Transpedicular and Costotransversectomy Approaches for Trauma: Indications and Techniques

Richard J. Bransford, Alireza K. Anissipour, Zachary A. Child, and Carlo Bellabarba

Introduction

Approximately 160,000 patients per year in the United States suffer traumatic spinal column injuries. Of these injuries, 10 to 30% have an associated spinal cord injury (SCI).1,2 The thoracolumbar junction is the location of 15 to 20% of these injuries, whereas 9 to 16% occur in the thoracic spine.^3,4 The rib cage stiffens the motion segments at each level of the thoracic spine, resulting in a 27% increase in bending stiffness in flexion.⁵ Therefore, considerable force is necessary to produce a compression or burst injury to the thoracic spine. Additionally, the transition from a long, stiff, and kyphotic thoracic spine to a mobile lordotic lumbar spine predisposes the thoracolumbar junction to significant injuries.

The primary goals in the management of thoracic and thoracolumbar trauma are (1) to provide stability to unstable segments while also trying to maintain as much residual physiological motion as possible, and (2) to achieve complete decompression of neural elements in cases of neurologic injury, when indicated. Fortunately, most thoracolumbar trauma can be treated conservatively. In cases of structural instability or neurologic injury, various surgical options are available based on the pathology and the comfort level of the surgeon. The primary considerations when selecting the surgical approach include an assessment of the mechanism of injury, of the degree and location of the instability, and of the location of neurologic compression. In cases of thoracic injuries, anterior compressive pathology, or instability or deformity involving the anterior column, a costotransversectomy or transpedicular decompression may be an effective option for the spinal surgeon. This chapter describes the indications, technique, advantages, and limitations of transpedicular decompression and costotransversectomy in treating thoracic and thoracolumbar spinal column injuries.

Treatment Options and Indications

Only a few studies have compared anterior and posterior surgery for thoracolumbar trauma. Stancić et al⁶ reported shorter operative time and less blood loss with the posterior approach in a series of mechanically unstable thoracolumbar burst fractures without neurologic deficits. However, the few comparative series to date have reported that the posterior and anterior approaches resulted in equivalent clinical 6,7 and radiographic⁷ results.

In managing thoracolumbar trauma, after the workup has been completed, the surgeon must determine whether surgical treatment is indicated. Typically most surgeons opt for surgery if (1) the injury is unstable biomechanically and baseline alignment is unacceptable; (2) the patient runs the risk of progressive, unacceptable alignment; or (3) there is a neurologic injury that is best managed with some form of decompression, either direct or indirect. Most surgeons then make a decision based on these criteria to proceed with an anterior approach to the spine to enable stabilization with or without decompression, a posterior approach, or a combined anterior and posterior approach. Many surgeons use an anterior approach in the setting of an axial load injury in which the posterior tension band is intact and there is significant vertebral body injury with ventral retropulsion into the canal. In contrast, most surgeons use a posterior approach in the setting of a failure of the posterior tension band (i.e., a flexion/distraction, Chance fracture, or fracture dislocation) or when there is posterior canal compression or entrapped neural elements in a laminar split fracture. Alternatively, many surgeons believe that a combined anterior and posterior approach is indicated in the setting of a failure of the posterior tension band with significant vertebral body injury or cord compression ventrally. Certainly, within these larger philosophical parameters are various nuances that help to steer a surgeon toward a particular treatment option, and there is a tremendous amount of controversy among surgeons individually and in the literature.

The transpedicular approach was first described by Patterson and Arbit⁸ as a novel approach to address thoracic herniated disks. A transpedicular approach has utility in its role of enabling posterior stabilization while also facilitating ventral canal decompression. The technique is a posterior-based approach for stabilization, and it uses transpedicular access for canal decompression. This enables a more direct decompression of the canal than with other standard posterior-based approaches, but it does not provide any anterior column support. The main potential indication for the utility of such an approach would be a patient with a fracture above the conus with a posterior tension-band failure and neurologic deficits, with canal intrusion from a ventral piece of bone between the pedicles where the dura and cord should not be retracted. In the lumbar spine below the conus, a transpedicular approach would not be necessary, as the dura could be retracted, enabling direct decompression of the fragment by either tamping the fragment forward or by direct removal.

The costotransversectomy was originally described in 1894 for the drainage of a paraspinal abscess associated with vertebral tuberculosis.⁹ Capener¹⁰ modified Ménard’s costotransversectomy in 1933 to directly remove posterolateral thoracic lesions. Larson et al,¹¹ at the Medical College of Wisconsin, further expanded the costotransversectomy to develop the lateral extracavitary approach, and it has been applied to traumatic lesions, thoracic disk herniations, and tumors.¹² A costotransversectomy approach enables posterior stabilization with a more thorough decompression of the canal than can be achieved with a transpedicular approach because it enables more thorough bony removal. This technique also provides anterior column support and deformity correction through the window used for access and corpectomy (Fig. 6.1). At L1 or L2, a transpedicular corpectomy, a modification of a costotransversectomy, can be performed, although this technique is more technically demanding, and management of the nerve root, which is usually not sacrificed as it is in the thoracic spine, can be difficult.¹³ The main potential indication for a costotransversectomy or transpedicular corpectomy (which for future reference we will group with costotransversectomy) is a patient who has a thoracic or thoracolumbar injury (L2 or above) with failure of the posterior tension band and significant anterior column injury, with or without a retropulsed ventral fragment and a neurologic deficit. The other indication is a neurologically intact patient with significant injury to the vertebral body, in whom surgeons would routinely do a corpectomy.

Fig. 6.1a–d A 53-year-old neurologically intact woman was involved in a mountain bike accident and sustained a T7 and T8 flexion-distraction injury with significant kyphosis and vertebral body compression. A decompression of the retropulsed bone was performed, with placement of an expandable interbody cage and posterior segmental instrumentation from T5 to T10. (a) Preoperative sagittal computed tomography (CT) scan. (b) Preoperative axial CT scan. (c) Sagittal CT scan post-costotransversectomy. (d) Axial CT scan post-costotransversectomy.

As will be discussed later, these techniques are not the only way to deal with certain fracture types, but they have their utility and advantages.

Technique

Transpedicular Approach

This approach can be used as an alternative to more invasive posterolateral approaches or in patients who are unable to tolerate a separate anterior approach.14

The setup for a transpedicular decompression is similar to that for a posterior-based approach. Typically, neuromonitoring is utilized except in cases in which there is an American Spinal Injury Association (ASIA) grade A SCI. As mentioned previously, this type of approach would be utilized in a patient with an injury between T2 and T12/L1 in which there is a retropulsed fragment in the typical location between the pedicles. Generally, the patient is positioned on a lordosing, radiolucent table. Exposure is performed subperiosteally, screws are placed, and a laminectomy is performed, enabling dorsal decompression. Once a standard decompression is complete, the pedicle is removed either unilaterally or bilaterally, based on the location of dural compression, and the fragment is accessed.^14,15 Based on the fracture morphology, the piece can be tamped anteriorly back into the fractured body or can be removed. Above the conus, it is imperative that no retraction be placed on the neural elements. In the thoracic region, the nerve root or bilateral roots may be sacrificed if this will facilitate access to the fragment. This will leave a sensory patch of numbness, but it ought to have no meaningful motor consequences. Any sort of cord retraction may make a deficit even worse, particularly given the location of the anterior horn cells. Once a satisfactory decompression has been achieved, the rods are placed and the procedure is completed in standard fashion.

Costotransversectomy

The preparation for a costotransversectomy is similar to that used for other standard dorsally based approaches. Exposure is done and pedicle screws are placed. Fixed or polyaxial screws are placed above and below the injured level. Our preference is to place the pedicle screws very close to the superior end plate of the vertebral body below the costotransversectomy to act as a restraint to subsidence of the cage or graft at the corpectomy level. In younger patients, every effort is made to preserve levels, often choosing to instrument one level above and below the fracture in the lower thoracic or lumbar spine, when combined with an anterior cage. Conversely, more proximal upper thoracic or midthoracic injuries are typically managed with two levels of pedicle screw instrumentation above and below the injury. In older patients or those with osteoporosis, high body mass index (BMI), or other significant biomechanical considerations, additional levels are often deemed necessary to combat these forces. If there are no neurologic deficits and the goal is purely biomechanical support, then a laminotomy is performed, leaving the spinous process and the contralateral posterior elements intact to aid with structural support and to provide a fusion surface. Exposure is from the pedicle above the injured segment to the pedicle below the injured segment. If, on the other hand, there is a neurologic deficit, necessitating decompression, then a full laminectomy is performed, enabling dorsal decompression, and either a unilateral or bilateral costotransversectomy will be done depending on the location of the cord compression and ease of technical access (Fig. 6.2).

After placement of screws and completion of a standard laminectomy, exposure in the thoracic spine is performed to approximately 4 cm from the origin of the rib from the costovertebral joint. At L1, exposure is performed to the tip of the transverse process. The transverse process and the pedicle are removed. In the thoracic spine, the rib is elevated off the pleura approximately 4 cm from the costovertebral junction. Cobb elevators are used to elevate the rib from the parietal pleura and are placed under the rib to protect against inadvertent violation of the pleura during resection. Our preference is to cut the rib with a Midas high-speed M-8 bur as opposed to a rib cutter, to provide a cleaner cut of the rib. The rib is then subperiosteally elevated to its origin and removed. Should the pleura be violated, it can be primarily repaired or patched, and a chest tube is not necessary as long as the lung has not been injured.

At this point, the nerve root is identified and ligated at its origin with an No. 0 silk suture in levels T2 to T11. Every effort is made to work around, as opposed to sacrificing, the root at T12, L1, and L2 if those are the affected levels. A subperiosteal exposure then provides access the lateral side of the injured vertebral body from the superior disk of the injured segment to the inferior disk of the injured segment. Our preference is to primarily utilize the left side for access so as to minimize potential sacrifice of the artery of Adamkiewicz.¹⁶ This, the largest anterior segmental medullary artery, may lie anywhere from T8 to L1 on the left side and, if sacrificed, may lead to the possibility of anterior spinal artery syndrome. At this point, it is recommended to place a stabilizing rod on the contralateral side to keep the injured segment from further collapse as the corpectomy is done, which may lead to neurologic injury. The caudal and cephalad disks are then cut and elevated off the uninjured proximal and distal vertebral bodies. One can then sequentially remove the injured vertebral body, creating a ventral “cavern.” If the patient is neurologically intact, the posterior cortex need not be removed but can be left intact; the surgeon needs only to create enough space for placement of an anterior cage or allograft to enable structural support. If there is a neurologic deficit, then the posterior, retropulsed fragment needs to be “pushed” into the cavern to enable a circumferential decompression of the neural elements.