## 4 Discussion
### Biomechanical Impact  
In the literature, nearly all studies available demonstrate an improvement in spinal stability following the implantation of third-generation PVAS devices. For the assessment of biomechanical functional recovery of the spine, many studies have relied on indirect parameters to evaluate vertebral deformity improvement, particularly focusing on the \"Beck Index\" (the ratio of anterior to posterior vertebral height) [22], and the vertebral xyphotic angle and the regional xyphotic angle (\(\alpha\)-angle and \(\gamma\)-angle, respectively), as determined by the Cobb method [23]. For example, in a study conducted by [PERSON] et al. which examined the use of titanium mesh cages (OsseoFix(r)) for unstable osteopororotic thoracolumbar burst fractures in 15 patients, the average xyphotic angle, measured using the Cobb method, significantly decreased from 9 degrees preoperatively to 8 degrees after 12 months (\(p<0.05\)) [21]. Furthermore, [PERSON] et al. conducted a biomechanical comparison between OsseoFix(r) and the kyrophplasty balloon, finding that the titanium mesh implant provided superior height restoration while requiring a smaller volume of \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Main Use** & **Material** & **Operating** \\  & & & **Principle** \\ \hline \multirow{3}{*}{Kyphon} & Treatment of recent fractures, osteoporosis, and metastasis & Elastomer & Balloon-based \\  & Manages both recent and older fractures, osteoporosis, metastasis & Titanium & Deformable \\ \hline \multirow{3}{*}{\begin{tabular}{c} SpineJack® \\ \end{tabular} } & Treatment of recent fractures, osteoporosis, metastasis & Titanium & \begin{tabular}{c} Balloon combined \\ with a deformable \\ metallic component \\ \end{tabular} \\  & & & \\ \hline \multirow{2}{*}{\
\begin{tabular}{c} OsseoFix® \\ \end{tabular} } & Osteoporotic vertebral collapse & Titanium &
\begin{tabular}{c} Deformable \\ metallic structure \\ \end{tabular} \\  & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characteristics of Third-Generation Vertebral Augmentation Devices. injected cement [20]. On the other hand, [PERSON] et al. conducted an in vitro biomechanical study using human cadaveric vertebrae to compare kyophplasty with third-generation PVAS implants, both with and without cement. Their findings revealed that the titanium mesh, regardless of cement usage, exhibited comparable biomechanical properties to balloon kyophoplasty [24]. Additionally, in a prospective study involving 32 patients with symptomatic osteopororotic or tumorous fractures, OsseoFix(r) demonstrated significant improvements in kyphotic angle and was effective in controlling pain and reducing the Oswestry Disability Index score [19]. For [PERSON] et al., in a study that addressed unstable thoracolumbar burst fractures in elderly patients using percutaneously applied titanium mesh cages and a transpecicular fixation system with expandable screws, the postoperative kyphotic angle and Cobb angle showed significant improvements, with the kyphotic angle decreasing from 13.7\({}^{\circ}\) to 7.4\({}^{\circ}\) (\(p<0.001\)) and the Cobb angle from 9.6\({}^{\circ}\) to 6.0\({}^{\circ}\) (\(p<0.002\)) [25]. Regarding osteopororotic vertebral compression fractures, a preclinical study investigated the relationship between applied forces and the kinematics of a deployable implant for percutaneous vertebral augmentation. Using ex vivo and cadaveric models equipped with strain gauges and sensors for precise measurements, the researchers found a proportional relationship between the actuator force and the implant deployment. The study also highlighted how bone condition (normal vs. osteopororotic) and implant positioning significantly affect the force required [26]. Furthermore, according to [PERSON] et al., in an analysis of 36 human cadaveric vertebrae, the SpineJack(r), demonstrated superior performance compared to kyphoplasty in restoring and maintaining vertebral height.