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This JAMA Guide to Statistics and Methods reviews the use of mediation analysis to evaluate possible mechanisms that the effects of interventions are presumed to work through. [ABSTRACT FROM AUTHOR]

Importance: The effects of altered neural processing, defined as altering neural networks responsible for perceptions of pain and function, on chronic pain remains unclear.Objective: To estimate the effect of a graded sensorimotor retraining intervention (RESOLVE) on pain intensity in people with chronic low back pain.Design, Setting, and Participants: This parallel, 2-group, randomized clinical trial recruited participants with chronic (>3 months) nonspecific low back pain from primary care and community settings. A total of 276 adults were randomized (in a 1:1 ratio) to the intervention or sham procedure and attention control groups delivered by clinicians at a medical research institute in Sydney, Australia. The first participant was randomized on December 10, 2015, and the last was randomized on July 25, 2019. Follow-up was completed on February 3, 2020.Interventions: Participants randomized to the intervention group (n = 138) were asked to participate in 12 weekly clinical sessions and home training designed to educate them about and assist them with movement and physical activity while experiencing lower back pain. Participants randomized to the control group (n = 138) were asked to participate in 12 weekly clinical sessions and home training that required similar time as the intervention but did not focus on education, movement, and physical activity. The control group included sham laser and shortwave diathermy applied to the back and sham noninvasive brain stimulation.Main Outcomes and Measures: The primary outcome was pain intensity at 18 weeks, measured on an 11-point numerical rating scale (range, 0 [no pain] to 10 [worst pain imaginable]) for which the between-group minimum clinically important difference is 1.0 point.Results: Among 276 randomized patients (mean [SD] age, 46 [14.3] years; 138 [50%] women), 261 (95%) completed follow-up at 18 weeks. The mean pain intensity was 5.6 at baseline and 3.1 at 18 weeks in the intervention group and 5.8 at baseline and 4.0 at 18 weeks in the control group, with an estimated between-group mean difference at 18 weeks of -1.0 point ([95% CI, -1.5 to -0.4]; P = .001), favoring the intervention group.Conclusions and Relevance: In this randomized clinical trial conducted at a single center among patients with chronic low back pain, graded sensorimotor retraining, compared with a sham procedure and attention control, significantly improved pain intensity at 18 weeks. The improvements in pain intensity were small, and further research is needed to understand the generalizability of the findings.Trial Registration: ANZCTR Identifier: ACTRN12615000610538. [ABSTRACT FROM AUTHOR]

Importance: The benefits of rehabilitation after immobilization for ankle fracture are unclear.Objectives: To determine the effectiveness of a supervised exercise program and advice (rehabilitation) compared with advice alone and to determine if effects are moderated by fracture severity or age and sex.Design, Setting, and Participants: The EXACT trial was a pragmatic, randomized clinical trial conducted from December 2010 to June 2014. Patients with isolated ankle fracture presenting to fracture clinics in 7 Australian hospitals were randomized on the day of removal of immobilization. Of 571 eligible patients, 357 chose not to participate and 214 were allocated to rehabilitation (n = 106) or advice alone (n = 108), with 194 (91%) followed up at 1 month, 173 (81%) at 3 months, and 170 (79%) at 6 months. There were no withdrawals attributed to adverse effects. Recruitment terminated early on December 31, 2013 (planned enrollment, 342; actual, 214), because funding was exhausted.Interventions: Supervised exercise program and advice about self-management (rehabilitation) (individually tailored, prescribed, monitored, and progressed) or advice alone, both delivered by a physical therapist.Main Outcomes and Measures: Primary outcomes were activity limitation assessed using the Lower Extremity Functional Scale (score range, 0-80; higher scores indicate better activity), and quality of life assessed using the Assessment of Quality of Life (score range, 0-1; higher scores indicate better quality of life), measured at baseline and at 1, 3 (primary time point), and 6 months.Results: Mean activity limitation and quality of life at baseline were 30.1 (SD, 12.5) and 0.51 (SD, 0.24), respectively, for advice and 30.2 (SD, 13.2) and 0.54 (SD, 0.24) for rehabilitation, increasing to 64.3 (SD, 13.5) and 0.85 (SD, 0.17) for advice vs 64.3 (SD, 15.1) and 0.85 (SD, 0.20) for rehabilitation at 3 months. Rehabilitation was not more effective than advice for activity limitation (mean effect at 3 months, 0.4 [95% CI, -3.3 to 4.1]) or quality of life (-0.01 [95% CI, -0.06 to 0.04]). Treatment effects were not moderated by fracture severity or age and sex.Conclusions and Relevance: A supervised exercise program and advice did not confer additional benefits in activity limitation or quality of life compared with advice alone for patients with isolated and uncomplicated ankle fracture. These findings do not support the routine use of supervised exercise programs after removal of immobilization for patients with isolated and uncomplicated ankle fracture.Trial Registration: anzctr.org.au Identifier: ACTRN12610000979055. [ABSTRACT FROM AUTHOR]