M86.521
BillableOther chronic hematogenous osteomyelitis, right humerus
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.521 an HCC code?
Yes. M86.521 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 M86.521
For M86.521 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 M86.521 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.521 is the ICD-10-CM diagnosis code for other chronic hematogenous osteomyelitis, right humerus. A chronic bone infection of the right upper arm bone (humerus) that originated from a bloodstream infection. M86.521 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, M86.521 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, M86.521 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.
The humerus is the long bone of the upper arm; ensure this is the documented site and not the shoulder joint. Because M86.521 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 M86.521 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •The humerus is the long bone of the upper arm; ensure this is the documented site and not the shoulder joint
- •Use M86.522 for left humerus infections
Clinical Significance
Other chronic hematogenous osteomyelitis of the right humerus represents a blood-borne bone infection that has become chronic, specifically affecting the right upper arm bone. This condition indicates systemic infection with targeted skeletal involvement requiring prolonged IV antibiotic therapy and monitoring, significantly impacting upper extremity function and overall patient health status.
Documentation Requirements
- ✓Documentation of chronic osteomyelitis diagnosis
- ✓Clear evidence of hematogenous (blood-borne) origin
- ✓Specific anatomic identification of right humerus involvement
- ✓Laboratory studies confirming systemic infection
- ✓Blood culture results or evidence of bacteremia
- ✓Treatment history including IV antibiotic duration
- ✓Imaging studies demonstrating right humerus infection
- ✓Assessment of upper extremity function and treatment response
Commonly Confused Codes
- •M86.522 — Other chronic hematogenous osteomyelitis, left humerus (wrong laterality)
- •M86.621 — Other chronic osteomyelitis, right humerus (not specifically hematogenous)
- •M86.321 — Chronic multifocal osteomyelitis, right humerus (multifocal rather than hematogenous)
- •M86.421 — Chronic osteomyelitis with draining sinus, right humerus (has draining component)