title: Predicting a clinically important outcome in patients with low back pain following McKenzie therapy or spinal manipulation: a stratified analysis in a randomized controlled trial.
abstract: BACKGROUND
  Reports vary considerably concerning characteristics of patients who will respond to mobilizing exercises or manipulation. The objective of this prospective cohort study was to identify characteristics of patients with a changeable lumbar condition, i.e. presenting with centralization or peripheralization, that were likely to benefit the most from either the McKenzie method or spinal manipulation.
  
  
  METHODS
  350 patients with chronic low back pain were randomized to either the McKenzie method or manipulation. The possible effect modifiers were age, severity of leg pain, pain-distribution, nerve root involvement, duration of symptoms, and centralization of symptoms. The primary outcome was the number of patients reporting success at two months follow-up. The values of the dichotomized predictors were tested according to the prespecified analysis plan.
  
  
  RESULTS
  No predictors were found to produce a statistically significant interaction effect. The McKenzie method was superior to manipulation across all subgroups, thus the probability of success was consistently in favor of this treatment independent of predictor observed. When the two strongest predictors, nerve root involvement and peripheralization, were combined, the chance of success was relative risk 10.5 (95% CI 0.71-155.43) for the McKenzie method and 1.23 (95% CI 1.03-1.46) for manipulation (P = 0.11 for interaction effect).
  
  
  CONCLUSIONS
  We did not find any baseline variables which were statistically significant effect modifiers in predicting different response to either McKenzie treatment or spinal manipulation when compared to each other. However, we did identify nerve root involvement and peripheralization to produce differences in response to McKenzie treatment compared to manipulation that appear to be clinically important. These findings need testing in larger studies.
  
  
  BACKGROUND
  Clinicaltrials.gov: NCT00939107.
authors.affiliation: Back Center Copenhagen, Copenhagen, Denmark. tom.petersen@suf.kk.dk.
authors.forename: Tom
authors.initials: T
authors.lastname: Petersen
authors.affiliation: Department of Rheumatology, Musculoskeletal Statistics Unit, The Parker Institute, Copenhagen University Hospital, Frederiksberg, Denmark. Robin.Christensen@frh.regionh.dk.
authors.forename: Robin
authors.initials: R
authors.lastname: Christensen
authors.affiliation: Department of Sports Science and Clinical Biomechanics, Research Unit for Musculoskeletal Function and Physiotherapy, University of Southern Denmark, Odense, Denmark. carsten.bogh.juhl@regionh.dk.|Department of Orthopedics, University Hospital of Copenhagen, Gentofte, Denmark. carsten.bogh.juhl@regionh.dk.
authors.forename: Carsten
authors.initials: C
authors.lastname: Juhl
mesh_terms: D000328:Adult; D000367:Age Factors; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D017116:Low Back Pain / Q000175:diagnosis* / Q000628:therapy*; D008159:Lumbar Vertebrae / Q000294:innervation; D008297:Male; D020393:Manipulation, Spinal / Q000379:methods*; D008875:Middle Aged; D026741:Physical Therapy Modalities; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012720:Severity of Illness Index; D013997:Time Factors; D016896:Treatment Outcome