Apply the original four-feature matrix per lumbar disc. Preserve discordant features and version identity; never turn a morphology grade into a pain diagnosis or treatment command.
{
"categories": [
{
"outcome_code": "I",
"structure": "homogeneous_bright_white",
"nucleus_annulus_distinction": "clear",
"T2_signal": "hyperintense_and_isointense_to_CSF",
"disc_height": "normal"
},
{
"outcome_code": "II",
"structure": "inhomogeneous_with_or_without_horizontal_bands",
"nucleus_annulus_distinction": "clear",
"T2_signal": "hyperintense_and_isointense_to_CSF",
"disc_height": "normal"
},
{
"outcome_code": "III",
"structure": "inhomogeneous_gray",
"nucleus_annulus_distinction": "unclear",
"T2_signal": "intermediate",
"disc_height": "normal_to_slightly_decreased"
},
{
"outcome_code": "IV",
"structure": "inhomogeneous_gray_to_black",
"nucleus_annulus_distinction": "lost",
"T2_signal": "intermediate_to_hypointense",
"disc_height": "normal_to_moderately_decreased"
},
{
"outcome_code": "V",
"structure": "inhomogeneous_black",
"nucleus_annulus_distinction": "lost",
"T2_signal": "hypointense",
"disc_height": "collapsed_disc_space"
}
],
"applicability": {
"use_for": "Gross morphologic grading of each lumbar intervertebral disc on routine midsagittal T2-weighted MRI.",
"classification_unit": "one_lumbar_intervertebral_disc_level",
"required_inputs": [
"disc_level",
"diagnostic_midsagittal_T2_image",
"disc_structure",
"nucleus_annulus_distinction",
"T2_signal_relative_to_CSF",
"disc_height"
],
"outside_scope": [
"disc_bulge_protrusion_extrusion_or_sequestration",
"annular_fissure",
"Modic_endplate_change",
"canal_or_foraminal_stenosis",
"pain_generator_identification",
"treatment_selection"
]
},
"acquisition_and_quality_gate": {
"primary_sequence": "Routine T2-weighted midsagittal lumbar MRI, matching the sequence used to develop and test the original system.",
"level_rule": "Identify and grade every requested disc level separately; do not transfer a grade from one level to another.",
"adequacy_rule": "If structure, T2 signal, nucleus-annulus distinction or height cannot be judged because the sequence, plane, artifact or coverage is inadequate, return no definitive grade and name the missing feature.",
"anatomy_variant_guard": "A congenitally small or transitional lumbosacral disc can have reduced height with relatively preserved signal. Do not call Grade V from height alone when the morphology suggests hypoplasia or segmentation variation."
},
"feature_model": {
"structure": "Homogeneous versus inhomogeneous internal morphology, including whether horizontal bands are present.",
"distinction": "Visibility of the boundary between nucleus pulposus and annulus fibrosus: clear, unclear or lost.",
"signal": "Qualitative T2 signal of the disc, with CSF as the original high-signal reference: hyperintense, intermediate or hypointense.",
"height": "Qualitative disc-space height: normal, slightly decreased, moderately decreased or collapsed; the original five-grade system does not define percentage cutoffs.",
"combined_rule": "Assign the grade from the complete four-feature pattern rather than from darkness, height or any single feature in isolation."
},
"classification_algorithm": [
{
"if_all": [
"homogeneous_bright_white",
"clear_nucleus_annulus_boundary",
"T2_hyperintense_isointense_to_CSF",
"normal_height"
],
"output_code": "I"
},
{
"if_all": [
"inhomogeneous_with_or_without_horizontal_bands",
"clear_nucleus_annulus_boundary",
"T2_hyperintense_isointense_to_CSF",
"normal_height"
],
"output_code": "II"
},
{
"if_all": [
"inhomogeneous_gray",
"unclear_nucleus_annulus_boundary",
"intermediate_T2_signal",
"normal_to_slightly_decreased_height"
],
"output_code": "III"
},
{
"if_all": [
"inhomogeneous_gray_to_black",
"lost_nucleus_annulus_boundary",
"intermediate_to_hypointense_T2_signal",
"normal_to_moderately_decreased_height"
],
"output_code": "IV"
},
{
"if_all": [
"inhomogeneous_black",
"lost_nucleus_annulus_boundary",
"hypointense_T2_signal",
"collapsed_disc_space"
],
"output_code": "V"
}
],
"boundary_and_conflict_rules": {
"I_versus_II": "Both retain high T2 signal, a clear nucleus-annulus boundary and normal height; internal homogeneity separates I from the inhomogeneity or horizontal bands of II.",
"II_versus_III": "Loss of high CSF-like signal and transition from a clear to an unclear nucleus-annulus boundary support III.",
"III_versus_IV": "Disc height overlaps and is not a reliable discriminator; use the transition from gray/unclear to gray-black/lost distinction together with signal loss.",
"IV_versus_V": "Grade V requires a collapsed disc space in addition to a black hypointense disc and lost distinction. A dark disc with preserved or only moderately reduced height remains IV.",
"discordant_features": "When the four features straddle adjacent grades, preserve the full feature vector and state the adjacent-grade uncertainty; do not average ordinal labels or force a grade from one feature."
},
"version_boundary": {
"original_map": "This decision map is the five-grade Pfirrmann 2001 system.",
"modified_map": "The later modified Pfirrmann system uses eight grades and explicit height-reduction bands; those grade numbers and thresholds are a separate derivative and must not be backported into this five-grade map.",
"fractional_or_AI_grades": "Fractional or continuous model outputs are not official grades in the original system. Convert only with an explicitly validated mapping and retain the native model output."
},
"separate_reporting_requirements": [
"Report disc herniation morphology and nerve-root effect separately from the Pfirrmann grade.",
"Report Modic marrow change, endplate defect, stenosis, spondylolisthesis, facet disease and postoperative findings separately.",
"Correlate degenerative morphology with symptoms and examination; the grade does not identify a pain generator."
],
"management_and_risk_context": {
"management_rule": "No Pfirrmann grade independently prescribes observation, injection, surgery or follow-up. Management depends on symptoms, neurologic findings, instability, stenosis, herniation and the broader clinical context.",
"risk_rule": "The ordinal grade expresses morphologic degeneration severity only. The original system does not provide a per-grade probability of pain, progression, neurologic deficit or future intervention.",
"research_rule": "Use exact per-level grades and the original version when comparing studies; do not mix the five-grade and eight-grade systems as if their numbers were interchangeable."
},
"output_contract": [
"lumbar_disc_level",
"sequence_and_technical_adequacy",
"structure_feature",
"nucleus_annulus_distinction",
"T2_signal_relative_to_CSF",
"disc_height_category",
"Pfirrmann_grade_I_to_V_or_adjacent_grade_uncertainty",
"separate_herniation_stenosis_endplate_and_postoperative_findings",
"no_treatment_or_pain_inference_from_grade_alone"
],
"missing_input_behavior": [
"If the midsagittal T2 image is absent or nondiagnostic, do not assign a definitive Pfirrmann grade.",
"If disc height is unknown in a dark disc, do not distinguish IV from V; report IV-versus-V uncertainty and request a height assessment.",
"If structure or nucleus-annulus distinction is not visible, do not classify from signal intensity alone.",
"If a transitional or hypoplastic disc is suspected, state that variant before interpreting reduced height as degeneration."
],
"interpretation_limits": [
"The scale was developed as a reliable gross-morphology classification, not a diagnosis of symptomatic discogenic pain.",
"It does not encode annular fissures, focal herniation, nerve compression, vertebral endplate changes or segmental instability.",
"Its qualitative height terms have no official percentage cutoffs in the original five-grade publication."
],
"source_locator": "Pfirrmann et al., Spine 2001;26:1873-1878, PMID 11568697, DOI 10.1097/00007632-200109010-00011, Table 1 for the four-feature grade matrix; Methods for midsagittal T2 application; Results and Discussion for reliability, feature-boundary disagreements, height use and the transitional-disc pitfall."
}