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Paraspinal Muscle Spindle Response to Intervertebral Fixation and Segmental Thrust Level During Spinal Manipulation
William R Reed1, Joel G Pickar
1From the Palmer Center for Chiropractic Research, 741 Brady Street, Davenport, IA.
Spine
|April 10, 2015
Summary
Intervertebral fixation reduces paraspinal muscle spindle activity during spinal manipulation in cats. Targeted manipulation maximizes response, but even non-targeted methods show significant muscle spindle engagement.
Area of Science:
- Biomechanical research
- Neuroscience
- Spinal manipulation research
Background:
- Spinal manipulation efficacy is theorized to involve mechanoreceptor activity.
- The impact of intervertebral fixation and thrust level on muscle spindle activity during HVLA-SM is not well understood.
Purpose of the Study:
- To investigate how intervertebral facet joint fixation and segmental thrust level influence paraspinal muscle spindle activity.
- To analyze changes in muscle spindle discharge during simulated spinal manipulation in a feline model.
Main Methods:
- An in vivo cat model was used to simulate spinal manipulation.
- Intervertebral fixation was achieved using facet screws at L4-L7 levels.
- Muscle spindle discharge was recorded during high-velocity, low-amplitude spinal manipulation (HVLA-SM) at varying thrust durations and levels.
Main Results:
- Facet screw fixation significantly increased lumbar spinal stiffness during HVLA-SM.
- Intervertebral fixation significantly decreased L6 muscle spindle response to HVLA-SM.
- Spinal manipulation delivered two segments rostral to the target still elicited 60-80% of the at-level muscle spindle response.
Conclusions:
- Intervertebral fixation diminishes paraspinal muscle spindle response during HVLA-SM in a feline model.
- While precise targeting of HVLA-SM maximizes muscle spindle response, non-targeted manipulation still generates substantial activity.
