A surgeon-controlled mode of robotic assistance with posterolateral approach helps achieve highly medialized cervical pedicle screw placement to avoid vertebral artery injury.

Abstract

The small pedicle widths, the thin lateral cortical shell next to the vertebral artery (VA), and the strongly tilted pedicle axis anteromedially narrow the safety margin for cervical pedicle screw (CPS) placement against vertebral artery (VA) injury. We have studied whether the minimally invasive surgery (MIS) of a posterolateral approach with a table-mounted, surgeon-controlled mode of robotic assistance (group R) improves the VA safety compared to C-arm fluoroscopy-guided conventional open technique (group F). Group R consisted of 165 screws in 37 patients and group F, 199 screws in 52 patients. The two groups covered a broad range of vertebral levels from C2 to C7 with comparable distribution (p = 0.0512) for treating a similar variety of diseases (p = 0.6958). Group R, compared with group F, showed a greater lateral-to-medial CPS inclination (p ≤ 0.0004) that even exceeded the obliquity of corresponding pedicle axis, leading to a higher rate of acceptable CPS placement (93.4% vs. 85.4%; p = 0.0164) with a lower rate of lateral breach (1.2% vs. 10.1%; p = 0.0004). For CPS placement, robot-assisted MIS obviously eliminates morbidity-prone soft-tissue dissection, radiation exposure to the surgical team, and human manual errors. The current study revealed its additional benefit of better safety against VA injury by allowing us to place CPS with a steep lateral-to-medial angulation owing to (1) a lack of counter pressure from the paravertebral muscles and (2) minimizing a navigation pitfall of untracked pressure-induced vertebral rotation.