Vertebroplasty for the Treatment of Vertebral Body Fractures

CHAPTER PREVIEW

CHAPTER SYNOPSIS:

Vertebroplasty was first described in 1984 and has emerged as a popular technique to surgically treat vertebral compression fractures (VCFs). The primary objective of vertebroplasty is to reduce pain, prevent further vertebra body collapse, and preserve vertebral height. Despite the low rate of complications for vertebroplasty, surgeons must remain aware of the possibility of extravertebral cement leakage, the percentage of bony destruction, and the degree of posterior wall destruction. This chapter discusses in depth the benefits, complications, different techniques, and implications of this procedure.

IMPORTANT POINTS:

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Diagnose VCF using appropriate imaging techniques including plain radiographs, magnetic resonance imaging (MRI), and computerized tomography (CT) when necessary.
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Understand the indications for vertebroplasty including osteoporotic VCF, some malignant and benign pathologic fractures, and persistent pain despite nonoperative efforts.
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Vertebroplasty aims to relieve pain, prevent fractured vertebra collapse, and improve vertebral height preservation.
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Classic wedge deformity on plain radiographs confirms VCF diagnosis.

CLINICAL/SURGICAL PEARLS:

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Correlate symptoms with radiographic images.
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All eligible patients should have a preoperative MRI scan.
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Use MRI or radionuclide scans, or both, to determine age of fracture and visualize bone edema.
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CT/MRI scans help differentiate osteoporotic and malignant fractures.
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Consider only vertebroplasty for stable fractures.
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Inject cement under fluoroscopic guidance to avoid extravertebral cement leakage.

CLINICAL/SURGICAL PITFALLS:

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Uncontrolled guidance of bone cement delivery into vertebral body.
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Polymethylmethacrylate (PMMA) can undergo an exothermic reaction and potentially harm adjacent anatomic structures.
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PMMA mixture is inconsistent.

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Osteoporosis, as defined by the Consensus Development Conference (1991), is characterized by low bone mass and the deterioration of bone tissue. Increased bone fragility can increase the risk for bone fracture, especially in aging men and women. Of the 25 million Americans with osteoporosis, women are more at risk for development of bone fractures because of the onset of postmenopausal estrogen loss. In women, hypersensitivity of the bone to parathyroid hormone usually causes the rapid loss of estrogen. In addition to low estrogen production, the development of osteoporosis can be caused by other predisposing medical conditions such as diabetes mellitus, emphysema, metabolic diseases that affect the liver and bowel, calcium deficiency, vitamin D deficiency, hormonal imbalances, malabsorption, alcoholism, and glucocorticoid use.

Potential peak bone mass is not achieved until early adulthood (age 17–28). Over time, many variables such as poor diet, lack of exercise, and chronic medication use can lead to a deficiency of the appropriate amount of peak bone mass. The loss of bone mass caused by osteoporosis results in decreased density of the central cancellous bone mass. This can then lead to the overall decline of the stability of the vertebral body, in turn shifting the biomechanical load to the cortical bone. Such changes reduce the overall carrying capacity of the vertebral column, therefore increasing the risk for vertebral compression fractures (VCFs). These fractures decrease the overall sagittal alignment and stability of the vertebral column and potentially lead to disability or even morbidity of the patient.

When the VCFs occur, vertebral column instability is characterized radiographically by the formation of an anterior wedge fracture. The middle column of the vertebra remains intact and can act as a pivot point resulting in progressive kyphosis. Overall, the vertebra experiences a loss in anterior height, but the posterior height remains unchanged. Physicians are often presented with patients with VCF who have pain in the general region of the fracture, a kyphotic deformity of the spine, and a history of minimal or limited trauma. Fortunately, most of these fractures remain confined to the anterior vertebral column, and thus do not usually cause any neurologic deficits.

In the past, rehabilitating an osteoporotic spine was complicated. Surgical intervention was reserved only for patients who displayed neurologic deficits and spinal instability. Osteoporosis, coupled with the patient’s multiple co-morbidities, made surgical intervention risky and complicated. Nonoperative treatment can decrease pain but also carries with it limitations in addressing the other symptoms related to the VCF such as ileus, decreased lung capacity, poor appetite, and progressive deformity. Currently, vertebroplasty serves as a surgical alternative to nonoperative treatment. This procedure can provide patients with sustained pain relief and restored daily functionality. As an image-guided, minimally invasive technique, vertebroplasty aims at stabilizing fractured vertebrae and relieving pain. To successfully stabilize the spine using fluoroscopic guidance, a surgeon needs to ensure proper placement of a percutaneous needle into the damaged vertebral body for bone cement injection.

INDICATIONS AND CONTRAINDICATIONS

Dr. Herve Deramond described the first case of vertebroplasty in 1984. Soon after, vertebroplasty was used to also treat patients with painful metastatic compressions and eventually osteoporotic compression fractures. Vertebroplasty was first performed in the United States in 1994.

It is important for the treating physician to understand the pathomechanics, clinical indications, and optimal technique to successfully treat VCFs. Despite the low rate of complications, it is crucial for surgeons to remain aware of the possibility of extravertebral cement leakage, the percentage of bony destruction, and the degree of posterior wall destruction.

Currently, in clinical practice, vertebroplasty is most commonly indicated to treat osteoporotic vertebral fractures in patients who have not responded to at least 6 to 8 weeks of conservative management. Conservative management can include brace management, pain medications, and activity modification. Vertebroplasty is indicated in patients who are usually older than 50 years with the acute onset of sudden mid to low back pain and minimal trauma. Patients will present with postural pain relief experienced in the supine position and increased discomfort when standing or walking. During physical examination of these patients, tenderness will be centered directly over the acutely fractured area. Physical examination of patients with uncomplicated compression fractures will yield negative straight-leg raises and a normal neurologic examination. Diagnosis of the VCFs can be further confirmed by the presence of the classic wedge deformity on plain radiographs.

The contraindications of vertebroplasty are less absolute. The few absolute contraindications include the presence of infection near the site of needle insertion or within the vertebral body or adjacent disc space, and the compromise of neural structures caused by the presence of a preexisting metastatic tumor. Contraindications of vertebroplasty also include systemic pathologic conditions such as sepsis, prolonged bleeding times, or cardiopulmonary conditions. It is important for the surgeon to also consider relative contraindications that can affect sedation or anesthesia. Deficient posterior cortices of vertebral bodies as in the presence of a burst fracture, three-column unstable fractures, or the presence of neurologic deficits remain contraindications to the procedure. Furthermore, vertebrae plana or nonacute or subacute fractures are also relative contraindications to the procedure. Patients with medical co-morbidities such as coagulopathy or cardiorespiratory problems should have a sufficient medical workup and clearance before recommending vertebroplasty as a treatment of VCFs in these patients. More contraindications to vertebroplasty include asymptomatic compression fractures of the vertebral body, some tumors, pregnancy, or preexisting radiculopathy caused by spinal stenosis.

Preoperative consultation has an advantage in allowing a personal explanation regarding the surgical procedure and the opportunity to review any medical conditions that can complicate the administration of sedation or anesthesia. It is important to correlate the patient’s symptoms of VCFs with the radiographic findings, especially in the case of multiple fractures.

Radiographic Analysis of Vertebral Compression Fractures

As a common means to assess VCFs, conventional radiographs cannot properly assess the decreasing bone mass density from osteoporosis. In the case of multiple VCFs, surgeons should use lateral chest radiographs and lateral digital radiographs together with computed tomographic (CT) images to adequately visualize the spine. Many potential causes of VCF include multiple myeloma, metastatic malignancy, and metabolic bone disease including osteomalacia, renal osteodystrophy, and hyperparathyroidism. Other contributing factors in the diagnosis of VCF include degenerative diseases, Scheuermann disease, Paget disease, hemangioma, infection, and dysplastic changes.

Osteoporotic and malignant pathologic fractures can be distinguished by their location observed on the radiographic images. On conventional radiographs, fractures above the T7 level of a malignant cause are often accompanied by a soft tissue mass, osseous destruction, and fractures of the posterior cortex of the vertebral body. Benign osteoporotic fractures can create a concave posterior cortex of the vertebra. Conversely, a malignant fracture will display a convex posterior cortex of the vertebrae. In further evaluation of malignant diseases using magnetic resonance imaging (MRI), the vertebral column will often include multiple skip lesions and associated soft tissue masses that are often encased in epidural malignancy. MRI can help delineate radiographic findings consistent with metastatic disease or primary malignancy to determine the malignant nature of a VCF. T1-weighted images demonstrate a diffuse low signal intensity and T2-weighted images a high signal intensity. Diffusion-weighted and gadolinium-enhanced MRI images can also contribute to a surgeon’s assessment in differentiating an osteoporotic and malignant VCF. The bone marrow pathology should be assessed before surgery using such MRI images. In the case of multiple myeloma as the diagnosis, MRI can allow a surgeon to visualize any diffuse bone marrow pathology that is not viewable on conventional radiographs separate from osteoporosis. The gadolinium-enhanced images further delineate the difference between necrotic tissue and viable or cystic tissue resulting from solid lesions.

CT can complement MRI by providing image quality that can assess the difference between an osteoporotic fracture and a malignant fracture. By directly identifying bony fracture patterns and the presence of destructive lytic lesions, CT scans can help define the overall stability of VCFs. CT scans can also help identify any fractures that were not identified on the plain films, identify the presence of a burst fracture, and help distinguish any complex fracture patterns. Spinal canal narrowing can also be assessed through the CT scan. CT is not able to depict bone marrow pathology as sufficiently as MRI.

Determining the age of a fracture using conventional radiographs is difficult. More recent acute fractures can be identified by the presence of cortical disruption and increasing density near the end plate from the trabeculae. Additional callous formation can be found near subacute fractures with high density present at the end plate. But these signs are not a reliable indicator of VCFs because high density adjacent to the end plate can appear to be minimal on conventional radiographs. Furthermore, underlying poor bone density or spinal deformity can limit the utility of plain radiographs as a diagnostic tool. MRI or radionuclide scans (RNS) can help a surgeon determine the age of a fracture. MRI remains the accepted standard means of assessment because an RNS has less sensitive properties and a delayed increase in uptake of osteoporotic bone. An MRI can offer a surgeon a more concrete image of bone marrow edema present in acute and subacute fractures. When distinguishing old fractures using RNS, the old osteoporotic fractures will have no abnormal signals, whereas more recent fractures will display a bone marrow edema pattern. This pattern present in new fractures will usually be parallel, bandlike, and located adjacent to the end plate.

When an MRI is not an option for assessment of VCFs, surgeons will often obtain transverse images together with sagittal and coronal multiplanar reformations (MPRs) using CT. MPRs are part of multidetector CT and are used to sufficiently assess the stability of VCFs. MPRs allow a surgeon to evaluate the integrity of the vertebral bodies in two planes instead of the one plane offered by traditional transverse images. In the presence of complex fractures or other suspicious symptoms, the surgeon should view the vertebral bodies in at least three planes.

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