Transcript Mechanisms of effect of HVLAT

Mechanisms of effect
of HVLAT
Proposed theories and clinical implications
What is HVLAT?Is this the same
thing as a manipulation?
• High Velocity Low Amplitude Thrust (HVLAT) is a technique
used by manual therapists such as Osteopaths, Chiropractors,
Physiotherapists, some Medical Practitioners and other
manual therapists (also known as manipulation!!!) and is
perhaps best well known as a treatment for Low Back Pain
(LBP) for which it is recommended by NICE guidelines (NICE,
2009).
• Problems in definition lead to confusion with regards to
treatment effect, especially regarding the necessity of a joint
cavitation in order for the technique to be ‘successful’ (to hold
therapeutic value)
• HVLAT has more recently been defined by Evans and Lucas as
a technique necessitating a force perpendicular to joint
surfaces, that separates joint articular surfaces resulting in a
cavitation (Evans & Lucas, 2010).
What is the research supporting
HVLAT?
• Research has provided evidence supporting 3
main possible mechanisms behind the
physiological effects of HVLAT; biomechanical,
muscular reflex-genic and neurophysiological
(Potter et. al 2005).
• Research into the effects of HVLAT tend to focus
on pain level and functional health status as
patient centred primary outcome measures
(Goertz et al., 2012)
HVLAT and pain
• HVLAT has been shown to have a clinically significant
analgesic effect when applied to spinal joints (Von
Heymann et al., 2012; Coronado et al., 2012; Millan et
al., 2012a)
• Placebo (although poorly understood itself) has been
thought to play a role in the reported analgesic success
rate of HVLAT, however Von Heymann et al. (2012) in a
recent randomised, double blinded placebo controlled
parallel trial with 3 arms, showed HVLAT treatment to be
significantly more successful than both placebo and
medication (specifically Diclofenac) in patients with acute
non-specific low back pain.
How does it decrease pain?
• Recent reviews (Coronado et al., 2012; Haavik & Murphy,
2012) and recent clinical trials on the effects of HVLAT (Pickar
& Bolton, 2012; Orakifar et al., 2012; Fryer & Pearce, 2012)
have supported the potential for a CNS mechanism including
one study on peripheral joint HVLAT (Grindstaff et al., 2011).
• These trials showed HVLAT to decrease neural excitability in 1)
the dorsal horn of the spinal cord (measured using the
Hoffman-reflex), and 2) the corticospinal tract (measured
using Motor Evoked Potentials).
• Excitability within the dorsal horn is considered to play a role
in nociceptive modulation and subsequent reflexes of αmotorneurones is thought to be important regarding
interruption of the ‘pain-spasm-pain’ cycle
Taking us back to definitions…
• Work by Haavik and Murphey (2012)
demonstrates neurophysiological changes both
at the dorsal horn and at cortical level following
spinal manipulation including; sensory
processing, motor output, functional
performance and sensorimotor integration.
However, no research to date can attribute these
effects to the ‘correction of segmental
dysfunction/alignment’. They may well be the
effects of the afferent barrage created by a
thrust technique (Haavik & Murphy, 2012).
How can we use this information?
• Research supporting the analgesic effects of spinal HVLAT
is strong. Technological advances (such as the use of
transcranial magnetic stimulation) have allowed a more
sophisticated and in-depth study of neural processes
associated with HVLAT.
Do we need to thrust the painful joint?
• No. Millan et. al (2012) in a review of 22 articles
concluded that “Manipulation of a ‘restricted motion
segment’ seemed not to be essential to analgesia”. This
is important as it has implications regarding indications
for HVLAT in clinical scenarios.
Functional outcomes
• A recent Systematic Review concluded that an increase in range of
movement (ROM) available at spinal joints following HVLAT was
limited to the cervical spine (Millan et al., 2012b). The authors claim
that differences between study methodology and variety of
outcome variables made meta-analysis impossible, although articles
which scored higher on the extensive quality checklist provided did
tend to show some increase in ROM following spinal HVLAT
• This point is endorsed by Snodgrass et al.’s (2012) review findings
that “The existing limited evidence does not support an association
between spinal stiffness and manipulative treatment outcomes”.
This seems contrary to the popular belief that hypomobility is a
clinical indication for HVLAT.
Other functional outcomes
• Other functional changes reported following HVLAT include
improvements in weight distribution (Grassi et al., 2011) increased
muscle recruitment (Grindstaff et al., 2011) and decreased muscle
inhibition (Suter et al., 1999).
• The effect of HVLAT on the autonomic nervous system (ANS) has
been measured in various ways, such as changes to cutaneous
blood flow following unilateral Lumbosacral HVLAT (Karason &
Drysdale, 2003), changes to edge light pupil cycle time following
atlanto-axial HVLAT (Gosling et al., 2005) and blood concentration
levels of norepinephrine (NE) and epinephrine (E) (Puhl & Injeyan,
2012).
• There appears to be little evidence supporting ‘stiffness’ or
hypomobility as clinical indications for spinal or peripheral joint
HVLAT, with the exception of the cervical spine. Effects of HVLAT
upon the ANS are still largely unknown.
A quick summary
There is a wealth of research showing HVLAT to be of clinical
value as an analgesic tool when applied to spinal joints, but is
inconclusive regarding changes to ROM (except within the
cervical spine) or regarding changes to spinal ‘stiffness’. The
clinical relevance of changes in muscle tone (as measured by
electromyography) is as of yet unknown (Lehman, 2012). As more
and more research indicates a CNS mechanism behind HVLAT it
seems probable that it may be useful when treating areas distal
to the site of cavitation, although research supporting ANS
mechanisms present a weak argument for treatment via
‘somatovisceral reflex’.