Saline injection technique to confirm pedicle screw path: a cadaveric study.

Pedicle screws are frequently misdirected during placement, which may lead to complications such as pedicle fracture, inadequate biomechanical strength, and neurologic deficit. Roentgenographic confirmation and manual probing are important but are not 100% accurate. We have developed a simple saline injection technique to assist in confirming the correct path of the pedicle screw prior to its insertion. In this study, five fresh frozen cadaveric spines were dissected from T-12 to L-5, and a total of 60 data points were recorded. Saline injection tests confirmed 31 of 32 (97%) drill paths that were in the pedicles. Two specimens were used to intentionally misdirect the pedicle drill path to determine the rate of false-negative results. Pedicle drilling was misdirected medially, laterally, superiorly, and and inferiorly (six of each). There were a total of 24 intentional and four unintentional, radiographically confirmed missed drillings of the pedicle. Of the 28 misdirected pedicle paths, the saline injection test correctly diagnosed the problem in 23 (82%) cases. Seven misdirected drillings were falsely negative by the injection test (five superior and two inferior directions). This study shows that a simple saline injection test can be a useful adjunct in confirming a correct pedicle path in 97% of the cases. If an incorrect path has been created, false-negative tests are possible in 18% of the cases.