Three-dimensional vertebral motions produced by mechanical force spinal manipulation

Area of Science:

• Biomechanics
• Spinal Manipulation
• Chiropractic Technology

Background:

• Chiropractic adjusting instruments are widely used for spinal manipulation.
• Understanding the biomechanical effects of these instruments is crucial for optimizing treatment.
• Previous research has not fully quantified the 3D motion responses generated by different chiropractic tools.

Purpose of the Study:

• To quantify and compare the 3-dimensional intersegmental motion responses produced by three common chiropractic adjusting instruments.
• To evaluate the influence of different force settings on spinal motion.
• To compare the performance of mechanical and electromechanical adjusting instruments.

Main Methods:

• Six adolescent Merino sheep were used to measure intersegmental motion.
• Triaxial accelerometers were attached to intraosseous pins on L1 and L2 spinous processes.
• Three instruments (Chiropractic Adjusting Tool, Activator Adjusting Instrument IV, Impulse Adjusting Instrument) delivered posteroanterior thrusts to T12 at varying force settings.

Main Results:

• Intersegmental motion responses were greatest along the axial axis, followed by posteroanterior and medial-lateral axes.
• The electromechanical Impulse instrument generated the most linear force increase and the greatest acceleration and displacement responses, especially at high force settings.
• Significantly greater motion responses were observed for Impulse compared to CAT and Activator IV at high force settings.

Conclusions:

• The Impulse instrument produced larger-magnitude, 3D intersegmental displacement and acceleration responses compared to mechanical instruments.
• The force-time characteristics of chiropractic adjusting instruments significantly influence spinal motion.
• Adjusting instruments can be tuned to deliver optimal force for spinal manipulation.