Spinal somatosensory evoked potential evaluation of acute nerve-root injury associated with pedicle-screw placement procedures: an experimental study

• Published in: Journal of orthopaedic research Vol. 21; no. 2; pp. 365 - 372
• Main Authors: Jou, I-Ming, Hsu, Che-Chia, Chern, Tai-Chang, Chen, Wen-Yi, Dau, Yuan-Chang
• Format: Journal Article
• Language: English
• Published: Hoboken Elsevier Ltd 01.03.2003; Wiley Subscription Services, Inc., A Wiley Company; Blackwell Publishing Ltd
• Subjects: Animals; Bone Screws - adverse effects; Disease Models, Animal; Evoked Potentials, Somatosensory - physiology; Lumbosacral Region; Postoperative Complications - etiology; Postoperative Complications - pathology; Postoperative Complications - physiopathology; Radiculopathy - etiology; Radiculopathy - pathology; Radiculopathy - physiopathology; Rats; Reproducibility of Results; Sciatic Nerve - pathology; Sciatic Nerve - physiopathology; Sensitivity and Specificity; Spinal Nerve Roots - injuries; Spinal Nerve Roots - pathology; Spinal Nerve Roots - physiopathology
• ISSN: 0736-0266; 1554-527X
• DOI: 10.1016/S0736-0266(02)00135-3

Pedicle screws for spinal fixation risk neural damage because of the proximity between screw and nerve root. We assessed whether spinal somatosensory evoked potential (SSEP) could selectively detect pedicle-screw-related acute isolated nerve injury. Because pedicle screws are too large for a rat’s spine, we inserted a K-wire close to the pedicle in 32 rats, intending not to injure the nerve root in eight (controls), and to injure the L4 or L5 root in 24. We used sciatic-nerve-elicited SSEP pre- and postinsertion. Radiologic, histologic, and postmortem observations confirmed the level and degree of root injury. Sciatic (SFI), tibial (TFI), and peroneal function indices (PFI) were calculated and correlated with changes in potential. Although not specific for injuries to different roots, amplitude reduction immediately postinsertion was significant in the experimental groups. Animals with the offending wire left in place for one hour showed a further non-significant deterioration of amplitude. Electrophysiologic changes correlated with SFI and histologic findings in all groups. SSEP monitoring provided reliable, useful diagnostic and intraoperative information about the functional integrity of single nerve-root injury. These findings are clinically relevant to acute nerve-root injury and pedicle-screw insertion. If a nerve-root irritant remains in place, a considerable neurologic deficit will occur.