Introduction

Thoracic fractures account for approximately 16% of all spinal fractures.⁴ Multiple classification systems have been developed in an attempt to characterize thoracic fractures as stable or unstable. While it is important to realize that no classification is perfect, these classification systems aid in making sound clinical decisions. They range in simplicity from the Denis three-column classification to the complicated Magerl (AO) classification.⁷ Regardless of the type of classification system employed, the presence of neurologic deficits, ligamentous injury, and a significant loss of height, angulation, translation, distraction, and/or rotation at the level of the vertebral injury must always increase suspicion for spinal instability.⁵

Basic Science

The thoracic spine is unique because of its articulations with the rib cage, which serves as an internal brace. The intact rib cage is thought to increase fourfold the capacity of the thoracic spinal region to resist axial load. As the ribs also limit thoracic rotation and ∗∗∗, most thoracic vertebral fractures are caused by flexion or compression forces.

The thoracic spine has a natural kyphotic curvature between 20 and 45 degrees. This curvature partly results from the thoracic vertebral bodies being shorter ventrally than they are dorsally. In turn, this kyphotic position places the thoracic vertebral bodies at an increased risk of sustaining compression fractures during axial loading. When the compressive force exceeds the strength of the ventral vertebral body, a compression fracture develops. If the axial force is sufficiently great, it will also exceed the strength of the dorsal vertebral body and ligamentous elements to produce a burst fracture.

The incidence of neurological deficits from thoracic fractures is about 10% or greater; this occurs for several reasons. First, the diameter of the thoracic spinal canal is smaller than the canal of the cervical or lumbar region, being narrowest at T3-T9.⁹ Second, the midthoracic cord is located in a watershed region between the blood supply to the cervicothoracic and thoracolumbar spines. Last, the high-energy mechanism of injury required for most thoracic fractures is transferred to the underlying cord and spinal nerve roots.

Clinical Practice Guidelines

Stable Thoracic Vertebral Fractures

Stable thoracic vertebral fractures are amenable to bracing with thoracolumbar spinal orthosis, accompanied by pain management. Spinal stability in the orthosis may be confirmed radiographically with upright anteroposterior (AP) and lateral x-ray films, which assess the alignment and the sagittal and coronal balance of the thoracic spine. The presence of any acute neurological deficit or persistent significant back pain should prompt further workup to reassess the degree of stability.

Stable vertebral fractures may be very painful. If conservative management fails to control the patient’s pain, a kyphoplasty, vertebroplasty, StaXx placement or percutaneous pedicle screw placement can be considered. Vertebroplasty and kyphoplasty have the advantage of possibly being performed under local anesthesia. In addition, kyphoplasty may restore greater vertebral height. StaXx allows vertebral restoration in the absence of an intact posterior vertebral wall. Percutaneous pedicle screw placement may provide additional support at the level of the fracture when used to supplement a vertebroplasty, kyphoplasty, or StaXx. Some authors believe that injecting cement in the vertebroplasty, kyphoplasty, and StaXx may not only help in partially restoring vertebral height and subsequently sagittal spinal balance, but also function in alleviating the patient’s pain by killing the responsible nerve endings in the vertebrae.

A significant percentage of thoracic compression fractures fail to heal within 3 to 6 weeks. Such fractures are prone to a progression in the kyphotic deformity and may cause severe back pain. In some instances, the pain is so debilitating that patients remain sedentary, placing them at increased risk for deep vein thrombosis, pneumonia, and bone resorption. Initially developed to treat painful vertebral hemangiomas, vertebroplasty and kyphoplasty offer marked to complete pain relief in 63% to 90% of nonhealing thoracic compression fractures.⁸

Careful patient selection is essential to successful outcomes with vertebroplasty and kyphoplasty. Especially in osteoporotic patients, there may be multiple vertebral compression fractures. Point tenderness that localizes to the radiographic location of the fracture is a reliable method of selecting the appropriate level for intervention. However, the absence of such tenderness does not preclude a nonhealing fracture, and performing a T2-weighted MRI sequence with fat suppression (such as short T1 inversion recovery [STIR]) is useful. Apart from showing increased T2 signal in acute, nonhealing fractures, MRI allows for the evaluation of the integrity of the posterior longitudinal ligament, exclusion of spinal canal stenosis, and identification of underlying neoplasms with gadolinium enhancement. X-rays are also useful for preoperative planning, as well as for comparison with older x-rays to detect new fractures or progression of deformity.

While there are few absolute contraindications to vertebroplasty and kyphoplasty, these interventions are strongly discouraged in the presence of systemic infection, bleeding diathesis, and spinal canal or neural foraminal stenosis leading to myelopathy or radiculopathy, respectively. Patients with pathologic compression fracture resultant from an underlying neoplasm are also candidates for vertebroplasty or for kyphoplasty; however, surgery must be coordinated with chemotherapy and/or irradiation.

For both vertebroplasty and kyphoplasty, the needle may be placed via a transpedicular or parapedicular approach. The transpedicular approach minimizes the risk of injury to the postganglionic nerve root and minimizes the leakage of cement because it entails a longer intraosseous path to the vertebral body. The parapedicular route enables the trajectory of the needle to be more medialized, especially in the upper to midthoracic spine, where the usual axis of the pedicles is directed more lateral.

Once the cannulated needle is satisfactorily positioned in the vertebral body using radiographic guidance, polymethyl methacrylate (PMMA) cement is instilled. In the case of kyphoplasty, a balloon is first inflated through the cannulated needle to create a cavity for the cement. This maneuver enables a 50% restoration in vertebral body height and alignment in two thirds of patients undergoing kyphoplasty.⁶

The StaXx kyphoplasty is a newer system that allows the firing of a series of PEEK wafers into the vertebral body through a device secured just inferior to the pedicle and at its lateral edge (Figure 45-1). This is performed under fluoroscopic guidance. The number of PEEK wafers required in the fractured vertebral body is determined once endplate reduction is obtained and appropriate vertebral body height correction is established. The wafers provide structural support to the vertebral body. A smaller amount of PMMA is then injected through the same channel around the PEEK construct, as compared to both vertebroplasty and kyphoplasty. The StaXx kyphoplasty system potentially offers an advantage over kyphoplasty alone, in which the space opened by the balloon may undergo some collapse before the PMMA is injected. In vertebroplasty, the PMMA simply flows to the spaces of least resistance, but does not offer height restoration.

FIGURE 45-1 A, cartoon illustrating PEEK wafers stacked at the level of a vertebral body fracture with the addition of PMMA. B, Lateral x-ray of T10 compression fracture with angulation and focal kyphosis. C, Lateral x-ray after StaXx and PMMA placement with satisfactory reduction of the focal kyphosis and height restoration.

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