Objective: To introduce a new kind of grade system for thoracic pedicle screws placement by performing postoperative computerized tomography (CT) scanning and discussion the clinical purpose.
Methods: Four hundred and fifty thoracic pedicle screws were implanted in 64 patients with the assistance of fluoroscopy. Postoperative CT scanning was conducted to determine a grade for each screw: Part A, screw entirely contained within pedicle; Part B(1), violate lateral or upper pedicle but screw tip entirely contained within the vertebral body (VB); Part B(2), violate medial or inferior of pedicle; Part B(3), tip penetrated anterior or lateral VB; Part C, violate pedicle or VB and endangers spinal cord, nerve roots, or great vessels. Based on anatomical morphometry, thoracic vertebral were subdivided into upper (T(1 - 2)), middle (T(3 - 6)), and lower (T(7 - 12)) regions. The mean follow-up period was 25.8 months.
Results: The postoperative CT scanning-documented grade were determined: Part A, 367 screws (81.6%); Part B, 78 (17.3%), B(1) 40 (8.1%); Part B(2), 23 (5.1%); Part B(3), 15 (3.4%); Part C, 5 (1.1%). There were not significant difference between upper and lower thoracic that the placement of pedicle screws in part B or C. In part C, 5 pedicle screws were all in the middle thoracic.
Conclusion: Postoperative CT scanning should be considered as a routine examination for evaluating thoracic pedicle screw placement.