Produce the complete classic 2D code only from a complete standing and flexibility series. Preserve the raw measurements, treat 1-6 as patterns rather than severity, and keep the 2026 3D extension explicitly separate.
{
"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."
}