ACCURACY OF PEDICLE SCREW PLACEMENT IN SC OLIOSIS SURGERY BY MEANS OFCOMPUTED-TOMOGRAPHY

With the increasing use of pedicle screws in instrumented pine surgery the neurological risk must be evaluated critically. Studies, which ev aluated the accuracy of pedicle screw placement in scoliosis surgery, have not been published up to date to our knowledge. In 25 consecutive patients with idiopathic scoliosis, who underwent posterior instrumen ted curve correction and stabilization, the accuracy of pedicle screw placement was evaluated using axial computed tomography. There was a t otal of 178 screws between T5 and L4. The Preoperative Cobb angle of t he curve averaged 60.7 degrees, the mean rotation of the instrumented vertebrae was 19,1 degrees according to Perdriolle. 145 pedicle screws (81.5%) were placed correctly within the pedicles, of which 4 screws (4,5%) penetrated the anterior aspect of the vertebral body with a mea n of 0,9 mm. 22 screws (12,4%) showed lateral penetration of the pedic le with a mean of 1,9 mm. of which one screw was placed completely lat eral of the pedicle, 8 screws (3,5%) penetrated the medial wall of the pedicle by 1,3 mm on average. One screw each penetrated the cranial a nd caudal border of the pedicle. Statistical analysis did not reveal a ny significant relationships between pedicle screw misplacement and gr ade of vertebral rotation or site of instrumentation. Neurological com plications were not noted in any of the cases. In our mind the risk of pedicle screw threaded curve correction and fusion in scoliosis surge ry in the hands of an experienced spine surgeon is calculated acceptab ly low.