Weber (Danis-Weber) classification of fibular ankle fractures

{
  "categories": [
    {
      "outcome_code": "A",
      "fibular_fracture_level": "below_distal_tibiofibular_syndesmosis",
      "synonym": "infrasyndesmotic"
    },
    {
      "outcome_code": "B",
      "fibular_fracture_level": "at_distal_tibiofibular_syndesmosis",
      "synonym": "transsyndesmotic"
    },
    {
      "outcome_code": "C",
      "fibular_fracture_level": "above_distal_tibiofibular_syndesmosis",
      "synonym": "suprasyndesmotic"
    }
  ],
  "applicability": {
    "use_for": "An acute ankle-region injury with an identifiable fibular fracture whose level can be compared with the distal tibiofibular syndesmosis.",
    "classification_unit": "one_ankle_with_one_index_fibular_fracture_level",
    "required_inputs": [
      "side",
      "complete_ankle_radiographs_including_mortise_and_true_lateral",
      "fibular_fracture_level",
      "mortise_alignment",
      "medial_malleolus_and_deltoid_assessment",
      "posterior_malleolus_assessment",
      "syndesmosis_assessment",
      "proximal_fibula_assessment_when_indicated"
    ],
    "outside_scope": [
      "isolated_medial_malleolus_fracture_without_fibular_fracture",
      "isolated_posterior_malleolus_fracture_without_fibular_fracture",
      "no_identifiable_fibular_fracture",
      "pediatric_physeal_or_transitional_fracture_requiring_another_system",
      "chronic_posttraumatic_deformity",
      "treatment_selection_from_type_alone"
    ]
  },
  "assignment_algorithm": [
    {
      "if": "fibular_fracture_is_distal_to_the_syndesmotic_level",
      "output_code": "A"
    },
    {
      "if": "fibular_fracture_crosses_or_is_centered_at_the_syndesmotic_level",
      "output_code": "B"
    },
    {
      "if": "fibular_fracture_is_proximal_to_the_syndesmotic_level",
      "output_code": "C"
    },
    {
      "if": "no_fibular_fracture_or_level_is_not_assessable",
      "output": "Weber_not_assignable"
    }
  ],
  "decisive_boundaries": {
    "level_only": "Assign A, B or C from fibular fracture level only. Do not change the category because the mortise appears stable or unstable.",
    "no_assumed_ligament_state": "The type does not establish whether the syndesmosis or deltoid ligament is intact, partially injured or completely disrupted.",
    "no_forced_category": "An isolated medial or posterior malleolar fracture and an ankle injury without a fibular fracture do not receive a Weber type.",
    "proximal_fibula_rule": "If the ankle pattern or medial clear-space findings raise concern for a high fibular injury, image and examine the whole fibula for a Maisonneuve pattern rather than assuming type B from the ankle field of view."
  },
  "stability_assessment_separate_from_type": {
    "direct_report_fields": [
      "mortise_congruence",
      "talar_shift",
      "medial_clear_space_and_technique",
      "medial_malleolus_fracture",
      "deltoid_injury_evidence",
      "posterior_malleolus_size_morphology_and_displacement",
      "tibiofibular_clear_space_and_overlap",
      "proximal_fibular_fracture",
      "open_injury",
      "neurovascular_status",
      "soft_tissue_condition"
    ],
    "weight_bearing_role": "For an isolated distal fibular fracture of uncertain stability, current practice may use weight-bearing radiographs when clinically appropriate rather than assuming stability from a non-weight-bearing Weber label.",
    "stress_and_intraoperative_role": "Stress imaging or intraoperative syndesmotic testing belongs to the stability evaluation and must be reported separately from the Weber type.",
    "CT_role": "CT is useful for complex patterns, posterior malleolar involvement, plafond extension or preoperative morphology; CT does not redefine A, B or C away from the fibular level rule."
  },
  "risk_interpretation": {
    "anatomic_association": "More proximal fracture levels can be associated with more extensive soft-tissue injury, but Weber type is an imperfect proxy for actual syndesmotic and medial-column integrity.",
    "cohort_limit": "In one 51-patient MRI study, the radiographic Weber/AO level classification had 47 percent sensitivity and 100 percent specificity for syndesmotic injury; these cohort estimates are not a patient's probability and show why level alone cannot exclude ligament injury.",
    "no_personal_prognosis": "No type supplies a calibrated individual probability of displacement, nonunion, post-traumatic arthritis, reoperation or functional outcome."
  },
  "management_boundary": {
    "immediate_actions_from_findings": "Open injury, neurovascular compromise or deformity requiring urgent reduction is managed from those findings, not from the Weber letter.",
    "stable_pathway": "A fracture proven stable may follow a functional or nonoperative pathway under the applicable protocol, regardless of a simplistic type stereotype.",
    "uncertain_pathway": "When stability is uncertain, arrange timely clinical review and supported stability imaging rather than declaring type A stable or type C operative by definition.",
    "unstable_pathway": "An unstable mortise or syndesmosis may require operative stabilization after patient-specific assessment, but the Weber letter alone does not mandate fixation, choose implants or define the surgical plan.",
    "BOAST_context": "BOAST recommends urgent reduction and splintage for deformity, true lateral and mortise radiographs, whole-leg imaging when a proximal fibular injury is suspected, weight bearing as tolerated for stable fractures, review with weight-bearing radiographs for uncertain stability, and direct assessment of syndesmotic stability when treating an unstable mortise."
  },
  "system_collision_boundary": {
    "AO_OTA_44": "AO/OTA 44A, 44B and 44C expand ankle fracture morphology beyond the base Weber level labels. Preserve the named system and do not silently equate every AO/OTA subtype with a complete Weber diagnosis.",
    "Lauge_Hansen": "Lauge-Hansen describes inferred mechanism and injury stage. Weber describes fibular level. Similar-looking patterns do not permit an automatic crosswalk without reconstructing all component injuries.",
    "Maisonneuve": "Maisonneuve is a named injury pattern with proximal fibular and syndesmotic or medial injury; report the full pattern rather than using C as its only description."
  },
  "agent_output_contract": [
    "Return side, examination views and whether the entire fibula was assessed when a proximal injury is possible.",
    "Return fibular fracture level, orientation, displacement and the named Weber type.",
    "Return mortise congruence, talar shift, medial and posterior malleolar findings, syndesmotic indicators and proximal fibular findings as independent fields.",
    "Return open or closed status, neurovascular findings and soft-tissue urgency separately when available.",
    "State whether stability is established, uncertain or unstable and identify the evidence; never infer it from the letter alone.",
    "Keep AO/OTA and Lauge-Hansen labels separate and do not turn the type into prognosis or an operative order."
  ],
  "missing_input_behavior": [
    "If the fibular fracture level is outside the field of view, request appropriate ankle or whole-leg imaging rather than forcing A, B or C.",
    "If no fibular fracture exists, return Weber_not_assignable and describe the actual medial, posterior or ligamentous injury.",
    "If mortise stability is unresolved, return stability_uncertain and the next supported assessment rather than using the Weber type as a substitute.",
    "If only a Weber letter is supplied, do not infer syndesmotic disruption, deltoid injury, mortise stability, treatment or prognosis."
  ],
  "supporting_sources": [
    {
      "role": "historical_classification",
      "citation": "Weber BG. Die Verletzungen des oberen Sprunggelenkes. 1972",
      "url": "https://cir.nii.ac.jp/crid/1130000795807421952"
    },
    {
      "role": "stability_and_management_review",
      "citation": "Lampridis et al. EFORT Open Rev. 2018;3:294-303",
      "doi": "10.1302/2058-5241.3.170057",
      "pmcid": "PMC5994620"
    },
    {
      "role": "ligament_prediction_limit",
      "citation": "Hermans et al. Skeletal Radiol. 2012;41:787-801",
      "doi": "10.1007/s00256-011-1284-2",
      "pmcid": "PMC3368108"
    },
    {
      "role": "current_trauma_standard",
      "citation": "BOAST 12: The Management of Ankle Fractures. 2016",
      "url": "https://www.boa.ac.uk/resource/boast-12-pdf.html"
    }
  ],
  "source_locator": "Weber 1972 monograph bibliographic record for lineage; Lampridis et al. 2018, PMC5994620, classification limitations, stability assessment, weight-bearing radiographs and treatment discussion; Hermans et al. 2012, PMC3368108, MRI correlation and sensitivity/specificity; BOAST 12, standards 1-16 for acute assessment, imaging, stability and syndesmosis."
}