M86.122
BillableOther acute osteomyelitis, left humerus
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.122 an HCC code?
Yes. M86.122 maps to Bone/Joint/Muscle Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. 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.
MEAT Criteria for M86.122
For M86.122 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 M86.122 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.122 is the ICD-10-CM diagnosis code for other acute osteomyelitis, left humerus. A bone infection (osteomyelitis) that develops suddenly in the left upper arm bone (humerus), typically caused by bacteria entering the bone through injury or bloodstream. M86.122 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, M86.122 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.209. Under the older V24 model, M86.122 mapped to the same category but with a base RAF weight of 0.482 — V28 recalibrated weights across the entire model. 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.
Verify laterality is documented as 'left' in the medical record before assigning this code. Because M86.122 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 M86.122 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 'left' in the medical record before assigning this code
- •Ensure the infection is acute (not chronic) and confirm the causative organism if documented for potential additional coding
Clinical Significance
Acute osteomyelitis of the left 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 left 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
- •M86102 — Acute hematogenous osteomyelitis of left humerus (blood-borne origin)
- •M86622 — Chronic osteomyelitis with draining sinus of left humerus (long-standing infection)
- •M86222 — Subacute osteomyelitis of left humerus (intermediate timeline)
- •M25512 — Pain in left shoulder (symptom only, not infection)
- •S42.302A — Unspecified fracture of shaft of left humerus (trauma-related)