|A comparison of physical therapy, chiropractic manipulation, and provision of an educational booklet for the treatment of patients with lower back pain
|Cherkin D C, Deyo R A, Battie M, Street J, Barlow W
This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn.
The McKenzie method, a popular form of physical therapy, and chiropractic manipulation for the treatment of patients with low back pain. In the McKenzie approach, patients are placed in one of three broad categories (derangement, dysfunction, and postural syndrome); patients are taught to perform exercises that centralise their symptoms and to avoid movements that peripheralise them; this method relies on patient-generated forces and emphasises self-care; the McKenzie Institute faculty trained the therapists before the study; patients were given McKenzie's Treat Your Own Back book and a lumbar-support cushion; therapists were asked to avoid adjuncts such as heat, ice, transcutaneous electrical nerve stimulation (TENS), ultrasonography, and back classes. Chiropractic manipulation involved the use of a short-lever, high-velocity thrust directed specifically at a "manipulable lesion" (as the most common method of chiropractic manipulation); no other physical treatments were permitted; an exercise sheet was used, which emphasised stretching and strengthening but excluded extension exercises (an important part of McKenzie therapy); patients' radiographs less than three years old were given to the chiropractors who also determined the need for additional radiographs; a chiropractor consultant observed the chiropractors at the start and end of the study and confirmed their compliance with the treatment protocol. After the first visit, up to eight visits during the one-month period of the treatment could be scheduled at the discretion of the therapist.
Economic study type
Patients, 20 to 64 years of age, who saw their primary care physician for low back pain and who still had pain seven days later. Patients were excluded if they had mild or no pain seven days after the visit to the physician, a history of back surgery, sciatica, systemic or visceral causes of the pain, osteoporosis, a vertebral fracture or dislocation, severe concurrent illness, had received corticosteroid therapy, were pregnant, were involved in claims for compensation or litigation because of the back injury, had received physical therapy or chiropractic or osteopathic manipulative treatment for their current back pain, or had visited practitioners other than their primary care physicians.
Primary care and chiropractic solo practice. The economic analysis was carried out in the USA.
Dates to which data relate
Effectiveness and resource use data corresponded to those patients recruited between November 1993 and September 1995. The price year was 1995.
Source of effectiveness data
The evidence for the final outcomes was based on a single study.
Link between effectiveness and cost data
Costing was conducted on the same patient sample as that used in the effectiveness analysis and appears to have been carried out retrospectively.
Power calculations were used to determine the sample size (the study was designed to have at least 80% power to detect a 2.5 point difference in the scores on the Roland Disability Scale and a 1.5 point difference in the scores on the 'bothersomeness' scale for the comparison between physical therapy and chiropractic care). Of 3,800 potential candidates, 714 (19%) fulfilled the study inclusion criteria. From these 714 eligible candidates, a total of 493 patients (69%) agreed to participate, and 323 remained eligible one week later. Two subjects were excluded after randomisation; and the remaining 321 were randomly assigned to receive either the booklet (n=66, mean (SD) age of 40.1 (11.2) years), chiropractic therapy (n=122, mean (SD) age 39.7 (9.4) years), or physical therapy (n=133, mean (SD) age 41.8 (11.5) years). Physical therapy was provided for one month by 13 therapists with a median of 14 years experience. The four chiropractors that performed the spinal manipulation had 6 to 14 years' experience, and one had a master's degree in exercise therapy.
The study was a randomised, controlled trial. The patients were recruited from two primary care clinics; physical therapy being provided in a facility adjacent to these clinics, and spinal manipulation was performed in 4 chiropractic solo practices. The duration of the follow-up was 2 years. Loss-to-follow-up at 12 weeks appears to have been 3 patients in the booklet group, 4 patients in the chiropractic group, and 16 patients in the physical-therapy group; it was reported that 4% of subjects in the chiropractic group and 3% in the physical therapy group did not visit their assigned provider at all; between 89% and 96% of the subjects responded to each of the follow-up questionnaires. Randomisation was based on the use of sealed, opaque envelopes. The 40-40-20% distribution of patients among the study groups was based on a pilot study that suggested a trend toward worse outcomes in the group that received the booklet. Data on outcomes at one and four weeks were collected by telephone; subsequent outcomes were assessed by mail with telephone follow-up. Interviewers were unaware of the subjects' study assignment; however, after the outcomes had been recorded at four weeks, subjects indicated which treatment they had been assigned.
Analysis of effectiveness
The principle used in the analysis of effectiveness was reported to have been intention-to-treat. The clinical outcome measures were 'bothersomeness' of symptoms (measured on an 11-point scale), the level of dysfunction (measured on the 24-point Roland Disability Scale), the number of days of reduced activity, missed work, recurrences of back pain, and adverse effects of treatment. The subjects were asked to rate their care for back pain (excellent, very good, good, fair, or poor) at one and four weeks. Analysis of variance was used to compare the groups in terms of 'bothersomeness' scores and the level of dysfunction scores, after adjustment for a set of baseline variables predictive of those scores. Since the primary outcomes were not normally distributed, a square-root transformation of the primary outcome data was performed so that the data better met the assumption of the parametric test. Nonparametric tests were used to confirm the results of the parametric analyses. There were some significant differences in baseline characteristics among the treatment groups; subjects in the chiropractic group were less likely to have used chiropractic services previously, subjects in the physical-therapy group had more bothersome symptoms, subjects in the booklet group reported fewer days with restricted activity and lower expectations that their condition would improve in a month's time.
After adjustment for base-line differences, the chiropractic group had less severe symptoms than the booklet group at four weeks (p=0.02), and there was a trend toward less severe symptoms in the physical therapy group (p=0.06). However, these differences were small and not significant after transformations of the data to adjust for their non-normal distribution. Differences in the extent of dysfunction among the groups were small and approached significance only at one year, with greater dysfunction in the booklet group than in the other two groups (p=0.05). For all outcomes, there were no significant differences among the groups in the number of days of reduced activity or missed work or in recurrences of back pain. About 75% of the subjects in the therapy groups rated their care as very good or excellent, as compared with about 30% of the subjects in the booklet group (p<0.001). No important adverse effects of treatment were reported in any of the groups.
For patients with low back pain, the study found that physical therapy and chiropractic manipulation had similar effects on symptoms, function, satisfaction with care, disability, recurrence of back pain, and subsequent visits for back pain. The study also found that patients who received chiropractic manipulation or physical therapy had only marginally better outcomes than those who received only an educational booklet did.
Measure of benefits used in the economic analysis
No summary benefit measure was identified in the economic analysis, and only separate clinical outcomes were reported.
Costs were not discounted as they were incurred in a two-year period of time. Resource use quantities were reported separately from the costs and cost items were reported separately. Cost analysis covered the costs of study treatments and supplies for 1 month (booklet, visits, plain film, McKenzie book, lumbar roll), and cost of care for first and second year after treatment (office visits, radiology, laboratory tests, and medications). The perspective adopted in the cost analysis appears to have been that of a large staff-model health maintenance organisation (HMO) or insurers. The subjects' use of health care for back-related problems was identified by a review of encounter forms completed by physical therapists and chiropractors, automated data on utilisation for HMO-covered services, and questionnaires on visits not covered by the HMO. The cost of care was determined from the HMO's cost-accounting system and reflects the costs to the HMO. The price year was 1995. The patients' co-payments were not included.
Statistical analysis of costs
Statistical analysis was performed on some resource use data but not on cost data.
The percentage of patients who reported missing work was reported as one of the outcomes of the study. However, no attempt was made to assign monetary values to these missed-work figures.
Estimated benefits used in the economic analysis
Over a two-year period, the mean costs of care were $437 for the physical-therapy group, $429 for the chiropractic group, and $153 for the booklet group.
Synthesis of costs and benefits
For patients with low back pain, the McKenzie method of physical therapy and chiropractic manipulation had similar effects and costs, and patients receiving these treatments had only marginally better outcomes than those receiving the minimal intervention of an educational booklet.
CRD COMMENTARY - Selection of comparators
The no-treatment strategy (provision of an educational booklet) was explicitly regarded as the comparator. An educational booklet was chosen as the comparator in order to minimise potential disappointment in those patients not receiving a physical treatment. A previous study had found that the use of this booklet as a supplement to standard care was not associated with improved outcomes, even though subjects considered it useful. The choice of the no-treatment strategy allowed the active values of the two interventions to be evaluated.
Validity of estimate of measure of effectiveness
The internal validity of the effectiveness results is likely to be high given the randomised nature of the study design, the power calculations performed, and the fact that adjustments were made for the predictive variables of the primary outcome scores. The effectiveness analysis was stated to have been based on intention-to-treat principle, but this does not appear to be borne out by the actual analysis, which was not based on the full sample initially included in the study. The study sample appears to have been representative of the study population.
Validity of estimate of measure of benefit
The authors did not derive a measure of health benefit. The analysis was therefore of cost-consequences design.
Validity of estimate of costs
The validity of the cost results may have been enhanced by the following: resource use quantities were reported separately from the costs; adequate details of methods of cost estimation were given; the price year and the perspective adopted in the cost analysis were reported; and statistical analyses were performed on some resource use. However, some of the limitations of the cost study were as follows: the effects of alternative procedures on indirect costs were not fully addressed in monetary terms; no statistical analysis appears to have been performed on cost data; cost results may not be generalisable outside the study settings; it was also noted that the resource use pattern may have reflected difference in practice styles (the number of visits was left to the discretion of the providers), rather than the pure effects of the interventions.
The authors' conclusion appears to be justified given the uncertainties in the data. Regarding the issue of generalisability to other settings or countries, it was noted that the generalisability of the study results was limited by the use of a single health care system, the use of specific forms of chiropractic and physical therapy, the use of one month of therapy, and the exclusion of patients with sciatica. Appropriate comparisons were made with other studies. The issue of whether the study sample was representative of the study population was discussed in the authors' comments.
Implications of the study
Given the limited benefits and high costs, it seems unwise to refer all patients with low back pain for chiropractic or McKenzie therapy. Ideally, there would be some way of identifying the subgroups that would be most likely to benefit from one or both of these therapies, though the authors were unable to identify any predictive characteristics.
Source of funding
Supported by grant HS07915 from the Agency for Health Care Policy and Research.
Cherkin D C, Deyo R A, Battie M, Street J, Barlow W. A comparison of physical therapy, chiropractic manipulation, and provision of an educational booklet for the treatment of patients with lower back pain. New England Journal of Medicine 1998; 339: 1021-1029
Other publications of related interest
Comment in: New England Journal of Medicine 1998;339(15):1074-5.
Comment in: New England Journal of Medicine 1999;340(5):388.
Comment in: New England Journal of Medicine 1999;340(5):388-9.
Comment in: New England Journal of Medicine 1999;340(5):389.
Comment in: New England Journal of Medicine 1999;340(5):389-90.
Comment in: ACP Journal Club 1999;130(2):42.
Subject indexing assigned by NLM
Adult; Chiropractic /economics; Disability Evaluation; Female; Health Care Costs /statistics & Humans; Logistic Models; Low Back Pain /classification /economics /therapy; Male; Middle Aged; Pamphlets; Patient Education as Topic /economics; Patient Satisfaction; Physical Therapy Modalities /economics; Recurrence; Severity of Illness Index; Statistics, Nonparametric; Treatment Outcome; numerical data
Date bibliographic record published
Date abstract record published