OBJECTIVETo explore the method of implanting upper-middle thoracic pedicle screws under monitoring by X-ray and evaluate accuracy and safety.

METHODS(1) Six normal adult thoracic spine samples (T1-T8) were selected, from which single spine units were separated. A surgical probe went in along the pedicle axis. By C-shaped arm X-ray, the four probe positions were recorded: at the entering point, the front end of the probe in the middle of the pedicle, at the pack of the spine, and under the cortex of the front of the spine. The position of the front end of the probe at the entering point, and the front end of the probe at different depth at central-side perspective position were analyzed. The related positions and their corresponding changing rules were also analyzed. (2) Based on the changing rules mentioned above, different steps were adopted under the guidance of the C-shaped arm X-ray, to safely implant upper-middle thoracic pedicle screws. First, six T1-T8 spine samples were used, and under the guidance of the C-shaped arm device, 96 pedicle screws were implanted. After the operation,the sping samples were scanned through CT, and the positions of the screws were determined.

RESULTSAccording to the result of the CT scanning, the result were excellent (the screw was safely inside the pedicle) in 90 screws; Medium (the screw penetrated a little of the inside or outside bone cortex, within 2 mm) in 6; No one was had (the screw penetrated a lot, more than 2 mm).

CONCLUSIONThe implantation of upper-middle thoracic pedicle screw under the guidance of the C-shaped arm X-ray perspective is a simple and feasible method, and improve the accuracy and safety.