two parts of the sternum transversely between the second and third rib.⁵⁵ This procedure does not involve disruption of the clavicle. Pointillart and colleagues reported resection of lesions to T1–2 without resection of the sternum and to T5 with removal of a portion of the manubrium without violating the sternoclavicular joints.⁵⁶ Teng and colleagues also described a preoperative method for determining the type of surgery based on the cervicothoracic angle (an angle formed between the axial plane of the suprasternal notch and the C7–T1 intervertebral disc). Lesions within this region were treated with the suprasternal approach, with occasional need for sternal splitting.⁵⁷

Anterior Reconstruction

After an anterior approach, a substantial construct is required to bear the axial loads exerted on the anterior and middle columns. In tumor patients with a short life expectancy, it is frequently unnecessary and unlikely to achieve a solid bone fusion owing to the inhibition of bone growth from radiation and chemotherapy. The rapid creation and immediate stability of a methyl methacrylate construct with vertically embedded Steinmann pins is a reasonable option in these cases.

Bony fusion is desirable for trauma, infection, degenerative disease, and benign tumors. Most neurosurgeons have experience with anterior cervical stabilization, and following the approach, anterior cervicothoracic fusions are not significantly different. Fibular strut grafts or iliac crest autografts supplemented with an anterior cervical plate and screws provide excellent structural results but require a straight anterior approach (Fig. 191-12).

FIGURE 191-12 A, Sagittal view of anterior plate and screw fixation after a T2 corpectomy with an iliac crest bone graft. B, An axial computed tomography view of the iliac crest bone graft stabilized by an anterior screw.

A Harms cage packed with autograft is another option for anterior support and eventual fusion, and recent additions of expandable cages and metal spacers can help facilitate reconstruction. Also, the use of free vascularized fibular strut grafts has been increasingly reported, particularly in correcting deformities.⁵⁸

Posterior Stabilization

Posterior cervicothoracic instrumentation ranges from a simple tension band to complex hook, rod, and screw constructs. Because the cervicothoracic junction is under significant biomechanical stress, surgical fixation should incorporate several segments above and below the level of injury (Fig. 191-13). Tension bands resist flexion and distraction and can be used for pure ligamentous disruption. These tension bands are usually interspinous wiring, which can exert significant resistive forces and are simple, safe, fast, and a useful adjunct to other techniques.

FIGURE 191-13 Posterior rod-and-screw construct spanning above and below the cervicothoracic junction.

Standalone anterior constructs have been reported to fail more commonly than posterior instrumentation, which affirms the mechanical advantage of posterior instrumentation.¹ O’Brien and colleagues used two-column injury models to demonstrate the feasibility of biomechanical stabilization from posterior instrumentation alone.⁴²

The Luque rectangle with sublaminar wires or Songer cables was a mainstay of internal fixation at the cervicothoracic junction. This relatively rigid construct combines segmental fixation with resistance to flexion, torsion, and some translation. This technique requires intact and healthy posterior elements and carries the risk of spinal cord injury with passage of the sublaminar wires. The construct should cover at least two levels above and two below the region of instability. However, recent biomechanical data demonstrate that posterior wiring might not increase stability when a lateral mass or pedicle screw construct has been used.⁴⁷

Pediatric Cotrel-Dubousset systems with laminar hooks and rods have been applied at the cervicothoracic junction (Fig. 191-14). This construct is stable, but it requires intact posterior elements at the points of fixation and may be limited by the narrow cervicothoracic spinal canal.

FIGURE 191-14 A, T2 and T4 pathologic fractures from metastatic carcinoma on a T1-weighted sagittal view (B). C, Laminar-hook and dual rod construct after decompression of compromised spinal canal through lateral parascapular extrapleural approach.

Other options exist when the posterior elements have been disrupted by trauma or have been removed surgically. Beginning with the lateral mass plates of Roy-Camille and colleagues,⁵⁹ new plate-and-rod–based fixation methods have emerged.⁶⁰ Some additions include minipolyaxial screws, dual-diameter rods, cervical cross-links, and interconnectors. Current stabilization techniques require experience with cervical lateral mass or pedicle screw placement, upper and lower thoracic pedicle screw placement, and thoracic transverse process, pedicle, and laminar hooks. When the lamina are intact, sublaminar wiring techniques can add to the construct’s stability and are especially useful in the cervical area where screw pullout can often occur. Also, quadrilateral stability can be achieved by using two cross-links. Placentonakis and colleagues demonstrated the evolution of posterior instrumentation techniques in tumor surgery from sublaminar hook-and-rod constructs to lateral mass and pedicle screw constructs with improved stabilization.²

An understanding of the anatomy of the cervicothoracic junction is required for appropriate instrumentation, and anatomic variations are common. In general, the lower cervical laminae are thinner and weaker than the upper thoracic laminae, and the narrow spinal canal often limits the use of hook-and-rod stabilization.

At C7, the vertebral artery is on average 18 mm from midline and 17 mm from the posterior cortex of the lateral mass.⁶¹ Vertebral artery injury can occur if a lateral mass screw is too long or is directed less than 14 degrees laterally from the midpoint of the lateral mass of C7. At T1, the vertebral artery is 22 mm from the midline and 22 mm from the posterior cortex of the transverse process. These relationships can change with significant kyphotic or scoliotic deformity and can increase the risk of injury. Additionally, a caudally placed lateral mass screw can lead to spinal nerve injury.

At C7, the facet and lateral mass is thinner and can provide inadequate screw purchase, and as a result, lateral mass plating might not produce a biomechanically stable construct at the cervicothoracic junction. Pedicle screw constructs, however, have shown excellent biomechanical stability in this region (Fig. 191-15).

FIGURE 191-15 A, T1 to T3 iliac crest autograft placement after T2 corpectomy for tuberculous osteomyelitis (B) followed by posterior stabilization with lateral mass screw placement at C7 and transpedicular screw fixation (C) at T2 and T3. D, Sagittal view of lower cervical lateral mass and upper thoracic transpedicular screw fixation (E).

A number of studies have reported the unique anatomic constraints of the cervicothoracic pedicles. An and colleagues⁶² found it difficult to determine pedicle alignment in a cadaveric study. Stanescu and colleagues⁶³ and Panjabi and coworkers⁶⁴ both found highly variable pedicle dimensions and angles in the lower cervical and upper thoracic spine. This work has shown that the mean pedicle width increases from 5 mm at C5 to 8 mm at T1 and then decreases again to 4.5 mm at T5. Based on these data, the pedicles at C7, T1, and T2 are often large enough to permit placement of a 3.5-mm screw.

Karaikovic and colleagues⁶⁵ studied 53 European-American cervical spines and found outer pedicle widths equal to or smaller than 4 mm in 13.2% of C5 and C6 and 6.6% of C7 pedicles. Miller and coworkers⁶⁶ used the technique of Jeanneret and colleagues⁶⁷ to attempt 3-mm pedicle screws in cadaveric cervical spines blindly or with a small laminotomy. They found potentially dangerous violations of the pedicle in 10 of 38 blinded placements and one of 40 placements after the advent of a laminotomy. In the thoracic spine, this group compared the Roy-Camille technique with the open lamina technique. They found grade II and III pedicle violations in 48 of 95 screws and 10 of 94 screws, respectively. In general, the T3 to T5 levels often have small, narrow pedicles that make screw placement challenging, often necessitating the use of thoracic hooks.

The medial inclination and variation in pedicle angle, as well as changes in pedicle length and proximity to the exiting superior and inferior nerve roots, are other factors that make safe screw placement difficult in the cervicothoracic region. The pedicle angle decreases from 50 degrees medially at C5 to 11 degrees medially at T5, and the pedicle length increases gradually from C5 to T5. The mean distance of the spinal nerve to the superior and inferior pedicles ranged between 0.8 and 2.3 mm. Because a greater separation exists between the nerve and the superior pedicle, a screw violation of the superior cortex can place the nerve at higher risk.

Despite anatomic concerns, cervicothoracic pedicle screws have been successfully employed in clinical practice. Abumi and colleagues⁶⁸ used pedicle screws in 13 patients with fracture-dislocations of the lower cervical spine with good results and no of complications. In another series,⁶⁹ these authors reported placement of 191 cervical pedicle screws (most by landmarks) with one transient screw thread–related radiculopathy.

Chapman and colleagues⁴⁰ published a series of 23 patients instrumented posteriorly using AO plates, as well as cervical lateral mass and thoracic pedicle screws. In this series, they reported a 100% fusion rate, no neurovascular complications, and no hardware complications requiring reoperation. Albert and colleagues³⁹ reviewed 21 patients who were treated with pedicle screws at C7 with the open lamina technique. They found no neurovascular complications and no instrument failures at 1-year follow-up. Lenoir and colleagues achieved fusion in all patients (n = 30) using posterior instrumentation with two delayed mechanical failures.⁶

New advances in intraoperative image guidance have led to improved accuracy in pedicle screw placement. Bledsoe and colleagues reported the use of three-dimensional image guidance for the placement of 150 pedicle screws. These authors noted 93% accuracy in screw placement with rare grade I pedicle violations based on postoperative CT scans.⁷⁰ Lee and colleagues compared the placement of thoracic pedicle screws using the open laminotomy technique against computer-assisted techniques and found improved screw placement using the image-guided systems.⁷¹ These findings demonstrate that a combination of an extensive anatomic understanding and a knowledge of current technologies offers the best outcome for patients.