[Reproducibility of readings of ISO C 3D and CT lumbar pedicle screw scans].

Purpose: This study was conducted to evaluate the reproducibility of the reading of lumbar pedicle screw scans using a C-arm-based imaging system in comparison to computed tomography. The influence of the technique and the experience of the rater should be determined.

Materials And Methods: The lumbar spines of 23 patients were stabilized using 102 pedicle screws. The position of the screws was controlled intraoperatively using an Arcadis Orbic 3D scanner. All scans were evaluated independently by three raters. The position of the implants in reference to the pedicle walls was described. Additionally, another 100 lumbar pedicle screws in 16 patients were evaluated postoperatively with a multirow CT. Kappa according to Fleiss was calculated for the reproducibility of the rater statements. Each rater repeated the analysis of 24 screws to assess the intraobserver variance.

Results: The reports of the CT scans showed significantly less variation. The consent of all 3 raters was achieved in 79.4 vs. 65.1 % of cases. The Kappa values were 0.56 and 0.29, respectively. Poor results were obtained especially for the medial pedicle wall (consent 70.0 vs. 50.0 %). The influence of the experience of the rater was not able to be verified.

Conclusion: The image quality of the ISO C 3D is worse than that of multirow CT scans for the evaluation of lumbar pedicle screws. This causes greater variance among the rater reports. We stopped using the ISO C 3D technique intraoperatively for the implantation of lumbar pedicle screws.