Patient-specific drill template for C2 transoral pedicle insertion in complete reduction of atlantoaxial dislocation: cadaveric efficacy and accuracy assessments

The clinical validity of atlantoaxial joint inclination angle and reduction index for atlantoaxial dislocation

Objective

Atlantoaxial dislocation patients with neurological defects require surgery. Sometimes, release surgery is necessary for irreducible atlantoaxial dislocation to further achieve reduction. Whether release surgery is essential relies on the surgeon's experience and lacks objective reference criteria. To evaluate the value of atlantoaxial joint inclination angle (AAJI) in sagittal and coronal planes and reduction index (RI) in the surgical approach selection for atlantoaxial dislocation.

Methods

Retrospectively analyzed 87 cases (42 males and 45 females, 9-89 years) of atlantoaxial dislocation from January 2011 to November 2020. In addition, 40 individuals without atlantoaxial dislocation were selected as the control group. Imaging parameters were compared between the two groups. According to surgical methods, the experiment group was divided into two groups including Group A(release surgery group) and Group B (conventional operation group). The parameters were measured based on CT and x-ray. The relevant imaging parameters and clinical scores, including the AAJI in sagittal and coronal planes, the atlas-dens interval (ADI) before and after traction, the RI, and JOA scores were measured and analyzed.

Results

The sagittal and coronal atlantoaxial joint inclination angles(SAAJI and CAAJI) in the control group were 7.91 ± 0.42(L), 7.99 ± 0.39°(R), 12.92 ± 0.41°(L), 12.97 ± 0.37°(R), in A were 28.94 ± 1.46°(L), 28.57 ± 1.55°(R), 27.41 ± 1.29°(L), 27.84 ± 1.55°(R), and in B were 16.16 ± 0.95°(L), 16.80 ± 1.00°(R), 24.60 ± 0.84°(L), 24.92 ± 0.93°(R) respectively. Statistical analysis showed that there was a statistical difference in the SAAJI between the control group and the experiment group (P < 0.01), as well as between groups A and B (P < 0.01). The RI in groups A and B was 27.78 ± 1.46% and 48.60 ± 1.22% respectively, and there was also a significant difference between the two groups (P < 0.01). There was negative correlation between SAAJI and RI.

Conclusions

The SAAJI and RI can be used as objective imaging indexes to evaluate the reducibility of atlantoaxial dislocation. And these parameters could further guide the selection of surgery methods. When the RI is smaller than 48.60% and SAAJI is bigger than 28.94°, anterior release may be required.

An Intraoperative Trajectory-Determined Strategy of Patient-Specific Drill Template for C2 Transoral Pedicle Insertion in Incomplete Reduction of Atlantoaxial Dislocation: An In Vitro Study

Objectives

This study aims to explore a novel intraoperative trajectory‐determined strategy of grouped patient‐specific drill templates (PDTs) for transoral C₂ pedicle screw insertion (C₂TOPI) for atlantoaxial dislocation (AAD) with incomplete reduction and to evaluate its efficiency and accuracy.

Methods

Ten cadaveric C₂ specimens were scanned by computed tomography (CT) and randomly divided into two groups (the PDT and freehand groups). A novel intraoperative trajectory‐determined strategy of grouped PDTs was created for AAD with incomplete reduction. C₂TOPI was performed by use of the PDT technique and the fluoroscopy‐guided freehand technique. After surgery, the screw deviations from the centroid of the cross‐section at the midpoint of the pedicle and screw position grades were assessed in both groups.

Results

Compared to the freehand group, the PDT group had a significantly shorter surgery time than the freehand group (47.7 vs 61.9 min, P < 0.001). The absolute deviations from the centroids between the preoperative designs and postoperative measurements on the axial plane of the pedicle were 1.19 ± 0.25 mm in the PDT group and 1.82 ± 0.51 mm in the freehand group. On the sagittal plane of the pedicle, the corresponding values were 1.10 ± 0.33 mm in the PDT group and 1.70 ± 0.49 mm in the freehand group. The absolute deviations of the free‐hand group on both the axial and sagittal planes were higher than that of the freehand group (P < 0.05 and P < 0.05, respectively). For the grade of screw insertion position, nine (90%) were observed in type I and one (10%) in type II in the PDT group, whereas five (50%) were in type I, three (30%) were in type II, and two (20%) in type III in the freehand group. Statistical differences could not be found between the groups in terms of the screw positions (P > 0.05).

Conclusion

The novel intraoperative trajectory‐determined strategy of grouped PDTs can be used as an accurate and feasible method for C₂TOPI for AAD with incomplete reduction.

Spiral CT measurement for atlantoaxial pedicle screw trajectory and its clinical application

OBJECTIVE

This study aimed to focus on the atlantoaxial pedicle screw placement and evaluate the effects of anatomical data and degree of surgical exposure of the atlantoaxial pedicle screw trajectory determined using spiral CT on the reference sites for pedicle screw insertion and various parameters in clinical application.

METHOD

The data of CT scan of cervical spine from individuals treated in our hospital were selected. Various anatomical parameters of the atlantoaxial pedicle screw trajectory were measured through multiplanar reconstruction (MPR) technology. Anatomical data and degree of surgical exposure of the atlantoaxial pedicle screw trajectory were obtained through spiral CT. Vernier calipers with least count of 0.01 mm was selected and the least count of the protractor was 0.2°. Prism 8.0 was adopted for graphical data analysis. The anatomical data of atlas of the local population were established. The measurement technique for pedicle screw trajectory and the method for pedicle screw insertion were mastered.

RESULTS

The results indicated that the intraoperative blood loss was between 30-280 ml with no case of excessive blood loss. Follow-up studies 10-18 months after the operations indicated stability of upper cervical spine without adverse conditions. The width of the pedicle screw was 13-24 mm, and the maximal inclination angle of the horizontal for the insertion was 17-21°.

CONCLUSION

The atlantoaxial pedicle screw placement was an effective surgical treatment for stabilizing the upper cervical spine. The measurement data of the atlantoaxial pedicle screw path was obtained through spiral CT and the surgical placement of pedicle screw was guided through individual data. Postoperative CT scan was adopted to evaluate the accuracy of pedicle screw placement, record the occurrence of secondary injuries, improve the stability of clinical applications, and reduce the risks for patients.