12-phase flow (12)

1. 1FRAME
   Low back pain is a symptom, not a diagnosis: triage-first. ≥90% is non-specific mechanical LBP; the engine exists to NOT miss the cannot-miss serious-secondary minority and to match care intensity to prognostic risk (Lancet 2018 Foster PMID 29573872; ACP 2017 Qaseem PMID 28192789)
   inputs: pain_duration_band, leg_pain_below_knee
   advance: Scope framed: acuity band + axial-vs-radicular established against the serious-secondary screen
2. 2ENTRY
   Acute (<6 wk) / subacute (6–12 wk) / chronic (>12 wk) LBP ± leg pain; flare of chronic LBP; inflammatory pattern; post-trauma; or explicit red-flag concern (ACP 2017 Qaseem; NICE NG59)
   inputs: pain_duration_band
   advance: Engine entered via a recognised trigger
3. 3CONTEXT
   Duration band, axial vs radicular distribution, age, trauma/osteoporosis/steroid, cancer history, immunosuppression/IVDU, fever/constitutional symptoms, occupation, prior LBP episodes and psychosocial yellow flags (ACP 2017 Qaseem; Lancet 2018 Foster)
   inputs: pain_duration_band, leg_pain_below_knee, age, cancer_history, immunosuppression_or_ivdu
   advance: Duration + phenotype + risk-driver context captured
4. 4RED_FLAGS
   Cannot-miss screen with explicit pre-test priors + LR±: CAUDA EQUINA (saddle anaesthesia / bilateral sciatica / urinary retention → post-void residual; surgical emergency, prior 0.1–1.9% ED), MALIGNANCY (history of cancer LR+ ≈ 7 — Verhagen Pain 2017; prior 0–0.7% primary care / 0–2.1% ED), SPINAL INFECTION (fever + IVDU/immunosuppression/indwelling line; prior 0–1.9% ED), VERTEBRAL FRACTURE (trauma / age >70 / osteoporosis / steroid; prior 0–7.2% ED), AAA (older arteriopath, pulsatile mass, tearing pain), and INFLAMMATORY BACK PAIN (ASAS pattern → axSpA route). Galliker Am J Med 2019 PMID 31278933; Verhagen Pain 2017 PMID 28708761
   inputs: cauda_equina_symptoms, cancer_history, immunosuppression_or_ivdu, fever_or_systemic_symptoms, significant_trauma_or_osteoporosis_steroid, progressive_neuro_deficit
   actions: workup.fracture_triage, panel.inflammation, panel.cbc
   advance: All serious-secondary red flags screened and escalated if present (cauda equina / progressive deficit → emergency routing)
5. 5INITIAL_WORKUP
   Mostly CLINICAL — no labs and NO routine imaging for red-flag-negative LBP. Targeted ESR/CRP + CBC ONLY if malignancy / infection / inflammatory suspicion (panel.inflammation, panel.cbc). Imaging deferred unless a red flag fires (Chou Lancet 2009 PMID 19200918; ACR Appropriateness Criteria Low Back Pain 2021; ACP 2017 Qaseem)
   inputs: fever_or_systemic_symptoms, cancer_history
   actions: workup.low_back_pain, panel.inflammation, panel.cbc
   advance: Clinical assessment complete; targeted labs sent only if a serious-secondary trigger present
6. 6BRANCHING_WORKUP
   Imaging by red flag ONLY: urgent whole-spine MRI for suspected cauda equina / cord-or-root compression / spinal infection / cord metastasis; XR ± CT via fracture-triage for trauma/osteoporotic fracture; HLA-B27 + sacroiliac-joint MRI if ASAS inflammatory-back-pain pattern → route axSpA. No imaging for red-flag-negative non-specific or radicular LBP within ~6 weeks (Chou Lancet 2009 PMID 19200918; ACR Appropriateness 2021; Sieper ASAS 2009 PMID 19147614)
   inputs: progressive_neuro_deficit, significant_trauma_or_osteoporosis_steroid, inflammatory_back_pain_features
   actions: workup.fracture_triage, panel.inflammation
   advance: Targeted imaging obtained ONLY for a fired red flag; inflammatory pattern routed to axSpA workup
7. 7DIFFERENTIAL
   Terminal phenotype: (1) non-specific mechanical LBP (≥90%); (2) radicular pain / lumbosacral radiculopathy (SLR LR− ≈ 0.29 rules OUT, crossed-SLR LR+ ≈ 2.8 rules IN — van der Windt Cochrane 2010 PMID 20166095); (3) symptomatic spinal stenosis (neurogenic claudication, older, flexion-relieved); (4) inflammatory back pain / axial spondyloarthritis (ASAS ≥4/5 → route rheum.axial-spondyloarthritis.core.v1); (5) serious-secondary (escalate). Look-alike: lumbar facet/spondylotic osteoarthritis shares the chronic axial phenotype (msk.osteoarthritis.core.v1)
   inputs: leg_pain_below_knee, inflammatory_back_pain_features
   advance: Phenotype assigned; inflammatory or serious-secondary routed; non-specific/radicular/stenosis retained for matched care
8. 8RISK_STRATIFICATION
   STarT Back tool (calc.start_back) → low / medium / high prognostic risk → matched-care intensity (stratified care: RMDQ benefit, +0.039 QALY, cost-saving — Hill Lancet 2011 PMID 21963002; external validation Morsø Trials 2018 PMID 29884217). Oswestry Disability Index (calc.oswestry_disability_index) for chronic functional baseline + serial tracking
   inputs: start_back_score, psychosocial_yellow_flags, oswestry_disability_index
   actions: calc.start_back, calc.oswestry_disability_index
   advance: STarT risk tier set (low → reassurance/self-management; medium → add structured physio; high → add psychologically-informed physio/CBT) and ODI baseline recorded for chronic
9. 9TREATMENT
   NON-PHARM FIRST. Acute/subacute: stay active + reassurance/education (favourable natural history — median recovery ~17 d, PACE Williams Lancet 2014 PMID 25064594), superficial heat, exercise, manual therapy. Chronic: structured exercise, CBT/MBSR, multidisciplinary biopsychosocial rehab (ACP 2017 Qaseem strong rec). PHARM SECOND: NSAID first-line (acute pain MD −7.29, disability MD −2.02; chronic pain MD −6.97 — Cashin Cochrane 2023 PMID 37014979) with the drug × comorbidity matrix (eGFR/CVD/PUD/pregnancy); short skeletal-muscle-relaxant course (small benefit + AE RR 1.6 — Cashin BMJ 2021 PMID 34233900); duloxetine 2nd-line CHRONIC (Skljarevski Spine 2010 PMID 20461028; ACP 2017). ACETAMINOPHEN MONOTHERAPY NOT EFFECTIVE for acute LBP (PACE HR 0.99 — PMID 25064594). GABAPENTINOIDS NOT RECOMMENDED for sciatica (PRECISE NEJM Mathieson 2017 PMID 28328324 — MD 0.5, NS, excess dizziness). Opioids last-line, lowest dose / shortest duration only after failed alternatives (Lancet 2018 Foster; McKenzie Spine J 2025 PMID 41077079). Cauda equina / progressive deficit = surgical emergency referral
   inputs: pain_duration_band, renal_hepatic_cv_gi_comorbidity, current_analgesics_and_opioids, pregnancy_status, start_back_score
   advance: Non-pharm core delivered + matched-care plan set; pharm escalated only on the evidence-based ladder; surgical referral made if indicated
10. 10DISPOSITION
    Almost all LBP is managed OUTPATIENT. ED → admit/urgent surgical referral ONLY for cauda equina, progressive/severe neurological deficit, suspected spinal infection, unstable/neoplastic fracture, or ruptured/symptomatic AAA (NICE NG59; ACR Appropriateness 2021)
    inputs: cauda_equina_symptoms, progressive_neuro_deficit
    advance: Level of care set: outpatient matched care, or emergency escalation for a fired red flag
11. 11MONITORING
    Re-screen red flags at each visit (new neuro deficit / cauda equina / systemic features). Reassess function with Oswestry Disability Index and re-run STarT Back if course changes. Expect acute recovery by ~6 weeks; non-improvement or worsening → re-triage and reconsider imaging. Monitor NSAID/opioid/SMR safety + opioid prescription count as a quality indicator (McKenzie Spine J 2025 PMID 41077079)
    inputs: oswestry_disability_index, start_back_score, progressive_neuro_deficit
    actions: calc.oswestry_disability_index, calc.start_back
    advance: Trajectory tracked; recovery on schedule OR re-triaged for persistence/worsening
12. 12FOLLOWUP
    Self-management, activity maintenance, exercise programme adherence, fear-avoidance counselling and early/sustained work participation (Lancet 2018 Foster PMID 29573872). Persistent or worsening LBP → re-evaluate phenotype, re-stratify, consider specialist/multidisciplinary referral; reinforce against opioid escalation and unnecessary imaging/surgery
    advance: Long-term self-management + work-participation plan in place with return precautions taught