M86.621
BillableOther chronic osteomyelitis, right humerus
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.621 an HCC code?
Yes. M86.621 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 M86.621
For M86.621 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 M86.621 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.621 is the ICD-10-CM diagnosis code for other chronic osteomyelitis, right humerus. A long-term bone infection in the right upper arm bone (humerus). M86.621 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, M86.621 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, M86.621 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 the infection is in the humerus specifically and on the right side. Because M86.621 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 M86.621 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify the infection is in the humerus specifically and on the right side
- •Confirm chronic nature of the infection in clinical documentation
Clinical Significance
Chronic osteomyelitis of the right humerus represents a serious bone infection affecting the primary bone of the upper arm, significantly impacting arm function and strength. This condition often requires prolonged treatment and may result in permanent functional limitations, affecting the patient's ability to perform activities requiring upper extremity use.
Documentation Requirements
- ✓Documentation of chronic duration (>6 weeks or recurrent episodes)
- ✓Specific involvement of right humerus bone
- ✓Non-hematogenous etiology (contiguous spread or direct inoculation)
- ✓Imaging studies demonstrating bone infection or destruction
- ✓Laboratory confirmation of infection (ESR, CRP, cultures)
- ✓Assessment of right arm function and range of motion
- ✓Documentation of treatment including antibiotics and surgical interventions
- ✓Evaluation of functional limitations and need for adaptive equipment
Commonly Confused Codes
- •M86.521 — Other chronic hematogenous osteomyelitis, right humerus (hematogenous origin)
- •M86.622 — Other chronic osteomyelitis, left humerus (opposite side)
- •M86.421 — Chronic osteomyelitis with draining sinus, right humerus (has sinus)
- •M86.121 — Other acute osteomyelitis, right humerus (acute phase)
- •S42.301A — Unspecified fracture of shaft of right humerus (trauma-related)