Research Review By Dr. Michael Haneline ©

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Date Posted:

September 2012

Study Title:

Predictors of outcome in neck pain patients undergoing chiropractic care: Comparison of acute and chronic patients


Peterson C, Bolton J, Humphreys K

Author's Affiliations:

University of Zürich and Orthopaedic University Hospital Balgrist, Zürich, Switzerland.

Publication Information:

Chiropractic & Manual Therapies 2012; 20:27.

Background Information:

Neck pain is the second most common complaint among chiropractic patients following low back pain, and like low back pain, a precise diagnosis is often elusive. Consequently, most patients are labeled as having non-specific or mechanical neck pain.

The research evidence in support of spinal manipulative therapy (SMT) or mobilization for neck pain is not as strong as it is for the treatment of low back pain. Also, the evidence has shown that SMT is more effective in the treatment of neck pain when combined with exercise.

Cervical SMT is considered a relatively safe treatment and recent research points to no increased risk of vertebral artery injury for neck pain patients that receive chiropractic manipulation versus those who seek care from physicians who do not utilize SMT (1-3).

Predictors for a positive response to chiropractic SMT in neck pain patients has been explored in a few studies, which have identified the following fairly robust predictors of an immediate positive response:
  1. Duration of symptoms,
  2. neck stiffness, and
  3. number of previous episodes of neck pain.
The purpose of this study was to further investigate the predictors of positive outcomes of chiropractic SMT in neck pain patients, and to determine whether these predictors are different between acute and chronic patients.

Pertinent Results:

Eighty-one (31%) of the 260 members of the Association of Swiss Chiropractors contributed 657 neck pain patients for this study, with 274 of them being acute, 124 subacute and 255 chronic. The 124 subacute patients were not included in the analysis because the authors wanted to be able to show a clear distinction between the acute and chronic patients. Also, 4 patients were deleted from the database because they could not be reached for follow-up. Thus, baseline data for 529 acute and chronic neck pain patients were included.

General Outcomes

The patients reported improvements as follows:
  • 77.8% of acute and 37.6% of chronic reported that they were ‘significantly improved’ at 1 week;
  • 86.6% of acute and 62.4% of chronic reported that they were ‘improved’ at 1 month; and
  • 84.3% of acute and 70.1% of chronic reported that they were ‘improved’ at 3 months.
Less than 4% of acute patients and less than 9% of chronic patients reported ‘worsening’ of their condition at any time point.

Prognostic Variables

At 1 week, univariate logistic regression analyses showed that no prognostic factors were associated with improvement for the acute patients and only 3 were predictors of improvement for the chronic patients. As a result, no multivariate analysis was conducted because of a lack of strong association between baseline variables and improvement at 1 week.

At 1 month, the univariate logistic regression analysis pointed to 6 variables as being associated with improvement for the acute patients and 2 variables for the chronic patients. In the multivariate analysis, 4 of the 6 variables for the acute patients were found to be independently associated with outcome improvement, including:
  • Patient Global Impression of Change (PGIC) scale at 1 week (these patients were almost 3 times more likely to report improvement),
  • change from baseline to 1 week Numeric Rating Scale (NRS) neck pain,
  • change from baseline to 1 week Bournemouth Questionnaire (BQ) for neck pain subscale, and
  • change from baseline to 1 week BQ depression subscale.
The PGIC at 1 week was the only factor in chronic patients that was predictive of improvement at 1 month. Patients who showed improvement on the PGIC at 1 week were about 4 times more likely to be improved at 1 month.

At 3 months, 16 variables were predictors of improvement for acute patients and 8 variables were predictors of improvement for chronic patients. However, only 2 variables in the acute patients and 1 variable in the chronic patients remained as independent predictors in the multivariate model, including:
  • The PGIC score at 1 week and change in the baseline to 1 month BQN score in acute patients, as well as
  • the PGIC at 1 month in the chronic patients.

Clinical Application & Conclusions:

The strongest predictor of improvement for both acute and chronic neck pain patients was their prior improvement. Acute patients were about 3 times more likely to be improved at 3 months if they reported being improved at 1 week, and chronic patients were more than 6 times as likely to report improvement at 3 months if they were improved at 1 month.

Neck pain patients who had concomitant cervical radiculopathy showed improvements in their neck pain similar to the patients who did not have these additional signs or symptoms. Additional leg pain has been reported to be a negative predictor of improvement in low back pain patients undergoing chiropractic treatment, but the corollary was not apparent in this study. Patients who reported associated dizziness also improved similar to the other patients in this study.

Previous studies (1, 2, 4) have indicated that the number of previous episodes of neck pain were predictors of outcome. However, this study did not find a connection between the number of previous episodes and the patients’ likelihood for improvement.

Practitioners who observe improvement in neck pain after 1 week of care in acute patients and after 1 month in chronic patients could reasonably tell to such a patient that this is a positive sign that they are more likely to experience additional improvement.

Study Methods:

This was a prospective cohort study in which neck pain patients who were receiving chiropractic care were followed for 3 months.

Consecutively presenting new patients with neck pain were recruited from multiple chiropractic practices in Switzerland. Patients had to be over the age of 18 and have neck pain of any duration in order to participate.

Patients were excluded if they had undergone chiropractic or manual therapy in the prior 3 months or if they had cervical spine pathologies that were considered to be contraindications to chiropractic SMT.

Participating chiropractors were recruited from the membership list of the Swiss Chiropractic Association which is comprised of 260 chiropractors. The members were notified about and asked to participate in this study by e-mail. They were instructed about the study’s protocol by email, as well as via verbal instructions that were given at the Association’s mandatory annual postgraduate convention where workshops were conducted by one of the authors on the use of outcome measures in practice.

The participating chiropractors were asked to not change their treatment methods, since the purpose of this study was to evaluate outcomes as would be found in routine chiropractic practice.

The primary outcome measures used in this study were:
  • the numerical rating scale (NRS) for neck pain,
  • the NRS for arm pain,
  • the Bournemouth Questionnaire for neck (BQN) disability questionnaire, and
  • the Patient Global Impression of Change (PGIC) scale.
The chiropractors also provided demographic information on each patient’s age, sex, marital status, paid employment, whether or not the pain was caused by trauma, the working diagnosis, whether or not the patient smoked, current pain medication use, duration of current complaint, number of previous episodes, whether or not cervical radiculopathy was present, whether or not the patient complained of dizziness and general health status.

Patients were classified as ‘acute’ if they had symptoms for less than 4 weeks and as ‘chronic’ if they had their symptoms for longer than 12 weeks. Sub-acute patients were not included in this study because the researchers wanted to be able to show a clear distinction between acute and chronic cases when analyzing the data.

The treating chiropractors collected the initial data in their offices, whereas follow-up data were collected via telephone interviews by trained research assistants. The follow-up interviews consisted of the NRS, PGIC scale, and the BQN questionnaire and occurred at 1 week, as well as at 1 and 3 months. The telephone interviews were conducted whether or not the patient was still receiving chiropractic treatment.

The statistical analyses compared baseline factors between acute and chronic patients using chi square or t-testing as appropriate. Univariate and multivariate regression analyses were carried out to determine statistically significant independent predictors of improvement.

Study Strengths/Weaknesses:

This was a well-conducted practice-based study that provides additional information on which factors lead to better outcomes in neck pain patients.

This was an observational study in that the patients were not randomized to groups and a control group was not included. Thus, its conclusions have limited generalizability and its findings will have to be verified by future research.

The study was pragmatic, wherein practicing chiropractors utilized their own particular treatment procedures, even though clinical studies typically incorporate a standardized treatment protocol. Thus, the patients experienced different treatment modalities from the various practitioners and the number of visits was not kept track of. The vast majority of Swiss chiropractors use Diversified technique, so it was assumed to be the primary chiropractic manipulation technique that was used.

Not including a control group prevents one from attributing the improvement that was observed to treatment. This is especially true for the acute patients, since acute neck pain often resolves on its own due to natural history. The fact that the chronic neck pain patients improved, however, was not likely attributable to this phenomenon.

Additional References:

  1. Rubinstein SM, Knol DL, Lebouef-Yde C, de Koekkoek TE, Pfeifle CE, van Tulder MW: Predictors of a favorable outcome in patients treated by chiropractors for neck pain. Spine 2008, 33:1451–1458.
  2. Thiel HW, Bolton JE: Predictors for immediate and global responses to chiropractic manipulation of the cervical spine. J Manipulative Physiol Ther 2008, 31:172–183.
  3. Cassidy JD, Boyle E, Côté P et al. Risk of vertebrobasilar stroke and chiropractic care: results of a population-based case–control and case-crossover study. Spine 2008, 33: S176–183.
  4. Tseng YL, Wang WTJ, Chen WY, Hou TJ, Chen TC, Lieu FK: Predictors for the immediate responders to cervical manipulation in patients with neck pain. Manual Therapy 2006, 11:306–315.
  5. Kongsted A, Leboeuf-Yde C. The Nordic back pain subpopulation program—individual patterns of low back pain established by means of text messaging: a longitudinal pilot study. Chiropr Osteopat 2009;17:11.
  6. Kongsted A, Leboeuf-Yde C. The Nordic back pain subpopulation program: course patterns established through weekly follow-ups in patients treated for low back pain. Chiropr Osteopat 2010;18:2.
  7. Axén I, Rosenbaum A, Röbech R, Wren T, Leboeuf-Yde C. Can patient reactions to the first chiropractic treatment predict early favorable treatment outcome in persistent low back pain? J Manipulative Physiol Ther 2002;25:450-4.