Pedicle screw placement with a free hand technique in thoracolumbar spine: is it safe?

STUDY DESIGN: Computerized tomography (CT) analysis of in vivo pedicle screw placement to determine their exact position in relation to the pedicle in thoracolumbar region (T10-L3).

OBJECTIVE: To evaluate the clinical accuracy of the placement of thoracolumbar pedicle screws with a free hand technique after reviewing preoperative imaging.

SUMMARY OF BACKGROUND DATA: CT scans have been used in research clinical settings to evaluate pedicle screw placement in thoracolumbar spine.

MATERIAL AND METHODS: Ninety-eight consecutive patients who underwent posterior stabilization using 640 transpedicular screws by 1 surgeon from T10 to L3 were analyzed. The mean age was 36.1+/-15.1 (13 to 73) years at the time of surgery. Pedicle screws were inserted using anatomic landmarks; specific entry sites, preoperative anteroposterior/lateral radiographs, and CT imaging were used to guide the surgeon. After preparation of entry point, a pedicle probe was carefully advanced free hand down the pedicle into the body. Careful palpation of all bony borders (flour and 4 pedicle walls) was performed before placement the screw. Postoperative CT scans were used to evaluate the position of all pedicle screws inserted. Screw cortical penetration was graded on the basis of anatomy (the wall penetrated) and distance of the penetration, with 2 mm of interval.

RESULTS: The number of screws inserted at each level were as follows: T10 (n=55), T11 (n=124), T12 (n=118), L1 (n=91), L2 (n=146), and L3 (n=106). Analysis of these pedicle screws using postoperative CT scans confirmed 37 (5.8%) violated screws, including 12 medial, 18 lateral, 2 superior, 1 inferior, and 4 anterolateral vertebral body penetrations. No neurologic, vascular, or pleural injuries occurred. No screws required postoperative repositioning.

CONCLUSIONS: Pedicle screw placement with a free hand technique after reviewing preoperative imaging seems to be accurate, reliable, and safe adjunct for the placement of thoracolumbar spine screws.