Cement Augmentation for the Treatment of High to Medium Osteoporotic Compression Fractures, Percutaneous High Viscosity Cement Vertebroplasty Versus Balloon Kyphoplasty

VP and BKP are common interventions for the treatment of osteoporotic FVC. The difference between VP and BKP is that BKP adds a balloon inflation procedure in the collapsed vertebrae. Both procedures use bone cement to stabilize the fracture. Clinical studies of different cement augmentation procedures have been encouraging. Several studies have suggested that VP and BKP improve quality of life, pain relief, functionality, and restore vertebral body height^ten. Zhao et al. performed a meta-analysis study that demonstrated that patients treated with BKP were more effective than VP based on higher scores for long-term VAS and Oswestry Disability Index, improved KA and the average height of the vertebral body and a significant reduction in the risk of cement leakage¹⁷. However, some studies have not supported that BKP is superior to VP for pain relief and functional improvement.^18.19. In this current study, VAS results reflecting pain relief after vertebral body augmentation at the upper to mid thoracic vertebrae were similar for HVC VP and LVC BKP.

The area most frequently involved in FVC is the thoracolumbar junction (T12-L2), followed by the lower lumbar area (L3-L5)²⁰. On the other hand, the incidence of FVC in the upper (T4-T6) and middle (T7-T9) thoracic vertebrae is lower and the associated research is limited. The thoracic spine is part of the rib cage, which serves to protect vital organs and provide rigid support to withstand and disperse substantial axial loading forces. Patients with a compression fracture over the upper to mid thoracic vertebrae may experience upper to mid back pain, which may be exacerbated by breathing and may radiate to the anterior chest. Anatomically, the thoracic vertebrae are characterized by small pedicles that narrow in diameter as the thoracic level rises. Therefore, nerve tissue would likely be intolerable if cement leaked into the thoracic canal. To minimize the risk of cement leakage, Liu et al. recommended that LVC BKP be preferred over LVC VP for osteoporotic FVC of mid-thoracic vertebrae²¹. Another key factor in reducing the incidence of cement leaks is the cement viscosity in VP. Alhashash et al. demonstrated that HVC VP had a relatively low risk of cement leakage for patients with FVC²². However, they focused primarily on the lower levels of the thoracic and lumbar spine. According to our study, cement leakage rate is lower with HVC VP compared to LVC BKP (36% versus 64%, p = 0.004) after cement augmentation for upper to middle thoracic vertebrae. A meta-analysis study by Chen et al. also confirmed that HVC VP holds the lowest cement leakage rate after cement increase compared to LVC BKP and LVC VP²³.

Cement injection volume has been reported as one of the risk factors for cement leakage in percutaneous VP and BKP. Zhu et al. recommended to inject 24. Similar results are also observed in BKP with Chen et al. demonstrating a decrease in cement injection volume could also reduce the incidence of cement leaks²⁵. Although most leaks are clinically asymptomatic, they carry a risk of pulmonary embolism and neurological compression which are considered major complications in cement augmentation procedures. In this study, the volume of cement injected was significantly lower in the HVC VP group (3.66 ml vs 4.40 ml, p

The biomechanics of the fractured segment is altered following the increase in cement. The reconstructed vertebra is stiffer than its adjacent segments. It acts as a vertical pillar that reduces the physiological inward bulging of the end plates of augmented vertebrae. Liao et al. performed a finite element model of osteoporotic FVC with cement augmentation with VP, BKP and spinal stents²⁶. The results showed that all of these procedures would increase the stresses on the vertebral endplates of adjacent segments, especially the upper levels during flexion. Another finite element study found that when the volume of cement filling reaches 30–40.5% of the volume of a vertebral body, it also increases the stress tolerated by adjacent segments. However, when the injected cement volume exceeded the defined range, the stress distribution on the fractured and adjacent vertebral bodies not only increased, but led to the development of adjacent vertebral fractures.²⁷. Clinically, the incidence of adjacent fractures varies from 5.5 to 52% after VP and BKP^17,28,29. In our study, the incidence of adjacent fractures after HVC VP and LVC BKP was 8.3% and 9.1%, respectively. We believed that the incidence of fractures adjacent to the upper to mid thoracic vertebral levels would be much lower than at the thoracolumbar junction as a smaller vertebral body size consequently has less cement injection and additional protection is encouraged. through the rib cage.

In this study, all radiographic findings including AVH, MVH, PVH, local kyphotic angle and Cobb angle showed significant postoperative improvement in both groups. The HVC VP group showed comparable radiographic findings to the LVC BKP group in terms of kyphotic reduction, but with less restoration of vertebral body height (determined by postoperative AVH and MVH). It is believed that the effect of balloon inflation on the injured vertebrae and more cement injected in the LVC BKP group resulted in these radiographic benefits immediately after surgery. However, more severe re-collapsed vertebrae were also shown in the LVC BKP group, resulting in final follow-up radiographic parameters that had no statistical difference between the two groups. These changes in the radiographic data did not influence the clinical results.

Over the past two decades, the majority of the published literature discusses the LVC VP and LVC BKP differences for vertebral compression fractures. However, studies that compare HVC VP and LVC BKP are very rare. After searching PubMed, we found only four published clinical research studies addressing the use of HVC VP versus LVC BKP in the treatment of osteoporotic FVC^13,14,30,31. Dr. Georgy was the first author to describe his experiences using HVC VP and BKP for osteoporotic FVCs, and his data showed that HVC VP had a significantly lower rate of cement leakage.³⁰. Data from Wang et al. revealed that the injected volume was higher with BKP but the cement leakage rate was lower with HVC VP¹⁴. Sun et al. and Lin et al. all demonstrated similar clinical outcomes for VAS and Oswestry Disability Index (ODI) scores with HVC VP or BKP, and middle vertebral height restoration appeared superior in the BKP group^13.31. The biggest difference between our study and the four reference articles above was that our study included cases involving only the upper to mid-thoracic spine, but the thoracolumbar junction accounted for the majority of cases in the reference articles. Nevertheless, our data yielded results similar to those in the references above.

Indeed, there are limitations to our study. First, the nature of a retrospective study may include inherent bias. Additionally, clinical outcomes for daily function such as the ODI or the Abbreviated 36-Item Survey (SF-36) would provide beneficial additional clinical functional information, but could not be assessed due to unavailability. data in a retrospective study. Second, the procedures were performed by different surgeons at our center and we were unable to account for variations in technique. Third, although the results were clear and comparable between groups, a longer follow-up period is needed to assess whether HVC can mitigate BKP-related risks in the treatment of osteoporotic FVC in upper to mid thoracic vertebrae. Fourth, the medical insurance policy in Taiwan does not subsidize the use of CT or MRI to assess bone cement leaks or adjacent fractures respectively, therefore, diagnosis using simple film inherently has a bearing high number of false negatives and therefore data may be limited.