Pulse-width Modulation During Pedicle Screw Stimulation

Objective: The aim of this project is to modulate the pulse-width (PWM) during stimulation of pedicle screws, and record the response thresholds associated with each PWM setting. The relationship between pulse-width and threshold will then be analyzed Methods: Upon completion of the pedicle screw placements, each screw will be stimulated utilizing three different pulse-width settings, 0.4 milliseconds, 0.2 milliseconds, and 0.05 milliseconds. The stimulation intensity required to elicit a compound muscle action potential (CMAP) will be recorded for each pulse-width parameter. Standard neurophysiological analyses for determining the CMAP response will be employed, including a minimum response amplitude of 20 millivolts, along with morphological and response-dynamic characteristics. Results: A logarithmic trend line with an R-square value of 0.6921 was found between the 3 PWM settings. Conclusion: We have established a relationship between stimulation pulse-width and response threshold for pedicle screw stimulation. With a larger data set, we may be able to correlate this relationship with inter-patient bone density variations, allowing further refinement of the pedicle screw stimulation technique.