In lumbar spine spinal cord is not under risk of injury but nerve roots which are responsible for lower extremity function can be injured by malpositioned pedicle screws. In the present study we aimed to evaluate the pedicle screw malpositions by pedicle probe and its use in lumbar spinal surgery cases.
Total number of pedicle screws applied was 126 which all were applied to the lumbar spine. All neuromonitoring was performed using transcranial motor-evoked potentials, sensoryevoked potentials, spontaneous and triggered electromyography. Pedicle screw positions were also checked by pedicle probe and fluoroscopy.
Eight of the 126 pedicle screws were accepted as malpositioned .One screw position at fluoroscopy images suggested superolateral malpositioning but normal response. Position of one screw was interpreted as accurate by both pedicle stimulation and fluoroscopy but screw violated the medial wall of the pedicle.
Intraoperative monitoring including pedicle stimulation in adjunct with somatosensorial evoke potentials and motor evoked potentials helps to decrease the risk of neurologic injury. However pedicle stimulation response can be normal in lateral, supero-lateral, and even in medial pedicle wall breech if screw do not contact nerve root. In conclusion, treating physician should use all available tools in order to detect screw malposition.
Keywords: pedicle screw, intraoperative neuromonitoring, pedicle screw stimulation