Comparison of stiffness values for five specimen groups in extension and flexion in NZ (sNZ) and EZ (sEZ). Incomplete burst fracture creation (2) resulted in a significant decrease of sNZ and sEZ in flexion as well as sNZ in extension. Posterior bisegmental instrumentation (3) restored sNZ but was not able to restore prefractured sEZ values in flexion. Hybrid augmentation (HA) takes advantage of changes in stiffness parameters by instrumentation (4). In addition, a significant change compared to fractured values of sEZ even for flexion was observed following HA. Stand-alone VP (5) increased sNZ on flexion and remained significantly lower than pre-fracture values. VP significantly increased sEZ in flexion compared to the fractured (2) state to reach approximately pre-fractured values.