Efficacy of Intraoperative Neurologic Monitoring in Surgery Involving a Vertical Expandable Prosthetic Titanium Rib for Early-onset Spinal Deformity

Background: The vertical expandable prosthetic titanium rib (VEPTR) device is used in the treatment of thoracic insufficiency syndrome and certain types of early-onset spinal deformity. The purpose of this study was to evaluate the risk of neurologic injury during surgical procedures involving use of the VEPTR and to determine the efficacy of intraoperative spinal cord neuromonitoring.

Methods: Data were collected prospectively during a multicenter study. Surgical procedures were divided into three categories: primary device implantation, device exchange, and device lengthening. Further retrospective evaluation was undertaken in cases of neurologic injury or changes detected with neuromonitoring.

Results: There were 1736 consecutive VEPTR procedures at six centers: 327 (in 299 patients) consisted of a primary device implantation, 224 were a device exchange, and 1185 were a device lengthening. Perioperative clinical neurologic injury was noted in eight (0.5%) of the 1736 cases: these injuries were identified after five (1.5%) of the 327 procedures for primary device implantation, three (1.3%) of the 224 device exchanges, and none of the 1185 device-lengthening procedures. Of the eight cases of neurologic injury, six involved the upper extremity and two involved the lower extremity. The neurologic deficit was temporary in seven patients and permanent in one patient, who had persistent neurogenic arm and hand pain. Intraoperative neuromonitoring demonstrated changes during six (0.3%) of the 1736 procedures: five (1.5%) of the 327 procedures for primary device implantation and one (0.08%) of the 1185 device-lengthening procedures. The surgery was altered in all six cases, with resolution of the monitoring changes in five cases and persistent signal changes and a neurologic deficit (upper-extremity brachial plexopathy) in one. Two patients had false-negative results of monitoring of somatosensory evoked potentials, and one had false-negative results of monitoring of somatosensory evoked potentials and motor evoked potentials during implant surgery; two had a brachial plexopathy and one had monoplegia postoperatively, with all three recovering.

Conclusions: Neurologic injury during VEPTR surgery occurs much more frequently in the upper extremities than in the lower extremities. The rates of potential neurologic injuries (neurologic injuries plus instances of changes detected by monitoring) during primary implantation of the VEPTR (2.8%) and during exchange of the VEPTR (1.3%) justify the use of intraoperative neuromonitoring of the upper and lower extremities during those procedures. As neuromonitoring did not demonstrate any changes in children without a previous VEPTR-related monitoring change and there were no neurologic injuries during more than 1000 VEPTR-lengthening procedures, intraoperative neuromonitoring may not be necessary during those procedures in children without a history of a neurologic deficit during VEPTR surgery.