The relation between the application angle of spinal manipulative therapy (SMT) and resultant vertebral accelerations in an in situ porcine model
ABSTRACT It has been hypothesized that the posterior tissues of the spine are frictionless and therefore allow only the normal force component of spinal manipulative therapy (SMT) to pass to underlying vertebrae. Given this assumption, vertebrae could not be moved in practitioner-defined directions by altering the application angle of SMT. To investigate this possibility, porcine lumbar spines were excised and then SMT applied at 90 degrees to the posterior tissues of the target vertebra. A standard curve was constructed of increasing SMT force versus vertebral acceleration. SMT forces were then applied at 60 degrees and 120 degrees and the resulting accelerations substituted into the standard curve to obtain the transmitted force. Results showed that vertebral accelerations were greatest at a 90 degrees SMT application angle and decreased in all axes at application angles not equa l90 degrees . The average decrease in transmitted force using application angles of 60 degrees and 120 degrees was within 5% of the predicted absolute value. In this model, SMT applied at a non-normal angle does not increase vertebral acceleration in that same direction, but acts to reduce transmitted force. This work provides justification for future studies in less available human cadavers. It is not yet known if variations in SMT application angle have relevance to clinical outcomes or patient safety.
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ABSTRACT: Like other factors that can influence treatment efficacy (eg, dosage, frequency, time of day), the site of treatment application is known to affect various physical interventions such as topical anesthetics and cardiopulmonary resuscitation. Like these examples, spinal manipulative therapy (SMT) is a physical intervention that may exhibit maximal benefit when directed to a specific site. Whereas numerous studies of SMT efficacy have produced mixed results, few studies have taken into account the site of SMT application. To determine if the site of SMT application modulates the effect of SMT in an anesthetized feline model. Spinal manipulative therapy applied to specific anatomic locations randomized in a Latin square design with a no-SMT control. Physiologic measures (spinal stiffness). Simulated SMT was delivered by a validated mechanical apparatus to the intact lumbar spine of eight anesthetized felines at four unique sites: L6 spinous process, left L6 lamina, left L6 mammillary process, and L7 spinous process. To measure spinal stiffness, a separate indentation load was applied mechanically to the L6 spinous process before and after each SMT application. Spinal stiffness was calculated from the resulting force-displacement curve as the average stiffness (k) and terminal instantaneous stiffness (TIS). Relative to the no-SMT control, significant decreases in spinal stiffness followed the SMT when L6 spinous and L6 lamina were used as the contact site. Terminal instantaneous stiffness significantly decreased -0.48 N/mm (upper, lower 95% confidence interval [-0.86, -0.09]) with L6 spinous as the contact site and decreased -0.44 N/mm (-0.82, -0.05), with the L6 lamina as the contact site. k increased 0.44 N/mm (-0.01, 088), using L6 spinous as the contact site. Decreases in terminal spinal stiffness were observed after SMT delivered at some application sites but not the others. The results suggest that SMT contact site modulates SMT's effect on spinal stiffness in a feline model. Changes in spinal terminal instantaneous spinal stiffness were similar in magnitude and direction to those observed in symptomatic human subjects who report benefits after SMT.The spine journal: official journal of the North American Spine Society 10/2013; DOI:10.1016/j.spinee.2013.07.480 · 2.80 Impact Factor
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ABSTRACT: Manually-applied movement and mobilization of body parts as a healing activity has been used for centuries. A relatively high velocity, low amplitude force applied to the vertebral column with therapeutic intent, referred to as spinal manipulative therapy (SMT), is one such activity. It is most commonly used by chiropractors, but other healthcare practitioners including osteopaths and physiotherapists also perform SMT. The mechanisms responsible for the therapeutic effects of SMT remain unclear. Early theories proposed that the nervous system mediates the effects of SMT. The goal of this article is to briefly update our knowledge regarding several physical characteristics of an applied SMT, and review what is known about the signaling characteristics of sensory neurons innervating the vertebral column in response to spinal manipulation. Based upon the experimental literature, we propose that SMT may produce a sustained change in the synaptic efficacy of central neurons by evoking a high frequency, bursting discharge from several types of dynamically-sensitive, mechanosensitive paraspinal primary afferent neurons.Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 02/2012; 22(5):785-94. DOI:10.1016/j.jelekin.2012.01.015 · 1.73 Impact Factor
Free Radical Biology and Medicine 01/2010; 49. DOI:10.1016/j.freeradbiomed.2010.10.413 · 5.71 Impact Factor