Introduction:
Pedicle screw fixation allows purchase of all three spinal columns without encroaching into the spinal canal improving fracture fixation, as well as deformity correction. Fortunately, neurologic injury associated with pedicle screw malposition is rare.
Case presentation:
A 19-year-old boy was surgically treated for severe right thoracic scoliosis associated with a Chiari Type 1 malformation and a C6 to T7 syringomyelia. Six months after the initial surgery, the patient was referred to our institution after three weeks of gait disturbances and repeated falls. Imaging showed the gross misplacement of the left T5 pedicle screw, which crossed the center of the vertebral canal. The initial surgery used a freehand technique of pedicle screw insertion, with anteroposterior and lateral postoperative X-ray control. During the surgery, no SEP modifications were noted during pedicle screw placement. However, after insertion of the second rod and scoliosis correction by posterior translation technique, SEP responses decreased considerably. Revision surgery was performed to remove the misplaced screw. During the first three months after screw removal, repeated clinical examinations showed progressive recovery of the neurological deficits. Gait and bladder functions were normal six months after screw removal, and clinical signs of spasticity disappeared. SEP explorations performed at final follow-up showed similar responses to those performed before the initial surgery for scoliosis correction.
Discussion and evaluation:
Neurologic injury associated with pedicle screw malposition is rare. In early or delayed neurological status worsening, intraoperative or postoperative imaging must be done to detect pedicle screw misplacement. In the current case, thanks to cobalt-chromium and titanium use, MRI and CT scan allowed good visualization of the spinal canal and spinal cord. Experimental studies have shown that neurophysiological monitoring of the spinal cord does not detect moderate compression. In that way, neurophysiological monitoring is an all-or-nothing technique which can misdiagnose early stage of spinal cord injuries. Major penetration of the spinal canal by pedicle screw may conduct to hardware removal.
Conclusions:
In early or delayed neurological status worsening, intraoperative or postoperative imaging must be done to detect pedicle screw misplacement. In the current case, thanks to cobalt-chromium and titanium use, MRI and CT scan allowed good visualization of the spinal canal and spinal cord. Major penetration of the spinal canal by pedicle screw may conduct to hardware removal.