M46.20 ICD-10-CM Code: Osteomyelitis of vertebra, site unspecified
HCC Buddy Code Card
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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Spondylopathies (M45-M49)
M46.20
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOsteomyelitis of vertebra, site unspecified
A bone infection (osteomyelitis) affecting one or more vertebrae in the spine, but the specific location is not documented.
Buddy Insight
Vertebral osteomyelitis is a serious bone infection that can lead to spinal instability, neurological complications, and sepsis.
CMS-HCC V28
MappedHCC 92
RAF 0.479
CMS-HCC V24
MappedHCC 39
RAF 0.401
ACA/HHS
MappedHCC 55
Varies by metal level
ESRD/PACE
MappedHCC 39
RAF 0.092
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for M46.20 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M46.20 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M46.20 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M46.20 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M46.20 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M46.20 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M46.20 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is M46.20 an HCC code?
Yes. M46.20 (Osteomyelitis of vertebra, site unspecified) maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis under V24), with a community non-dual aged RAF of 0.479. It is billable for payment year 2026.
Coder answer: M46.20 is billable and maps to V28 HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- M46.20
- Description
- Osteomyelitis of vertebra, site unspecified
- HCC (V28)
- HCC 92 — Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
- RAF
- 0.479
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
Work M46.20 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for M46.20
For M46.20 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed M46.20 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
M46.20 is the ICD-10-CM diagnosis code for osteomyelitis of vertebra, site unspecified. A bone infection (osteomyelitis) affecting one or more vertebrae in the spine, but the specific location is not documented. M46.20 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering spondylopathies (m45-m49).
Under the CMS-HCC V28 risk adjustment model, M46.20 maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.479. Under the older CMS-HCC V24 model, M46.20 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 39) with a community, non-dual, aged base RAF weight of 0.401. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
This is an unspecified code; always attempt to obtain documentation of the specific vertebral region to use a more specific M46.2x code. Because M46.20 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M46.20 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is an unspecified code; always attempt to obtain documentation of the specific vertebral region to use a more specific M46.2x code
- •Osteomyelitis is typically infectious; verify if causative organism is documented for potential additional coding
Clinical Significance
Vertebral osteomyelitis is a serious bone infection that can lead to spinal instability, neurological complications, and sepsis. This condition requires aggressive antibiotic therapy and close monitoring for complications including spinal cord compression.
Documentation Requirements
- ✓Documentation of bone infection (osteomyelitis) in vertebrae
- ✓Clinical signs of infection including fever, pain, or elevated inflammatory markers
- ✓Imaging findings consistent with vertebral osteomyelitis
- ✓Laboratory evidence supporting infection diagnosis
- ✓Documentation that specific vertebral site is unspecified
- ✓Exclusion of other causes of back pain
- ✓Treatment with appropriate antimicrobial therapy
- ✓Assessment for complications such as abscess or neurological symptoms
Commonly Confused Codes
- •M46.21-M46.28: Site-specific vertebral osteomyelitis codes when location is known
- •M86.9: Osteomyelitis unspecified site doesn't specify vertebral involvement
- •M46.30-M46.39: Infection of intervertebral disc is different structure
- •G06.1: Intraspinal abscess may coexist but is different condition
- •A41.9: Sepsis may be consequence but is systemic infection