Transmuscular Ultrasonography of the Placement of Thoracolumbar Pedicle Screws: A Cadaveric Study.

BACKGROUND: Transpedicular screw fixation has a biomechanical advantage of improving fusion rates. In posterior thoracolumbar immobilization, a large number of screws cause perforation to the pedicle or vertebral body. Radiography and computed tomography (CT) have been used to minimize this complication. The ability of ultrasound (US) to detect the pedicle breach during placement of the screw is unknown. The aim of this study was to evaluate the sensitivity of US for detecting breaches.

METHODS: A B-type transducer was used to scan 216 titanium pins inserted into cadaveric pedicles. Of the pins, 180 were intentionally misplaced: 90 pins breached the lateral wall of the pedicle, and 90 pins pierced the anterior wall of the vertebral body. US images were reviewed by 3 examiners blinded to both the procedure and the corresponding CT findings. The perforation length of pins was measured by 3 radiologists on CT images.

RESULTS: CT data were divided into 2 groups. In group 1 (perforation length 0-2 mm), sensitivity of US for detecting lateral wall and anterior wall perforation was 80.95% and 76.42%, respectively; in group 2 (perforation length 2-4 mm), sensitivity was 94.79% and 91.93%. Overall sensitivity of US to detect lateral wall and anterior wall perforation was 89.63% and 86.30%, respectively. The sensitivity of US for detecting perforation was greater in the lateral wall than in the anterior wall. Sensitivity of US was greater in group 2 than group 1 for both lateral and anterior perforation.

CONCLUSIONS: US can be applied to detect perforation of ≤4 mm. Use of US may improve patient safety.