Learning Objectives/Outcomes: After participating in this CME/CNE activity, the provider should be better able to:
1. Summarize the indications for vertebroplasty.
2. Examine the controversy surrounding its use.
3. Identify potential complications of vertebroplasty.
4. Outline sedation for a patient with multiple comorbidities undergoing the procedure.
Percutaneous vertebroplasty (PV) was first described by Deramond in 1984. At that time, it was indicated only for the treatment of aggressive vertebral angiomas.1 Now, PV is used as a palliative treatment for osteoporotic and malignant vertebral lesions, which weaken the vertebrae and cause chronic pain.2-3 Patients are selected based on pain refractory to medical management (bed rest, analgesics, calcitonin, or external bracing) and age of fracture. As a result, the best candidates have an identifiable fracture that is 1 to 7 months old. Exclusion criteria for PV include vertebral body height loss of 100%, posterior wall involvement, involvement of the spinal cord, bleeding diathesis, or a patient's inability to undergo emergency decompressive surgery.2 Most of the exclusion criteria relate to potential complications.
What Is Vertebroplasty?
PV is a fluoroscopically guided injection of a substance, usually bone cement, into a compressed vertebral body. The cement is made of liquid methylmethacrylate (MMA), powder polymethylmethacrylate (PMMA), and a radiopaque substance for visualization.
There are several steps involved in PV: vertebral puncture, spinal biopsy, vertebral venography, and injection of PMMA.2-4 Vertebral puncture gives access to the surgical site. Spinal biopsy is usually done when there is suspicion of metastatic invasion and avoided if an angioma is suspected. Vertebral venography identifies perivertebral venous drainages and extravasation of cement into epidural or perivertebral veins. The final step, PMMA injection, is stopped when the cement reaches the posterior vertebral wall or fills perivertebral veins.
A further advance in PV is kyphoplasty. During this procedure, a balloon is inserted under direct vision into the vertebral space and blown up to tamponade or compress the bone. PMMA can then be injected into the space so created with less chance of leakage.4-7 Unlike PV, which only prevents further vertebral destruction, kyphoplasty fixes spinal deformity and increases height. Contraindications to either technique are outlined in the box.
Complications
Complications are associated with each step of the vertebroplasty and kyphoplasty procedures8:
Vertebral puncture can enter surrounding structures: veins, arteries, and pleura. The needle can disrupt the internal cortex of the pedicle, thereby, increasing the risk of PMMA leakage.
Further increasing risk of extravasation is the involvement of osteoporotic and osteolytic lesions; rarely does this cause a clinical problem but it may cause postoperative mechanical problems.
Leakage of PMMA into perivertebral veins is not infrequent and can cause radiculopathy or embolization.9 Although pulmonary embolization is rare, it may be delayed for months. Chest x-ray is recommended at the end of the procedure.
Radicular pain has occurred with PMMA leakage into the neural foramina via cortical fractures, microfractures, or destruction of venous channels. It has also occurred without an identifiable leak. The latter has been successfully treated with nonsteroidal anti-inflammatory drugs (NSAIDs), suggesting an inflammatory reaction to the cement.
The most severe complication of PMMA leakage is spinal cord compression. It is for this reason that exclusion criteria include inability to undergo decompression surgery.
Other complications particular to PMMA are hypotension, hypoxemia, and cardiac dysrhythmias. Although hypotension occurs so predictably during orthopedic surgical procedures that some have dubbed it the bone cement implantation syndrome, only acute transient hypotension has been reported with PV, no doubt due to the minimal amount of PMMA used in the procedure and its containment.
Transient decreases in pulse oximetry readings are common.
Rothermich et al10 reported 6 deaths due to cardiopulmonary cement embolization, giving an incidence of 2% to 26%, depending on imaging technique. The event either occurred during the procedure or was delayed for months. The complication is diagnosed by chest pain and respiratory difficulties, with a sudden decrease in Spo2. Treatment is with anticoagulation, whereas endovascular removal or wedge resection is rarely indicated. Risk factors arise in patients with more comorbidities.11-13
Questions have arisen as to whether PMMA, the most commonly used filling material during kyphoplasty and PV, may have some inherent and unavoidable drawbacks. PMMA bone cement tends to leak during injection, which can lead to injury of the spinal nerves and spinal cord. Moreover, the mechanical strength of PMMA-augmented vertebral bodies is very high and might predispose to adjacent vertebral fractures. More recently, a biodegradable calcium phosphate-based nanocomposite (CPN) for augmentation has been developed to potentially avoid these issues.14 Never-theless, as CPN is not generally available, yet another recent meta-analysis looked at the risk of adjacent vertebral fractures during both PV and kyphoplasty and found no increase in fractures.15
Who Performs PV?
Neurointerventionalists were among the first to perform PV. Accredited in 2000 in the United States, requirements for this specialty include a residency in neurosurgery, neurology, and/or radiology, followed by a fellowship in neurointerventional surgery of 1 to 2 years. More recently, pain specialists have entered the field and, after appropriate training, perform these procedures.
Where Is PV Done?
Initially done in the interventional radiology (IR) suite, the procedure has now been performed in other settings as well. Problems with IR include that the setting might be an off-site area where equipment may not be similar to that immediately available in the operating room (OR), personnel may not be OR trained, and distance from the central core may make communication difficult. For example, cell phone coverage is often poor or lacking. In addition, if the operator does not have admitting privileges at the adjacent hospital, recovery facilities may not be readily available. A recent study has shown office-based PV and kyphoplasty, using only local anesthesia with minimal sedation, to be a viable alternative.16
The Procedure
Most patients presenting for these procedures are elderly women (as exemplified in the case provided in the sidebar). Patients tend to present with multiple comorbidities, such as cardiac compromise, urinary tract infections, and frequent bouts of pneumonia. Osteoporosis decreases respiratory ability. A restrictive lung pattern lowers vital capacity and forced expiratory volume in 1 second (FEV1). Vertebral fractures also decrease abdominal space. Opioid consumption leads to constipation with decreased nutrient absorption. Added to these comorbidities are insomnia and the depressive effects of pain.
Cardiac consultation is often warranted to determine whether the patient's condition can be improved before the procedure. Medications should be documented, such as over-the-counter preparations such as herbal compounds (St. John's wort, in particular) that can increase bleeding risk and interfere with the absorption of other medications, especially cardiac drugs. Fentanyl and morphine patches should be removed, as pain relief is often immediate after the procedure.
Consideration must also be made for postprocedural care. Although the aim is to allow the patient to return home the same day, there should be confirmation that a responsible adult is available who will stay with the patient, especially now that the direction is toward care in ambulatory and outpatient facilities.16
Patients are placed prone on the table. Positioning involves ensuring that the vertebrae are in line, allowing for mechanical limitation of movement, avoiding stretch on the brachial plexus and limb girdle, and placing the hands and feet in anatomically neutral positions.
A Typical Case
An 85-year-old Chinese (Mandarin-speaking) woman with marked osteoporosis and several lumbar and thoracic vertebral fractures is scheduled for vertebroplasty in interventional radiology. She has been followed up in the pain clinic for some years without significant improvement, despite recent epidural steroid injections and several courses of opioid patches. Now she is bedridden and has had several bouts of aspiration pneumonia and repeated urinary tract infections. Hemoglobin level is 9.9 g. She is unable to lie flat because of pain. Medications include hydrochlorothiazide, metoprolol, oxycodone, acetaminophen, omeprazole, albuterol inhaler, and sertraline.
The patient suffering from osteoporotic and/or vertebral fracture deserves special mention. It may be too painful for the patient to move or be moved. In these instances, anesthetic induction on the gurney or administration of adequate analgesia before movement to the operating table is indicated, but only after the application of monitors, especially pulse oximetry. The flat position required may also prove difficult and airway assistance may be indicated.
In addition to the normal positioning techniques, osteoporotic patients have limited range of motion and greater chance for fracture. If possible, the range of motion should be assessed preoperatively. Radiolucent bolsters or an air mattress should be considered.
Implications for sedation/analgesia depend largely on the tolerance of the patient and the comorbidities, and can be challenging.17 Preference is for an awake, mildly sedated patient who can respond to the operator's questions and breathe spontaneously without desaturation.
Only in rare circumstances is general anesthesia required. Small doses of remifentanil (a very short-acting narcotic) and dexmedetomidine (0.1-0.2 [mu]g/kg/min) have been used successfully.18 Low-dose midazolam 0.25 mg (understanding that the duration of action of the benzodiazepines is prolonged in geriatric patients), fentanyl 25 [mu]g, or propofol 25 mg, or as an infusion of 20 to 50 [mu]g/kg/min.
Other studies have noted the successful management with only local anesthesia combined with over-the-counter analgesics.19,20 Whatever the sedation plan used, a supraglottic airway, which can be quickly inserted in the prone position, must be available to secure the airway, should desaturation occur or if the patient becomes unresponsive.
The patient should be fully awake and responsive at the end of the procedure. Transfer to a postanesthetic care area is desirable with a stay for several hours to ensure no new neurologic changes. If deeper planes of anesthesia were necessary, then 24-hour or overnight admission is required.
Controversies
During the past 2 decades, thousands of reports have been made of successful and long-lasting excellent results after PV and kyphoplasty at all levels of the spine.4,21-26 However, several studies published in 2009 indicated that similar results can be obtained with lidocaine alone and that PV was a sham procedure without lasting results.27-29
For a study in Australia and New Zealand, Buchbinder et al performed a multicenter, randomized, double-blind, placebo-controlled trial in which participants were randomly assigned to undergo vertebroplasty (n = 35) or a sham procedure (n = 36). The participants had 1 or 2 painful osteoporotic vertebral fractures that were of less than 12 months' duration and unhealed, as confirmed by MRI.
The authors found no beneficial effect of vertebroplasty as compared with a sham procedure, at 1 week or at 1, 3, or 6 months after treatment. The findings were published in the New England Journal of Medicine and generated much controversy.
In a second multicenter trial and in the INVEST trial (investigational vertebroplasty efficacy and safety trial), Kallmes et al,28 and later, Gray et al,29 published 2 more reports. Kallmes et al28 randomly assigned 131 patients who had 1 to 3 painful osteoporotic vertebral compression fractures to undergo either vertebroplasty (n = 68) or a simulated procedure without cement (control group; n = 61). They reported that improvements in pain and pain-related disability associated with osteoporotic compression fractures in patients treated with vertebroplasty were similar to the improvements in a control group. Given that so many practitioners had achieved excellent results, again, considerable debate followed questioning as to whether the researchers were not completely blinded (as to insurance codes for example), whether patient selection was not appropriate, or whether the numbers were too small.30-32
Buchbinder et al33 emphasized the findings of his group in the Australian Medical Journal later in 2009:
Two randomised placebo-controlled trials show the importance of establishing the efficacy of procedures before adopting them into clinical practice.
Vertebroplasty appears no better than placebo for painful osteoporotic spinal fractures, and has potential to cause harm.
Buchbinder et al34,35 continued with Cochrane database analyses in 2015 and again in 2018, maintaining that in the opinion of the authors, PV was of no further benefit than sham procedures. Added in 2018 was this:
Numerous serious adverse events have been observed following vertebroplasty. However, due to the small number of events, we cannot be certain about whether or not vertebroplasty results in a clinically important increased risk of new symptomatic vertebral fractures and/or other serious adverse events. Patients should be informed about both the high- to moderate-quality evidence that shows no important benefit of vertebroplasty and its potential for harm.
The impact of these reports was an initial decrease in PV performed by generalists but no decrease by interventionalists.
Recent studies have again reported on improved quality of life and decrease in pain after PV.36 Filippiadis et al37 noted that, as not all vertebral compression fractures are the same, a tailored-based approach is necessary for efficacy and safety.
With different cements and materials as alternatives to the original PMMA, limitations and the risks governing the use of PV are reduced.37 Other studies have suggested better patient selection and diagnosis.7,38,39 Further consideration as to positioning has been made for special groups such as obese individuals and those with pulmonary disease.40 Guidelines have been drawn up and implemented by the Cardiovascular and Interventional Radiological Society of Europe.41
Going Forward
Several new techniques are undergoing pilot studies. In one study, percutaneous minimal invasive procedure used glass acrylate (PMMA) and digital subtraction angiography. The researchers found that catheterization laboratory unit (cath lab PV) can be combined effectively to provide pain relief without problems related to acrylate viscosity and injection.42 Significant (90%) pain relief was achieved within 24 to 48 hours in 18 (81.81%) patients, allowing early mobility and without analgesics.
Contraindications to Vertebroplasty and Kyphoplasty
* Untreated coagulopathy;
* Lack of a definable level of vertebral collapse;
* Osteoporotic vertebral fractures that are completely healed or are responding to conservative management;
* Symptomatic spinal cord compression at the level of the fracture;
* Severe cardiopulmonary disease; and/or
* Active infection such as sepsis, osteomyelitis, discitis, or epidural abscess.
Another early study reviewed the feasibility of augmented intelligence-based and artificial intelligence-based navigation during PV. The technique proved accurate and safe, and facilitated lower patient radiation exposure compared with standard fluoroscopic guidance.43
Yet another advance is the combination of PV with 125I seeds in the treatment of metastatic spinal tumors.44 In a total of 161 patients, no radiation myelopathy developed and the treatment was found to be effective palliative therapy.
ACS and ASA Data
The American College of Surgeons National Surgical Quality Improvement Program identified 850 patients for vertebral augmentation.45 The average age was 79 years and 71% were female. Adverse events (AEs) occurred in 9.9%, deemed serious in 6.6%. Death occurred in 1.5% and readmission within 30 days in 11%. AEs and death were significantly associated with American Society of Anesthesiologists (ASA) 4 and general anesthesia. Readmission was associated with pulmonary disease and inpatient status before the procedure.
Conclusion
While much controversy and debate still surrounds percutaneous vertebroplasty and kyphoplasty, it is impossible to ignore case reports and even some trials that show these procedures can benefit a patient population that does not improve otherwise. For practitioners who will perform these procedures, it is crucial to be aware of the seemingly conflicting evidence, and to consider each patient individually, especially in weighing the potential benefits against the rare but significant risks. Practitioners should also remain aware of continuing clinical trials for new injectates, pilot studies for new techniques, and guidelines from national and international societies.
References