A novel percutaneous sacral endplate penetrating screw technique: enhanced fixation strength with the M-probe:...

L5-S1 pedicle screw (PS) fixation is commonly used to stabilize lumbosacral degenerative disease. Rigid S1 PS fixation is challenging due to sacral morphology. Various S1 PS techniques have been developed to increase screw insertion torque, including the penetrating S1 endplate screw (S1 PES) technique. This study introduces percutaneous sacral endplate penetrating screw (PSEPS) technique using S1 percutaneous pedicle screw (PPS) with a safer and longer screw trajectory and a novel modified hollow probe (M-probe). Penetrating the S1 superior endplate with a conventional straight hollow probe is challenging due to the thickening of the S1 endplate and the shape of the anterior S1 endplate. Therefore, we developed the M-probe that can easily penetrate the S1 endplate. First, the conventional straight probe was inserted 20 degrees inward and directed towards the cranial aspect until it reached the cranial margin of the S1 endplate. It was then confirmed that the probe was positioned beyond the posterior wall of the vertebral body in the lateral view. The M-probe was replaced through the guidewire, and the guidewire was replaced with a cannula before the M-probe was advanced. The M-probe was advanced toward the anterior one-third of the S1 vertebral body endplate. When the tip arrives at the S1 endplate, the M-probe should be oriented cephalad to facilitate penetration of the endplate and then advanced to penetrate the endplate. Rotating the tip of the M-probe enlarges the bone hole in the S1 endplate, eliminating the need for tapping. The PSEPS technique demonstrated significantly higher insertion torque at S1 compared to L5, despite lower Hounsfield unit values at S1 PSEPS: 394.0±104.8 cNm). The M-probe allowed for easier endplate penetration and higher insertion torque without the need for tapping. The PSEPS technique using the M-probe offers enhanced stability and safety for lumbosacral interbody fusion.