Determining the Impact of a Physiotherapist-Led Primary Care Model for Low Back Pain: Protocol and Analysis Plan for a Cluster Randomized Controlled Trial and Embedded Process Evaluation

BACKGROUND: Low back pain (LBP) is a common and disabling condition that is costly for health systems and society. Interprofessional primary care models may improve care quality and reduce this burden. OBJECTIVE: This protocol and analysis plan communicates the methods for a cluster randomized trial with the following objectives: (1) evaluate the effectiveness of a physiotherapist-led (PT-led) primary care model for LBP at improving disability (primary outcome), pain intensity, quality of life, global rating of change, patient satisfaction, and adverse events compared with usual physician-led primary care; and (2) determine the impact of the PT-led primary care model for LBP on the health care system and society (health care access, health care use, missed work, cost-effectiveness). Both objectives are evaluated over a 1-year period. A multimethod process evaluation is embedded to assess model implementation, mechanisms, perspectives of patients and providers, and contextual influences. METHODS: This study is a cluster randomized controlled trial with 20 primary care practices (clusters) in Canada, randomized 1:1 to a PT-led or usual physician-led primary care model for LBP. Adults seeking care from their primary care team for LBP are recruited over 1 year. Data collection occurs at baseline, 6 weeks, and 3, 6, 9, and 12 months. Effectiveness will be analyzed using linear mixed regression. The process evaluation analysis will include: descriptive and comparative analyses to assess implementation; descriptive and mediation analyses to assess potential mechanisms; qualitative interpretive description to understand experiences and perspectives of patients, PTs, and other health professionals; and mixed methods to determine contextual influences on implementation. RESULTS: Recruitment of primary care sites (clusters) was completed in June 2023, following delays related to the COVID-19 pandemic. Cluster randomization occurred in July 2023. Recruitment of patient participants began in October 2023 and concluded in November 2024 (n=739). The final self-reported patient data was collected on November 25, 2025. Extraction of electronic health record data is scheduled for completion on December 19, 2025. Data analysis will be conducted in accordance with the study protocol and analysis plan and will begin once all data collection activities are complete. No interim analyses have been performed. CONCLUSIONS: The results of this trial will provide evidence for knowledge users to determine whether a PT-led primary care model for LBP is effective and should be adopted more widely. Knowledge users have identified the impact of the new model of care on disability, quality of life, and cost-effectiveness as key evidence needed to inform key decision-making. The multimethod process evaluation will provide critical evidence to interpret trial results and inform future scale and spread of this model of care if effective. TRIAL REGISTRATION: ClinicalTrials.gov NCT04287413; https://clinicaltrials.gov/study/NCT04287413. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/89004.