AO Spine TL AO Spine thoracolumbar injury classification and TL AOSIS

{
  "feature_groups": [
    {
      "id": "morphology",
      "choose_one_exact_subtype_per_injury": true,
      "codes": [
        "A0",
        "A1",
        "A2",
        "A3",
        "A4",
        "B1",
        "B2",
        "B3",
        "C"
      ]
    },
    {
      "id": "clinical_neurologic_status",
      "choose_one": true,
      "codes": [
        "N0",
        "N1",
        "N2",
        "N3",
        "N4",
        "NX"
      ]
    },
    {
      "id": "modifiers",
      "codes": [
        "M1",
        "M2"
      ],
      "rule": "M1_adds_one_point; M2_adds_zero_points_but_must_remain_explicit_context"
    }
  ],
  "score_map": {
    "formula": "morphology_points + neurologic_points + M1_points",
    "management_bands": [
      "0_to_3_nonoperative_trial",
      "4_or_5_either_pathway",
      "6_or_more_surgical_intervention_recommended"
    ],
    "nonabsolute_rule": "The total is consensus treatment guidance, not a standalone order or prognosis."
  },
  "applicability": {
    "use_for": "acute_traumatic_thoracolumbar_spine_injury",
    "classification_unit": "one_injury_or_injured_motion_segment_with_every_additional_level_reported_separately",
    "required_inputs": [
      "CT_or_adequate_radiographic_morphology",
      "reliable_clinical_neurologic_examination_or_NX",
      "M1_tension_band_uncertainty",
      "M2_patient_specific_context"
    ],
    "exclusions_and_boundaries": [
      "do_not_use_as_an_osteoporotic_fragility_fracture_score",
      "do_not_substitute_cervical_AO_or_SLIC_rules",
      "do_not_infer_neurology_from_canal_narrowing"
    ]
  },
  "morphology_hierarchy": [
    {
      "code": "A0",
      "parent": "A",
      "label": "minor_nonstructural_injury",
      "definition": "insignificant_process_or_lamina_fracture_without_material_instability",
      "posterior_wall": "not_a_burst_pattern",
      "points": 0
    },
    {
      "code": "A1",
      "parent": "A",
      "label": "wedge_compression_or_impaction",
      "definition": "endplate_impaction_without_a_fracture_line_connecting_to_the_posterior_wall",
      "posterior_wall": "intact",
      "points": 1
    },
    {
      "code": "A2",
      "parent": "A",
      "label": "split_or_pincer",
      "definition": "both_endplates_involved_without_posterior_wall_involvement",
      "posterior_wall": "intact",
      "points": 2
    },
    {
      "code": "A3",
      "parent": "A",
      "label": "incomplete_burst",
      "definition": "one_endplate_and_posterior_wall_involved",
      "posterior_tension_band": "maintained_unless_separately_injured",
      "points": 3
    },
    {
      "code": "A4",
      "parent": "A",
      "label": "complete_burst",
      "definition": "both_endplates_and_posterior_wall_involved",
      "points": 5
    },
    {
      "code": "B1",
      "parent": "B",
      "label": "transosseous_posterior_tension_band_disruption_Chance",
      "definition": "monosegmental_complete_osseous_failure_of_the_posterior_tension_band_extending_into_the_vertebral_body",
      "points": 5
    },
    {
      "code": "B2",
      "parent": "B",
      "label": "posterior_tension_band_disruption",
      "definition": "posterior_osseoligamentous_or_soft_tissue_and_bony_failure_without_translation",
      "points": 6
    },
    {
      "code": "B3",
      "parent": "B",
      "label": "hyperextension",
      "definition": "anterior_tension_band_failure_through_disc_or_vertebral_body_in_hyperextension",
      "context": "commonly_seen_in_ankylotic_disorders",
      "points": 7
    },
    {
      "code": "C",
      "parent": "C",
      "label": "translation_or_dislocation",
      "definition": "displacement_or_dislocation_with_separation_of_anterior_and_posterior_components_in_any_plane",
      "points": 8
    }
  ],
  "morphology_assignment_algorithm": [
    {
      "step": 1,
      "question": "Is there displacement, dislocation or translation?",
      "yes": "C",
      "no": "continue"
    },
    {
      "step": 2,
      "question": "Is an anterior or posterior tension band disrupted?",
      "anterior": "B3",
      "posterior_purely_transosseous_monosegmental": "B1",
      "posterior_other": "B2",
      "no": "continue"
    },
    {
      "step": 3,
      "question": "Does a vertebral-body fracture involve the posterior wall?",
      "yes_one_endplate": "A3",
      "yes_both_endplates": "A4",
      "no_both_endplates_connected": "A2",
      "no_wedge_or_impaction": "A1",
      "only_minor_nonstructural_fracture": "A0"
    },
    {
      "step": 4,
      "rule": "For B and C injuries, record the injured motion-segment level and any associated A subtype in parentheses rather than discarding it."
    }
  ],
  "neurologic_status": [
    {
      "code": "N0",
      "definition": "neurologically_intact",
      "points": 0
    },
    {
      "code": "N1",
      "definition": "transient_neurologic_deficit_that_has_resolved",
      "points": 1
    },
    {
      "code": "N2",
      "definition": "radicular_symptoms_or_nerve_root_injury",
      "points": 2
    },
    {
      "code": "N3",
      "definition": "incomplete_spinal_cord_injury_or_any_degree_of_cauda_equina_injury",
      "points": 4
    },
    {
      "code": "N4",
      "definition": "complete_spinal_cord_injury",
      "points": 4
    },
    {
      "code": "NX",
      "definition": "cannot_be_examined_or_neurologic_status_unknown",
      "points": 3
    }
  ],
  "neurologic_gate": {
    "source": "Use the time-stamped clinical neurologic examination; CT or MRI canal compromise cannot assign N0-N4.",
    "continued_compression_suffix": "Add the separate plus descriptor when continued spinal cord compression is present in a patient with neurologic deficit; it has no independent TL AOSIS point value.",
    "reassessment": "If sedation, intoxication, shock, head injury or other confounding prevents examination, use NX and update the record when examination becomes reliable."
  },
  "modifiers": [
    {
      "code": "M1",
      "definition": "indeterminate_tension_band_injury_on_imaging_with_or_without_MRI_or_examination",
      "points": 1,
      "use": "preserve_uncertainty_that_may_affect_stabilization"
    },
    {
      "code": "M2",
      "definition": "patient_specific_comorbidity_or_condition_that_may_argue_for_or_against_surgery",
      "examples": [
        "ankylosing_spinal_disorder",
        "burn_or_soft_tissue_problem_over_the_operating_site"
      ],
      "points": 0,
      "use": "context_not_numeric_severity"
    }
  ],
  "calculation": {
    "formula": "TL_AOSIS = morphology_points + neurologic_points + M1_points; M2 contributes context and zero points.",
    "morphology_points": {
      "A0": 0,
      "A1": 1,
      "A2": 2,
      "A3": 3,
      "A4": 5,
      "B1": 5,
      "B2": 6,
      "B3": 7,
      "C": 8
    },
    "neurologic_points": {
      "N0": 0,
      "N1": 1,
      "N2": 2,
      "N3": 4,
      "N4": 4,
      "NX": 3
    },
    "modifier_points": {
      "M1": 1,
      "M2": 0
    },
    "arithmetic_rule": "Use one exact morphology per classified injury, one N code and optional M1; do not add parent A/B/C points or sum unrelated levels into one patient score."
  },
  "treatment_guidance": {
    "bands": [
      {
        "total": "0_to_3",
        "recommendation": "initial_trial_of_nonoperative_management"
      },
      {
        "total": "4_or_5",
        "recommendation": "operative_or_nonoperative_management_is_acceptable"
      },
      {
        "total": "6_or_more",
        "recommendation": "surgical_intervention_recommended"
      }
    ],
    "subtype_consequences": {
      "type_A": "The parent A label spans morphology scores 0 through 5; neurology and M1 can cross a treatment band, so A alone cannot select management.",
      "type_B": "B1 starts at 5 and is intermediate when N0/M1 absent; B2 and B3 start at 6 and 7. Always name the subtype before applying the algorithm.",
      "type_C": "C contributes 8 morphology points and therefore exceeds the surgical-guidance threshold before neurologic points; urgent specialist assessment remains subject to resuscitation, contraindications and patient-specific context."
    },
    "evidence_boundary": "The 2016 thresholds came from international surgeon recommendations. They guide initial management but do not replace examination, instability assessment, polytrauma priorities, goals of care or specialist judgment."
  },
  "decisive_boundaries": {
    "A1_versus_A3": "Posterior vertebral-body wall involvement makes the injury a burst pattern A3/A4, not A1.",
    "A2_versus_A4": "Both endplates with an intact posterior wall is A2; both endplates plus posterior wall is A4.",
    "A3_versus_A4": "One fractured endplate with posterior-wall involvement is A3; both endplates with posterior-wall involvement is A4.",
    "B1_versus_B2": "Pure monosegmental transosseous posterior tension-band failure is B1; osseoligamentous or non-pure posterior disruption is B2.",
    "B_versus_C": "Tension-band failure without translation is B; any displacement/dislocation or translation in any plane takes precedence as C.",
    "lamina_guard": "A vertical lamina fracture accompanying a burst injury reflects compression and does not by itself prove posterior tension-band disruption."
  },
  "risk_interpretation": {
    "construct": "TL AOSIS encodes expert-perceived injury severity and treatment tendency, not an observed probability model.",
    "prohibited_inferences": [
      "individual_paralysis_probability",
      "mortality_probability",
      "late_kyphosis_probability",
      "pain_or_functional_outcome",
      "operative_success_probability"
    ],
    "M2_boundary": "M2 can move a real decision toward or away from surgery despite adding zero points; zero does not mean clinically irrelevant."
  },
  "system_collision_boundary": {
    "TLICS": "TLICS separately scores morphology, posterior ligamentous complex integrity and neurology with thresholds 3/4/5; do not convert an AO subtype or TL AOSIS total into TLICS.",
    "subaxial_cervical_AO_or_SLIC": "Cervical injury codes and modifiers are different. Do not import the SLIC ongoing-compression point into TL AOSIS.",
    "osteoporotic_fracture_classification": "Fragility fractures require the appropriate osteoporotic fracture framework and clinical context; a similar A label is not interchangeable."
  },
  "agent_output_contract": [
    "Report every injured level and identify the most consequential injury without summing unrelated levels.",
    "Return the exact A0-A4, B1-B3 or C morphology and the raw feature that determined each branch.",
    "For B or C, name the motion segment and preserve the associated A subtype.",
    "Return the time-stamped clinical N code, examination reliability and the continued-compression plus descriptor when supported.",
    "Return M1 and the explicit M2 context separately.",
    "Show morphology + neurology + M1 arithmetic, total, threshold band and why the band is guidance rather than an automatic order.",
    "Keep canal compromise, instability, prognosis and definitive treatment as separate outputs."
  ],
  "missing_input_behavior": [
    "If posterior-wall involvement or endplate count is unresolved, return the bounded A1/A2 versus A3/A4 alternatives and request the decisive CT feature.",
    "If tension-band injury is indeterminate rather than established, retain the best A morphology and add M1; do not silently promote it to B.",
    "If the neurologic examination is unavailable, use NX rather than N0 and state the confounder.",
    "If only parent A or B is supplied, do not calculate a unique score or management band; request the subtype.",
    "If only a TL AOSIS total is supplied, do not reverse-engineer morphology, neurology, M1, prognosis or treatment."
  ],
  "supporting_sources": [
    {
      "role": "classification_primary",
      "citation": "Vaccaro et al. Spine. 2013;38:2028-2037",
      "doi": "10.1097/BRS.0b013e3182a8a381"
    },
    {
      "role": "score_primary",
      "citation": "Kepler et al. Global Spine J. 2016;6:329-334",
      "doi": "10.1055/s-0035-1563610",
      "pmcid": "PMC4868575"
    },
    {
      "role": "treatment_algorithm_primary",
      "citation": "Vaccaro et al. Eur Spine J. 2016;25:1087-1094",
      "doi": "10.1007/s00586-015-3982-2",
      "pmid": "25953527"
    },
    {
      "role": "official_operational_reference",
      "citation": "AO Spine Thoracolumbar Injury Classification pocket card and Surgery Reference",
      "url": "https://surgeryreference.aofoundation.org/spine/trauma/thoracolumbar/further-reading/rationale-for-fracture-classification-a0-a1-a2-a3-a4-b1-b2-b3-c"
    },
    {
      "role": "evidence_boundary",
      "citation": "Dailey et al. Neurosurgery. 2019;84:E24-E27",
      "doi": "10.1093/neuros/nyy372",
      "pmid": "30202904"
    }
  ],
  "source_locator": "Vaccaro et al. Spine 2013, DOI 10.1097/BRS.0b013e3182a8a381, morphology/neurology/modifier tables; Kepler et al. 2016, DOI 10.1055/s-0035-1563610, Tables 3-4; Vaccaro et al. Eur Spine J 2016, DOI 10.1007/s00586-015-3982-2, abstract treatment bands; AO Spine pocket card and Surgery Reference flow chart."
}