M87.845
BillableOther osteonecrosis, left finger(s)
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M87.845 an HCC code?
Yes. M87.845 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 M87.845
For M87.845 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 M87.845 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M87.845 is the ICD-10-CM diagnosis code for other osteonecrosis, left finger(s). Death of bone tissue in one or more fingers of the left hand due to interrupted blood supply. M87.845 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, M87.845 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, M87.845 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.
Confirm left-sided involvement in documentation to avoid miscoding as right or bilateral. Because M87.845 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 M87.845 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm left-sided involvement in documentation to avoid miscoding as right or bilateral
- •Note the number and specific fingers affected for complete clinical documentation
Clinical Significance
Left finger osteonecrosis represents a chronic condition that can significantly impact hand function and quality of life. This diagnosis has important risk adjustment implications as it indicates ongoing orthopedic care needs and potential requirement for specialized surgical intervention, with particular significance if affecting the dominant hand.
Documentation Requirements
- ✓Clear specification of osteonecrosis affecting left finger bones
- ✓Documentation that the condition results from causes other than idiopathic or drug-related
- ✓Imaging evidence confirming bone necrosis in left finger(s)
- ✓Clinical presentation including left finger pain, dysfunction, and mobility limitations
- ✓Exclusion of infectious or traumatic etiologies
- ✓Assessment of impact on hand dominance and functional capacity
- ✓Documentation of specific fingers affected when known
- ✓Provider evaluation of treatment complexity and rehabilitation needs
Commonly Confused Codes
- •M87.045 — Idiopathic aseptic necrosis of left finger(s) - specifically idiopathic etiology
- •M87.049 — Idiopathic aseptic necrosis of unspecified finger(s) - different cause and lacks laterality
- •M86.845 — Other osteomyelitis, left finger(s) - infectious bone disease rather than necrosis
- •S62.602A — Fracture of unspecified phalanx of left index finger - acute injury rather than chronic necrosis
- •M20.012 — Mallet finger of left finger(s) - tendon condition rather than bone necrosis