A new method to precisely control the depth of percutaneous screws into the pedicle by counting the rotation number of the screw with low radiation exposure: technical note.

STUDY
DESIGN: Technique note.
OBJECTIVES: To report a new method for precisely controlling the depth of percutaneous pedicle screws (PPS)-without radiation exposure to surgeons and less fluoroscopy exposure to patients than with conventional methods. PPS is widely used in minimal invasive spine surgery; the advantages include reduced muscle damage, pain, and hospital stays. However, placement of PPS demands repeated checking with fluoroscopy. Thus, radiation exposure is considerable for both surgeons and patients.
METHODS: The PPS depth was determined by counting rotations of the screws. The distance between screw threads can be measured for particular screws; thus, full rotations of the PPS results in the screw advancing in the pedicle the distance between screw threads. To fully insert screws into the pedicle, the number of full rotations is equal to the number of threads in the PPS.
RESULTS: We applied this technique in 58 patients with thoracolumbar fracture. The position and depth of the screws was checked during the operation with the C-arm and after operation by anteroposterior X-ray film or computed tomography. No additional procedures were required to correct the screws; we observed no neurological deficits or malpositioning of the screws. In the screw placement procedure, the radiation exposure for surgeons is zero, and the patient is well protected from extensive radiation exposure.
CONCLUSIONS: This method of counting rotation of screws is a safe way to precisely determine the depth of PPS in the placement procedure. LEVEL OF EVIDENCE: IV.