Lenke 2D classification of operative adolescent idiopathic scoliosis

{
  "categories": [
    {
      "outcome_code": "1",
      "label": "main_thoracic",
      "proximal_thoracic": "nonstructural",
      "main_thoracic": "structural_major",
      "thoracolumbar_lumbar": "nonstructural"
    },
    {
      "outcome_code": "2",
      "label": "double_thoracic",
      "proximal_thoracic": "structural",
      "main_thoracic": "structural_major",
      "thoracolumbar_lumbar": "nonstructural"
    },
    {
      "outcome_code": "3",
      "label": "double_major",
      "proximal_thoracic": "nonstructural",
      "main_thoracic": "structural_major",
      "thoracolumbar_lumbar": "structural"
    },
    {
      "outcome_code": "4",
      "label": "triple_major",
      "proximal_thoracic": "structural",
      "main_thoracic": "structural",
      "thoracolumbar_lumbar": "structural",
      "major_curve": "main_thoracic_or_thoracolumbar_lumbar_whichever_has_the_largest_Cobb_angle"
    },
    {
      "outcome_code": "5",
      "label": "thoracolumbar_lumbar",
      "proximal_thoracic": "nonstructural",
      "main_thoracic": "nonstructural",
      "thoracolumbar_lumbar": "structural_major"
    },
    {
      "outcome_code": "6",
      "label": "thoracolumbar_lumbar_main_thoracic",
      "proximal_thoracic": "nonstructural",
      "main_thoracic": "structural",
      "thoracolumbar_lumbar": "structural_major_and_at_least_5_degrees_larger_than_main_thoracic"
    }
  ],
  "applicability": {
    "intended_use": "Classification of deformity patterns in operative adolescent idiopathic scoliosis and standardized communication/research using the classic two-dimensional Lenke system.",
    "classification_unit": "one_patient_with_a_complete_radiographic_series_and_one_full_curve_type_lumbar_modifier_sagittal_modifier_designation",
    "population_gate": "Use for adolescent idiopathic scoliosis after excluding congenital, neuromuscular, syndromic and other etiologies and after the treating team has established the relevant operative-evaluation context.",
    "outside_scope": [
      "early_onset_scoliosis",
      "congenital_scoliosis",
      "neuromuscular_or_syndromic_scoliosis",
      "adult_degenerative_deformity",
      "surgical_indication_from_classification_alone",
      "automatic_fusion_level_selection",
      "growth_or_progression_risk_without_Cobb_and_maturity",
      "three_dimensional_rotation_or_trunk_shape_without_3D_reconstruction"
    ]
  },
  "required_imaging_and_measurements": {
    "standing_coronal": "Technically adequate standing full-spine PA or AP radiograph including the entire deformity and pelvis, with vertebral levels, end vertebrae, apices, directions and Cobb angles recorded.",
    "standing_lateral": "Standing full-spine lateral radiograph including T2 through the pelvis, with regional kyphosis measurements and T5-T12 thoracic kyphosis.",
    "flexibility": "Supine right and left side-bending radiographs adequate to measure residual Cobb angles of candidate minor curves.",
    "pelvis_and_CSVL": "Pelvis sufficiently included and level to construct the central sacral vertical line for the lumbar modifier.",
    "prohibited_shortcut": "Do not infer structurality from the standing coronal image alone and do not assign a complete Lenke code without the bending and sagittal data."
  },
  "regional_curve_model": {
    "proximal_thoracic": "PT region; an apical thoracic curve in the proximal thoracic region, evaluated for coronal flexibility and T2-T5 kyphosis.",
    "main_thoracic": "MT region; thoracic apex from T2 through the T11-T12 disc, with the principal thoracic curve commonly represented here.",
    "thoracolumbar": "TL region when the apex is at T12 or L1, including the T12-L1 disc boundary convention.",
    "lumbar": "Lumbar apex from the L1-L2 disc through L4.",
    "direction_and_level_rule": "Retain curve direction, upper/lower end vertebrae, apex and exact Cobb angle for every regional curve; the type number alone discards clinically important geometry."
  },
  "structurality_algorithm": {
    "major_curve": "The largest Cobb-angle curve is the major curve and is structural by definition.",
    "minor_coronal_threshold": "A minor curve is structural when its residual Cobb angle on the appropriate side-bending film is at least 25 degrees.",
    "proximal_thoracic_sagittal_threshold": "A proximal thoracic minor curve is also structural when T2-T5 kyphosis is at least 20 degrees.",
    "main_thoracic_or_TL_L_sagittal_threshold": "A main thoracic or thoracolumbar/lumbar minor curve is also structural when T10-L2 kyphosis is at least 20 degrees.",
    "logical_operator": "A qualifying coronal bending threshold OR the applicable sagittal kyphosis threshold makes the minor curve structural.",
    "boundary_rule": "Exactly 25 degrees residual Cobb or exactly 20 degrees regional kyphosis meets structurality. Preserve measurement uncertainty when positioning or end-vertebra choice can cross the boundary.",
    "type_3_6_boundary": "Both have structural MT and TL/L curves with nonstructural PT. Type 3 has the MT major curve; Type 6 has the TL/L major curve at least 5 degrees larger than MT.",
    "type_4_correction": "All three regional curves are structural, but the major curve may be MT or TL/L. Do not force MT to be major."
  },
  "lumbar_modifier": {
    "reference": "Relationship of the central sacral vertical line to the apical lumbar vertebra on the standing coronal radiograph.",
    "A": "CSVL passes between the pedicles of the apical lumbar vertebra.",
    "B": "CSVL touches the apical lumbar vertebral body but does not pass between its pedicles.",
    "C": "CSVL does not touch the apical lumbar vertebral body; the apical body lies entirely lateral to the line.",
    "allowed_combinations": "Curve types 1-4 may pair with A, B or C. Curve types 5-6 pair with C in the classic combination set.",
    "quality_rule": "Pelvic obliquity, truncation or uncertain lumbar apex makes the modifier indeterminate; do not estimate the CSVL relationship."
  },
  "thoracic_sagittal_modifier": {
    "measurement": "Standing T5-T12 thoracic kyphosis by the declared Cobb method.",
    "minus": "less_than_10_degrees",
    "N": "10_to_40_degrees_inclusive",
    "plus": "greater_than_40_degrees",
    "boundary_rule": "10 degrees is N, and 40 degrees is N. Use minus only below 10 and plus only above 40."
  },
  "full_designation_and_combinations": {
    "format": "curve type number followed by lumbar modifier letter and sagittal modifier symbol or N, for example 1AN or 3C+.",
    "required_output": "Never return only 1-6 when the request is for a complete Lenke classification; return missing-modifier status if the full series is unavailable.",
    "classic_combination_count": "Fourteen permitted curve-type/lumbar-modifier combinations multiplied by three sagittal modifiers produce 42 classic patterns.",
    "no_severity_order": "Types 1-6 are morphologic patterns, not an ascending severity scale."
  },
  "reliability_and_uncertainty": {
    "original_developer_results": "Original curve-type interobserver and intraobserver kappa were 0.92 and 0.83 for developers; among seven independent scoliosis surgeons they were 0.740 and 0.893. Independent lumbar-modifier values were 0.800 and 0.840, and sagittal-modifier values 0.938 and 0.970.",
    "independent_study_limit": "In a separate 51-patient, five-observer operative series, all observers agreed on the complete classification in only 41 percent; mean interobserver kappa was 0.62 and intraobserver kappa 0.73. Proximal-thoracic structurality and the lumbar modifier were frequent disagreement sources.",
    "interpretation": "These are study-specific reliability results. Expose measurements and boundary uncertainty rather than presenting the output as perfectly reproducible."
  },
  "clinical_management_and_risk_boundary": {
    "planning_role": "The classification organizes deformity morphology and was developed to assist decisions about arthrodesis extent, but it does not encode a mandatory fusion construct or level set.",
    "required_management_context": [
      "symptoms_and_function",
      "Cobb_angles_and_curve_flexibility",
      "coronal_and_sagittal_balance",
      "shoulder_balance_and_trunk_shift",
      "axial_rotation_and_clinical_trunk_shape",
      "skeletal_maturity_and_growth_remaining",
      "neurologic_and_other_clinical_findings",
      "patient_goals_and_surgeon_judgment"
    ],
    "progression_risk": "The curve type does not provide a per-type natural-history probability. Progression assessment requires magnitude, serial change and maturity measures such as Sanders or explicitly named Risser convention.",
    "no_futility_or_outcome_claim": "Do not infer surgical outcome, complication risk, pulmonary impact or long-term disability from the type number alone."
  },
  "three_dimensional_extension_boundary": {
    "current_extension": "The SRS-Lenke-Aubin 3D classification, published online in 2025 and in Spine Deformity 2026, retains the classic curve/lumbar/sagittal base and adds transverse-plane modifiers for PT, MT and TL/L regions.",
    "transverse_modifiers": "Each P, T and L region receives an orientation of the plane of maximum deformity category ORPD 1-3 and an apical vertebral rotation category AVR small, medium or large derived from 3D reconstruction.",
    "noninterchangeability": "Do not invent transverse modifiers from standard two-dimensional radiographs and do not silently append them to or replace a classic Lenke code.",
    "correction": "A May 2026 correction replaced Figure 5 because the lumbar AVR in the example had been inadequately rounded. Any implementation of the 3D example must use the corrected article."
  },
  "agent_output_contract": {
    "always_return": [
      "population_and_etiology_scope",
      "imaging_series_adequacy",
      "each_regional_curve_direction_end_vertebrae_apex_Cobb_and_structurality_basis",
      "major_curve_identity",
      "curve_type_1_to_6",
      "lumbar_modifier_A_B_or_C_with_CSVL_relationship",
      "T5_T12_kyphosis_and_sagittal_modifier",
      "complete_classic_code",
      "boundary_uncertainty_and_missing_inputs",
      "classic_2D_or_SRS_Lenke_Aubin_3D_framework_name"
    ],
    "clinical_separation": "Return morphology separately from surgical indication, proposed fusion, progression risk and prognosis."
  },
  "missing_input_behavior": [
    "Without side-bending films, label minor-curve structurality unresolved and do not manufacture a curve type.",
    "Without standing lateral regional measurements, structurality and the sagittal modifier are incomplete.",
    "Without a level pelvis and visible lumbar apex, return the lumbar modifier as indeterminate.",
    "When residual Cobb or regional kyphosis is near a threshold, return the measured value, uncertainty and adjacent possible types.",
    "When the etiology is not adolescent idiopathic scoliosis, do not apply the operative-AIS map as if validated.",
    "Without 3D reconstruction, return only the classic 2D designation and explicitly withhold ORPD and AVR modifiers."
  ],
  "supporting_sources": [
    {
      "role": "primary",
      "citation": "Lenke et al. J Bone Joint Surg Am. 2001;83:1169-1181",
      "pmid": "11507125"
    },
    {
      "role": "open_classification_review",
      "citation": "Slattery and Verma. Clin Orthop Relat Res. 2018;476:2271-2276",
      "doi": "10.1097/CORR.0000000000000405",
      "pmcid": "PMC6259994"
    },
    {
      "role": "independent_reliability",
      "citation": "Ogon et al. Spine. 2002;27:858-862",
      "doi": "10.1097/00007632-200204150-00014",
      "pmid": "11935109"
    },
    {
      "role": "three_dimensional_extension",
      "citation": "Aubin et al. Spine Deform. 2026;14:655-668",
      "doi": "10.1007/s43390-025-01253-2",
      "pmcid": "PMC13282214"
    },
    {
      "role": "three_dimensional_correction",
      "citation": "Aubin et al. Spine Deform. 2026;14:1045-1047",
      "doi": "10.1007/s43390-026-01393-z",
      "pmcid": "PMC13282327"
    }
  ],
  "source_locator": "Lenke et al. 2001, PMID 11507125, Methods/Results for three-component system and reliability; Slattery and Verma 2018, PMC6259994, Curve Types, Structural Curves, Lumbar Spine Modifiers and Thoracic Sagittal Modifier; Ogon et al. 2002, PMID 11935109; Aubin et al. 2026, PMC13282214, classification framework; correction PMC13282327, corrected Figure 5."
}