An institutional study on accuracy of freehand cervical C1 C2 screws placement by knock and drill technique in craniovertebral anomalous bony anatomy: An evaluation of more than 600 screws based on SGPGI screw accuracy criteria

Abstract

Purpose: To assess the accuracy of freehand cervical C1 C2 screws placement by knock and drill (K and D) technique in craniovertebral anomalous bony anatomy.

Materials and methods: From January 2017 to December 2022, 682 consecutive C1 C2 screws in 215 patients with craniovertebral junction (CVJ) anomalies were enrolled. All patients underwent posterior fixation with K and D technique without any fluoroscopic guidance. The patient's demographic details, clinical details, radiological details, major intraoperative events, and postoperative complications were noted. The screws malposition grades and direction on CT images in the axial and sagittal plane were defined as new per proposed "SGPGI accuracy criteria." All patients had a clinical evaluation at 3-month follow-up.

Results: Total 682 C1, C2 screws were placed in 215 patients for CVJ anomalies using K and D technique. The accuracy of screws placement by freehand technique was 84.46% (576/682). So with technique explained the rate of malplacement in simple (16.35%) and complex (15.19%) groups were almost comparable and comparison difference was not significant (P = 0.7005).

Conclusion: The freehand technique, as described, is effective in cases of anomalous bony anatomy, and it is mandatory in complex CVJ anomalies. The accuracy of screw placement and VA injury is comparable with major studies. This technique is supposedly cost-effective and less hazardous to both health-care workers and patients.

Keywords: Atlantoaxial dislocation; SGPGI accuracy criteria; knock and drill technique; simple and complex craniovertebral junction anomalies.

Figure 1

(a and b) Dissection plane from laminae (black arrow) to pars (blue arrow) to C2 pedicle (red arrow) exposed C1-C2 facet joint. (c and d) Showing C1 C2 joint with exposed facets with foramina transversarium (lateral end of green arrow)

Figure 2

Distribution of patients according to Nurick gradings in preoperative and at 3 months’ postoperative period

Figure 3

First image showing entry point (blue dot) for C1 LM screw and direction (blue arrow). Second image blue arrow showing the entry point for C1 LM screw placement. Drilling of the inferior facet of C1 is shown to see sagittal orientation with medial (suction tip) and lateral borders exposed to see axial orientation for direct screw placement. Green arrow showing C2 pars. Third image showing C1 LM screw placed

Figure 4

First image showing entry points for C2 pedicle screw (blue dot) and C2 pars screw (red dot) with direction for C2 pedicle screw (blue arrow) and C2 pars screw (red arrow). Second image showing medial border of C2 pedicle with the dissector tip and blue arrow showing the pedicle. Third image showing the entry point for C2 pedicle screw insertion