M86.121 ICD-10-CM Code: Other acute osteomyelitis, right humerus
M86.121 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 · HCC Buddy coding tools
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Other osteopathies (M86-M90)
M86.121
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOther acute osteomyelitis, right humerus
A sudden bacterial bone infection in the right upper arm bone (humerus) that is not blood-borne in origin, often resulting from trauma, surgery, or local spread of infection.
Buddy Insight
Acute osteomyelitis of the right humerus represents a serious bone infection requiring immediate antibiotic therapy and potential surgical intervention to prevent bone destruction and systemic complications.
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 M86.121. Check the code and parent instructions in the Code Book.
Excludes 2
Official- arthropathic psoriasis (L40.5-)Inherited from M00-M99, M86
- certain conditions originating in the perinatal period (P04-P96)Inherited from M00-M99, M86
- certain infectious and parasitic diseases (A00-B99)Inherited from M00-M99, M86
- compartment syndrome (traumatic) (T79.A-)Inherited from M00-M99, M86
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from M00-M99, M86
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from M00-M99, M86
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from M00-M99, M86
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from M00-M99, M86
- neoplasms (C00-D49)Inherited from M00-M99, M86
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from M00-M99, M86
- ostemyelitis of:Inherited from M00-M99, M86
- orbit (H05.0-)Inherited from M00-M99, M86
- petrous bone (H70.2-)Inherited from M00-M99, M86
- vertebra (M46.2-)Inherited from M00-M99, M86
Related Codes
Includes
OfficialNo Includes notes are included in this display for M86.121. Check the code and parent instructions in the Code Book.
Excludes 1
Official- postprocedural osteopathies (M96.-)Inherited from M86-M90, M86
- osteomyelitis due to:Inherited from M86-M90, M86
- echinococcus (B67.2)Inherited from M86-M90, M86
- gonococcus (A54.43)Inherited from M86-M90, M86
- salmonella (A02.24)Inherited from M86-M90, M86
Code First
OfficialNo Code First sequencing instructions are included in this display for M86.121. Check the code and parent instructions in the Code Book.
Use Additional
Official- code (B95-B97) to identify infectious agentInherited from M86
- code to identify major osseous defect, if applicable (M89.7-)Inherited from M86
Code Also
OfficialNo Code Also instructions are included in this display for M86.121. 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 M86.121 an HCC code?
Yes. M86.121 (Other acute osteomyelitis, right humerus) 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: M86.121 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
- M86.121
- Description
- Other acute osteomyelitis, right humerus
- 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 M86.121 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for M86.121
For M86.121, 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
Get the V28 mapping + MEAT cheat sheet
One printable reference: check representative V28 mappings and the documentation reminders your note needs. Free, no card.
Free PDF. No card. Unsubscribe anytime.
What This Code Means
M86.121 is the ICD-10-CM diagnosis code for other acute osteomyelitis, right humerus. A sudden bacterial bone infection in the right upper arm bone (humerus) that is not blood-borne in origin, often resulting from trauma, surgery, or local spread of infection. M86.121 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering other osteopathies (m86-m90).
Under the CMS-HCC V28 risk adjustment model, M86.121 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. No V24 mapping is shown for M86.121; use the applicable model and payment year when reviewing the V28 mapping. 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.
Verify laterality is documented as right; if not specified, use M86.129. For M86.121, 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 M86.121 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify laterality is documented as right; if not specified, use M86.129
- •Distinguish from hematogenous osteomyelitis which spreads through bloodstream
Clinical Significance
Acute osteomyelitis of the right humerus represents a serious bone infection requiring immediate antibiotic therapy and potential surgical intervention to prevent bone destruction and systemic complications. This condition significantly impacts patient mobility and quality of life, often requiring prolonged treatment courses.
Documentation Requirements
- ✓Specific identification of right humerus involvement
- ✓Documentation of acute onset (symptoms less than 2 weeks)
- ✓Clinical evidence of bone infection (pain, swelling, fever)
- ✓Imaging findings confirming osteomyelitis (MRI, bone scan, or CT)
- ✓Laboratory evidence of infection (elevated WBC, ESR, CRP)
- ✓Causative organism identification when available
- ✓Exclusion of hematogenous osteomyelitis
- ✓Treatment plan including antibiotic therapy duration
Commonly Confused Codes
- •M86101: Acute hematogenous osteomyelitis of right humerus (blood-borne origin)
- •M86621: Chronic osteomyelitis with draining sinus of right humerus (long-standing infection)
- •M86221: Subacute osteomyelitis of right humerus (intermediate timeline)
- •M25511: Pain in right shoulder (symptom only, not infection)
- •S42.301A: Unspecified fracture of shaft of right humerus (trauma-related)