• Ryuya Maejima, Mikinobu Takeuchi, Norimitsu Wakao, Mitsuhiro Kamiya, Masahiro Aoyama, Masahiro Joko, Koji Osuka, and Masakazu Takayasu.
• Department of Neurological Surgery, Aichi Medical University, Nagakute, Aichi, Japan.
• World Neurosurg. 2019 May 1; 125: e257-e261.

ObjectiveThe purpose of this study was to determine the sensitivity and specificity of using the spinal midline (M line) on a radiographic anteroposterior (AP) view for detecting pedicle screws (PSs) breaching the medial pedicle wall.MethodsWe retrospectively reviewed 145 patients who underwent fusion surgery using PSs between January 2006 and May 2017. We defined the M line as a line that connected the upper and lower spinous processes through the fixed vertebrae. The M line was positive if the tip of the PS crossed the M line. The reference standard was a computed tomography scan. The reliability of the M line was examined.ResultsThe subjects included 145 patients (70 men and 75 women; mean age, 63.4 years). A total of 599 PSs were examined. Most cases were because of spondylolisthesis (66.9%). Most screws were inserted at a lower lumber level (77.6%). Analysis of the diagnostic accuracy of the M line yielded a sensitivity of 74.1% and a specificity of 95.3%. In addition, the positive predictive value of the M line was 42.6%, and the negative predictive value of the M line was 98.7%.ConclusionsAssessment of the M line via an intraoperative radiographic AP view is a simple, readily available, complementary method for detecting PSs that have breached the medial pedicle wall in the thoracic, lumbar, and sacral spine. In particular, the M line has a strong negative predictive value, which is much more meaningful.Copyright © 2019 Elsevier Inc. All rights reserved.

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