Acceptable errors with evaluation of 577 cervical pedicle screw placements

Techniques of cervical pedicle screw insertion in lower cervical spine - A review

“…Wang et al 41 specifically evaluated only lateral perforations with free hand technique, similar to Abumi et al, and reported 12.64% lateral perforations. In contrast, we can see that the lateral perforations are lesser than medial perforations in the last two studies by Mahesh et al 42 and Pan et al 43 Pan et al 43 took an entry point near the notch on the lateral mass (Fig. 2), much lateral to the entry point described by Abumi et al, 1 closer to the projection of the pedicle axis as shown by morphometric studies.…”

“…Recently, a study has proposed the concept of "acceptable errors" in CPS placements where a marginal medial and superior placements were regarded as acceptable placements. 42 Similar efforts to correlate clinical complications as compared to radiological misplacements have been reported in thoracolumbar pedicle screw placements by an outcome based study. 51…”

“…This has been seen to be true for percutaneous cervical pedicle screw insertions 44 or navigated screw insertions 34 where the medial angulation of the screws is nearing 50 . In contrast Mahesh et al 42 have noted lesser lateral perforation even at 30 medial angulation of the screws. They have attributed the lesser lateral perforations to medialization of the screws with partial drilling of the medial pedicle wall, calling it a medial cortical pedicle screw (MCPS) technique (Figs.…”

“…Off the 324 pedicle screws assessed, they reported a total of 20.98% (68) screw perforations among which 73.5% , just lateral to the centre of the lateral mass along the lateral notch, just below articular margin. "X" is the modified entry point for medialised screws used in "funnel technique", 29 Medial cortical pedicle screw technique, 42 medial funnel technique, 38 laminoforaminotomy technique 39 and also by Jeanneret et al 22 The lateral entry along the notch is used by the Lateral vertebral notch technique, 43 by Reinhold M, 33 Sakamoto T, 28 and others.…”

Letter to the Editor on “Transpedicular Screw Placement Accuracy Using the O-Arm Versus Freehand Technique at a Single Institution. Global Spine Journal” by Crawford et al

“… 2 An outcome-based classification for assessment of pedicle screw placement has also been proposed which correlates better with the clinically observed results—this classification grades the pedicle screw placement into “acceptable,” “unacceptable” or “grievous” placements. 4 , 5 Unlike the Gertzbein grading system, this also takes into account the direction of the breach—a lateral perforation in thoracolumbar spine may be more acceptable compared to a medial perforation, but the opposite would be true for the cervical spine. Furthermore, real-time visual feedback provided by navigation allows the surgeon to place the screw in a trajectory that matches the longitudinal midline axis of the pedicle—typically, this would have a more lateral starting point and a more medial insertion angle than that seen with the freehand technique.…”