Research Review By Dr. Ceara Higgins©

Audio:

Download MP3

Date Posted:

November 2016

Study Title:

Effect of Spinal Manipulation of Upper Cervical Vertebrae on Blood Pressure: Results of a Pilot Sham-Controlled Trial

Authors:

Goertz CM, Salsbury SA, Vining RD, et al.

Author's Affiliations:

Palmer College of Chiropractic, Davenport, IA; Parker University, Dallas, TX; Dartmouth College, Hanover, NH; The Dartmouth Institute for Health Policy and Clinical Practice, Lebanon, NH; Columbia University Medical Center, New York, NY, USA.

Publication Information:

Journal of Manipulative & Physiological Therapeutics 2016; 39(5): 369–380.

Background Information:

Hypertension affects almost 30% of adults in the United States (1). A few small clinical trials and observational studies have shown a blood pressure (BP) lowering effect for select patients when treated with spinal manipulative therapy (SMT) (2). Overall this body of literature is not strong, as many of these studies have a high risk of bias. EDITOR’S NOTE: For example, many proclaimed the results of the study by Bakris et al. (8) were highly suggestive that chiropractic care could reduce blood pressure. The Bakris et al. study, however, used a very specific and uncommon treatment approach (NUCCA – or National Upper Cervical Chiropractic Association), was not high-quality and suffered from a number of irreconcilable biases/flaws. To date, the largest clinical trial on this subject included 140 patients with high-normal (or stage 1) hypertension. That study showed that full-spine diversified SMT along with dietary modification showed no advantage over dietary modification alone (3). The study reviewed here attempted to replicate the Bakris et al. paper by investigating the treatment effect and safety of toggle recoil SMT (more commonly used by chiropractors) to the C1-C2 vertebrae in the management of blood pressure.

Pertinent Results:

Average changes in blood pressure (BP) from baseline to week 6 were greater in the sham treatment group, but the difference was not statistically significant. This indicates that toggle recoil SMT has no benefit for BP in individuals with SBP from 135-159 mm Hg and DBP ranging from 85-99 mg Hg. No serious adverse events were reported. The results of this study do not support conducting subsequent, large clinical trials of toggle recoil SMT for the treatment of high BP.

Clinical Application & Conclusions:

Toggle recoil SMT did not show any benefit for lowering BP when compared with sham manipulation. This study suggests that DCs are able to adopt clinical practices to support the identification, monitoring, and proper referral of patients with high BP. DCs can also make lifestyle recommendations for patients consistent with antihypertensive treatment (7). Currently, SMT cannot be recommended as a treatment for hypertension, particularly as a substitute for other commonly used treatment methods (like medication, diet and exercise modifications etc.).

Study Methods:

Participants with diagnosed prehypertension or stage 1 hypertension were recruited through targeted direct mailers, American Heart Association events, and press releases.

Inclusion Criteria:
  • Systolic blood pressure (SBP) ranging from 135-159 mm Hg or diastolic blood pressure (DBP) ranging from 85-99 mm Hg over 3 qualifying screening visits.
  • Misalignment of either or both of the first 2 cervical spinal segments (C1-C2) as measured using standardized radiography.
  • Age 21-75 years.
Exclusion Criteria:
  • Cardiovascular diseases or surgery in the past 12 months.
  • History of stroke.
  • Body Mass Index (BMI) greater than 39 mg/m2.
  • Pregnancy.
  • Unwillingness to forego other forms of manual therapy during the study.
  • Current use of specific medications (anticoagulations, anabolic steroids, glucocorticoids, corticosteroids, bromocriptine, cyclosporine, tracrolimus, erythropoietin, or MAO inhibitors).
  • Drug or alcohol abuse.
  • Serious concomitant illness.
  • Abnormal laboratory values.
  • Inability to read or speak in English.
  • Unwillingness to receive either treatment.
  • Inability to maintain the study schedule.
  • Cervical spine instability.
  • Spinal or rib fracture.
  • Vertebrobasilar Insufficiency.
  • Arnold Chiari malformation.
  • Active rheumatoid arthropathies.
  • Severe osteoporosis.
  • Cervical spine surgery.
  • Severe atherosclerosis of major blood vessels.
  • Advancing neurologic deficits.
  • Space-occupying lesions within or adjacent to the spinal cord.
Participants were randomly assigned to the Toggle recoil group or the sham manipulation group. All participants underwent 4 baseline evaluations including clinical outcomes, vital signs, health history, medications, urinalysis, an examination with a chiropractor, cervical spine radiographs, blood chemistry, and a series of 3 qualifying blood pressure measurements taken by a registered nurse. The radiographs were assessed by a chiropractic radiologist to rule out contraindications to upper cervical manipulation and by a clinician proficient in toggle recoil to assess for vertebral misalignment at the occiput, C1 and/or C2 (4).

All participants remained on their BP medications and were asked not to make any other lifestyle changes for the length of the study. A registered nurse assessor took BP measurements after treatments 1, 6, and 12 in a quiet room in a different area than the treatment was given. Each BP assessment included 3 or 5 seated BP measurements with the first measurement taken after a 5-minute quiet rest period, with a 5-minute rest period between each measurement. The average BP from three measurements was calculated if they were within 10 mm Hg of each other. If they were not within 10 mm Hg of each other, 2 more measurements were taken, the highest and lowest were eliminated and the average was taken. The SF-36 Health Survey, Perceived Stress Scale, Medication lists, Morisky Medication Adherence Scale, and questionnaires about lifestyle, treatment expectations, and pain in the past 24 hours were taken at baseline and at week 6.

Participants in both groups met with a DC trained in toggle recoil SMT with more than 5 years of clinical practice experience twice a week for 6 weeks. Clinicians performed a thermographic scan, palpatory examination, and leg check to assess the need for cervical spine SMT. They then performed either a toggle recoil adjustment or the sham procedure and then had the participant sit quietly in the treatment room for up to 10 minutes before sending them on to the BP assessment.

Participants in the toggle recoil group rested in a side-lying position with the treatment side in the up position. The clinician lightly contacted the skin over C1-C2 with one pisiform while stabilizing the wrist with the other hand. The thrust was delivered through rapid elbow extension (toggle) followed by immediate retraction (recoil). The thrust depth was approximately 1cm causing the headpiece of the table to drop 1cm. All participants in this group received toggle recoil SMT on their first visit and then in subsequent treatments when clinically indicated.

Participants in the sham treatment group rested in a supine position with their head rotated approximately 45 degrees to the right. The clinician knelt next to the table and cradled the participant’s head with their forearm while stabilizing the head by resting the opposite hand on the mastoid process and temporal bone area. The clinician gradually increased downward pressure on the headpiece until it rapidly dropped 1 cm. No thrust was delivered. Participants in this group received the sham procedure on their first visit and then based on a computerized random assignment for between 4 and 8 visits.

All participants, with the exception of the treating clinicians, were blinded to group allocations and clinicians and study coordinators were blinded to BP and clinical outcomes. Nurse assessors were blinded to non-BP clinical outcomes.

Study Strengths / Weaknesses:

Strengths:
  • The sham procedure used was developed for cervical SMT studies (5) and validated in neck pain trials (6).
  • The participants were drawn from a self-referred community-based pool making the results more widely applicable.
  • The use of multiple experienced DCs more accurately reflects clinical practice.
  • An established BP measurement protocol was followed and a rigorous and ongoing quality control process was used throughout the trial.
Weaknesses:
  • More participants from the SMT group were receiving multiple classes of antihypertensive medications, which may indicate that they had more refractory hypertension that was less likely to respond to the study treatments.
  • The sham procedure followed was developed for neck pain rather than BP studies, and while there was no thrust, the drop mechanism was activated which may have resulted in some force being applied to the cervical vertebrae (as we have discussed many times, finding an adequate sham procedure for spinal manipulation is challenging!).

Additional References:

  1. Cutler JA, Sorlie PD, Wolz M, et al. Trends in hypertension prevalence, awareness, treatment, and control rates in United States adults between 1988-1994 and 1999-2004. Hypertension 2008; 52: 818-827.
  2. Knutson GA. Significant changes in systolic blood pressure post vectored upper cervical adjustment vs resting control groups: a possible effect of the cervicosympathetic and/or pressor reflex. J Manipulative Physiol Ther 2001; 24: 101-109.
  3. Goertz CH, Grimm RH, Svendsen K, et al. Treatment of Hypertension with Alternative Therapies (THAT) study: a randomized clinical trial. J Hypertens 2002; 20: 2063-2068.
  4. Strazewski J. The essentials of toggle recoil; 2008.
  5. Vernon H, MacAdam K, Marshall V, et al. Validation of a sham manipulative procedure for the cervical spine for use in clinical trials. J Manipulative Physiol Ther 2005; 28: 662-666.
  6. Vernon HT, Triano JJ, Ross JK, et al. Validation of a novel sham cervical manipulation procedure. Spine J 2012; 12: 1021-1028.
  7. Hawk C, Schneider M, Evans MW, et al. Consensus process to develop a best-practice document on the role of chiropractic care in health promotion, disease prevention, and wellness. J Manipulative Physiol Ther 2012; 35: 556-567.
  8. Bakris G, Dickholtz M, Meyer PM et al. Atlas vertebra realignment and achievement of arterial pressure goal in hypertensive patients: a pilot study. J Human Hypertens 2007; 21: 347–352.