M86.641
BillableOther chronic osteomyelitis, right hand
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.641 an HCC code?
Yes. M86.641 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 M86.641
For M86.641 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 M86.641 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.641 is the ICD-10-CM diagnosis code for other chronic osteomyelitis, right hand. A chronic bone infection affecting the bones of the right hand, causing persistent inflammation and potential functional impairment. M86.641 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, M86.641 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, M86.641 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.
Ensure documentation specifies 'right hand' and clarify which specific hand bones are involved if documented. Because M86.641 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 M86.641 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure documentation specifies 'right hand' and clarify which specific hand bones are involved if documented
- •Consider impact on hand function and document any complications affecting grip or dexterity
Clinical Significance
Chronic osteomyelitis of the right hand represents a complex bone infection affecting the intricate anatomy of hand bones, significantly impacting fine motor function and activities of daily living. This condition often requires specialized hand surgery expertise and extensive rehabilitation to preserve hand function.
Documentation Requirements
- ✓Documentation of chronic duration (>6 weeks or recurrent episodes)
- ✓Specific involvement of right hand bones (metacarpals, phalanges, carpals)
- ✓Non-hematogenous etiology (contiguous spread or direct inoculation)
- ✓Imaging studies demonstrating bone infection in hand
- ✓Laboratory confirmation of infection or inflammatory response
- ✓Assessment of right hand function and grip strength
- ✓Documentation of treatment including hand surgery interventions
- ✓Evaluation of impact on activities requiring manual dexterity