Myerson Lisfranc Original Myerson-modified Hardcastle classification of Lisfranc fracture-dislocations

{
  "categories": [
    {
      "outcome_code": "A",
      "congruity": "total_incongruity",
      "displaced_metatarsals": "M1_through_M5",
      "direction": "same_direction_homolateral_lateral_or_dorsoplantar"
    },
    {
      "outcome_code": "B1",
      "congruity": "partial_isolated_incongruity",
      "displaced_metatarsals": "M1",
      "direction": "medial"
    },
    {
      "outcome_code": "B2",
      "congruity": "partial_isolated_incongruity",
      "displaced_metatarsals": "one_or_more_of_M2_through_M5",
      "direction": "lateral"
    },
    {
      "outcome_code": "C1",
      "congruity": "partial_divergent_incongruity",
      "displaced_metatarsals": "M1_medial_plus_fewer_than_all_four_lateral_metatarsals",
      "direction": "divergent"
    },
    {
      "outcome_code": "C2",
      "congruity": "total_divergent_incongruity",
      "displaced_metatarsals": "M1_medial_plus_all_M2_through_M5_lateral",
      "direction": "divergent"
    }
  ],
  "applicability": {
    "use_for": "Morphologic communication of an acute Lisfranc tarsometatarsal fracture-dislocation with visible incongruity or displacement.",
    "classification_unit": "one_injured_foot",
    "required_inputs": [
      "side",
      "M1_through_M5_alignment",
      "direction_of_each_displaced_metatarsal_base",
      "extent_of_tarsometatarsal_incongruity",
      "weightbearing_status",
      "radiograph_or_CT_adequacy"
    ],
    "outside_scope": [
      "occult_or_subtle_stability_determination",
      "ligament_integrity",
      "Nunley_Vertullo_athletic_staging",
      "2015_type_D_subtyping",
      "operative_indication",
      "patient_specific_prognosis"
    ]
  },
  "classification_algorithm": [
    {
      "step": 1,
      "question": "Are all five metatarsal bases displaced together in the same direction?",
      "yes": "A",
      "no": "continue"
    },
    {
      "step": 2,
      "question": "Is only the first ray displaced medially while the lateral rays remain congruent?",
      "yes": "B1",
      "no": "continue"
    },
    {
      "step": 3,
      "question": "Are one or more lateral four metatarsal bases displaced laterally without medial M1 divergence?",
      "yes": "B2",
      "no": "continue"
    },
    {
      "step": 4,
      "question": "Is M1 displaced medially while lateral rays displace laterally?",
      "yes": "C_branch",
      "no": "out_of_schema_or_unresolved"
    },
    {
      "step": 5,
      "question": "In a divergent injury, are all four lateral metatarsals displaced?",
      "yes": "C2",
      "no": "C1"
    }
  ],
  "imaging_and_quality_gate": {
    "initial_assessment": "Use a complete foot radiographic series; when safe and feasible, bilateral weightbearing views improve assessment of subtle alignment and physiologic instability.",
    "CT_role": "CT defines occult fractures, articular comminution and three-dimensional displacement and is useful for operative planning, but a nonweightbearing CT does not by itself prove physiologic stability.",
    "MRI_role": "MRI can assess the Lisfranc ligament complex when radiographs or CT do not resolve a suspected ligamentous injury; ligament status is an additional variable, not an A-C code.",
    "current_ACR_next_test": "When acute Lisfranc injury remains suspected and radiographs are normal or equivocal, current ACR guidance rates CT without contrast or MRI without contrast as usually appropriate alternatives.",
    "adequacy_rule": "If the full first-through-fifth tarsometatarsal complex or displacement direction cannot be followed, return unclassifiable or the competing patterns rather than assigning from one projection."
  },
  "stability_and_variant_boundaries": {
    "morphology_not_stability": "The original A-C pattern describes displacement topology. It does not encode whether a subtle or reduced injury is stable under load.",
    "type_D_2018_extension": "Sivakumar and colleagues' 2018 topical review proposed D1 for a stable or nondisplaced injury with C1-M2 distance at most 2 mm and D2 for an unstable or displaced injury over 2 mm, with D2L ligamentous and D2B bony subtypes.",
    "noninterchangeability": "Type D is not part of the original five-code 1986 output. Do not silently append D1 or D2, or use its 2 mm stability boundary to redefine A, B or C.",
    "Nunley_Vertullo": "The Nunley-Vertullo system stages subtle athletic Lisfranc injury using clinical and weightbearing or stress information; it answers a different question and cannot be converted one-to-one to Myerson A-C.",
    "reduced_injury": "A previously reduced or spontaneously aligned injury may be clinically unstable yet out of schema for the original displaced-pattern classification."
  },
  "reporting_contract": {
    "required_output": "Report side, Myerson code and plain-language displacement pattern, then separately describe fractures, columns or joints involved, comminution, instability evidence, ligament injury and associated midfoot injury.",
    "no_code_only": "Because observer performance and applicability vary by image set and injury spectrum, never return the code without its anatomic descriptor.",
    "uncertainty": "If B2 versus C1 depends on uncertain M1 medial displacement, report that exact boundary and request a better aligned or weightbearing examination when clinically safe."
  },
  "management_boundary": {
    "historical_context": "In the original displaced-injury series, restoration and maintenance of anatomic alignment were central, and reduction quality strongly related to outcome; historical thresholds and operations are not a universal current per-code prescription.",
    "current_decision_inputs": "Treatment depends on displacement and instability, bony versus ligamentous anatomy, soft-tissue condition, reducibility, articular damage, patient factors, timing and specialist assessment.",
    "nonoperative_guard": "Do not infer that every B or C pattern mandates the same operation, and do not infer that a normal-appearing nonweightbearing study is safe for unrestricted loading.",
    "urgent_context": "Open injury, threatened skin, neurovascular compromise, compartment syndrome or irreducible dislocation requires urgent clinical action independent of the Myerson label."
  },
  "risk_and_reliability": {
    "original_cohort": "The 1986 historical cohort included 72 patients with 76 injuries; among the long-term analyzed feet, only 49 percent had excellent or good results, direct crush did poorly, reduction quality was a major determinant, and late instability or degeneration drove symptoms. These results are not calibrated per-type probabilities for contemporary care.",
    "reliability_2015": "After observer training on 39 radiographs, mean intraobserver ICC was 0.94 and interobserver ICC 0.81, supporting reproducibility in that study.",
    "reliability_2023": "A later 31-case radiograph-plus-CT study reported Myerson interobserver ICC 0.277 and intraobserver ICC 0.505, and many cases were considered non-applicable; differences in cohort, images and methods explain why reliability must not be advertised as universal.",
    "prognosis_guard": "Code alone does not predict post-traumatic arthritis, need for fusion, return to sport or patient-reported outcome; alignment, ligamentous damage, energy, cartilage injury and treatment quality materially affect prognosis."
  },
  "missing_input_behavior": [
    "If weightbearing or stress stability is unknown in a subtle injury, return stability unknown and do not force an A-C type.",
    "If M1 direction is not visible, do not distinguish B2 from C1 by guessing.",
    "If not all lateral rays are evaluable, do not distinguish C1 from C2.",
    "If the injury has been reduced before imaging, state that the original displacement pattern may be unrecoverable.",
    "If the requested code includes D1, D2, D2L or D2B, identify it as the later extension and do not claim it came from the 1986 five-pattern system."
  ],
  "supporting_sources": [
    {
      "role": "primary_classification_and_outcomes",
      "citation": "Myerson et al. Foot & Ankle. 1986;6:225-242",
      "doi": "10.1177/107110078600600504",
      "pmid": "3710321"
    },
    {
      "role": "later_type_D_extension",
      "citation": "Sivakumar et al. Orthopedics. 2018;41:e168-e175",
      "doi": "10.3928/01477447-20180213-07",
      "pmid": "29451936"
    },
    {
      "role": "imaging_application",
      "citation": "Siddiqui et al. RadioGraphics. 2014;34:514-531",
      "doi": "10.1148/rg.342125215"
    },
    {
      "role": "reliability_study",
      "citation": "Mahmoud et al. International Orthopaedics. 2015;39:2215-2218",
      "doi": "10.1007/s00264-015-2939-8",
      "pmid": "26224617"
    },
    {
      "role": "reliability_and_applicability_study",
      "citation": "Engelmann et al. Fuss und Sprunggelenk. 2023;21:333-340",
      "doi": "10.1016/j.fuspru.2023.07.007"
    },
    {
      "role": "current_imaging_guidance",
      "citation": "ACR Appropriateness Criteria Acute Trauma to the Foot",
      "doi": "10.1016/j.jacr.2020.01.019",
      "pmid": "32370964"
    }
  ],
  "source_locator": "Myerson et al. 1986, DOI 10.1177/107110078600600504, primary classification and historical outcome series; Sivakumar et al. 2018, DOI 10.3928/01477447-20180213-07, proposed type D extension; Siddiqui et al. 2014, DOI 10.1148/rg.342125215, Myerson table and imaging assessment; Mahmoud et al. 2015, PMID 26224617, observer reliability; Engelmann et al. 2023, DOI 10.1016/j.fuspru.2023.07.007, reliability and non-applicability; current ACR Acute Trauma to the Foot Variant 5 for CT or MRI after normal or equivocal radiographs."
}