Vertebroplasty and kyphoplasty in malignant vertebral fracture

Background

Most oncologic patients (∼70%) eventually will develop a metastatic vertebral fracture/lesion because of their underlying disease. Although these fractures/lesions can be located at any spine level, most commonly they are encountered in the thoracic and lumbar spine. These fractures lead to augmented tumor load, vertebral body height reduction, and consequent spinal deformity along with intractable pain and mobility impairment. These symptoms lead to reduction of physical and social function, reduced lung capacity, negative influence on nutrition as well as on quality of life, and lead to hospitalization and an increase in mortality rates.

The therapeutic archer’s quiver includes conservative therapy (bisphosphonates, bed rest and bracing, oral analgesics and opioids, etc.), chemotherapy, radiotherapy, and surgical options. In approximately one-third of these patients, these treatments do not result in significant pain reduction, increase in mobility, or improvement in quality of life. In these patients, vertebral augmentation by means of vertebroplasty or kyphoplasty can be performed by aiming at vertebral body stabilization, with subsequent pain decrease and restoration of mobility.

Vertebroplasty was introduced to everyday clinical practice in 1987 when for the first time ever Galibert and Deramond performed the technique for the treatment of an aggressive hemangioma in the cervical spine. The technique involves the image-guided, percutaneous needle placement in the vertebral body and the injection of a viscous implant (polymethyl methacrylate [PMMA]) for vertebral stabilization. Ever since along with the technological innovations, the indications of the technique expanded, including osteoporotic and traumatic vertebral fractures as well as metastatic lesions including lesions from multiple myeloma and lymphoma. In addition, the fact that the technique can be combined to other minimally invasive techniques for local tumor treatment plans further expands the indication list to include specific benign primary tumors (e.g., aneurysmal bone cyst, eosinophilic granuloma) and complex metastatic lesions (e.g., osteoblastic metastases). More recent technologies provide vertebral augmentation combining PMMA injection to the assistance of specific devices such as radiofrequency electrodes, stents, and peek cages.

Kyphoplasty is another percutaneous, image-guided procedure used to treat symptomatic vertebral fractures and, in addition, aims in vertebral height restoration with subsequent reduction of the spine’s biomechanical alterations. ^, The technique was introduced to everyday clinical practice in 1998 in the United States by an orthopedic surgeon. During kyphoplasty, cannulas are, bilaterally or unilaterally, introduced inside the vertebral body, a cavity is drilled, and inflatable balloon bone tabs are used to elevate the vertebral endplates, thus reducing the deformity and attempting to, at least temporarily, more or less restore the initial vertebral height. The intravertebral cavity created is subsequently filled with bone cement (PMMA). More recent technologies have reduced the size and diameter of the instruments used in kyphoplasty.

PMMA is a biocompatible and nonabsorbable implant that is injected in a viscous form and that rapidly solidifies, providing mechanical stability within a few hours postinjection. ^, Concerning interventional oncology, the use of PMMA as the viscous implant has proved useful, as it deters tumor growth. The reason for this behavior of tumor cell in contact with PMMA is not yet clear, but the predominant hypothesis is that the exothermic reaction during polymerization creates a necrotic zone, which has an antimitotic effect on local tumor. This energy release is directly proportional to the amount of cement injected and is limited by convective heat transfer due to blood perfusion. PMMA bone cement is suggested to be designed in a way that the maximum temperatures during this reaction are limited to 70˚C. Several studies have shown that the therapeutic temperatures raised during PMMA polymerization do not cause any damage in the spinal cord or surrounding nerve roots as long as the cement is confined to the boundaries of the vertebral body and does not come in direct contact (at large volumes) with the aforementioned nerve structures. Another advantage of PMMA for interventional oncology is the fact that it does not undergo vascular invasion and bone or tumor ingrowth, resulting in resorption and remodeling.

Concerning interventional oncology, both techniques constitute symptomatic (palliative) rather than curative treatments. ^, Although both techniques seem to be governed by excellent success rates (concerning pain reduction and mobility improvement) and low complication rates, it is beyond doubt that specifically for the application of percutaneous kyphoplasty in interventional oncology, more and extensive studies and meta-analyses are necessary. The same is true for all of the most recently developed vertebral augmentation techniques that combine cementoplasty to implantation of a specific biocompatible material (e.g., cage or stent).

Patient selection

Proper patient selection is critical for a safe and efficacious technique. To begin with, one must consider the histology of the tumor, the general condition of the patient, the degree of bone destruction, and the potential of combining osteoplasty with other surgical or minimally invasive image-guided therapies. These considerations will assist to define whether the therapy will have curative intent (e.g., a case of solitary metastasis treated by a combination of chemoembolization, ablation, and cementoplasty), locoregional tumor control, or palliative intent (e.g., a case of multiple lesions treated with multilevel vertebroplasty or kyphoplasty aimed at pain reduction and mobility improvement).

Biopsy of the lesion for histologic conformation is necessary and can be performed either prior to or at the same session with cementoplasty depending on treatment type. Indications for performing a biopsy include the possibility of lesions originating from unknown primary neoplasm, presence of more than one primary neoplasm coexisting and cases where imaging findings do not clearly attribute the lesions to the primary neoplasm.

In general, the ideal candidate is a patient with symptomatic vertebral lesion of an osteolytic nature (metastasis, multiple myeloma, and lymphoma lesions) with pain, mobility impairment, and risk of compression fracture ( Figure 29-1 ). Osteoblastic lesions require a more complex technique during which, prior to cementoplasty, some osseous space must be created for PMMA to be injected (e.g., a cavity or osseous channels, formed by specific instruments) ( Figure 29-2 ). Finally, in cases of aggressive benign vertebral tumors such as hemangioma, giant cell tumor (GCT), and aneurysmal bone cyst (ABC), the aim of vertebroplasty is to strengthen the vertebral body and devascularize the lesion, thus resulting in lowering of pain. In such cases, vertebroplasty can be combined to intralesional sclerotherapy.

Disruption of the posterior wall is no longer considered a contraindication for both vertebroplasty and kyphoplasty. Retropulsed osseous fragment is a relative contraindication for kyphoplasty but not for vertebroplasty. ^, Other contraindications include a patient unwilling to consent, restricted span of life, local or systemic infection, allergy to any of the materials used (cement, opacifiers etc.), uncorrectable coagulopathy, and lesions that do not produce symptoms.

Preprocedural care

Preprocedural imaging in oncologic patients should include magnetic resonance scans (including fat-saturated sequences prior to and after intravenous (IV) gadolinium chelate administration and short tau inversion recovery [STIR] sequence), bone scintigraphy exams, and computed tomography (CT) scans (extremely helpful in deferring osteolytic/osteoblastic lesions). Thorough medical record uptake and physical examination is combined to imaging and neurophysiologic studies. Correlation of physical examination findings to those of imaging and neurophysiology will provide most of the answers in clinical and diagnostic dilemmas.

Prior to the session, laboratory workup is necessary, including complete blood count and coagulation profile as well as electrocardiogram and cardiopulmonary control. Consultation with the anesthesiologist is performed after the aforementioned workup and prior to the therapeutic session.

Choice of anesthesia is left to the responsible anesthesiologist and varies from local anesthesia to general anesthesia (including epidural anesthesia with or without sedation). It is to be kept in mind that cement injection in neoplastic lesions can be quite painful; thus local anesthesia is usually not considered a choice.