Operational phenotyping for chronic low back pain: a narrative review and methodology for developing routing and escalation pathways across spine care.

Abstract

Background and objective: Chronic low back pain (CLBP) is clinically heterogeneous and generates substantial symptom burden, functional limitation, psychological distress, work disability, and health-care utilization. Existing phenotyping approaches often describe subgroups but do not specify how subgroup assignment changes routing, conservative-care dose, imaging, interventional escalation, surgical evaluation, or outcome monitoring. The objective of this narrative review was to define operational phenotyping as a practical method for developing routable, auditable spine-care pathways and to distinguish this methodology from descriptive subgrouping, Subgroups for Targeted Treatment Back Screening Tool (STarT Back)-style risk stratification, and machine-learning phenotyping.

Methods: We conducted a narrative review using structured methods. PubMed/MEDLINE was the primary database, supplemented by Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), PsycINFO, Cochrane Central Register of Controlled Trials (CENTRAL), Scopus/Web of Science when available, guideline and trial-registry review, and reference-list screening. Searches covered January 2000 through January 2026. Studies were synthesized using an Inputs-Decision-Pathway-Outcome (IDPO) framework. The Berlin deep-phenotyping program was used as a contextual exemplar of multidomain measurement, not as evidence of treatment efficacy.

Key content and findings: The synthesis yielded five operational findings. First, phenotype labels are implementation-ready only when linked to explicit pathway decisions. Second, minimal universal inputs should be separated from targeted add-ons. Third, escalation gates require illustrative thresholds and safety overrides rather than open-ended care drift. Fourth, diagnostic procedures, including diagnostic medial branch blocks, may themselves define a pain generator phenotype and should not be treated only as downstream treatment. Fifth, surgical referral should be framed as entry into shared decision-making evaluation rather than an automatic indication for surgery.

Conclusions: Operational phenotyping is best understood as a methodology for developing a field guide rather than a completed field guide for all settings. It translates deep phenotyping and stratified-care concepts into locally deliverable pathways by requiring the same four elements for each phenotype: feasible inputs, explicit decision logic, an actionable pathway, and measurable outcomes.