OBJECTIVE: To carry out a neurophysical evaluation that can identify these cases during surgery, and that prevents misplacement of pedicular screws. METHODS: A total of 6739 screws were placed in 293 patients submitted to scoliosis correction via the posterior route with pedicular screws using the freehand technique. Of this total, eight patients (2.7%), with a mean age of 24 years, developed postoperative radiculopathy. Lumbar CT scans showed 10 misplaced lumbar screws (2L1-3L2-4L3-1L4), with minimal protrusion of the lower part of the screw. EMG thresholds of the screw and track were evaluated. RESULTS: In the initial surgery, no anomalies were detected on palpation of the screw track or in the radioscopic control; neither were any neurophysiological alterations detected in the neurophysiological stimulation with t-EMG. All the patients had radicular pain in the standing and seated positions, which disappeared when lying on the bed. The screws were surgically removed at an average of 37 days after surgery (range: 4-182). In this surgical procedure, the neurophysiological monitoring was repeated, again showing normal thresholds (>11mA). After screw removal, stimulation of the probe within the track showed very low thresholds (range: 3.9-10.7 mA) at mid pedicular track. After a mean follow-up time of 4.4 years (Range: 2.6-6.8), five patients reported occasional radicular discomfort, and had minimal motor deficit in the affected limb. CONCLUSIONS: A type of misplacement of lumbar pedicle screws is presented that produces radicular pain in the standing and seated positions, and that may not be detected by conventional monitoring. Neurophysiological stimulation of the mid pedicular track, after removal of the screw, produces low stimulation thresholds. Systematic stimulation of the track prior to insertion of the lumbar pedicular screw is recommended.
Radiculopathy; Spine; Bone screws
