Saturday, June 20, 2009

Spine manipulation: the HVLA technique


Spinal manipulation (SM) is a popular form of manual therapy used by variety of manual medicine practitioners to treat patients with low back and neck pain. The HVLA or the high velocity low amplitude thrust technique is one the most common form of SM application. HVLA characterized by following:

1. High-velocity (duration less than 150 ms),
2. low-amplitude (segmental translation less than 2 mm, rotation less than 4 degrees , and applied force 220-889 N)
3. Impulse thrust.

The skill set for success in applying an HVLA-SM lies in the practitioner's ability to

1. Control the duration and magnitude of the load (ie, the rate of loading).
2. The direction in which the load is applied.
3. The contact point at which the load is applied.

Clinical effects are highly dependant on the control over its mechanical delivery. This procedures set up biomechanical changes & that is responsible for physiological consequences especially by changes in sensory signaling from paraspinal tissues (6).

Effects of altering the duration of loading & amplitude of loading on spindle discharge: Reports from animal models (6).

Anesthetized cats ware subjected to Impulse thrusts of duration: 12.5, 25, 50, 100, 200, and 400 ms; amplitude 1 or 2 mm. These thrusts are posterior to anterior applied to the spinous process of the L6 vertebra of the cat. The finding of different amplitude & duration of thrust are as follows:

1. As thrust duration became shorter, the discharge of the lumbar paraspinal muscle spindles increased in a curvilinear fashion. A concave-up inflection occurred near the 100-ms duration eliciting both a higher frequency discharge compared with the longer durations and a substantially faster rate of change as thrust duration was shortened. This pattern was evident in paraspinal afferents with receptive fields both close and far from the midline.

2. Paradoxically, spindle afferents were almost twice as sensitive to the 1-mm compared with the 2-mm amplitude thrust.

These findings suggest that with HVLA thrust the sensory system in connection to paraspinal muscle spindle is stimulated more. Clinically, these parameters may be important determinants of an HVLA-SM's therapeutic benefit.

Reference:
Pickar JG et al; Spine J. 2007 Sep-Oct;7(5):583-95. Epub 2007 Jan 10.

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