Objective: In this study the authors aimed to evaluate the rate of malposition, including pedicle breach and superior facet violation, after percutaneous insertion of pedicle screws using the coaxial fluoroscopic view of the pedicle, and to assess the risk factors for pedicle breach.
Methods: In total, 394 percutaneous screws placed in 85 patients using the coaxial fluoroscopic view of the pedicle between January 2014 and September 2017 were assessed, and 445 pedicle screws inserted in 116 patients using conventional open procedures were used for reference. Pedicle breach and superior facet violation were evaluated by postoperative 0.4-mm slice CT.
Results: Superior facet violation was observed in 0.5% of the percutaneous screws and 1.8% of the conventionally inserted screws. Pedicle breach occurred more frequently with percutaneous screws (28.9%) than with conventionally inserted screws (11.9%). The breaches in percutaneous screws were minor and did not reduce the interbody fusion rate. The angle difference between the percutaneous and conventionally inserted screws was comparable. Insertion at the L3 or L4 level, right-sided insertion, placement around a trefoil canal, smaller pedicle angle, and a small difference between the screw and pedicle diameters were found to be risk factors for pedicle breach by percutaneous pedicle screws.
Conclusions: Percutaneous pedicle screw placement using the coaxial fluoroscopic view of the pedicle carries a low risk of superior facet violation. The screws should be placed carefully considering the level and side of insertion, canal shape, and pedicle angle.
Keywords: accuracy; coaxial view; lumbar; minimally invasive; pedicle screw fixation; percutaneous.