## 4 Discussion  
VP and BKP are common interventions for the treatment of osteoporotic compression fracture of the spine vertebrae. VS can achieve controlled anatomical restoration before bone cement augmentation and has gained popularity recently. Although the height restoration and augment material property may vary, these interventions all use bone cement to stabilize fracture cracks. The aim of this study was to investigate the biomechanical effects on osteoporotic compression fracture of these different interventions. Clinical studies of different cement augmentation procedures have been encouraging. Several studies have suggested both VP and BKP not only improved quality of life, pain \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Flexion** & **Extension** & **Lateral Bending** & **Axial Rotation** \\ \hline Bone cement & & & & \\ VP & 3.90 & 2.37 & 2.48 & 2.13 \\ BKP & 3.59 & 3.61 & 2.73 & 1.85 \\ VS & 5.91 & 3.74 & 3.12 & 3.54 \\ Lower & & & & \\ T11 endplate & & & & \\ VP & 19.52 & 13.41 & 11.61 & 8.74 \\ BKP & 18.46 & 13.99 & 10.91 & 9.13 \\ VS & 20.97 & 12.25 & 12.19 & 8.63 \\ Upper & & & & \\ L1 endplate & & & & \\ VP & 13.74 & 13.41 & 11.34 & 8.1 \\ BKP & 13.79 & 13.52 & 11.36 & 5.84 \\ VS & 13.50 & 14.27 & 11.17 & 8.32 \\ \hline \hline \end{tabular} VP: Vertebroplasty; BKP: Balloon kyrophoplasty; VS: Vertebrae stent.  
\end{table} 
Table 2: Maximum von Mises stresses of the three surgical models (MPa). Figure 7: Force-displacement curve of the treated vertebrae after three different surgical procedures. relief, improved functionality, and restored vertebral body height [22]. A meta-analysis by [PERSON] et al. showed patients treated with BKP are more effective according to the long term Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), improved kybosis angle, mean vertebral body height, and experience significantly reduced risk of cement leakage [23]. Clinical outcomes of VKP and VS (SpineJack) cement augmentations were also compared in previous studies. [PERSON] et al. demonstrated both procedures were safe and led to significant clinical improvement for patients with osteoporortic vertebral compression fractures [5]. In 2019, a prospective, international, randomized study compared an implantable titanium vertebral augmentation device versus BKP in the reduction of vertebral compression fractures and found non-inferiority of the titanium augmentation device with an excellent risk/benefit profile for results up to 12 months [24]. Furthermore, in vitro biomechanical cadaver studies demonstrated height restoration was significantly better in the VS (SpineJack) group compared with the BKP group [25]. The clinical implications include a better restoration of the sagittal balance of the spine and a reduction of the kybotic deformity. From our results, the VS group has the highest von Mises stress among the three surgical interventions of 5.94 MPa. The usual maximum compressive strength of PMMA is 93 MPa, which is far more than the measured maximum stress in the VS group [26]. Therefore, it is reasonable that the compressive strength of PMMA is well within the safe range for all three surgical procedures. The effect of cement augmentation on the adjacent vertebral body has been debated. Many studies have reported the incidence of adjacent level fractures, but the results were not consistent. [PERSON] et al. conducted a meta-analysis which encompassed 12 studies with 1081 patients [27]. They concluded that BKP and VP are both safe and effective procedures for treating osteoporortic vertebral compression fractures. There were no statistical differences in VAS, ODI, cement leakage rates, and adjacent vertebral fracture rates. Similarly, [PERSON] et al. found both VP and BKP had a similar effect on short-term pain relief, posterior vertebral body weight, and adjacent-level fractures [23].