OBJECTIVETo introduce a new kind of grade system for thoracic pedicle screws placement by performing postoperative computerized tomography (CT) scanning and discussion the clinical purpose.

METHODSFour 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.

RESULTSThe 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.

CONCLUSIONPostoperative CT scanning should be considered as a routine examination for evaluating thoracic pedicle screw placement.