Acceptable errors with evaluation of 577 cervical pedicle screw placements

Cadaveric studies have discouraged the use of cervical pedicle screws (CPS) with high misplacement rates. However, the clinical results show minimal screw-related complications and have highlighted the advantages of using CPS. We introduce "acceptable errors classification" in the placement of cervical pedicle screws to bridge the gap between the high radiological perforation rates and low clinical complications.

Ninety-nine patients with average age of 49 years were operated between December 2011 and June 2017 using CPS. Sixty-one patients had trauma, 33 had CSM, 3 had tumors and 2 patients had fracture with ankylosing spondylitis. The screws were inserted using the medial cortical pedicle screw technique. Axial and sagittal CT reconstructed images along the axis of the inserted screws were evaluated for screw placements both in the medio-lateral and supero-inferior directions.

A total of 577 pedicle screw placements (C3 to C7) were assessed in 99 patients using the conventional grading of screw perforations and acceptable errors classification in both medio-lateral and supero-inferior directions. There were 25.64% (148/577) screw perforations and 74.35% (429/577) screw placements within the pedicle using the conventional perforation grading system. The same set of screws, assessed using the "Acceptable errors classification", showed 529 screws (91.68%) having acceptable placements and 48 screws (8.31%) having unacceptable placements.

The acceptable errors classification in placement of CPS seems to bridge the gap between the high radiological perforation rates and the low clinical complications. The present study reinforces studies reporting minimal clinical complications with high rates of screw misplacements. These slides can be retrieved under Electronic Supplementary Material.