doi:10.1016/j.jmpt.2007.04.013

ORIGINAL ARTICLES

THE BENEFITS OUTWEIGH THE RISKS FOR PATIENTS

UNDERGOING CHIROPRACTIC CARE FOR NECK PAIN:

APROSPECTIVE, MULTICENTER, COHORT STUDY

Sidney M. Rubinstein, DC, MSc,

Charlotte Leboeuf-Yde, DC, MPH, PhD,

Dirk L. Knol, PhD,

Tammy E. de Koekkoek, DC,

Charles E. Pfeifle, DC,

and Maurits W. van Tulder, PhD

f,g

ABSTRACT

Objective:

This study describes both positive clinical outcomes and adverse events in patients treated for

neck pain by a chiropractor.

Methods:

This study was a prospective, multicenter, observational cohort study. Patients with neck pain of any

duration who fulfilled the inclusion criteria were recruited in a practice-based study. Data were collected on the

patients and from the chiropractors at baseline, the first 3 visits, and at 3 and 12 months. Clinical outcome

measures included (1) neck pain in the 24 hours preceding the visit, (2) neck disability, (3) treatment satisfaction,

(4) global assessment, and (5) adverse events. Recovery was defined as bcompletely improvedQ or bmuch betterQ

using the global assessment scale. An adverse event was defined as either a new related complaint or a worsening

of the presenting or existing complaint by N30% based upon an 11-point numerical rating scale.

Results:

In all, 79 chiropractors participated, recruiting 529 subjects, representing 4891 treatment

consultations. Follow-up was possible for 90% and 92%, respectively, at 3 and 12 months. Most patients had

chronic, recurrent complaints; mild to moderate disability of the neck; and a mild amount of pain at baseline;

and two thirds had sought previous care for the presenting complaint in the preceding 6 months. Adverse

events following any of the first 3 treatments were reported by 56%, and 13% of the study population reported

these events to be severe in intensity. The most common adverse events affected the musculoskeletal system or

were pain related, whereas symptoms such as tiredness, dizziness, nausea, or ringing in the ears were

uncommon (b8%). Only 5 subjects (1%) reported to be much worse at 12 months. No serious adverse events

were recorded during the study peri od. Of the patients who returned for a fourth visit, approximately half

reported to be recovered, whereas approximately two thirds of the cohort were recovered at 3 and 12 months.

Conclusion:

Adverse events may be common, but are rarely severe in intensity. Most of the patients report

recovery, particularly in the long term. Therefore, the benefits of chiropractic care for neck pain seem to

outweigh the potential risks. (J Manipulative Physiol Ther 2007;30:408Q418)

Key Indexing Terms:

Neck pain; Chiropractic; Manipulation, Spinal; Adverse effects; Cervical vertebrae

408

Research Fellow, Institute for Research in Extramural Medicine

(EMGO-Institute), VU University Medical Center, 1081 BT

Amsterdam, the Netherlands.

Research Professor, The Back Research Center, Part of Clinical

Locomotion Science, University of Southern Denmark, DK-5750

Ringe, Denmark.

Statistician, Institute for Research in Extramural Medicine

(EMGO-Institute), VU University Medical Center, 1081 BT

Amsterdam, the Netherlands.

Private practice, Soest, the Netherlands.

Private practice, Oosterhout, the Netherlands.

Professor of Health Technology Assessment, Institute for

Research in Extramural Medicine (EMGO-Institute), VU Univer-

sity Medical Center, Amsterdam, the Netherlands.

Professor, Department of Health Economics and Health

Technology Assessment, Institute of Health Sciences, Faculty of

Earth and Life Sciences, Amsterdam, the Netherlands.

Submit requests for reprints to: Sidney Rubinstein, DC,

MSc, Resear ch Fel low, Institute for Research in Extramural

Medicine (EMGO-Institute), VU University Medical Center,

Van der Boechorststraat 7, 1081 BT Amsterdam, the Netherlands

(e-mail: [email protected]).

Paper submitted January 10, 2007; in revised from April 11,

2007; accepted 15 April 2007.

0161-4754/$32.00

doi:10.1016/j.jmpt.2007.04.013

eck pai n is a common and costly complaint

in Western society.

1,2

Studies of manipulation

for nonspecific neck pain have suggested that

manipulation is an effective therapy, particularly when

combined with exercise.

3,4

However, as with other interven-

tions for the treatment of neck pain, such as nonsteroidal anti-

inflammatory drug use,

5-7

cervical spine manipulation is not

without adverse events. On the one hand, cases of stroke fol-

lowing cervical spine manipulation are rare but well-docu-

mented,

8-10

whereas on the other hand, much less is known

about the much more common adverse, but benign, events.

Previous observational studies have shown that adverse

events, such as increased pain or stiffness and, to a lesser

degree, radiating symptoms and headache, following

manipulative treatment to the neck and/or back are relatively

common, mild in intensity, and self-limiting.

11-15

Only one

previous study has specifically targeted cervical spine

manipulation and examined the relationship of these adverse

events to positive outcome measures. That study concluded

that subjects with adverse events were less satisfied with

care, perceived less improvement in their neck symptoms,

and had more pain and disability at all follow-up measure-

ments.

In contrast, studies of low back pain involving

manipulation have identified certain adverse events as a

positive predictor of outcomes.

16,17

It must be noted here that various terms have been used

in previous literature to describe adverse events following

chiropractic treatments, such as unplea sant reactions, side

effects,oradverse reactions. However, according to

international clinical trial terminology, the established term

for this phenomenon is adverse even ts and is the term that

will be used furt her throughout this article. This has been

further operationally defined in the bMethodsQ section.

The primary objective of this present report, therefore, is

to describe both positive clinical outcomes and adverse

events following the first 3 treatments in a large cohort

presenting with neck pain to 79 chiropractors. A secondary

objective is to describe the sociodemographic and clinical

profile of these subjects.

METHODS

Study Design and Source Population

A prospective, multicenter, practice-based cohort study

was conducted for patients with neck pain. Subjects who

fulfilled the inclusion criteria (defined below) were recruited

by chiropractors in their private clinics throughout the

Netherlands and were followed up after 3 and 12 mont hs.

Each participating chiropract or was asked to recruit 10

consecutive new patients.

Recruitment of Chiropractors and Subjects

Chiropractor Inclusion Criteria and Recruitment.

All 189 chiro-

practors who were members in good standing of the

Netherlands Chiropractors’ Association were invited to

participate. Participants were required to carry out the

examination and treatment personally. Chiropractors under-

going their internship were excluded. Recruitment was

pursued by means of a flyer mailed to all members of the

Netherlands Chiropractors’ Association, by personal invita-

tion, and through a presentation at a national chiropractic

association meeting.

Patient Inclusion and Exclusion Criteria. All new patients between

the ages of 18 and 65 years with neck pain of any duration

who had not undergone chiropractic care or manual therapy

in the prior 3 months were eligible for recruitm ent. In this

report, neck pain includes those with neck and neck-related

pain, that is, cervicothoracic and/or periscapular pain.

Although inclusion was based upon a primary complaint of

neck pain, pati ents who also had pain in other areas were not

excluded. Patients were required to have a basic under-

standing of the Dutch language and be able to independently

complete th e series of questionnaires. Subjects were

recruited between September 1, 2004, and April 15, 2005.

Subjects were excluded if they had a red flag (eg,

suspected infection, fracture, tumor, metastasis, or intra-

venous drug use) or any other condition thought to be a

contraindication for cervical spine manipulation (eg, luxa-

tion or instability of the vertebral articulations). This was

left to the judgment of the chiropractor.

In order to check for possible recruitment bias during the

inclusion phase, a sample was taken in 5 practices in which

the number of subjects recruited to the study was cross-

checked with the actual number of eligible patients during

the recruitment period. The total number of new patients

seen in these practices during this period was also recorded.

Selection of these practices was based upon geographic

proximity to the research center.

Study Protocol. Prior to the start of data collection, a number

of training sessions were conducted with the chiropractors

throughout the countr y in order to present the study

methods, increase consistency among chiropractors in

applying these, and limit problems associated with patient

recruitment. Both the chiropractor and his/her assistant(s)

were asked to attend.

Data Collection and Clinical Outcome Variables

Procedure.

Data were collected from patients within

individual practices by means of a sel f-administered

questionnaire at baseline and prior to treatment at the

second and fourth visits. In order to increase the response

rate, patients were also provided with an envelope in which

to place their co mpleted questionnaires. All forms were

precoded in order to ensure anonymity. Additional follow-

ups were conducted from a central data collection center at

the universit y at 3 and 12 months using postal question-

naires. If the participant failed to respond to a written

reminder at 12 months, a shortened structure d telephone

interview was conducted. This interview consisted of 5

questions regarding pain, perceived recover y, and treatment

Rubinstein et alJournal of Manipulativ e and Physiological Therapeutics

Adverse Events With Chiropractic CareVolume 30, Number 6

409

satisfaction. The clinical outcome measures used throughout

the study were pain and disability,

18-20

perceived recov-

ery,

21-23

treatment satisfaction,

15,24

and adverse events (or

concomitant symptoms) following treatment.

Chiropractor

Chiropractors completed a questionnaire administered

once at the beginning of the study relating to basic

sociodemographic information concerning himself/herself

and treatment practices (eg, years of experience, types of

techniques and/or therapies commonly used).

Patient

Pain, Disability, and Recovery.

At all points of data collection,

an 11-point numerical rating scale (NRS) was used to assess

pain in the 24 hours preceding the visit. Disability was also

measured at these times using the Neck Disability Index

(NDI); however, disability was not record ed at the second

visit.

25,26

The NDI has been demon strated to be a sensitive

and valid instrument.

Perceived recovery was meas ured at

all follow-up times and scored using a 6-point Likert scale,

as follows: (1) bcompletely improved,Q (2) b much better,Q

(3) bsomewhat better,Q (4) bunchanged,Q (5) bsomewhat

worse,Q and (6) bmuch worse.Q Those subjects who were

either bcompletely improvedQ or bmuch betterQ were

considered to be brecovered.Q

Treatment Satisfaction. Satisfaction wa s measured at the

fourth visit and at 3 and 12 months using a 10-item

instrument

that was used in a prior study of adverse events

to cervical spine manipulation.

15,24

Two other questions

were also posed at these same time intervals: (1) bHow

satisfied are you with the treatment by your chiropractor?Q

(11-point NRS, ranging from bvery dissatisfiedQ to bvery

satisfiedQ) and (2) bWould you visit a chiropractor again

with this or a similar complaint?Q (yes/no).

Adverse Events. The following symptoms were assessed at

every time interval, except items 1 and 2, which were not

measured at baseline because they relate only to the

previously administered treatment: (1) increased pain/stiff-

ness at the treated area, (2) increased pain/stiffness in another

treatment-related area, (3) headache, (4) tire dness/fatigue, (5)

radiating pain in the arm or hand, (6) dizziness or light-

headedness, (7) nausea, (8) ringing in the ears, (9) confusion

or disorientation, (10) depres sion or fear, and (11) any other

not specified reaction. Adverse events were measured using a

similar questionnaire as in the Scandinavian studi es.

13,14,29

Intensity of adverse events was also graded using an 11-point

NRS. At the second visit, patients were queried about any

potential events following the first visit. In the data analysis,

an adverse event reported at the second visit was defined as

either (1) a new related complaint that was not present at

baseline or (2) a worsening of the presenting complaint or an

existing complaint by N30% compared with baseline. Thirty

percent was chosen as a cutoff because it has been

demonstrated that this represents a minimally clinically

important difference on an 11-point NRS.

At the fourth

visit, patients were queried about any events following the

second or third visit. A similar definition was used to define

adverse events at the fourth visit as the second visit; however,

at the fourth visi t, the comparison was made with the second

visit, not baseline. Intense adverse events were defined as any

adverse event fulfilling our definition of an adverse event and

that also scored z8 in intensity on the 11-point NRS. This

term must not be confused with serious adverse events, which

refer to events resulting in death, life-threatening situations,

the need for admittance to a hospital, or temporary or

permanent disability.

The following were also assessed at baseline: age, sex,

sociodemographics, and the nature and severity of the

presenting complaint. Patients were also queried about

previous chiropractic, manual therapy, and medical care

for the same or similar complaints. Fear of, or apprehension

concerning, the treatment and treatment expectation were

also assessed using 11-point NRS scales. Health status was

measured on a 100-point vertical scale, ranging from worst

(0) to best (100) possible health; and fear of movement or

reinjury was measured through the 17-item Tampa Scale for

Kinesiophobia.

Intervention

The treatment was left to the discretion of the chiro-

practor. The type of manipulative and/or mobilization

technique used was recorded on standardized forms

immediately follow ing the first and third treatment, as well

as the use of any adjunct therapy, the number of adjustments

given, the area that was treated, whether the chiropractor

considered that rotation was used, and whether multiple

manipulative attempts were directed at a single segment.

Approval

The study was approved by the Institutional Review

Board of the Vrije University Medical Centre, Amsterdam,

the Netherlands. Informed consent was not required because

this is an observational study.

Statistical Methods

Mean values and standard deviation (SD) were calculated

for continuous variables. These variables were also exam-

ined for skewness and kurtosis; and where relevant, medians

and interquartile ranges (IQRs) were presented instead of the

mean. Frequency distributions were calculated for catego-

rical variables. For reporting of many of the baseline

variables, there were few missing values (b5% of cohort);

therefore, in many cases, only a percentage is reported.

Response-function imputation was used for missing data for

the disability questionnaire, the Tampa Scale for Kinesi-

ophobia, and the patient satisfaction scale when V50% of

the data was missing, although this was only necessary for a

small percentage of patients; and in most cases, V10% of the

data was missing.

Imputation was performed separately

410

Journal of Manipulative and Physiological TherapeuticsRubinstein et al

July/August 2007Adverse Events With Chiropractic Care

for each of the aforementioned questionnaires and based the

correlation between each variable with a missing value with

the other responses in those questionnaires. All data were

analyzed in SPSS version 12.0 (SPSS Inc, Chicago, Ill).

Accuracy of the entered data was checked using a random

sample of 25 patients. The baseline data entry form was

used, which contained 94 variables. Two data entry mistakes

were discovered, resulting in an error of 0.1%; and it was

concluded that the data had been accurately enter ed.

RESULTS

Participating Chiropractors

In total, 79 chiropractors (79 of 190; 42% of the available

population) participated in the study. Reasons among the

chiropractors for not participating included residing outside

the country (n = 2), pregnancy leave (n = 3), retiring (n = 3),

not interested (n = 4), and did not regularly perform

manipulative techniques (n = 2). One chiropract or was

exclude d b e cau se of pend in g statutory problem s. The

remaining 96 did not respond to various requests. Three

chiropractors who agreed to participate did not recruit any

patients. Of those who did recruit subjects, each chiropractor

recruited 7.6 F 2.9 (mean F SD) patients.

Study Population

During the 7-month recruitment period, 579 patients were

recruited. Fifty subjects were excluded for various reasons

(Fig 1), resul ting in a cohort of 529 subjects. Ninety-six

percent and 87% of the study population returned for a second

and fourth visit, respectively, whereas 90% and 92%

responded to the long-term follow-up at 3 and 12 months,

respectively. Twelve percent of the 92% that responded at

Fig 1. Flowchart demonstrating recruitment and follow-up

throughout the study period.

Table 1. Sociodemographic and clinical baseline characteristics

for patients in the Netherlands chiropractic neck pain cohort study

(n = 529)

Sociodemographic variables Percentage (%)

Sex, female 69.0

Age, y (mean, SD) 41.2 (11.5)

Highest level of education achieved

Elementary school 4.8

High school 31.4

Technical school 55.0

University or postgraduate education 8.8

Employment status

Full-time (N32 h/wk) 44.2

Part-time 33.3

Not working (including unemployed, hous e-

wives)

12.2

Sick leave or workers compensation 7.2

Retired 3.1

Clinical baseline variables

Duration of the presenting complaint

1d-b4 wk 8.4

4-12 wk 16.8

N12 wk-1 y 23.2

N1 y 51.6

Self-assessed health trend regarding the presenting complaint

Getting better 4.6

Getting worse 21.2

Staying the same 26.1

Rather varied 48.1

Previous episode with this complaint (% yes) 71.6

Radiating pain in an upper extremity (% yes) 52.0

Paresthesia and/or bdeadQ feeling in an upper

extremity (% yes)

39.3

Morning pain related to the chief complaint

(% yes)

70.1

Night pain related to the chief complaint (% yes) 36.9

Presently involved in judicial proceedings in

regard

to this complaint (% yes)

2.5

Medication use

None 65.8

Over-the-counter pain medication 5.5

Prescription pain medication 6.2

Other prescription (nonpain) medication 21.9

Bruxism (% yes) 24.2

Who have you seen for this complaint? (% yes)

General practitioner 66.9

Specialist 18.9

Chiropractor or manual therapist 36.7

Physical therapist 25.5

Cesar/Mensendieck therapy

(ie, postural and exercise therapy)

3.4

Acupuncturist 2.6

Other doctor or therapist than those mentioned

above

10.4

Multiple answers possible.

Rubinstein et alJournal of Manipulativ e and Physiological Therapeutics

Adverse Events With Chiropractic CareVolume 30, Number 6

411

12 months were evaluated using the shortened telephone

assessment instead of completing the written questionnaire.

Potential response bias was assessed in order to compare

responders to nonresponders. However, an analysis at 3 and

12 months showed no obvious differences between these

2 groups in the baseline variables (available upon request). A

total of 4891 treatment consultations were registered during

the 12-month period, and chiropractors delivered 9.3 F 5.3

(mean F SD; median, 8.0; range, 0-38) treatments per patient.

Almost all patients (90%) returned for a second visit within 8

days of the first visit, and 90% returned for a fourth visit

within 6 weeks of the first visit.

Baseline Characteristics for the Chiropractors

The participating chiropractors were 37.6 F 9.4 years old

(mean F SD; range, 22-74) and had 10.2 F 6.3 years of

experience (mean F SD; median, 9.5; range, 1-28 years).

Most were male (65%), had received their ch iropractic

education at a European institution (66%), worked full-time

(96%), and regularly used the following techniques (in

hierarchal order, from more to less common): diversified

manipulation (a high-velocity, low-amplitude manipulative

technique commonly used by chiropractors), Activator (a

hand-held, spring-loaded instrument designed to deliver a

measured force), soft-tissue massage or trigger point

therapy, and/or mobilization.

Baseline Characteristics for the Patients

Sociodemographic and clinical baseline characteristics are

presented in Table 1. The recruited subjects were predom-

inantly female, middle-aged, had a high school or technical

school education, and were employed. Most of the patients

had a chronic complaint that was intermittent in nature, had

morning pain, had at least one prior episode related to the

complaint, and were not currently using any medication. Two

thirds had seen a general practitioner for the presenting

complaint, and approximately one fifth had seen a specialist

in the 6 months prior to a visit to the chiropractor.

Approximately one third had undergone prior chiropractic

care or manual therapy ever. The subjects had little fear of, or

apprehension concerning, the treatment (median, 0; IQR, 0-

2), expected the treatment to be effective (mean, 7.0; SD, 2.0),

and were generally healthy (mean, 67.8; SD, 17.2), whereas

most (87%) had mild to moderate disability. Only 7% had a

high level of kinesiophobia (mean, 34.1; SD 6.2).

Concomitant Symptoms at All Measurement Periods

At baseline, 94% of the patients had at least one

concomitant symptom other than neck pain; and half of the

cohort had 3 or more other symptoms (Table 2). Twenty-two

percent rated at least one of these symptoms as severe in

intensity (z8 on the 11-point NRS scale). The most common

symptoms were headache, tiredness, dizziness, or radiating

pain, and less frequently, nausea or ringing in the ears. At the

second and fourth visits, only 34% and 22%, respectively, of

the cohort had concomitant symptoms. At 3 and 12 months,

when most patients had likely discontinued care or had been

discharged, the estimated prevalence of these concomitant

symptoms approached the baseline values once again.

Treatment Techniques and Type of Care Delivered

The treat ment techniques and other therapies used at the

first and third visits are presented in Table 3. The principal

techniques used at the first and third visits were diversified,

soft-tissue or trigger point therapy, Activator, and mobi-

lization. Most patients (85%) underwent an upper or lower

cervical spine manipulation at both the first and third visits.

In almost all subjects (97%), a manipulative technique (ie,

diversified, Activator, Gonstead, or toggle-recoil) was used

at any of the first 3 treatments; and occasionally, chiro-

practors used multiple manipulative attempts directed at

the same segment.

Table 2. Concomitant symptoms reported at baseline and throughout the study period

Type of other symptom and

severity of the complaint

Baseline

(n = 529) (%)

2nd visit

(n = 509) (%)

4th visit

(n = 458) (%)

3mo

(n = 476) (%)

12 mo

(n = 485) (%)

Tiredness or fatigue 77.3 22.0 14.0 66.0 66.1

Headache 75.4 26.2 16.0 71.8 71.5

Dizziness or light-headedness 60.0 18.1 10.6 48.9 53.5

Radiating pain 52.0 18.9 14.1 55.7 55.3

Nausea 34.8 11.8 5.7 21.4 21.0

Depression or fear 28.6 4.8 3.1 22.7 22.2

Confusion or disorientation 27.3 6.7 4.8 22.1 19.8

Ringing in the ears 23.0 9.9 7.1 29.8 29.5

Other symptoms – 2.6 4.7 5.8 5.5

Median no. of symptoms

per patient (IQR)

3 (2-5) 0 (0-2) 0 (0-0) 2 (1-5) 2 (0-4)

En dash (–) indicates unrecorded data.

Responses are ordered according to prevalence at baseline from highest to lowest.

412

Journal of Manipulative and Physiological TherapeuticsRubinstein et al

July/August 2007Adverse Events With Chiropractic Care

Clinical Outcome Measures

The clinical outcome measures are presented for all time

intervals in Table 4. Pain and disability of the neck steadily

decreased up to 3 months, but there was no further improve-

ment at 12 months. Approximately one fifth (21%, n = 105 of

509) and one half of the subjects (48%, n = 219 of 458) were

recovered from their presenting complaint at the second and

fourth visit, respectively, whereas approxi mately two thirds

(65%, n = 308 of 476; 64%, n = 310 of 485) were recovered

at 3 and 12 months, respectively. Of those recovered at 3

months, 18% (n = 55 of 308) were no longer recovered at

12 months; and of those not yet recovered at 3 months,

30% (n = 49 of 165) went on to recover at 12 months.

Therefore, although the overall percentage of recovery at 3

and 12 months was approximately the same for the study

population, at 3 months, some sub jects continued to

improve, whereas others that were recovered had recurrent

symptoms. At 3 and 12 months, only 2 and 5 subjects,

respectively, reported to be much worse. Most patients

were moderately to highly satisfied with their chiropractors

and their treatments throughout the study period, and most

(range, 84%-99%) would visit a chiropractor again for this

or any other spinal complaint.

Adverse Events After Treatment

Prevalence of Adverse Events.

Forty-eight percent of those

subjects who returned for a second visit indicated a new,

related complaint or worsening of the presenting or existing

complaint following the first visit (as reported at the second

visit), and 26% of those who retur ned for a fourt h visit

indicated an adverse event following the second or third

visit. In total, 56% of the study population indicated an

adverse event following any of the first 3 treatments. At the

second visit, most of the subjects (90%) indicated that the

event began within 2 days of the treatment. Most (85% and

81% at the second and fourth visits, respectively) perceived

the event to have no to minor influence on their activities of

daily living.

Type, Frequency, and Severity of Adverse Events. In all, 571 and 166

adverse events were registered at the second and fourth

treatments, respectively; and only a relatively small percent-

age of these adverse events were deemed to be severe in

intensity (14% and 15%, respectively) (Table 5). The most

common adverse events reported at the second and fourth

visits were musculoskeletal or pain related (72% and 75% of

all events, respectively). Individual nonmusculoskeletal

adverse events such as tiredness, dizziness, nausea, or ringing

in the ears were relatively uncommon (b 8%), although 19%

of the study population reported at least one nonmusculoske-

letal adverse ev ent at any of the first 3 treatments.

The total number of adverse events recorded by individual

patients at the second and fourth visits are presented in

Table 6. Of those subjects who had an adverse event at the

second or fourth visit, the median number of events per

patient was 2 (IQR, 1-3) and 1 (IQR, 1-1), respectively. In

total, 13% (n = 67 of 529) reported an intense adverse event at

any of the first 3 treatments. Of these, 64% (n = 43 of 67)

reported only one intense event. However, none of the

subjects with an inte nse adverse event were worse or much

worse at the end of the study period. Finally, no serious

adverse events were reported during the study period.

DISCUSSION

In contrast to clinical trials of prescription medication,

researchers in the area of conservative care for muscu-

Table 3. Treatment techniques used, therapies performed, and

other treatment parameters recorded at the first and third

treatments

Techniques, therapies, and

other treatment parameters

1st visit

(n = 529) (%)

3rd visit

(n = 458) (%)

Technique used (% yes)

a,b

Diversified 78.3 76.7

Soft-tissue or Nimmo

(trigger point therapy)

28.9 33.8

Activator 15.1 19.7

Traction 12.3 12.9

Gonstead 11.0 8.7

Mobilization 9.3 12.3

Sacrooccipital technique

or cranial technique

4.7 5.3

Toggle 2.6 2.8

Other therapies used (% yes)

a,b

Exercise advice 35.7 24.8

Heat or ice 17.4 11.5

Other technique or therapy

(eg, acupuncture, homeopathy,

heel lifts, Thompson drop)

17.3 17.6

Dietary advice 5.3 2.1

Total no. of adjustments given in the neck

None 15.2 9.6

1 25.2 20.3

2-3 49.6 60.2

N3 10.0 10.0

Treated area

Upper cervical spine (C0-C2) 49.9 48.8

Mid-lower cervical spine (C3-C7) 53.7 57.3

Upper thoracic spine (T1-4) 53.9 52.4

Mid-lower thoracic spine (T5-T12) 40.1 34.0

Lumbar spine 13.4 16.8

Pelvis/sacrum 23.4 18.9

Rotation was used during the

treatment (% yes)

56.6 58.8

Multiple manipulative attempts were

performed during the treatment at

the same segment (% yes)

16.9 19.5

Responses are ordered according to prevalence at the first visit, from

highest to lowest.

Multiple responses possible.

Rubinstein et alJournal of Manipulativ e and Physiological Therapeutics

Adverse Events With Chiropractic CareVolume 30, Number 6

413

loskeletal complaints have focused their at tention on

treatment effectiveness and, to a much lesser degree, on

adverse events. This study, consisting of patients treated

in a wide variety of chiropractic practices and settings,

describes both positive and negative, and short- and long-

term clinical outcomes for a relatively large study

population with neck pain. Although adverse events have

been described in previous clinical trials of treatment

effectiveness with cervical spine manipulation,

4,34

studies

such as these provide limited information on these types

of events because of their small sample sizes. Earlier

studies on adverse events following spinal manipulation

have focused on describing types and patterns of adverse

events of the entire spine,

12-14,29

but did not describe

positive outcomes. To our knowledge, only one other

study has examined both positive and negative clinical

outcomes in patients with neck pain undergoing chiro-

practic treatments

; howe ver, our study has a larger

sample size. In addition, given the study design chosen, it

was possible to examine a large number of treatments

delivered by a diverse group of chiropractors and was not

specifically aimed at the effect of spina l manipulation

alone. Therefore, these findings might be more general-

izable to clinical practice than those obtained in a single-

center, controlled trial setting.

In short, there are 2 major findings. Firstly, in relation to

brisks,Q despite the fact that more than half of the study

population experienced an adverse event, only 1% (5

subjects) of a cohort who had undergone 4891 treatment

consultations reported to be much worse at the end of the

study period; and there were no serious n eurologic

complications reported within this time frame. Although

Table 4. Clinical outcomes for all measurements at baseline, second visit, fourth visit, 3 months, and 12 months

Clinical outcome

measures

Baseline (n = 529) 2nd visit (n = 509) 4th visit (n = 458) 3 mo (n = 476) 12 mo (n = 485)

n%n %n %n%n%

Neck pain in the 24 h preceding the visit (0-10)

None (0) 28 5.4 20 4.0 32 7.0 103 21.6 124 25.6

Mild (1-3) 127 24.6 181 35.9 210 45.9 212 44.5 203 41.9

Moderate (4-7) 302 58.4 263 52.2 195 42.6 146 30.7 127 26.2

Severe (8-10) 60 11.6 40 7.9 21 4.6 15 3.2 30 6.2

Mean (SD) 4.8 (2.4) 4.3 (2.2) 3.6 (2.2) 2.8 (2.4) 2.8 (2.6)

NDI (0-50)

None (0-4) 39 7.4 – 87 19.0 165 34.7 160 38.8

Mild (5-14) 298 56.9 – 283 61.8 241 50.6 193 46.8

Moderate (15-24) 160 30.5 – 80 17.5 59 12.4 49 11.9

Severe or bcompleteQ

disability (N25)

27 5.2 – 8 1.7 11 2.3 10 2.4

Median (IQR) 12.0 (8.0-17.0) – 8.0 (5.0-12.0) 6.0 (3.0-11.0) 7.0 (3.0-11.0)

Patient satisfaction

Would you visit a

chiropractor again for

this or any other

complaint? (% yes)

– 99.4 98.7 89.9 83.8

Degree of satisfaction

with the chiropractor

(0-10)

(mean [SD])

– 7.7 (1.7) 7.8 (1.8) 7.7 (1.8) 7.6 (2.0)

Treatment satisfaction

(0-40)

– – 33.5 (5.2) 32.7 (6.3) 32.9 (6.7)

Global assessment

Completely improved 3 0.6 13 2.9 45 9.5 70 14.6

Much better 102 20.6 206 45.5 263 55.6 240 50.0

Somewhat better 194 39.2 175 38.6 107 22.6 83 17.3

Unchanged 145 29.3 39 8.6 50 10.6 67 14.0

Somewhat worse 43 8.7 18 4.0 6 1.3 15 3.1

Much worse 8 1.6 2 0.4 2 0.4 5 1.0

En dash (–) indicates missing or unrecorded data.

Ranging from no pain (0) to excruciating pain (10).

Ranging from no disability (0) to severely disabled (50).

Ranging from not satisfied (0) to very satisfied (10).

Ranging from not satisfied (0) to very satisfied (40) according to the scale from Cherkin et al.

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July/August 2007Adverse Events With Chiropractic Care

the number of patients with an intense adverse event seems

high, none of these patients were worse or much worse at

the end of the study period; therefore, these adverse events

should in no way be misconstrued as a measure or

indication of harm or be confused with (the lack of)

perceived recovery. In addition, only 2 subjects reported

to be much worse at 3 months, when most patients are likely

to have completed or discontinued care.

Secondly, regarding bbenefits,Q although many of the

subjects had chronic, recurrent neck pain and had undergone

prior care for this complaint, many patients experienced

benefit from the treatment (based upon diminished pain and

disability, the percentage of patients recovered and percentage

satisfied with care). Furthermore, many responded relatively

quickly to treatment (48% were recovered at the fourth visit);

and a significant proportion of patients continued to improve

up to 3 months (65%). It is, however, difficult to compare

these findings to other studies, especially regarding the rate of

recovery and involving other forms of therapy, because both

the inclusion criteria and outcome measures may differ. The

most similar study is a multicenter study of persistent low

back pain treated by chiropractors.

Although the pattern of

recovery was different, the percentage of patients who

became worse was similarly low in both studies.

The results of this study also confirm earlier work that

suggests that adverse events are most prevalent at the

beginning of treatment and diminish thereafter in fre-

quency.

13,14

This should have clinical consequences for

the practitioner, who might choose to modify his/her

treatment approach or limit himself/herself to certain

interventions at the start of treatment when the patient is

more likely to have a reaction.

Another important finding was that some of the same

symptoms that are often viewed as a consequence of

treatment, such as headache, nausea, dizziness, tiredness, or

depression, were p resent in many subjects at baseline.

Table 5. Type, frequency, and severity of adverse events, and frequency of intense adverse events recorded at the second and fourth visits

Type of adverse event

2nd visit compared with baseline (n = 509) 4th visit compared with second visit (n = 458)

Intensity Intense events

Mean (SD) n %

Increased treatment-related pain (musculoskeletal)

Increased pain at the

treated area

148 29.1 5.0 (2.1) 20 3.9 7 1.5 4.7 (1.9) 0 0

Increased pain N30% in

the 24 h preceding the

visit

112 22.0 4.8 (2.0) 8 1.6 85 18.6 5.1 (2.0) 12 2.6

Increased pain at an other

treatment-related area

100 19.6 4.7 (2.4) 16 3.1 11 2.4 5.9 (2.3) 2 0.4

Headache 51 10.0 5.6 (2.3) 14 2.8 13 2.8 3.7 (1.9) 1 0.2

Radiating pain – – – – – 9 2.0 5.3 (2.7) 3 0.7

Nonmusculoskeletal

Tiredness or fatigue 39 7.7 5.9 (1.9) 8 1.6 8 1.7 4.0 (2.8) 1 0.2

Dizziness or light-

headedness

38 7.5 5.0 (2.1) 5 0.9 6 1.3 3.8 (2.6) 0 0

Nausea 28 5.5 3.8 (2.2) 1 0.2 6 1.3 4.2 (2.2) 0 0

Ringing in the ears 19 3.7 3.4 (1.8) 0 0 4 0.9 3.0 (1.6) 0 0

Other type of adverse

event

13 2.6 5.6 (2.7) 4 0.8 9 2.0 6.8 (2.5) 6 1.3

Psychological

Confusion or

disorientation

14 2.8 4.9 (2.2) 1 0.2 6 1.3 1.5 (0.5) 0 0

Depression or fear 9 1.8 4.3 (2.4) 1 0.2 2 0.4 1.0 (0) 0 0

Total no. of events 571 78 166 25

En dash (–) indicates unrecorded data (ie, no baseline comparison).

As defined in the text.

Defined as an adverse event that scored z8 in severity.

Percentage of the total number of patients at that measurement period.

For these symptoms, a reaction was considered to be any new symptom (ie, z1 on the 11-point NRS).

Other complaints include strange feeling in the head, cannot focus/cannot see well, concentration problems/problems with trying to find words to

express oneself, bad dreams, burning feeling (location unspecified), problems with jaw, neck bcracks,Q stomach pain, joints crack, tired/heavy arms, tingling

in the fingers.

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Furthermore, more than one fifth noted that the symptom was

severe in intensity at baseline. This underlies the fact that

without a proper reference, there is the real potential to

erroneously ascribe previously unreported symptoms to the

treatment. In fact, according to our study, many of these

concomitant symptoms decreased following the first treat-

ment and continued to improve following the second and

third treatments. However, the prevalence of these symptoms

returned to their baseline values at 3 and 12 mo nths,

suggesting either a short-term positive effect of the treatment

or placebo effect.

There are some limitations to this study, however. Firstly,

in relation to the data collection, the questionnaires used have

not been previously validated, although they were modeled

after previous side effects studies.

13,14

Furthermore, given the

method of data collection in the clinics (ie, close-ended, self-

reported questionnaires), the possibility of response bias

cannot be ruled out, meaning it is possible that prompting a

patient about the presence of a symptom via the question-

naires might h ave led to overreporting.

Secondly, the lack of a control group means that it cannot

be determined whether the observed adverse events or

recovery is a response to the treatment or the result of

natural history. Although a contr ol group is obviously

desirable, studies such as this one are best designed to

describe patterns and changes over time, to investigate the

relationship between prognostic factors and outcomes, and

to identify subgroups most likely to respond to manipulation

for investigation in future clinical trials. Additional reports

are forthcoming from this data set.

Thirdly, although this was a prospective study, there is also

the potential for recall errors because patients were required

to remember and report something about a reaction that took

place at prior visit(s). However, almost all (90%) of the

second visits had taken place shortly following the first visit,

whereas most (79%) of the fourth visits took place within a

month of the first visit, so this error is likely to be minimal.

Fourthly, because a convenience sampling of chiroprac-

tors was used to collect data, it is possible that more

cautious and conservative chiropractors participated. How-

ever, a comparison of the practice charact eristics of the

participating chiropractors with the results o f a recent

study conducted in the Netherlands,

and with a relatively

recent European study,

suggests that participants in this

study were sociodemographically similar to their non-

participating colleagues.

Fifthly, it is possible that those patients deeme d by the

practitioners likely to have a favorable outcome were more

readily recruited. Analysis of recruitment in a sample of 5 of

the participating practices revealed that, on average, 78% of

the eligible patients were recruited; therefore, recruitment

bias was likely to be minimal. Furthermore, practices that

saw the highest number of new patients during the recruit-

ment period recruited the fewest eligible patients; therefore,

it seems more likely that failure to include individual

patients was the result of time constraints in the practices.

Lastly, imaging of the cervical spine was only performed

when necessary, at the discretion of the chiropractor. In the

Netherlands, few chiropractors have their own radiograph

apparatus; and few refer for imaging. Consequently, it is

possible that underlying pathology might have been missed

by the clinician. However, only one patient was found to

have serious pathology; and she was identified at the

beginning of the study (based upon history and physical

examination) and was excluded from participation. Further-

more, we had a high follow-up rate at the end of the study

and no other cases were identified during this period, so this

is unlikely to have influenced our results.

Implications for Clinical Practice

Patients respond quickly to care, with the most dramatic

improvement occurring in the first 3 treatments. After 3

months, a small percentage will have recurrent symptoms,

whereas some will continue to improve; however, most of

the patients remain stable. Clinicians should be aware that

extended treatment programs might have limited added

value when patients do not demonstrate some reasonable

improvement by the fourth visit.

Table 6. Total number of adverse events and severe adverse events observed in individual patients at the second and fourth visits

No. of events

per patient

2nd visit (n = 509) 4th visit (n = 458)

Adverse event Intense event

n% n %n % n %

0 266 52.3 456 89.6 339 74.0 436 95.2

1 95 18.7 35 6.9 94 20.5 20 4.4

2 61 12.0 12 2.4 12 2.6 1 0.2

3 40 7.9 5 1.0 8 1.7 1 0.2

4 20 3.9 1 0.2 3 0.7

5 15 2.9 1 0.2

6 8 1.6 0 0

z7 4 0.8 1 0.2

Defined as an adverse event according to our definition, which also scored z8 in intensity on an 11-point NRS.

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Journal of Manipulative and Physiological TherapeuticsRubinstein et al

July/August 2007Adverse Events With Chiropractic Care

Implications for Research

Many symptoms resembling an adverse event were

present in nearly all the subjects at baseline and diminished

in frequency in the population during the first 3 months.

This demonstrates the need to record baseline status for

concomitant symptoms to avoid errone ously ascribing their

incidence to treatment.

CONCLUSION

Despite the fact that adverse events following treatment

are common, and in some cases severe in intensity, this

study shows that the benefits of chiropractic care for neck

pain seem to outweigh the potential risks.

ACKNOWLEDGMENT

This study was partially funded by The European

Chiropractors’ Union (grant number A.03-1) and by the

Foundation for Chiropractic Education and Research (Fel-

lowship number 06-03-04).

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! Most patients in this study had chronic, recurrent

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