PURPOSE

Experimental assessment of the efficiency of intraosseous ultrasound (IOUS) utilizing the mini probe of endoscopic ultrasound (EUS) is performed to determine the accuracy of pedicle screw hole placements in thoracolumbar spine.

METHODS

Drill holes in 76 pedicles of thoracolumbar spines from 2 cases of goats. Each pedicle screw hole is subjected to a 360° circumferential IOUS scanning with a catheter-type mini ultrasound probe of EUS and to a CT examination. Subsequently, all ultrasound images were independently interpreted by 3 reviewers without knowledge of the real position of screw holes and the results of the CT examination for the assessment of screw hole malposition and pedicle cortex breach. Finally, according to the conclusion of CT, a Chi-square test is employed to assess the differences of interpretations of the screw hole malposition among the all reviewers and the relevant relationship between the recognition of the misplaced screw holes and imaging methods utilized.

RESULTS

CT revealed 13 correctly positioned holes and 63 holes deviating from correct position (including holes that penetrated the cortex). All ultrasound images with malposition identified by CT were correctly interpreted, with no false negatives and no intra-reviewer differences. There were no omissions of severe malposition (including the spinal canal was penetrated into). Excluding six false positives misjudged due to the intersection of screw holes on both sides, there was also no discrepancy between the EUS and CT imaging in the interpretation of screw hole malposition. The examination time of each pedicle screw hole with EUS took less than 15 s.

CONCLUSION

EUS-based IOUS is an immediate, reliable and lower-cost technique for accurate determination of pedicle screw hole malposition. With a probe that is both flexible and not easily bendable, the EUS is particularly suitable for IOUS, especially in the narrow space of the bone gaps or bone canals, and minimally invasive spine surgery (MISS).