Comparison of Mechanical Force of Manually Assisted Chiropractic Adjusting Instruments

Authors

• Christopher J. Colloca, DC
• Tony S. Keller, PhD
• Pierre Black, MSc
• Martin C. Normand, PhD, DC
• Deed E. Harrison, DC
• Donald D. Harrison, PhD, DC

Publication

Journal of Manipulative and Physiological Therapeutics 2005;28(6):414-422.

Article Link

Comparison of Mechanical Force of Manually Assisted Chiropractic Adjusting Instruments

Abstract

Objective: To quantify the force-time and force-delivery characteristics of six commonly used handheld chiropractic adjusting devices.
Methods: Four spring-loaded instruments, the Activator Adjusting Instrument; Activator II Adjusting Instrument, Activator III Adjusting Instrument, and Activator IV Adjusting Instrument, and two electromechanical devices, the Harrison Handheld Adjusting Instrument and Neuromechanical Impulse Adjusting Instrument, were applied to a dynamic load cell. A total of 10 force-time histories were obtained at each of three force excursion settings (minimum to maximum) for each of the six adjusting instruments at preload of approximately 20 N.
Results: The minimum-to-maximum force excursion settings for the spring-loaded mechanical adjusting instruments produced similar minimum-to-maximum peak forces that were not appreciably different for most excursion settings. The electromechanical adjusting instruments produced short duration (~2-4 ms), with more linear minimum-to-maximum peak forces. The force-time profile of the electromechanical devices resulted in a more uniform and greater energy dynamic frequency response in comparison to the spring-loaded mechanical adjusting instruments.
Conclusions: The handheld, electromechanical instruments produced substantially larger peak forces and ranges of forces in comparison to the handheld, spring-loaded mechanical devices. The electromechanical instruments produced greater dynamic frequency area ratios than their mechanical counterparts. Knowledge of the force-time history and force-frequency response characteristics of spinal manipulative instruments may provide basic benchmarks and may assist in understanding mechanical responses in the clinical setting. (J Manipulative Physiol Ther 2005;28:414Q422)