Treatment of Thoracic Vertebral Fractures

Published on 11/04/2015 by admin

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45 Treatment of Thoracic Vertebral Fractures

Samer Ghostine, Kamal Woods, Shoshanna Vaynman, Ali Shirzadi, Stephen Scibelli, Srinath Samudrala, J. Patrick Johnson

KEY POINTS

• Stable thoracic vertebral fractures may be treated conservatively with external bracing and pain management.

• When patients with stable vertebral compression fractures have persistent back pain despite conservative measures, they may benefit from kyphoplasty, vertebroplasty, StaXx, or percutaneous instrumentation.

• Unstable thoracic vertebral fractures necessitate stabilization with instrumentation and fusion. A variety of surgical approaches are available either as stand-alone procedures or in combination, including anterior, posterior, and/or lateral approaches.

• Neurologic deficit is present in about 10% of thoracic fractures, and urgent spinal decompression with thoracic laminectomies is necessary.

• Fractures that cause thoracic deformity, with or without myelopathy, may require deformity correction using pedicle subtraction osteotomy, Smith-Peterson osteotomy, pedicle screw instrumentation, and/or arthrodesis.

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.

Clinical Case Examples

Case 1: Kyphoplasty

An 80-year-old male with steroid-induced osteoporosis presented with mid-back pain of 10 week’s duration. X-rays of the thoracic spine showed T7, T8, and T9 compression fractures with significant height loss and mild kyphotic deformity (Figure 45-2A). MRI showed a T2 hyperintensity at T8 consistent with acute fracture, while the other two fractures appeared chronic. Despite undergoing thorough conservative management, the patient continued to experience back pain that significantly limited both function and mobility.

FIGURE 45-2 A, Lateral thoracic x-ray showing T7, T8, and T9 compression fractures. B, Intraoperative fluoroscopy after PMMA injection at T8 level with height restoration.

He underwent a kyphoplasty of the T8 with satisfactory restoration of height and reduction of his kyphotic deformity (Figure 45-2B). Postoperatively, the patient had no significant residual back pain and returned to his premorbid function.

Case 2: Percutaneous Instrumentation

An 84-year-old female presented 1 month after she was involved in a motor vehicle accident in which she sustained a T9 Chance fracture (Figure 45-3A). Thoracic MRI performed hours after the accident showed a spinal epidural hematoma at the level of the fracture and an intact posterior ligamentous complex. The patient underwent multilevel thoracic laminectomies and evacuation of the epidural hematoma. Subsequent MRI showed no residual spinal cord compression; however, she had persistent spinal cord injury and was unable to lift the lower extremities against gravity. She also had severe back pain, which limited her mobility and rehabilitation. We opted to perform percutaneous T6-12 instrumentation (Figure 45-3B). Two months later, the patient was tolerating rehabilitation well, and her lower extremity strength was markedly improved.

FIGURE 45-3 A, Preoperative CT demonstrating T9 Chance fracture. Postoperative AP (B) and lateral (C) x-rays showing bilateral T6-8 and T10-12 pedicle screw and rod fixation.

Case 3: Pedicle Subtraction Osteotomy

A 57-year-old male presented with progressive myelopathy, including gait disturbance due to spasticity progressing over a 5-year period. Bowel and bladder control had been compromised, and the lower extremities were diffusely weak to resistance. He reported severe paresthesias in his lower extremities. Bilateral Babinski signs and bilateral ankle and knee clonus were present. He also had a palpable nontender gibbus in the upper thoracic spine.

MRI and CT scans revealed severe compression of the ventral spinal cord due to a 30-degree focal kyphotic deformity at the level of T3-T4. A T2 signal change was detected within the spinal cord at the same level, consistent with advanced spinal cord injury (Figure 45-4A and B).

FIGURE 45-4 A, T2-weighted MRI sequence sagittal view, showing the ventral spinal cord compression and stretching resulting from the posttraumatic focal kyphosis at the level of T4. At the T4 level, the spinal cord is markedly atrophied and shows a significantly increased signal consistent with spinal cord injury. B, Sagittal thoracic CT scan showing a healed compression fracture at T4 the level with a resultant focal kyphosis of approximately 30 degrees.

A posterior transpedicular osteotomy was performed using biplane fluoroscopy, which guided the resection of a wedge of the superior T4 vertebra (Figure 45-5A-C). Rib osteotomies were completed at the level of T4, and lateral wall osteotomies with preservation of the pleura were accomplished. After a spontaneous partial reduction of the osteotomy, the Mayfield head holder was elevated to reduce the gibbus and correct the alignment of the upper thoracic spine. Longitudinal rods were contoured and placed at the level of T1, T2, and T3 after reduction was completed manually, with biplane fluoroscopy and intraoperative evoked potentials, by closing the bony defect created by the vertebral osteotomy (Figure 45-5 C-D). The longitudinal rods were placed into a reduced position, achieving complete reduction of the kyphotic and sagittal plane deformity and annihilating the gibbus deformity (Figure 45-5E). Biplane fluoroscopy confirmed alignment of the sagittal and coronal plane at the instrumented levels with complete resolution of the gibbus, and evoked potentials remained unchanged (Figure 45-5E and F).

FIGURE 45-5 A, Intraoperative fluoroscopy showing placement of bilateral 5.5-mm and 6.5-mm pedicle screws from T1 to T10. The inferior part of the spinous process and laminae of T3 are resected, as well as the inferior facets of T3 bilaterally. The superior facets of T4 and the pedicles of T4 are resected, creating a giant foramen containing both T3 and T4 nerve roots. Rib heads at the level of T4 are osteomized along with the transverse processes. B, Under fluoroscopic guidance, a wedge of the vertebral body of T4 is removed with different sizes of curettes and an electric drill. Rongeurs are used to osteomize the lateral edges of the vertebral body. C, Placement of the contoured rods at T1, T2, and T3 allows manual reduction of the focal kyphosis at the level of T3 with the guidance of biplane fluoroscopy and intraoperative evoked potentials (D) by closing the bony defect created by the vertebral osteotomy. E, The longitudinal rods were placed into a reduced position, where a complete reduction of the kyphotic and sagittal plane deformity was achieved, annihilating the gibbus deformity and closing the bony wedge defect created by the PSO. F, Biplane fluoroscopy confirmed alignment of the coronal plane at the instrumented levels.

Two days after the surgery, the patient was transferred from the intensive care unit to the floor, where he quickly recuperated his baseline strength and was discharged home ambulating independently with the use of a cane. Postoperative CT scans confirmed the established correction of the sagittal plane deformity (Figure 45-6A and B).

FIGURE 45-6 A, Preoperative sagittal CT scan of the thoracic spine showing the wedge resection planning. B, Postoperative sagittal CT scan of the thoracic spine showing the “closing” of the wedge resected by the PSO, and subsequent “shortening” of the spine at T4.

Anterior approaches to treat a spinal deformity can also be performed. However, any multisegment anterior fusion construct is subject to sustaining increased mechanical stress, which can thereby result in the failure of the anterior spinal fusion.³ In addition, the upper thoracic spine is a difficult region to access anteriorly due to the presence of major vascular elements as well as vital structures ventral to the spine.² Moreover, Boockvar et al reported that anterior reconstruction alone might not meet the biomechanical needs of the upper thoracic spine. Recent advances in anesthesia, neural monitoring, and posterior instrumentation have made a posterior approach to the upper thoracic spine possible and treatment of the upper thoracic spine achievable.¹

In some cases, PSO may be safely used to correct abnormal severe focal kyphotic deformities, which result in spinal cord stretching and ventral compression, because it allows for significant correction through one spinal segment by shortening the spinal column and reestablishing sagittal alignment. When PSO is performed, instrumented fusions are usually necessary, and dural buckling needs to be ruled out with thoracic laminectomies at the osteotomy sites.