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Activator Methods International Ltd.
2950 N. Seventh Street, Suite 200
Phoenix, AZ 85014
ofc 602-224-0220
fax 602-224-0230
toll free 1-800-598-0224
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Subject:The Activator® Adjusting Instrument – Biomechanical
Title:The Effective Forces Transmitted by High-Speed, Low-Amplitude Thoracic Manipulation
Reference:Herzog W, Kats M, Symons B. The effective forces transmitted by high-speed, low-amplitude thoracic manipulation. Spine 2001; 26(19): 2105-11
Abstract:
Study Design:Twenty Asymptomatic Volunteers each received three spinal manipulative treatments to the thoracic spine. The treatments consisted of a straight posterior-to anterior high-speed, low-amplitude thrust to the transverse process of T3-T10 using a reinforced hypothenar contact. All treatments were given by a full-time practicing clinician with three years of experience.
Objective:The primary objective of this study was to quantify local measures of loading applied by the clinician on the volunteers during spinal manipulative treatments and to compare these local measures of loading with previously described global measures.
Summary and Background Data. The sparse information on the mechanics of spine manipulative treatments deals exclusively with global force or pressure measurements. On the basis of these global data, incorrect conclusions may be drawn about the beneficial effects of spine manipulative therapy, the loading of internal structures, and the risks associated with these treatments.
Methods. Twenty asymptomatic subjects each received three posterior-to anterior high-speed, low-amplitude spinal manipulative treatments to the transverse process of the thoracic spine. Total force, local force, contact area, peak pressure, and average pressure at the contact interface between clinician and subject were measured continuously by use of a thin, flexible pressure pad. Local and global measures of loading were compared and analyzed by use of nonparametric statistics (a = 0.01).
Results. The average peak total force was 238.2 N. The average peak local force over a target area of 25 mm was 5N, indicating that global measures of loading vastly overestimate the local effective forces at the target site. The peak pressure point moved, on average, 9.8 mm during the course of the manipulation.
Conclusions:To the authors’ best knowledge, this is the first study to quantify local, effective measures of loading and compare them with the global measures typically used. The conclusions are limited because the study used a single clinician. The effective loading of specific target sites is much smaller than the global measures might suggest. This result occurs because as the forces during spinal manipulative treatment increases, so does the contact area; therefore, much of the total treatment increases, so does the contact area; therefore, much of the total treatment force is taken up by non-target specific tissues. Because of the vast discrepancy between the global and local measures of loading, it is suggested that risk-benefit assessments of high-speed, low amplitude spinal manipulative treatments should be made, including local measures of loading. Finally, because theoretical approaches and the inverse dynamics approach can be provided only global measures of loading, the res ults of such studies should be interpreted with caution.
Keywords:Manipulative treatment, forces, pressures, thoracic spine, chiropractic, spinal mechanics, treatment risk, efficacy, treatment effects Spine 2001; 2105-2111
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