Research Review by Dr. Shawn Thistle©

Date:

Oct. 2006

Study Title:

Immediate effects on neck pain and active range of motion after a single cervical high-velocity low-amplitude manipulation in subjects presenting with mechanical neck pain: A randomized controlled trial

Authors:

Martinez-Segura R et al.

Publication Information:

Journal of Manipulative and Physiological Therapeutics 2006; 29: 511-517.

Summary:

Neck pain is a common affliction, with a lifetime incidence between 45-55%. Similar to the lumbar spine, there are many potential pain-generating structures in the cervical spine. Mechanical dysfunction is common in the neck, and can be related to many types of headache complaints, thoracic pain, and functional shoulder problems.

Spinal manipulation is a common method used to treat mechanical neck dysfunction. Clinically, we have all seen immediate effects of manipulation reducing pain (or pressure-pain threshold) and ROM. The literature to date is relatively sparse, but seems to support the idea that manipulation can (at least transiently) increase ROM and reduce pain in the cervical spine.

Debate is continuous however, on whether manipulation is superior to mobilization, and whether any advantage justifies the proposed increase in risk.

It has been a number of years since a study was performed investigating immediate results of high-velocity low -amplitude (HVLA) SMT for the cervical spine (I believe Pikula 1999 was the last one).

This study from Spain is simple in its design, has a relatively large sample size for this type of study, and is well controlled. As with most studies in this area, patient and therapist blinding is next to impossible.

The aim of this study is evident in the title. Seventy patients (25 males, 45 females aged 25-55 [average 37]) with mechanical neck pain were randomized to the experimental group - which received one HVLA thrust to a dysfunctional segment between C3-C5, or a control group - which received a single manual mobilization procedure.

Patients were included if they satisfied the following criteria…
  1. complaint of mechanical neck pain for at least one month
  2. clinical presentation of C3-C5 joint dysfunction diagnoses with a lateral glide test (essentially a supine joint challenge)
…and excluded if:
  1. SMT was contraindicated
  2. previous diagnosis of fibromyalgia
  3. previous history of whiplash injury or cervical surgery
  4. radiculopathy or myelopathy
  5. underwent SMT treatment within a month of the study
  6. exhibit a positive extension-rotation test (Houle's/George's)
All patients over the age of thirty had plain film radiographs taken of their neck to rule out the presence of excessive degenerative change.

Dysfunctional segments were identified in both groups utilizing a "lateral glide" test - described as a patient-supine joint challenge using the index finger of the examiner's hand. The HVLA manipulation described would be familiar to chiropractors as a routine cervical manipulation utilizing lateral flexion and contralateral rotation. An audible cavitation was noted with all manipulations in this study. The mobilization procedure used in the control group was a standard supine lateral flexion mobilization - held for 30 seconds with no additional thrust.

It is important to note that in BOTH GROUPS, the side of treatment was randomized with no regard for palpatory findings.

Active ROM was measured with a cervical goniometer, a reliable measurement tool which has been shown to correlate well with radiographic measurements of cervical flexion and extension. Pain was measured pre/post intervention with a visual analogue scale.

Pertinent Results:

  • there were no significant differences between the experimental and control groups in terms of age, pain level, and ROM
  • in the HVLA SMT group - significant improvements in both pain and ROM were noted post-treatment
  • the control group also improved in pain and ROM, but to a lesser degree, and interestingly not in cervical rotation (the SMT group did increase rotation)
  • remember, both groups received the intervention on a randomized side, which didn't necessarily correlate with their symptomatic side
  • males and females improved equally in both groups
  • a negative correlated was noted between ROM and neck pain - that is, with increased ROM, pain decreased

Conclusions & Practical Application:

This study demonstrated that a single manipulation was more effective for reducing pain and increasing active ROM in mechanical neck pain patients. It is important to remember that the mobilization group also improved, but only small to moderate effect sizes were seen compared to the large effects in the SMT group.

I think a very interesting finding in this study is the improvement in both groups despite randomizing the side of treatment.

This has a couple of implications. First, SMT may have a non-specific effect that can affect the biomechanics or neurology of the neck regardless of side of application. Also, it may indicate that the therapists in this study were unable to be side-specific with the intervention - that is, the effect of the manipulation may not occur directly at the level it is applied to (as we all know, published literature already suggests that manipulation is relatively non-accurate in the lumbar and thoracic spines).

These results are in agreement with previous studies, and strengthen the existing evidence supporting the immediate effects of cervical SMT on pain and ROM. Although this study does not clarify long-term effects of SMT, most patients with neck pain will appreciate the immediate effects. As always, proper rehabilitation and active care should be employed to facilitate longer-term effects. More studies in this area are certainly required.

The mechanism by which SMT exerts its effect is still being investigated. Popular theories include stimulation of mechanoreceptors in the facet capsules, reflex inhibition of overactive cervical musculature, and "resetting" of muscle spindle activity. A difficult topic to study to say the least, the answer likely lies in a combination of many factors.