Michael J. Nanaszko and U. Kumar Kakarla

Abstract

The thoracic region is one of the most common anatomic sites for vertebral fractures, including compression type, burst, chance, and translation–rotation injuries. Associated spinal cord injury can also be found in these patients, and the treatment remains controversial despite many decades of widely accepted surgical treatment. Treatment indications include the need for stabilization, the need for decompression of neural elements, and persistent pain despite conservative management. Fundamental to the formulation of an appropriate treatment plan are a detailed patient history and a thorough physical examination, in combination with imaging (e.g., plain radiographs, computed tomograms, and magnetic resonance imaging [MRI]) of the region of interest. MRI of the spinal region of interest is used to evaluate the soft-tissue injury, the integrity of intervertebral discs and the posterior ligamentous complex, and spinal hematomas. The two main surgical approaches that allow posterior stabilization of the thoracic spine are open and percutaneous pedicle screw fixation, both of which can facilitate the goals of surgery: reduction of the fracture, stabilization with decompression of the neural elements, and reconstruction of the normal spinal alignment. Early stabilization of the spine is generally recommended to optimize patient outcomes. An alternative posterior treatment approach in select patients is kyphoplasty, a minimally invasive, percutaneous technique that uses a fast-setting polymer to help reconstruct the pathologic vertebral body. Posterior segmental fixation, whether through an open or a percutaneous approach, and kyphoplasty can lead to both fracture stabilization and good long-term pain and neurologic outcomes, but thoughtful patient selection and meticulous surgical technique are paramount to achieving these results.

Keywords: kyphoplasty, minimally invasive technique, pedicle screw fixation, thoracic spine fracture

26.1 Introduction

Traumatic or pathologic fractures of the thoracic spine may lead to neurologic injury, may compromise spinal alignment, may cause instability of the vertebral column, and may serve as the source of acute or chronic pain. In contrast to fractures involving the lumbar spine, fractures of the thoracic spine put the spinal cord at increased risk. Posterior reduction and instrumentation are recommended for most uncomplicated thoracic spine fractures when there is injury to the posterior ligamentous complex, gross instability, or worsening neurologic function in a patient with spinal canal compromise. A posterior approach can be used to treat fractures that involve the anterior, middle, or posterior columns, with a relatively simple and better complication profile, and with results that are at least comparable to those of an anterior or lateral approach. Individual patient factors, such as osteoporosis or concurrent injuries, should be considered when deciding whether to perform an anterior, a lateral, or a posterior approach.

Two main approaches, open and percutaneous, allow posterior stabilization of the thoracic spine. Since each technique has numerous advantages and disadvantages, the decision underlying the optimal approach depends both on the pathology of the fracture and on the surgeon’s experience and preference.

Unlike spinal fixation, kyphoplasty is a relatively simple and safe procedure that facilitates relief of pain from and healing of simple compression fractures of the thoracic spine. Properly selected patients who have no significant comorbidities, no bleeding diathesis, and no canal compromise may benefit from vertebral augmentation with polymethyl methacrylate (PMMA) cement.

26.2 Open Posterior Approach

26.2.1 Indications

Careful patient selection is important in determining whether to perform an open reduction, that is, an internal fixation of a thoracic spine fracture from a posterior approach. Patients with multiple medical comorbidities, especially those involving the cardiopulmonary system, must be thoroughly evaluated and cleared medically for surgery. As always, conservative management, including bracing, should be attempted first in patients without neurologic deficits and gross instability on supine or upright radiographs.

Surgical fixation of a thoracic spine fracture is indicated in the presence of a progressive neurologic deficit, retropulsed bone fragments or hematoma requiring decompression of the spinal cord, malalignment of the spine, or gross instability. Other indications for surgical fixation include the failure of conservative management, including persistent pain despite adequate nonoperative treatment and delayed fracture healing or nonhealing. Most pathologic conditions (dorsal, lateral, or ventral) can be addressed by using an open posterior approach.

26.2.2 Surgical Technique

Neuromonitoring is critical, and we recommend the use of somatosensory evoked potentials (SSEPs) of both the upper and lower extremities, as well as motor evoked potentials (MEPs). After the patient is positioned, anteroposterior (AP) or lateral fluoroscopy can be used in conjunction with MEPs to verify spinal alignment and rule out compression of the spinal cord, especially in patients with gross spinal instability or retropulsed fragments that could migrate after positioning or during the operation.

In patients whose MEPs of the lower extremities diminish or disappear after positioning, one should first eliminate technical error before increasing the mean arterial pressure to greater than 85 mm Hg to allow for increased spinal cord perfusion. One should also consider AP or lateral fluoroscopy to determine whether cord compression has been caused by a change in spinal alignment. Irrespective of whether this is the case, the goal should be to decompress the spinal cord as quickly as possible when there is a change in MEPs indicating potential neural compromise.

Localization is easiest with AP fluoroscopy, given the presence of the thoracic ribs and the lack of proximity to the L5-S1 disc space or C2 vertebral body. When localizing the vertebral level, one should verify that the vertebral body end plates are aligned; the fractured level is often apparent on imaging. Lateral fluoroscopy can be difficult to use for localization, particularly in the upper thoracic spine, because of thoracic kyphosis and the angle of the ribs. Lateral fluoroscopy can also be difficult to use in obese patients, osteoporotic patients, and patients with severe spinal deformities.

After the skin is infiltrated with the surgeon’s choice of analgesic, a standard midline posterior approach is performed, followed by opening of the fascia and subperiosteal dissection of the paraspinal muscles to identify the relevant anatomy, including the spinous process, lamina, and bony anatomy, spanning medially from the facet to the lateral tip of the transverse process. We attempt to limit soft-tissue exposure to only the planned fixation levels and, most importantly, to avoid disruption of the facet capsules located above and below those levels. As a general rule, thoracic spine fractures are treated by instrumenting a minimum of one level above and one level below the index level of disruption. When adequate fixation is unlikely, such as because of poor bone quality, the instrumentation can usually be increased to two or three levels above and below the disrupted level. The disc space above the apex of the construct must be intact to decrease the risk of proximal junctional kyphosis or failure.