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M51 vs S33.121

M51 (Thoracic, thoracolumbar, and lumbosacral intervertebral disc disorders) compared with S33.121 (Dislocation of L2/L3 lumbar vertebra), from the official CMS tabular data.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Summary

These codes should not be reported together because S33.121’s tabular entry lists M51 under Excludes1.

Official rule
What is different?

The conditions named and chapter.M51 is “Thoracic, thoracolumbar, and lumbosacral intervertebral disc disorders”; S33.121 is “Dislocation of L2/L3 lumbar vertebra”. M51 sits in M00-M99 — Diseases of the Musculoskeletal System and Connective Tissue (M00-M99); S33.121 in S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88).

Registry fact

Can these codes be reported together?

No.S33.121’s entry carries an Excludes1 note covering M51: “nontraumatic rupture or displacement of lumbar intervertebral disc NOS (M51.-)”. Both may be reported only when the documentation shows the two conditions are unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes1 relationship?

Yes.S33.121’s tabular entry: “nontraumatic rupture or displacement of lumbar intervertebral disc NOS (M51.-)”. The note covers M51.

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes2 relationship?

None.Neither entry carries an Excludes2 note that names the other code. M51 carries 2 Excludes2 notes and S33.121 carries 9 Excludes2 notes covering other codes; the side-by-side table quotes them.

Official rule

Is one more specific?

Not comparable.The codes sit in different categories; specificity is only comparable within one category.

Is one a parent or header code?

Both are headers.Both are non-billable headers, and neither contains the other.

Registry fact

Are there sequencing instructions?

None.Neither entry carries a Code First or Use Additional Code note that names the other.

Official rule

Are there other coding relationships?

None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.

MedCoder-derived

Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels

Can these codes be reported together?

Excludes1 — generally not reported together

Excludes1 conflict

S33.121
Dislocation of L2/L3 lumbar vertebra
↔
M51
Thoracic, thoracolumbar, and lumbosacral intervertebral disc disorders

What we found

No — do not report together.S33.121 carries an Excludes1 note covering M51: “nontraumatic rupture or displacement of lumbar intervertebral disc NOS (M51.-)”

Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

What to review

Report one of the two. Both may be reported only when the documentation shows the two conditions are unrelated to each other.

Guide: Excludes1 vs Excludes2Check these on a claim

Why it matters

An Excludes1 note means the two conditions are not ordinarily reported together for the same encounter, because the classification treats them as mutually exclusive forms of the same condition. The documented exception is when the two conditions are unrelated to each other.

Source / rule

CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a

Official guidance behind these answers

  • Section I.A.12.a — Excludes1 · applies to: Excludes1

    A type 1 Excludes note is a pure excludes note. It means “NOT CODED HERE!” An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition. An exception to the Excludes1 definition is the circumstance when the two conditions are unrelated to each other. If it is not clear whether the two conditions involving an Excludes1 note are related or not, query the provider. For example, code F45.8, Other somatoform disorders, has an Excludes1 note for "sleep related teeth grinding (G47.63)," because "teeth grinding" is an inclusion term under F45.8. Only one of these two codes should be assigned for teeth grinding. However psychogenic dysmenorrhea is also an inclusion term under F45.8, and a patient could have both this condition and sleep related teeth grinding. In this case, the two conditions are clearly unrelated to each other, and so it would be appropriate to report F45.8 and G47.63 together.

    ICD-10-CM Official Guidelines FY2027

Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum

Side by side

M51Thoracic, thoracolumbar, and lumbosacral intervertebral disc disordersS33.121Dislocation of L2/L3 lumbar vertebra
Billing statusNon-billable header

Report instead: M51.04, M51.05, M51.06, M51.14, M51.15

Non-billable header

Report instead: S33.121A, S33.121D, S33.121S

ClassificationM00-M99 — Diseases of the Musculoskeletal System and Connective Tissue (M00-M99)S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88)
DefinitionThoracic, thoracolumbar, and lumbosacral intervertebral disc disorders is a non-billable ICD-10-CM category code (M51).Dislocation of L2/L3 lumbar vertebra is a non-billable ICD-10-CM category code (S33.121).
7th character—The appropriate 7th character is to be added to each code from category S33
Includes—
avulsion of joint or ligament of lumbar spine and pelvis
laceration of cartilage, joint or ligament of lumbar spine and pelvis
sprain of cartilage, joint or ligament of lumbar spine and pelvis
traumatic hemarthrosis of joint or ligament of lumbar spine and pelvis
Excludes1
current injury - see injury of spine by body region
discitis NOS (M46.4-)
nontraumatic rupture or displacement of lumbar intervertebral disc NOS (M51.-)
obstetric damage to pelvic joints and ligaments (O71.6)
Excludes2
cervical and cervicothoracic disc disorders (M50.-)
sacral and sacrococcygeal disorders (M53.3)
fracture of lumbar vertebrae (S32.0-)
dislocation and sprain of joints and ligaments of hip (S73.-)
strain of muscle of lower back and pelvis (S39.01-)
burns and corrosions (T20-T32)
effects of foreign body in anus and rectum (T18.5)
effects of foreign body in genitourinary tract (T19.-)
effects of foreign body in stomach, small intestine and colon (T18.2-T18.4)
frostbite (T33-T34)
insect bite or sting, venomous (T63.4)
Code also—
any associated:
open wound of abdomen, lower back and pelvis (S31)
spinal cord injury (S24.0, S24.1-, S34.0-, S34.1-)
any associated open wound

Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on.

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Derived from the official CMS ICD-10-CM tabular data (FY2027). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources