# OPF/PMMA Page System as an Alternative Approach for the Treatment of Vertebral Correctomy
## 3 Results
### Cadaveric Testing  
Figure 4 illustrates the bending angle outcomes vs. the applied moments for two loading conditions, flexion/extension and right/left lateral bending. Data were recorded for all four scenarios including a normal/intact spine, normal with posterior fixation, corpectomy with posterior fixation, and fixation with corpectomy plus cage.  
The condition of the spine resulted in different kinematic outcomes. In the intact spine (Normal), the L\({}_{2}\)/L\({}_{4}\) segment moved from \(-4.3^{\circ}\) in extension to \(+4.7^{\circ}\) in flexion. Upon fusing the spine with instrumented rods and screws (Normal + Rod), these motions were greatly reduced to less than 1\({}^{\circ}\) showing the significant effect of rods and fusion. After performing corpectomy of the vertebral body and adjacent discs (Cavity + Rod), the flexion/extension motions were significantly increased by up to 82%, to about \(-8^{\circ}\) to \(+7^{\circ}\). Finally, the OPF hydrogel was placed between the L\({}_{2}\) and L\({}_{4}\) (Cavity + Rod + OPF) segment and PMMA injected in the lumen to form the OPF/PMMA cage. During flexion (when the superior verteb moves anteriorly), the L\({}_{2}\)/L\({}_{4}\) segment moved \(+3.2^{\circ}\), which was only 32% lower than that of the intact spine, and considerably less than the posteriorly stabilized spine with an unrepaired corpectomy defect. In extension (when the superior verteb moves posteriorly and tends to separate from the scaffold system), however, the OPF/PMMA cage did not help improve the spine motion as it was not attached to the top and bottom vertebral bodies. This can be noticed in the graph by looking at the extension profiles of the Cavity + Rod + OPF and Cavity + Rod which show similar behaviors. In lateral bending, the L\({}_{2}\)-L\({}_{4}\) segment of the intact spine moved \(-6.9^{\circ}\) to the left and \(+5.8^{\circ}\) to the right. However, the remaining scenarios provided a much smaller ROM from \(-2.8^{\circ}\) to \(+2.6^{\circ}\), stiffening the  
Figure 4: Flexion/extension and left/right lateral bending ranges of motion (ROM) for L\({}_{2}\)/L\({}_{4}\) and L\({}_{2}\)/S.  
segment mainly due to pedicles and screws. It is important to note that in this motion the effect of the cage is minimum as there is no superior/inferior attachment to the endplates. The decrease in motion compared to the Cavity + Rod could be attributed to the friction of the PMMA with the endplates.  
The motions of the L2/S segment are also shown in Figure 4. Compared with the L2/L4 outcomes, all motions were considerably larger, for example, the intact spine ranged from \(-13^{\circ}\) in flexion to \(15.5^{\circ}\) in extension. All remaining scenarios showed a similar pattern to that observed in the intact spine. The lateral bending for the intact spine varied from \(-12.4^{\circ}\) to \(+12^{\circ}\), with the remaining scenarios showing lower and similar outcomes with each other. The L2/S analyses, showing larger ranges of motion compared to the L2/L4 segment, are expected, as in the former case there are additional segments which are not fused, increasing the overall ROM of the construct.