Performance and Reliability of a Variable Rate, Force/Displacement Application System

Abstract

Objective Spinal manipulation therapy (SMT), an intervention used to treat low back pain, has been demonstrated to affect the stiffness of the spine. To adequately quantify the effects of SMT on stiffness, a device capable of applying specific parameters of manipulation in addition to measuring force-displacement values has been developed previously. Previously developed indentation techniques that quantify stiffness have been modified for novel use in evaluating SMT parameters. The reliability of stiffness measurements performed by the newly adapted device was assessed in this study. Methods Seven springs of varying stiffness were each indented 10 times by a Variable Rate Force/Displacement (VRFD) device. Indentations were performed at a rate of 0.5mm/s to a maximal displacement of 4 mm. The stiffness coefficients for a middle portion of the resulting force-displacement graph and the terminal instantaneous stiffness (stiffness at end displacement) were calculated. The intra class correlation and confidence interval were calculated for these stiffness measurements to assess device reliability. Results Repeated spring stiffness measures yielded an ICC value of 1.0. The mean stiffness values had narrow 95% confidence intervals ranging from 0.01 N/mm to 0.06 N/mm and small coefficients of variation. Conclusion This VRFD device provides highly reliable stiffness measurements in controlled conditions. Although in vivo reliability remains to be established, the results of this study support the use of the VRFD device in future trials investigating the impact of SMT various parameters on spinal stiffness.

The effect of duration and amplitude of spinal manipulative therapy (SMT) on spinal stiffness

“…The high reliability of spinal stiffness measurements obtained with this device has been reported previously (Vaillant et al 2010). The subject’s respiration was held at full exhalation through controlled ventilation for the duration of SMT applications and measurements of stiffness (<10s).…”

A structured review of spinal stiffness as a kinesiological outcome of manipulation: Its measurement and utility in diagnosis, prognosis and treatment decision-making

“…It is acknowledged that animal (Colloca et al, 2009) and non-biological models (Vaillant et al, 2010) have provided a basis for the development of spinal stiffness measurement methods and have been used to investigate effects of manipulation on stiffness (Haussler et al, 2010;Ianuzzi et al, 2010). However, this review focused on human studies in order to provide more direct relevance for the practicing clinician.…”

Neural responses to the mechanical characteristics of high velocity, low amplitude spinal manipulation: Effect of specific contact site

“…Several groups using electromechanical devices to deliver controlled, repeatable HVLA-SMs (Pickar and Wheeler, 2001; Vaillant et al, 2010; Descarreaux et al, 2013) have been systematically investigating how variations in an HVLA-SM’s biomechanical characteristics affect neuromuscular, biomechanical and neurophysiological responses. In healthy humans Descarreaux and colleagues found that increasing thrust force but decreasing either thrust duration or preload force produces linear increases in the magnitudes of EMG responses evoked during and following the manipulative thrust (Nougarou et al, 2013; Page et al, 2014; Francois et al, 2014).…”