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19-03-2012 | General practice | Article

Patients with thoracic spine pain may benefit from different HVLA force generation strategies


Free abstract

MedWire News: The method of force generation during administration of a single high-velocity, low amplitude (HVLA) spinal manipulation procedure has a significant influence on the characteristics of the mechanical load applied, say Canadian researchers.

The findings arise from a comparison of three distinct strategies of force development for the same HVLA thoracic spine procedure, and may assist in the identification of populations of thoracic spine pain patients "for whom one procedure or other may be more effective."

Writing in Manual Therapy, Edward Cambridge (University of Waterloo, Ontario) and team explain that the loading characteristics of spinal manipulative therapy (SMT) are "critical pieces in understanding the underlying mechanisms of its therapeutic potential."

They therefore examined the cross correlation of force-time histories across three distinct strategies of force production for the same HVLA thoracic spine procedure.

Strategy one (S1) involved a muscular thrust, where the operator's elbow remained flexed during the procedure, with force application primarily by muscular contraction of the elbow extensors. The second strategy (S2) required the operator to use a straight arm to transmit the force from a lower body release to the patient through the arms and hands. In the third strategy (S3), the upper body was controlled by the lower body (to minimize spine motion of the operator), but the force was transmitted directly from the clinician's thorax to the hands and into the patient.

A total of 19 healthy males, aged 27 years on average, received the three treatment procedures. They were delivered by three clinicians with a 1-week interval between procedures.

The force-time history of each strategy was recorded using a table mounted force plate. Secondary measures were peak force, preload force, slope of the thrust, instantaneous loading rate (ILR), and thrust duration of the total force magnitude.

Cambridge and co-investigators report similar force-time profiles for each of the strategies of force development. However, components within the force-time histories demonstrated significant differences according to the variation of force-development strategy.

S1 achieved midrange scores on all secondary measures, while S2 was the slowest procedure, evidenced by the lowest ILR and slope. S3 was significantly different from S1 and S2 in four of the five characteristics, resulting in the lowest preload, the highest peak force, and the fastest loading range characteristics (highest ILR and slope).

The authors admit that the study was only conducted on healthy individuals. Nonetheless, "we believe the data in this study, demonstrating that different techniques employ different force profiles, is transferable to patient populations and hence, can be used to assist clinical decision making in the future," they say.

"Future studies investigating clinical implications from these differences… will require systematic study of patient response in conjunction with physiological biomarkers and biomechanical measures."

By Nikki Withers

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