title: Neural Response During a Mechanically Assisted Spinal Manipulation in an Animal Model: A Pilot Study.
abstract: BACKGROUND
  Mechanoreceptor stimulation is theorized to contribute to the therapeutic efficacy of spinal manipulation. Use of mechanically-assisted spinal manipulation (MA-SM) devices is increasing among manual therapy clinicians worldwide. The purpose of this pilot study is to determine the feasibility of recordingin vivomuscle spindle responses during a MA-SM in an intervertebral fixated animal model.
  
  
  METHODS
  Intervertebral fixation was created by inserting facet screws through the left L5-6and L6-7facet joints of a cat spine. Three L6muscle spindle afferents with receptive fields in back muscles were isolated. Recordings were made during MA-SM thrusts delivered to the L7spinous process using an instrumented Activator IV clinical device.
  
  
  RESULTS
  Nine MA-SM thrusts were delivered with peak forces ranging from 68-122N and with thrust durations of less than 5ms. High frequency muscle spindle discharge occurred during MA-SM. Following the MA-SM, muscle spindle responses included returning to pre-manipulation levels, slightly decreasing for a short window of time, and greatly decreasing for more than 40s.
  
  
  CONCLUSIONS
  This study demonstrates that recordingin vivomuscle spindle response using clinical MA-SM devices in an animal model is feasible. Extremely short duration MA-SM thrusts (<5ms) can have an immediate and/or a prolonged (> 40s) effect on muscle spindle discharge. Greater peak forces during MA-SM thrusts may not necessarily yield greater muscle spindle responses. Determining peripheral response during and following spinal manipulation may be an important step in optimizing its' clinical efficacy. Future studies may investigate the effect of thrust dosage and magnitude.
authors.affiliation: Palmer Center for Chiropractic Research, Davenport, IA, USA.
authors.forename: William R
authors.initials: WR
authors.lastname: Reed
authors.affiliation: Department of Neurosurgery, Baylor College of Medicine, Houston, TX, USA.
authors.forename: Michael A K
authors.initials: MA
authors.lastname: Liebschner
authors.affiliation: Research Service Line, Michael E. DeBakey VA Medical Center, Houston, TX, USA.
authors.forename: Randall S
authors.initials: RS
authors.lastname: Sozio
authors.affiliation: Exponent Failure Analysis, Houston, TX, USA.
authors.forename: Joel G
authors.initials: JG
authors.lastname: Pickar
authors.forename: Maruti R
authors.initials: MR
authors.lastname: Gudavalli
keywords: Cat; Manual therapy; Muscle spindle; Neurons afferent; Neurophysiology; Spinal fixation; Spinal manipulation; Zygapophyseal joint