A novel plain radiographic measurement for precise detection of pedicle screws breaching the medial pedicle wall in thoracic and lumbar spine.

Purpose: To evaluate a novel measurement method based on X-ray images for accurately determining the relationship between pedicle screws and the medial wall of the pedicle in thoracic and lumbar spine surgery.

Methods: A total of 650 pedicle screws from 126 patients who underwent thoracic or lumbar internal fixation surgery were included. Postoperative X-ray images were used to calculate the distance between the medial edge of the screw threads and the medial wall of the pedicle ("b-x") based on our measurement method. This distance was also measured using postoperative CT ("Y"). The agreement of "b-x" and "Y" was assessed using Spearman's correlation analysis, intraclass correlation coefficient (ICC) and Bland-Altman plot analysis. The cutoff value of "b-x" and its accuracy in predicting "Y" value was evaluated using the receiver operating characteristic (ROC) curve.

Results: Of the 650 screws, 59 (9.08%) showed medial wall breaching on CT. A strong positive correlation (r = 0.82) and strong agreement (ICC = 0.855) were shown between "b-x" and "Y" in Spearman's correlation and ICC analysis, respectively. Bland-Altman plot analysis indicated most values (96.2%) fell within the 95% confidence interval. The cutoff value for predicting medial wall breaching ("Y" < 0) was determined as "b-x" < 0.97 mm, with sensitivity of 89.83% and specificity of 88.49%.

Conclusion: This novel measurement method, based on X-ray images, accurately determines the relationship between the pedicle screws and medial wall of the pedicle. It offers the advantages of high efficiency and low cost, facilitating timely detection and correction of screws that breach the medial pedicle wall during surgery.