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A new technique of pedicle screw placement with the use of sequential multilevel navigation templates based on patient-specific 3D CT reconstruction model: applicability in spine deformity.

INTRODUCTION
The technique of placement of pedicle screws has gradually improved, but even misplacement observed in 1.2 to 20% of cases, have appeared techniques fluoroscopic, tomographic and electromagnetic navigation, which led it to 1.3 to 4.3%, but nevertheless they are expensive and complex technologies. Present technique pedicle screw placement by using templates with a modification in the art, performing tomography and reconstruction in the same surgical position and with the templates of 3 or more levels.


METHODS
Five cases of idiopathic scoliosis were performed, with correction and instrumentation with pedicular screws, where a three-dimensional model of the spine was performed with a tomography in a surgical position, whose images were exported to a 3D printer to reconstruct the desired trajectory of the screws in a template using cylinders resting on the inverse surface of the vertebrae. The direction of the screw was planned in the center of the pedicle and parallel to the upper platform of the vertebra. Each template was of several levels and transoperative X-rays were not used.


RESULTS
Under electrophysiologic monitoring transoperative «red alerts» were not reported, the placement of the screws in postoperative CT scan was evaluated, showing a standard deviation in placement of 1.9 and 2.2 mm on the right and left respectively pedicles, with respect to their planning.


DISCUSSION
This technique is simple and safe, besides not requiring great technology, its use is suggested in beginner spine surgeons and in severe deformities, it can be performed in any hospital where spinal surgery is performed.