Article Review - May 2012

Critical Review of a Research Article

Comparison of the Effectiveness of Three Manual Physical Therapy Techniques in a Subgroup of Patients With Low Back Pain Who Satisfy a Clinical Prediction Rule

Reviewer: Amy Fahlman BSc. PT. MCl.Sc. MT UWO. Current practice Ottawa, ON

Cleland JA, Fritz JM, Kulig K, Davenport TE, Eberhart S, Magel J, Childs JD. Comparison of the Effectiveness of Three Manual Physical Therapy Techniques in a Subgroup of Patients With Low Back Pain Who Satisfy a Clinical Prediction Rule. Spine 2009; 34(25):2720-2729.

Affiliations: The United States Military Heath System; out-patients physical therapy clinics affiliated with Concord Hospital, Concord, NH; Intermountain Healthcare, Salt Late City, UT; and the University of Southern California, Los Angeles, CA.

Background: A recent clinical prediction rule (CPR) has been developed to identify patients with low back pain (LBP) that are likely to respond favourably to a thrust manipulation technique (1). If the patient presents with 4/5 criteria of symptoms < 16 day, no symptoms distal to the knee, Fear Avoidance Beliefs Questionnaire (FABQ) <19, at least one lumbar hypomobile segment, and hip internal rotation > 35 degrees, they are positive on the rule and there is a 95% probability (likelihood ratio 24.38) of improvement to disability and pain complaints with a supine thrust manipulation technique (1). The CPR was derived using a single thrust manipulation technique, and it is unknown if the rule is generalizable to various manual therapy techniques.

Purpose:

  1. To determine if 3 manual therapy techniques could be generalized to a spinal manipulation CPR by comparing the Oswestry Disability Questionnaire (ODQ) and Numeric Pain Rating Scale (NPRS) scores in patients 18-65 and positive on the CPR at 1 week, 4 weeks, and 6 months.
  2. To determine the generalizability of the CPR in different practice settings.

Study Methods: Subjects were randomly assigned to 1 of 3 treatment groups in their respective treatment facilities: Supine thrust, side lying thrust, or prone non- thrust groups. During the first week, subjects received 2 manual therapy treatments as specified and 1 ROM exercise. The remaining 3 weekly treatments consisted of a standardized exercise program and did not differ between groups.

The primary and secondary hypotheses were examined using a linear mixed model for repeat measures with the time and treatment group as fixed and the ODQ or the NPRS as the dependent variable. Group by time interactions were measures as well as a pair-wise comparison of the estimated marginal means. A chi-square test was used to compare the percentage of patients in each manual therapy group achieving a successful outcome at each follow-up.

Pertinent Results: Group x time interactions were significant for the ODQ (P > 0.001) and NPRS scores (P > 0.001). Significance levels for the ODQ were a 50% reduction in score as previously established (2). Pair-wise comparisons of ODQ and NPRS scores showed no differences between the 2 thrust manipulation groups at any follow-up, with both thrust groups showing significant differences from the non-thrust group with ODQ and NPRS scores at 1 (P > 0.001) and 4 weeks (P>0.001), and in ODQ scores at 6 months (P _>0.009). There was no time by clinic interaction present for ODQ (P >0.14) or NPRS (P >0.41) scores; however, unbalanced sample sizes compromise the results of this hypothesis.

Critical Appraisal: There are several limitations to this study. The lack of an exercise only group does not eliminate the possibility that the results may be due to exercise intervention. Manual therapy was used only during the first week; however, the disability and pain scores of all treatment groups continue to improve over a 6 month follow-up. If the NPRS and ODQ score continued to improve as demonstrated, it is questionable if the ODQ scores would continue significantly differ at a one year follow up. This may favour the exercise intervention responsible for continued improvements after the one week follow up. Further research is required to control for effects of the exercise intervention.

As noted in an editorial by Hancock and Maher, patients negative on the CPR were excluded; it is therefore unknown if their results would differ (3). The study was conducted assuming validity of the CPR, yet only a single validation study has been conducted with positive results (4). A second validation study did not support the CPR; however only 5% of the subjects in this independent validation study received a thrust technique, while the others received various mobilizations techniques (5). It is likely the lack of clinically important change can be explained by the results of the current study.

It is also noteworthy that a patient may be positive on the CPR but still inappropriate to manipulate. In an article written by Sun et al on the critical appraisal of subgroups, it is suggested that a biological rational to the predictors strengthens the validity to the rule (6). In this CPR, three of the predictors (duration of symptoms, FABQ score, symptoms distal to the knee) lack an anatomical or biomechanical link to their response to a manipulation. With these considerations, clinicians are cautioned to be mindful of the exclusion criteria noted with the CPR as well an encouraged to practice within an evidence based medicine model and integrate individual client needs, clinical expertise and the best available evidence when clinical decision making (7).

References

  1. Flynn T, Fritz J, Whitman J, Wainner R, Magel J, Rendeiro D, Butler B, Garber M, Allison S. A clinical prediction rule for classifying patients with low back pain who demonstrate short- term improvement with spinal manipulation. Spine (Phila Pa 1976). 2002 Dec 15;27(24):2835- 43.
  2. Fritz JM, Childs JD, Flynn TW. Pragmatic application of a clinical prediction rule in primary care to identify patients with low back pain with a good prognosis following a brief spinal manipulation intervention. BMC Fam Pract. 2005 Jul 14;6(1):29.
  3. Hancock MJ, Maher CG. Letter to the editor concerning “Comparison of the effectiveness of three manual physical therapy techniques in a subgroup of patients with low back pain who satisfy a clinical prediction rule. A randomized clinical trial. Spine 2010; 35(7): 839.
  4. Childs JD, Fritz JM, Flynn TW, et al. Validation of a clinical prediction rule to identify patients with low back pain likely to benefit from spinal manipulation. Ann Intern Med 2004;141:920–8
  5. Hancock MJ, Maher CG, Latimer J, Herbert RD, McAuley JH. Independent evaluation of a clinical prediction rule for spinal manipulative therapy: a randomised controlled trial. Eur Spine J. 2008 Jul;17(7):936-43. Epub 2008 Apr 22.
  6. Sun X, Briel M, Walter SD, Guyatt GH. Is a subgroup effect believable? Updating criteria to evaluate the credibility of subgroup analyses. BMJ. 2010 Mar 30; 340:117.
  7. Carter MJ. Evidence-based medicine: an overview of key concepts. Ostomy Wound Manage. 2010 Apr 1;56(4):68-85.

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