One-year follow-up comparison of the effectiveness of McKenzie treatment and strengthening training for patients with chronic low back pain: outcome and prognostic factors.

STUDY DESIGN: A randomized controlled trial with multivariable analyses of prognostic factors. OBJECTIVE: To report the long-term outcome of McKenzie treatment compared with strengthening training. Further, to determine patient-related factors associated with poor outcome 14 months after completion of treatment. SUMMARY OF BACKGROUND DATA: Exercise therapy is widely recommended for patients with chronic low back pain. However, reports vary considerably concerning characteristics of patients who will not respond to treatment. Knowledge of factors associated with poor outcome may assist identification of patients requiring special attention. METHODS: A total of 260 patients with chronic low back pain were included in a previously reported randomized controlled trial of McKenzie therapy versus strengthening training. Outcome variables were: functional status, pain level, work status, and use of healthcare services during follow-up. Also, factors associated with withdrawal during the intervention were sought identified. The following factors of possible prognostic significance were determined: levels of pain and disability, pain-distribution, duration of symptoms, smoking habits, leisure activities, workload, job satisfaction, treatment preference, outcome expectations, treatment modality received, compliance with home exercises during follow-up, and demographic variables such as age, gender, work status, and application for pension. Association between variables was examined by multiple logistic regression analysis and odds ratios. RESULTS: No differences in outcomes were found between the treatment groups at 14 months of follow-up. Low level of pain intensity and disability, sick leave at entry, low pretreatment expectations of future work ability, withdrawal during treatment, and discontinuance of exercises after the end of the treatment period were associated with poor outcome. CONCLUSION: Poor long-term outcome of exercise therapy for chronic low back pain can be explained by a number of patient-related factors. Different prognostic factors were associated with different outcomes. These factors were more important in determining outcome than the exercise-programs studied.