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

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.