AB - Objective: To document the per patient rate of vasovagal reactions and other complications of cervical vs. lumbar translaminar epidural steroid injections. Background: Anecdotal observations at our institution suggested that vasovagal reactions are much more common during cervical epidural steroid injections than lumbar injections, and more frequent than previously reported. Methods: Records of 249 patients undergoing their first cervical epidural steroid injection were reviewed for vasovagal reactions and other adverse events. For comparison, a first lumbar epidural steroid injection performed by the same staff physician was matched to each cervical procedure and reviewed for complications. Results: The incidence of vasovagal reaction was 7 points more common (P < , 95% confidence interval -) in the cervical group (8%) than in the lumbar group (1%). This correlates to an additional vasovagal reaction for every 14 patients who were treated with cervical injection in comparison with those treated with lumbar injection. Discussion: The risk of vasovagal reaction is significantly higher for cervical translaminar epidural steroid injections than for lumbar injections. The risk of vasovagal reaction remained higher for cervical injection even when adjusting for differences between the two populations. The higher rate of cervical vasovagal reactions may result from a combination of anxiety, the prone position with neck flexed, head drapes, and stimulus from a neck procedure. Conclusion: Increased vigilance for patients undergoing translaminar cervical epidural steroid injections may be warranted. Clinicians may choose to consider these results when counseling patients regarding risk and the need for conscious sedation during the procedure.
Biomechanics of the spine is altered by the implantation of spinal devices used to stabilize the segment [ 29 ]. Along with many devices currently available in the market to treat spinal disorders, many new designs are also being developed in the hope to improve clinical outcomes. It is essential to evaluate their biomechanical efficacy among other issues, prior to clinical use [ 30 ]. The spinal implants can be evaluated by comparing the stability of the construct to the intact spine stability and/or stability provided by a predicate device. The biomechanical effects of decompression and stabilization provided by implants can be assessed using in vitro studies [ 31 , 32 ]. In vitro studies involving ligamentous spine specimens from human cadaver or other species like sheep, calf, and rabbit are carried out using standard test protocols [ 30 ]. Finite element analysis (FEA) in spine biomechanics is very helpful to perform the structural analysis of bone and bone implant composites of complicated geometry. Since it is difficult to get all the parameters from experimental studies, finite element models can be used to address the remaining issues [ 33 , 34 ]. Thus, in vitro and FE-based biomechanical studies provide valuable information on implants safety and effectiveness prior to their clinical use [ 30 ].