Neurophysiologic response to intraoperative lumbosacral spinal manipulation

Area of Science:

• Neuroscience
• Orthopedics
• Biomedical Engineering

Background:

• Spinal manipulation mechanisms are poorly understood, with clinical effects attributed to mechanical, neurophysiologic, and reflexogenic processes.
• Previous research in animals and humans identified mechanosensitive afferents and neuromuscular responses, but basic neurophysiologic mechanisms in humans remain largely unidentified.

Observation:

• A feasibility study was conducted during lumbar spinal surgery to record intraoperative neurophysiologic responses to spinal manipulation.
• Mixed-nerve root action potentials were measured from the S1 nerve root in response to manually assisted spinal manipulative thrusts applied internally and externally.

Findings:

• Mixed-nerve root action potentials were successfully recorded in response to both internal and external spinal manipulative thrusts.
• Observed differences in amplitude and discharge frequency indicated sensitivity to segmental contact points and force vectors.
• Amplitudes ranged from 200-2600 mV for internal and 800-3500 mV for external thrusts.

Implications:

• Intraoperative monitoring of nerve root discharges during spinal manipulation in human subjects is feasible.
• Neurophysiologic responses are sensitive to the specifics of the spinal manipulative thrust, including contact point and force vector.
• Further research is needed to elucidate the precise neurophysiologic mechanisms and neural pathways involved in spinal manipulation.