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Vertebroplasty and Kyphoplasty
Vertebroplasty and kyphoplasty are minimally invasive, percutaneous procedures in which a fast-setting polymer is injected into a pathologic vertebral body with the goal of relieving pain or disability. These treatments have been applied to painful osteoporotic compression fractures, painful neoplasms, and structurally compromised vertebrae. They represent an evolving set of technologies for treating a common and important problem with limited medical and open surgical treatments.
Before the introduction of vertebroplasty and kyphoplasty, treatment of compression fractures consisted of bed rest, pain control (with nonsteroidal antiinflammatory medications, calcitonin, and narcotics), and back bracing. This regimen can be effective, and many people eventually experience at least partial relief from their pain as the fracture heals. However, approximately half of patients continue to have substantial pain after 3 months of conservative treatment. These people will often continue to require analgesic medications, and they risk the development of gradually worsening kyphotic deformity. Even in those whose compression fractures do heal over time, the recovery period is time consuming, requiring at least several weeks. The experience is often profoundly unpleasant and can be marked by periods of insufficient pain control, delirium, and constipation. Such patients are sometimes bedridden, with the attendant risks of deep vein thrombosis, pulmonary embolism, and pneumonia. The prolonged immobility accelerates bone resorption and predisposes one to additional injury. Finally, the long-term effects of even a healed fracture may be substantial: kyphotic deformity, decreased lung capacity, and altered forces on intervertebral discs and facet joints.
The vertebroplasty procedure was introduced in France in 1984 by a group who used the technique to treat symptomatic vertebral hemangiomas. They found that the “internal casting” provided by polymethylmethacrylate (PMMA) injected into the pathologic vertebral body provided substantial pain relief. This success led to expansion of the procedure to the treatment of pain from myeloma and metastatic neoplasms of the vertebrae. In 1993, the technique was introduced in the United States, where its chief use has been to treat the pain from osteoporotic compression fractures. Kyphoplasty was introduced in 1999 as the proprietary technology of Kyphon Inc. Kyphoplasty differs from vertebroplasty by adding the insertion and inflation of a balloon before cement delivery. It has the added goal of restoring vertebral body height and spine alignment.
The remarkable success of the procedures documented in early case series spurred increasing clinical use. However, two randomized controlled trials published in 2009 suggested that vertebroplasty did not provide superior long-term pain relief when compared with a sham procedure. , There was a subsequent downtrend in national utilization of vertebroplasty and kyphoplasty. , However, the randomized controlled trials published in 2009 were not without flaw, and more recent trials have shown benefits of vertebroplasty and kyphoplasty in carefully selected patients (see Benefits).
Indications
The primary indication for vertebroplasty and kyphoplasty is a painful, unhealed compression fracture. These fractures may be the result of osteoporosis, hematopoietic or lymphoid neoplasm (e.g., leukemia, multiple myeloma), or hematogenous metastasis. People with no fracture but pain resulting from lytic metastatic neoplasm or the rare symptomatic hemangioma are also candidates for vertebroplasty. People with chronically nonhealing traumatic fractures (e.g., osteonecrosis) may be candidates. In all these circumstances, there should be congruent historical, physical, and imaging findings. Vertebroplasty can also be performed prophylactically to stabilize a weakened vertebra before planned surgery.
Contraindications
There are few absolute contraindications to vertebroplasty and kyphoplasty. These contraindications are: (1) recent systemic or spinal infection, (2) uncorrected bleeding diathesis, (3) insufficient cardiopulmonary health to tolerate sedation or general anesthesia, and (4) fracture-related compromise of the spinal canal sufficient to result in myelopathy or radiculopathy. In addition, these procedures are generally not performed for fractures that are painless or have already healed.
There are also specific fracture features that do not represent absolute contraindications but substantially increase the risk or technical difficulty of the procedure. Disruption of the posterior cortex increases the risk of posterior cement leakage and therefore the risk of spinal cord or nerve root compression; this feature is rare in osteoporotic compression fractures but frequent in burst fractures and metastatic neoplasm. Substantial canal narrowing (without clinical evidence of myelopathy or radiculopathy) increases the risk that even a small amount of cement leakage will produce neurologic compromise. Marked loss of vertebral body height makes the procedure more difficult because there may be little space for needle placement. Poor visualization of osseous structures on fluoroscopy increases the risk of improper needle placement and symptomatic cement leakage but can be overcome with the use of computed tomography (CT). Treatment of patients whose fractures have these features should be performed only by the most experienced practitioners.
Preprocedure Evaluation
A thorough preprocedure evaluation is necessary for patients being considered for vertebroplasty or kyphoplasty. The pain of an acute fracture can be difficult to distinguish from the many other sources of pain in the back. Most people with osteoporotic vertebral compression fractures are elderly, and they often suffer from more than one painful pathologic fracture. A combination of careful history, physical examination, and advanced imaging is needed to make sure that (1) the patient is likely to benefit from treatment, (2) vertebroplasty or kyphoplasty is the best alternative, (3) all pathologic vertebrae suitable for treatment are identified, and (4) the treatment is performed safely. The excellent outcomes reported with these procedures are grounded in the careful selection of appropriate candidates.
History
The classic symptoms from an acute vertebral compression fracture include deep pain with sudden onset, midline location, and exacerbation by motion and standing. These fractures may occur with little or no trauma. The pain often diminishes little in the first week, then fades gradually over the next several weeks to 3 months. , Lateral radiation may be present, but persistent radiation of the pain in a radiculopathic pattern is rare. When there is substantial kyphosis, patients may also suffer from difficulty breathing, anterior chest wall pain, and gastrointestinal discomfort.
In addition to evaluating the nature of the pain, the interview should include assessment of the effect of the pain on activities of daily living and sense of well-being. One may choose to quantify these factors using such questionnaires as the Oswestry Disability Questionnaire, Roland-Morris Disability Questionnaire, and Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). Such indices can be used in conjunction with a visual analogue pain scale to follow the success of treatment.
The physician should evaluate ongoing or potential treatment of the underlying disease process. For osteoporotic patients the interview is an opportunity to make sure that appropriate treatment of the osteoporosis is under way. The severity of osteoporosis and the use of antiosteoporosis medications will substantially alter the risk of additional fractures. For patients with neoplasm, timing of the treatment may be affected by ongoing chemotherapy and radiation.
The physician should evaluate the patient’s general health and coexisting medical problems to perform the procedure safely. This evaluation will allow one to determine the feasibility of the procedure and safest and most effective means of providing analgesia and anxiolysis during the procedure. The physician should search for possible contraindications to the procedure (e.g., anticoagulation) and for allergies to planned pharmaceutical use (e.g., prophylactic antibiotic).
Physical Examination
The practitioner should perform a directed physical examination. This examination includes inspection of the back, palpation for focal areas of tenderness, and correlation of the site of pain with anatomic landmarks. In difficult cases, examination of the sites of pain and tenderness can be performed with fluoroscopic assistance to localize the pain to specific anatomic structures. Although point tenderness at the spinous process of the fractured vertebra is the typical finding in unhealed compression fractures, the absence of typical focal tenderness does not preclude the presence of such a fracture. Imaging is a more reliable test than this portion of the physical examination. Assessment of lower extremity neurologic function is especially important in patients with symptoms suggestive of myelopathy, radiculopathy, or spinal stenosis. Evaluation of the heart and lungs is necessary for the safe use of sedation for the procedure.
Imaging
Imaging of the spine is undertaken in all cases to confirm the clinical diagnosis and to plan the procedure. Radiographs are the imaging study of choice for the initial imaging evaluation ( Fig. 158.1 ). Anteroposterior (AP) and lateral views should be obtained. This study allows one to confirm the presence of fracture, determine the location of fractures, assess the degree of height loss and kyphosis, and identify anatomic variants. Whenever possible, comparison to prior studies is valuable. A single radiograph almost never allows one to distinguish a new or unhealed fracture from a chronic, healed fracture. With prior radiographs (“old gold”) for comparison, new compression fractures can be identified. If serial radiographs taken several weeks apart show a new compression fracture in a patient with classic history and symptoms, no further imaging may be necessary. However, because back pain is a difficult diagnostic problem, most patients benefit from advanced imaging.
Magnetic resonance imaging (MRI) is the test of choice for this additional evaluation. The main goals of MRI are to: (1) distinguish new or unhealed fractures from healed fractures, (2) identify other causes of pain, and (3) evaluate the risk of symptomatic cement leakage during the procedure. For these purposes, the single most useful sequence is a T2-weighted sequence with fat suppression. We prefer using inversion recovery (i.e., a STIR sequence) to achieve the fat suppression because it is less prone to artifact than frequency-selective fat saturation techniques. On these magnetic resonance (MR) sequences, recent or unhealed fractures show hyperintense signal within the bone marrow ( Fig. 158.2 ). This signal may be present in poorly marginated areas filling much of the vertebral body or as discrete curvilinear fracture clefts. In contrast, healed fractures have marrow signal similar to that of unfractured vertebra. These sequences also provide an adequate evaluation of the spinal canal and will show most alternative causes of pain that might mimic fracture. Additional imaging with a sagittal T1-weighted sequence and axial T1- and T2-weighted images may be helpful. In most patients with a typical clinical history and physical examination for osteoporotic compression fracture, the STIR sequence alone is adequate, and one can reserve the full set of MR sequences for patients whose pain is atypical or with STIR abnormalities that require clarification. We have found value in obtaining an additional MRI shortly before the procedure when either (a) there has been worsening of the patient’s pain since the initial evaluation or (b) the imaging study used for the initial evaluation is more than 3 months old.
Dual energy CT is an emerging technology that shows promise as an alternate to MRI for assessment of marrow edema ( Fig. 158.3 ). By subtracting calcium from bone, the edema/hemorrhage in bone marrow that accompanies acute fractures becomes evident. Several studies have compared dual energy CT with MRI, showing a high negative predictive value (>90%) and accuracy for detecting edema in the vertebral bodies, showing promise for this technology as a supplement or alternative for patients who have contraindications or cannot tolerate an MRI. CT is also useful for preprocedural evaluation in patients with burst fractures or metastases, where there may be loss of integrity of the posterior vertebral body cortex and associated increased risk of posterior leakage of cement or posterior displacement of bone or tumor ( Fig. 158.4 ). CT is also the test of choice for postprocedure evaluation of unexpected symptoms (see later section on Risks).
Bone scan is an alternative imaging modality that may be useful in patients who cannot tolerate MRI (e.g., those with a pacemaker). Bone scan does not provide any evaluation of the soft tissues or spinal canal, but it does allow the differentiation of healed and recent fractures. The recent fractures will take up the injected 99m Tc-methylene diphosphonate tracer in much higher concentrations.
Procedure—Vertebroplasty
Sedation
Analgesia is necessary to perform vertebroplasty and kyphoplasty safely and with minimal discomfort. This process begins with the informed consent. Fully informing the patient of what to expect in the operating room or procedure suite facilitates patient comfort, cooperation, and satisfaction. Satisfactory analgesia usually can then be achieved with local anesthetics and moderate sedation, but in some cases general endotracheal anesthesia is needed. Vertebroplasty has generally been performed with moderate sedation while kyphoplasty has more commonly been performed with general anesthesia. At our institution, both are usually performed using moderate sedation with intravenous midazolam and fentanyl. Continuous patient monitoring is performed with electrocardiography, blood pressure measurement, and pulse oximetry. The drug delivery and monitoring are performed by certified nursing personnel. In patients with substantial preexisting respiratory or cardiac disease, an anesthesiologist is asked to evaluate the patient and determine if monitored anesthesia care is warranted.
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