  Spinal fixation procedures are currently limited by the rigidity of the
existing instruments and pedicle screws leading to fixation failures and rigid
pedicle screw pull out. Leveraging our recently developed Concentric Tube
Steerable Drilling Robot (CT-SDR) in integration with a robotic manipulator, to
address the aforementioned issue, here we introduce the transformative concept
of Spatial Spinal Fixation (SSF) using a unique Flexible Pedicle Screw (FPS).
The proposed SSF procedure enables planar and out-of-plane placement of the FPS
throughout the full volume of the vertebral body. In other words, not only does
our fixation system provide the option of drilling in-plane and out-of-plane
trajectories, it also enables implanting the FPS inside linear (represented by
an I-shape) and/or non-linear (represented by J-shape) trajectories. To
thoroughly evaluate the functionality of our proposed robotic system and the
SSF procedure, we have performed various experiments by drilling different I-J
and J-J drilling trajectory pairs into our custom-designed L3 vertebral
phantoms and analyzed the accuracy of the procedure using various metrics.
