M46.28 ICD-10-CM Code: Osteomyelitis of vertebra, sacral and sacrococcygeal region
M46.28 maps to CMS-HCC V28 92. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools
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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Spondylopathies (M45-M49)
M46.28
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOsteomyelitis of vertebra, sacral and sacrococcygeal region
A bone infection affecting the sacral vertebrae and the area where the sacrum connects to the coccyx (tailbone).
Buddy Insight
Osteomyelitis of the sacral and sacrococcygeal vertebrae represents a serious bone infection requiring prolonged antibiotic therapy and close monitoring.
CMS-HCC V28
MappedHCC 92
Coefficient HCC 92: 0.479 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 055
Code-level coefficient reference
ESRD/PACE
MappedHCC 39
Code-level coefficient reference
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for M46.28. Check the code and parent instructions in the Code Book.
Excludes 2
Official- arthropathic psoriasis (L40.5-)Inherited from M00-M99
- certain conditions originating in the perinatal period (P04-P96)Inherited from M00-M99
- certain infectious and parasitic diseases (A00-B99)Inherited from M00-M99
- compartment syndrome (traumatic) (T79.A-)Inherited from M00-M99
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from M00-M99
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from M00-M99
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from M00-M99
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from M00-M99
- neoplasms (C00-D49)Inherited from M00-M99
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from M00-M99
Related Codes
Includes
OfficialNo Includes notes are included in this display for M46.28. Check the code and parent instructions in the Code Book.
Excludes 1
OfficialNo Excludes 1 notes are included in this display for M46.28. Check the code and parent instructions in the Code Book.
Code First
OfficialNo Code First sequencing instructions are included in this display for M46.28. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for M46.28. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for M46.28. Check the code and parent instructions in the Code Book.
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 M46.28 an HCC code?
Yes. M46.28 (Osteomyelitis of vertebra, sacral and sacrococcygeal region) maps to HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.479. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: M46.28 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
- M46.28
- Description
- Osteomyelitis of vertebra, sacral and sacrococcygeal region
- HCC (V28)
- HCC 92 — Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
- RAF reference coefficient
- 0.479
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work M46.28 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for M46.28
For M46.28, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
Coder workflow notes
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What This Code Means
M46.28 is the ICD-10-CM diagnosis code for osteomyelitis of vertebra, sacral and sacrococcygeal region. A bone infection affecting the sacral vertebrae and the area where the sacrum connects to the coccyx (tailbone). M46.28 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, M46.28 maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis (HCC 92) with a source-labeled community, non-dual, aged reference coefficient of 0.479. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Confirm the infection involves the sacral and/or sacrococcygeal region; this is a less common site for vertebral osteomyelitis. For M46.28, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for M46.28 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm the infection involves the sacral and/or sacrococcygeal region; this is a less common site for vertebral osteomyelitis
- •Document any associated complications such as abscess formation or neurological involvement
Clinical Significance
Osteomyelitis of the sacral and sacrococcygeal vertebrae represents a serious bone infection requiring prolonged antibiotic therapy and close monitoring. This condition significantly impacts patient mobility and quality of life, often requiring months of treatment and potential surgical intervention.
Documentation Requirements
- ✓Specific anatomical location (sacral and sacrococcygeal region)
- ✓Evidence of bone infection (imaging studies, lab values)
- ✓Causative organism if identified
- ✓Acute vs chronic phase documentation
- ✓Response to antibiotic therapy
- ✓Any associated complications or sequelae
- ✓Duration of infection if known
- ✓Treatment plan and monitoring requirements
Commonly Confused Codes
- •M46.20: Osteomyelitis of vertebra, site unspecified when location is not documented
- •M86.9: Osteomyelitis of other bones when infection affects non-spinal bones
- •M49.80: Spondylopathy in diseases classified elsewhere when secondary to another condition
- •S32.19XA: Fracture of sacrum when traumatic injury rather than infection