A lot has happened, and not much has happened, in the field of vertebral augmentation since 1984, when a small team of doctors decided to treat a painful hemangioma of the C2 vertebra via a transoral route by placing a bone needle within the lesion and injecting radiopaque acrylic bone cement under fluoroscopic guidance. It was not until just under a decade later that this technology underwent transatlantic dissemination and was initially utilized not for tumors of the spine but for the treatment of painful osteoporotic vertebral compression fractures.¹ The anecdotal case reports and case series were strikingly favorable, and the ability of interventionally-inclined radiologists to learn readily and adopt this technology into their practices led to the rapid proliferation of the vertebroplasty procedure. Not long after, in the late 1990s, technological innovation led to development of an inflatable balloon tamp that could be used in an attempt to improve patient outcomes by generating a better treatment effect beyond pain relief, specifically, height restoration and kyphosis correction, and by potentially decreasing the chances of procedure-related cement extravasation via the mechanism of cavity creation.² This technology appealed to many operators, spine surgeons in particular, and the kyphoplasty procedure developed its identity and its own CPT code. A tremendous dialogue and debate ensued between vertebroplasty proponents and kyphoplasty advocates as to which of these procedures was “better”.³  It was at this moment that two randomized controlled trials poured a bucket of ice water on the heated debate; the results of these trials suggested that the procedures might not be as effective as initially touted.⁴ With the equity of clinical belief in these procedures called into question, the performance of them experienced a decline, as the supporters of these procedures rallied in an attempt to preserve their appropriate clinical usage.⁵ While subsequent innovation moved with the same speed as high viscosity cement (essentially a refined acrylic bone cement cocktail designed to reduce the incidence of cement leaks⁶), the application of these vertebral augmentation techniques returned to treating patients with pathologic vertebral compression fractures and re-directed from the C2 vertebra down to the sacrum in order to treat painful sacral insufficiency fractures.

It is in the context of this abbreviated historical prelude and the aforementioned controversies that we dedicate this month’s AJNR Digest to several important topics in the realm of what is now referred to as vertebral augmentation. The first article in this series deals with the principal underlying cause of vertebral compression fractures, bone mineral density and osteoporosis. In “Bone Mineral Density Values Derived from Routine Lumbar Spine Multidetector Row CT Predict Osteoporotic Vertebral Fractures and Screw Loosening,” Schwaiger et al were able to validate a method for evaluating bone mineral density on routine multidetector CT examinations of the lumbar spine.⁷ These authors were able to derive highly correlative formulas at both 120 and 140 kVp. The potential implications of this application for patients with osteoporotic vertebral compression fractures are significant, as many of these patients undergo CT imaging evaluation prior to their vertebral augmentation procedures. Given the possibility of identifying a vertebral body at risk for subsequent fracture, as is shown by Schwaiger et al, could prove extremely useful not only as a prognostic tool but also as a treatment planning tool. This could add further knowledge to the impact of the natural history of osteoporosis on the incidence of vertebral compression fractures following a vertebral augmentation procedure.⁸ Additionally, it may contribute to more information on the controversial topic of prophylactic vertebral augmentation.⁹ For example, if a non-compressed vertebral body that is located between two vertebral compression fractures shows, with the analytic tool described in this paper, that this vertebra is at very high risk of imminent fracture, should this vertebra be treated prophylactically? Or, should the patient be immediately and aggressively treated for osteoporosis? The answers to questions like this, as we take practice back to science, can eventually help operators provide better care of what is in so many ways a fragile group of patients.

Another paper, by Dohm et al (not commented upon here), “A Randomized Trial Comparing Balloon Kyphoplasty and Vertebroplasty for Vertebral Compression Fractures due to Osteoporosis,” compares the efficacy and safety of balloon kyphoplasty against that of vertebroplasty.¹⁰ This industry-sponsored randomized control trial compares treatment results and adverse events between kyphoplasty and vertebroplasty in an attempt to establish if one procedure is better than the other. Some prior reports have suggested that kyphoplasty might be more efficacious than vertebroplasty.¹¹ Though enrollment in this study fell short of expectation (32.7%), 191 patients underwent vertebroplasty and 190 patients underwent kyphoplasty, and the follow-up period extended to 2 years. This study found no statistically significant difference between the two procedures with respect to pain relief, disability improvement, and adverse events, including cement leakage and subsequent radiographic fracture. The only reported difference between the two procedures was that the vertebroplasty procedure was on average 8 minutes shorter in duration as compared to the kyphoplasty procedure. The study did not compare the procedures with respect to the topic of height restoration, but did show a statistically favorable benefit of kyphosis correction in favor of kyphoplasty at the 24-month time point only for the 100 kyphoplasty patients (compared with 91 vertebroplasty patients) who completed this follow-up.

As stated earlier, the use of vertebral augmentation in the treatment of painful sacral insufficiency fractures or sacral lesions is a relatively new procedure that is showing promise in these specific patient populations. Gupta et al report their results with this technique in their paper “Safety and Effectiveness of Sacroplasty: A Large Single-Center Experience.”¹² The authors retrospectively review their single-center experience in 53 patients (29 with cancer-related sacral fractures) using the Visual Analog Scale, a functional mobility scale, an analgesic scale, and a four-level pain scale at short-term follow-up (27 days). The majority of these procedures were performed with CT guidance (91%); a small number were performed with fluoroscopy. There were no significant adverse events in this study population, and statistically significant improvements with respect to the aforementioned outcome measures were seen. These outcomes are consistent with what has been previously reported in the literature.¹³

As can be seen by the prior article, and with its initial application for the treatment of a primary tumor of the spine, the use of vertebral augmentation in the treatment of pathologic spine lesions has shown significant promise. In their thoughtful and thorough meta-analysis (not commented upon here), “Vertebral Augmentation in Patients with Multiple Myeloma: A Pooled Analysis of Published Case Series,” Khan et al report their review of 23 studies that included 923 patients with multiple myeloma.¹⁴ This review showed that both vertebroplasty and kyphoplasty provided significant and sustainable pain relief (4.8 pain score reduction at 1 week and 4.4 pain score reduction at 1 year) in patients with multiple myeloma with painful fractures. The authors cited a subsequent fracture rate of 7.3% in patients treated with vertebroplasty, compared with 6.8% of patients treated with kyphoplasty. A total of 3 major complications were seen in this patient population (one case of infection, one case of myocardial infarction, and one case of pulmonary embolism). This review concludes that vertebral augmentation is safe and effective in the treatment of patients with multiple myeloma.

The next paper in our series, “Vertebral Augmentation for Neoplastic Lesions with Posterior Wall Erosion and Epidural Mass," is by Cianfoni et al and deals with the very challenging task of treating patients with painful pathologic fractures and/or lytic vertebral body lesions at risk for collapse, in which the posterior vertebral body cortex has been eroded by tumor.¹⁵ This unique subset of cancer patients is either in severe pain and bedridden or placed at bedrest in anticipation of imminent vertebral collapse, and their oncologists often want to provide more to them than just palliative pain management. Cianfoni and his group elucidate a treatment approach to a group of patients who are at high risk for possible neurologic compromise. In their series of 48 patients, the authors utilized a combination of plasma-mediated radiofrequency (59/70 levels) for the purpose of cavity creation within the pathologically compromised vertebral body and the meticulous fluoroscopy-monitored injection of high viscosity bone cement. It must be stressed that these are very advanced techniques and carry a risk of symptomatic cement extravasation even in the best of experienced hands. The overall rate of cement extravasation in this group of patients, as shown by CT, was 14%. Only one patient had a foraminal leak with T1 radicular compromise that partially responded to steroid medication. Excellent to good cement fill, as determined by CT, was seen in 65/70 levels. A subgroup of 18 patients with pain referable to the treated levels also showed a favorable reduction in pain scores. As the authors stress in their conclusion, it is important to tailor the procedure to the specific lesion with a primary objective of minimizing complications.

In “Radiographic Local Control of Spinal Metastases with Percutaneous Radiofrequency Ablation and Vertebral Augmentation,” Wallace et al utilized radiofrequency ablation, a heat-based treatment, prior to vertebral augmentation in a group of 55 patients with known metastatic disease from various primary tumors, 34 of whom had radiation-resistant neoplasms.¹⁶ The primary outcome for this retrospective study was evidence of radiographic tumor control at the treated level, and this was shown to be 89% (41/46 patients) at 3 months, 74% (26/35 patients) at 6 months, and 70% (21/30 patients) at 1 year. No complications were encountered. Of note was the observation that of the 9 cases in which local radiographic tumor control was not achieved, 8 of these had residual or recurrent tumor within the posterior vertebral body or epidural space, an area that is difficult to treat. This same institution also contributes a second article to our series on pathologic vertebral lesion treatment and shares their experience with another form of thermal therapy, in this case cryotherapy. In “Spine Cryoablation: Pain Palliation and Local Tumor Control for Vertebral Metastases,” Tomasian et al summarize their experience in the treatment of 31 neoplastic lesions in 14 patients using image-guided cryoablation.¹⁷  In this series, the authors assess both short-term pain control and local tumor control, as well as complications in this small group of patients. A significant decrease in pain scores with concomitant reduction of analgesic use was observed. The authors also noted that local tumor control was achieved in 30/31 lesions, with a median follow-up of 10 months. Only two minor transient focal neurologic complications were reported. And so, we gradually move within the spectrum of pathologic vertebral lesion treatment from technical considerations and advancements to pain control and tumor control. The efficacy and safety of these innovative tumor targeting treatment strategies indicate a role for these therapies in specific clinical situations where pain palliation and local tumor control are needed. Furthermore, this will increase the integral role of operators who can perform image-guided percutaneous ablation therapies and vertebral augmentation as important members of the patient’s oncology team.¹⁸

References

1. Mathis JM, Barr JD, Belkoff SM, et al. Percutaneous vertebroplasty: a developing standard of care for vertebral compression fractures. AJNR Am J Neuroradiol 2001;22:373–81
2. Lieberman IH, Dudeney S, Reinhardt MK, et al. Initial outcome and efficacy of "kyphoplasty" in the treatment of painful osteoporotic vertebral compression fractures. Spine 2001;26:1631–38
3. Mathis JM, Ortiz AO, Zoarski GH. Vertebroplasty vs kyphoplasty: a comparison and contrast.  AJNR Am J Neuroradiol 2004;25:840–45
4. Kallmes DF, Comstock BA, Heagerty PJ, et al. A randomized trial of vertebroplasty for osteoporotic spinal fractures. N Engl J Med 2009;361:569–79, 10.1056/NEJMoa0900563
5. Goz V, Errico TJ, Weinreb JH, et al. Vertebroplasty and kyphoplasty: national outcomes and trends in utilization from 2005 to 2010. Spine J 2015;15:959–65, 10.1016/j.spinee.2013.06.032
6. Georgy BA. Clinical experience with high-viscosity cements for percutaneous vertebral body augmentation: occurrence, degree, and location of cement leakage compared with kyphoplasty. AJNR Am J Neuroradiol 2010;31:504–08, 10.3174/ajnr.A1861
7. Schwaiger BJ, Gersing AS, Baum T, et al. Bone mineral density values derived from routine lumbar spine multidetector row CT predict osteoporotic vertebral fractures and screw loosening. AJNR Am J Neuroradiol 2014;35:1628–33, 10.3174/ajnr.A3893
8. Song D, Meng B, Gan M, et al. The incidence of secondary vertebral fracture of vertebral augmentation techniques versus conservative treatment for painful osteoporotic vertebral fractures: a systematic review and meta-analysis. Acta Radiol 2015;56:970–79, 10.1177/0284185114544240
9. Kamano H, Hiwatashi KH, Kobayashi N, et al. New vertebral compression fractures after prophylactic vertebroplasty in osteoporotic patients. AJR Am J Roentgenol 2011;197:451–56, 10.2214/AJR.10.5937
10. Dohm M, Black CM, Dacre A, et al. A randomized trial comparing balloon kyphoplasty and vertebroplasty for vertebral compression fractures due to osteoporosis. AJNR Am J Neuroradiol 2014;35:2227–36, 10.3174/ajnr.A4127
11. Han S, Wan S, Ning L, et al. Percutaneous vertebroplasty versus balloon kyphoplasty for treatment of osteoporotic vertebral compression fracture: a meta-analysis of randomized and non-randomised controlled trials. Int Orthop 2011;35:1349–58, 10.1007/s00264-011-1283-x
12. Gupta AC, Chandra RV, Yoo AJ, et al. Safety and effectiveness of sacroplasty: a large single-center experience. AJNR Am J Neuroradiol 2014;35:2202–06, 10.3174/ajnr.A4027
13. Kortman KE, Ortiz AO, Miller T, et al. Multicenter study to assess the efficacy and safety of sacroplasty in patients with osteoporotic sacral insufficiency fractures or pathologic sacral lesions. J NeuroIntervent Surg 2013;5:461–66, 10.1136/neurintsurg-2012-010347
14. Khan OA, Brinjikji W, Kallmes DF. Vertebral augmentation in patients with multiple myeloma: a pooled analysis of published case series. AJNR Am J Neuroradiol 2014;35:207–10, 10.3174/ajnr.A3622
15. Cianfoni A, Raz E, Mauri S, et al. Vertebral augmentation for neoplastic lesions with posterior wall erosion and epidural mass. AJNR Am J Neuroradiol 2015;36:210–18, 10.3174/ajnr.A4096
16. Wallace AN, Tomasian A, Vaswani D, et al. Radiographic local control of spinal metastases with percutaneous radiofrequency ablation and vertebral augmentation. AJNR Am J Neuroradiol published online before print December 3, 2015, 10.3174/ajnr.A4595
17. Tomasian A, Wallace A, Northrup B, et al. Spine cryoablation: pain palliation and local tumor control for vertebral metastases. AJNR Am J Neuroradiol 2016;37:189–95, 10.3174/ajnr.A4521
18. Gangi A, Buy X. Percutaneous bone tumor management. Semin Intervent Radiol 2010;27:124–36, 10.1055/s-0030-1253511

Image modified from: Cianfoni A, Raz E, Mauri S, et al. Vertebral augmentation for neoplastic lesions with posterior wall erosion and epidural mass.