Research Review Corner: Paradigm Shift in Manual Therapy

Shawn Thistle
January 31, 2009
Written by Shawn Thistle
Study Title: Paradigm shift in manual therapy? Evidence for a central nervous system component in the response to passive cervical joint mobilization

Author(s): Schmid A, Brunner F, Wright A & Bachmann M

Publication Information: Manual Therapy 2008; 13: 387-396.

It has long been postulated that the benefit of cervical spine manipulation or mobilization is gleaned from a combination of local mechanical and segmental and/or suprasegmental neurological mechanisms. 

Recently, an increasing number of studies have suggested that passive spinal joint mobilization may activate various areas in the central nervous system (CNS), producing a “multisystem response that extends beyond the specific joints and spinal segments stimulated.” [p. 388]

The goal of this systematic review was to evaluate the current evidence on the consistency and nature of CNS responses to passive cervical joint mobilization (CJM). NOTE: This review did not include studies investigating high-velocity manipulation techniques.
 
Pertinent Results:
  • the literature search yielded 15 studies that met inclusion criteria
  • the overall quality of the studies was consistently high (no studies meeting inclusion criteria were excluded due to methodological issues)
  • there were consistent results suggesting that CJM is associated with hypoalgesia, sympathetic nervous system excitement (skin conductance, blood pressure, heart rate and respiratory rate changes), and perhaps changes in motor function
  • all of the above suggest a role of the CNS in co-ordinating a response to manual therapy treatments
Outcomes for three different parameters could be appropriately assessed:

Pain Related Measures

  • various outcomes have been studied including Pain Pressure Threshold (PPT), Thermal Pain Threshold (TPT), and Visual Analogue Scale (VAS) ratings
  • there is consistent evidence that passive CJM increases PPT locally, and in a more widespread manner, including the upper quarter on the side of treatment
  • unlike PPT, no consistent effect on TPT has been noted in three separate studies
  • there is evidence for improvement in VAS at rest, and 24 hours after spinal manual therapy

Sympathetic Nervous System Indicators
  • there is high quality evidence that CJM increases skin conductance in a widespread manner in both upper limbs – this effect appears to last for several minutes
  • two studies have demonstrated that heart rate, respiratory rate, and diastolic blood pressure increase after CJM1,2
  • there is conflicting evidence on the effect of CJM on skin temperature

Motor Function Measures
  • there is some evidence for CJM increasing pain-free grip strength
  • there is conflicting evidence around the effect of CJM on deep neck flexor activity
  • existing evidence suggests that in healthy people, CJM has little effect on motor function
  • in patients with existing impairments, there may be a role to play for CJM but data to date is insufficient to make recommendations

Conclusions and Practical Application:
Drawing conclusions for practice, based on this literature review, may be premature. That being said, this review of passive cervical joint mobilization has two main findings. Overall, there is enough evidence to suggest that CJM can produce changes that are thought to be indicators of sympathetic nervous system function, and that these changes can extend beyond the treated area. Further, there appears to be concurrent activation of pain modulation systems, suggesting that higher brain function is involved in integrating these responses. This includes mechanical, but not thermal hypoalgesia.

Although this review did not include literature on high velocity manipulation techniques, it is important for all chiropractors to be aware of the potential benefits of CJM, as it represents a viable treatment alternative to high velocity manipulation.

Study Methods:
The authors conducted a comprehensive literature search (search strategy borrowed from the Cochrane Collaboration) of relevant databases up to the end of 2007.Studies were included only if they met the following criteria:

  • randomized controlled trial design on subjects > 18 years of age
  • investigated the immediate effect of passive accessory cervical joint mobilization in healthy humans or those with neck or upper limb pain

Trials on animals were excluded, as well as those investigating high velocity manipulation techniques, or mobilization to any other part of the spine except the neck.

Methodological quality was assessed using guidelines outlined by the Cochrane Collaboration Back Review Group.

Study Strengths/Weaknesses:
One of the main drawbacks in this body of literature is that its has been conducted primarily by the same group of researchers.  This could contribute to publication bias leading to an inflation of the agreement between studies.

Regarding this review in particular, the reader must remember that it did not include any literature on high velocity manipulation techniques. •

References:
  1. McGuiness J, Vicenzino B, Wright A.  Influence of a cervical mobilization on respiratory and cardiovascular function. Manual Therapy 1997; 2(4): 216-220.
  2. Vicenzino B, Cartwright T, Collins D, Wright A. Cardiovascular and respiratory changes produced by lateral glide mobilization of the cervical spine. Manual Therapy 1998; 3(2): 67-71.

Dr. Shawn Thistle is the founder and president of Research Review Service Inc., an online, subscription-based service designed to help busy practitioners to integrate current, relevant scientific evidence into  their practice. Shawn graduated from CMCC and holds an Honours Degree in Kinesiology from McMaster University. He also holds a certificate in Contemporary Medical Acupuncture from McMaster University, and is a Certified Active Release Techniques (ART®) Provider.  For more information about the Research Review Service, visit  www.researchreviewservice.com .

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