VAT fell out of favor for a brief period of time shortly after studies in the New England Journal of Medicine published in 2009 by Buchbinder et al. and Kallmes et al. showed no benefit of VP over a sham procedure [62, 63]. This led the American Academy of Orthopaedic Surgeons to advise against the use of VP. There were, however, some important shortcomings of these studies. The patients were primarily outpatients, with pain scores as low as 3 out of 10. Additionally, patients with chronic fractures were included (>4 months old), which do not traditionally respond as favorably to VAT. Furthermore, the studies were not appropriately powered for subset analysis, which would have been necessary for evaluation of the subset of patients included in these studies with acute, severe pain. These are important factors in such studies as patients who typically benefit from these treatments are those with acute fractures associated with severe pain. Subsequent studies including the VERTOS I, VERTOS II, CAFE, and FREE trials have shown dramatic pain reduction after vertebral augmentation therapies using appropriately selected patients [64–67]. More specifically, patients having acute fractures with associated moderate to severe pain demonstrated a more dramatic, measurable benefit after VAT in these studies.

Although VAT are most commonly used in the case of painful osteoporotic fractures, there are several other indications. VP is used to treat painful primary bone tumors such as hemangiomas, treat painful fractures due to osteonecrosis (Kummel disease), reinforcement of the vertebrae prior to fixation surgery, and for treatment of painful vertebrae with malignant infiltration causing instability or fracture [59, 60]. The common malignancies that can affect the vertebral bodies include multiple myeloma, lymphoma and metastatic disease with breast, prostate, lung, bladder and thyroid cancers having a predilection to metastasize to the bone [58].

In the case of malignancy, indications for VAT are frequently tailored to the patient. The first and most obvious indication is pain associated with the VCFs with a common recommendation of at least 4 out of 10 on a base 10 visual analog scale (VAS) [15]. The second indication is edema on magnetic resonance imaging (MRI) or a positive bone scan (Fig. 18.3), indicating the acuity of the fracture. This indication is, however , occasionally flexible as good results have also been obtained in subacute or chronic VCFs refractory to conservative measures [67–69]. Bone scan can also indicate a recent neoplastic process at a compression fracture site [6, 15, 18, 21]. Imaging studies should also be used to rule out other possible causes of the patient’s pain. In addition, clinical examination should correspond with imaging studies to confirm fracture as the primary cause of pain and exclude alternative etiologies [9].

Life expectancy of the patient is also an important consideration. Patients not expected to live for 6 months may not be good surgical candidates and in many cases may benefit from a VAT to improve their quality of life [70–72]. It should also be noted that when life expectancy is very short, VAT may be of limited value or in some cases may be an unacceptable risk. Ultimately this should be evaluated on a case-by-case basis balancing risks, benefits, patient values, and treatment goals.

Several absolute and relative contraindications exist for VP and KP. The most well established contraindications include overt instability and cord compression [15]. Cord compression on imaging is considered a relative contraindication by some in the field with special precautions taken during VAT in this population of patients [11, 18, 73]. A combination of VAT with laminectomy with or without additional instrumentation can also be used in appropriately selected cases [74]. Infection at the fracture site, bleeding disorder, low platelet count, allergy to contrast, and contraindications to local or general anesthesia are also contraindications to VAT [15]. A full preoperative work up should always be performed.

Vertebroplasty is performed under sedation or general anesthesia with the guidance of biplane fluoroscopy or CT. Polymethylmethacrylate is the most common cement that is used. A needle is placed into the vertebral body prior to cement preparation. A transpedicular approach is typically used for the lumbar and thoracic levels due to inherent safety, but a parapedicular or infrapedicular route can be used if the pedicles are too small or destroyed. An anterolateral approach is often used in the cervical vertebrae. A bipedicular approach is frequently used, although in many cases, a unipedicular approach can just as effectively be utilized depending on the patient’s anatomy (Fig. 18.1) [75]. The cement is injected in the polymerization phase to reduce risk of it entering the venous circulation or leaking outside of the vertebra. Injection is done under imaging, which allows early detection of epidural and lateral leaks. The anterior two-thirds of the vertebral body are filled evenly with cement, and the needle is removed prior to cement setting.

In kyphoplasty , bone needles are inserted into the vertebral body after which a balloon is inserted through the bone needle and inflated prior to cement injection (Fig. 18.2). A bipedicular approach is typically utilized. The goal is to create a cavity within the vertebral body and also to attempt to restore or improve vertebral body height. Cement is then injected to fill the cavity, typically starting from the anterior third of the vertebral body in a retrograde fashion as the needle is slowly retracted into the middle third of the vertebral body. Cement injection is stopped when it reaches the posterior third of the vertebral body. Because a cavity has been formed, injection of cement is under lower pressure than during injection with VP [18].

Significant pain relief has been described in many previous studies and can be expected in the appropriately selected patient population [20, 21, 65–67, 76]. Pain relief is more pronounced in VAT done in acute fractures although some improvement has been shown in more subacute and chronic fractures [67, 76]. Vertebral body height restoration of up to 34–36 % with 3–7.6° of improved sagittal alignment has been described [3, 6, 9, 15, 18, 19, 67, 75]. This has been shown to encourage upright posture, reduced future fractures, and reduced flexion movements of the involved vertebrae [77, 78]. Furthermore, multiple levels can be done simultaneously. No significant increase in operative time or morbidity rate has been seen with 3–4 levels augmented at one time [15]. The number of augmented levels per procedure should be planned on a patient-by-patient basis.

The most frequent complication of VP and KP is leakage of cement with the greater majority of cases being asymptomatic. This is particularly more risky into the posterior canal given tumors frequently involve or destroy the posterior cortex of the vertebra (Fig. 18.4). For hematogenously spread tumors, this is likely facilitated by the vascular anatomy, with blood supply entering through the basiverteral foramen posteriorly [42]. Extravasation of cement is less frequent in KP, likely due to the lower pressure during cement injection [15, 18, 76]. Many less frequent complications have been reported with the most notable being fatal penetration into vital structures; however, the rate of serious complication is very low [75, 79, 80]. Adjacent fractures can also occur although the incidence is similar or reduced compared to conservative treatment [16].

Initially it was hypothesized that pain resolution after VAT was that PMMA destroys pain fibers due to the exothermic effect of cement polymerization or direct toxicity from the monomer [81–84]. Other studies challenged this due to only minimal osteonecrosis, no evidence of intraosseous neural tissue necrosis, and similar pain reduction seen with calcium phosphate cement which crystallizes at room temperature [85–87]. PMMA may also simply affect vertebral body nerve fibers by mechanical disrupt during balloon inflation or the filling of the central vertebral body with cement. Cement may also simply provide internal fixation preventing pain fiber irritation [85, 86].

There is also some disagreement among experts in the field regarding the appropriate amount of cement used with no definitive amount established. Some studies suggest that smaller cement volumes may restore vertebral body strength and stiffness with adequate pain control [88]. Others propose larger amounts produce better biomechanical results. Larger volumes of cement have been shown to better correct deformities and maintain vertebral body height [89, 90]. One study specifically found that cement volume was the most important predictor for pain alleviation in a dose-dependent pattern [91]. The exact mechanism by which VP/KP provide pain relief remains somewhat controversial.

Appropriate prophylactic use of VP and KP is currently a point of disagreement. Prophylactic VP and KP have been used in vertebral bodies adjacent to the level augmented for fracture to reduce stress on those adjacent levels and prevent subsequent fractures [92]. A specific example of this is performing prophylactic augmentation in between two augmented vertebrae as this vertebra is exposed to increased forces on either side (Fig. 18.2).

Discussion more recently has been directed towards the treatment of metastatic disease prior to fracture. There is some controversy as to whether this will help reduce future fractures and patient morbidity or cause tumor spread. Combining VAT with conventional radiation is one approach, providing bone stabilization with additional local control [46]. Newer techniques such as radiofrequency ablation and cryotherapy combined with cement augmentation and radiation seem to be the next step in the treatment of metastatic spinal disease [10, 93, 94], which are discussed further in this chapter.