Efficacy of classification-specific treatment and adherence on outcomes in people with chronic low back pain. A one-year follow-up, prospective, randomized, controlled clinical trial

Background: It is unknown if low back pain (LBP) outcomes are enhanced by classification-specific treatment based on the Movement System Impairment classification system. The moderating effect of adherence to treatment also is unknown. Objectives: Compare the efficacy of a classification-specific treatment (CS) and a non classification-specific (NCs) treatment and examine the moderating effect of adherence on outcomes. Design: 2 center, 2 parallel group, prospective, randomized, clinical trial. Method: Participants with chronic LBP were classified and randomized. Self-report data was obtained at baseline, post-treatment, and 6 and 12 months post-treatment. The primary outcome was the modified Oswestry Disability Index (mODI; 0-100%). Treatment effect modifiers were exercise adherence and performance training adherence. An intention to treat approach and hierarchical linear modeling were used. Results: 47 people received CS treatment, 54 people received NCs treatment. Treatment groups did not differ in mODI scores (p > 0.05). For both groups, scores improved with treatment (p < 0.05), plateaued at 6 months (p > 0.05), and minimally regressed at 12 months (p < 0.05). Performance training adherence had a unique, independent effect on mODI scores above and beyond the effect of exercise adherence (p < 0.05). There were no treatment group effects on the relationship between mODI scores and the two types of adherence (p < 0.05). Conclusions: There were no differences in function between the two treatment groups (CS and NCs). In both treatment groups, people with chronic LBP displayed clinically important long-term improvements in function. When both forms of adherence were considered, the improvements were uniquely related to adherence to performance training.