Introduction

Low back pain (LBP) is the leading cause of disability worldwide and represents a substantial burden for healthcare systems, particularly in primary care settings [1]. In Switzerland, 50% of people report recurrent LBP, which is associated with work limitations, and increased healthcare utilization [2]. Despite well-established clinical guidelines [[3], [4], [5]], the management of LBP in primary care remains highly variable, with underuse of high-value care, and overuse of low-value care strategies [6,7]. Therefore, effective strategies are needed to improve the integration of guideline-concordant care in primary care [8].

Unhelpful beliefs about LBP, such as thinking that the back is fragile and that LBP is caused by serious injury, are frequently identified among healthcare professionals [9,10], patients with LBP [11] and the general population [12,13]. These beliefs are associated with maladaptive behaviors and reduced use of high-value care [14,15]. They are also associated, together with other psychological factors, with an increased risk of chronic disabling LBP [16]. Moreover, clinicians report limited confidence and lack of practical tools to identify and address these psychological risk factors in daily practice [17,18]. Interventions that support clinicians to address these factors early and to align care with patients’ risk of chronicity may improve recovery and reduce unnecessary investigations and costs [19,20].

Supporting clinicians to integrate best practice recommendations requires more than education alone. Multilevel, theory-informed interventions co-designed with stakeholders, adapted to local contexts, and supported by implementation strategies such as reminders, decision-support tools, audit and feedback are more likely to lead to sustainable behavior change [[21], [22], [23], [24]]. Effectiveness–implementation hybrid designs have been recommended to simultaneously evaluate clinical effectiveness and implementation processes, while optimizing research efficiency [[25], [26], [27]].

The PRImary care MultilEvel intervention for low back pain (PRIME Back Study) was co-developed by clinicians, LBP experts and people with lived experience of LBP to improve the integration of high-value care in primary care through a coordinated, multilevel strategy. The intervention was designed to help general practitioners (GPs) and physiotherapists to address psychological risk factors of chronicity, reduce low-value care and increase high-value care strategies.

The primary objective of this effectiveness-implementation hybrid trial is to evaluate the effectiveness of PRIME compared with usual care at three levels: cost-effectiveness (system-level); imaging prescription rate (practitioner-level), and self-reported back-related disability (patient-level). These three distinct, complementary primary outcomes will facilitate a rigorous evaluation to ascertain whether it is advisable to implement the PRIME intervention. Cost-effectiveness was selected as the system-level primary outcome because demonstrating value for money is essential for health policy decisions in LBP care [28]. The imaging prescription rate was selected as the practitioner-level primary outcome because it is a direct, objective indicator of guideline-concordant GP behavior and a key target of PRIME's clinician-facing components [29]. Self-reported back-related disability was selected as the patient-level primary outcome because it is recommended as a core outcome in LBP research [30]. Usual care in this trial reflects standard primary care practice in a healthcare network in French-speaking Switzerland, where GPs already participate in regular quality circle meetings and have unrestricted access to specialist referral, physiotherapy, and interdisciplinary rehabilitation. This high-quality, ecologically valid comparator was chosen to demonstrate the added value of PRIME over existing care. Secondary objectives include evaluating the effectiveness of PRIME on opioid and sick leave prescriptions, clinicians' beliefs and confidence in treating patients with LBP (practitioner-level), as well as pain intensity, work participation, health-related quality of life, global perceived change, pain self-efficacy, fear avoidance beliefs, and beliefs about LBP (patient-level). In addition, implementation processes and outcomes will be examined among healthcare practitioners, including acceptability, appropriateness, feasibility, adoption, fidelity, and barriers and facilitators to implementation. Finally, patients' experience and acceptability of PRIME will be investigated qualitatively.