M87.379
BillableOther secondary osteonecrosis, unspecified toe(s)
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M87.379 an HCC code?
Yes. M87.379 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 M87.379
For M87.379 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 M87.379 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M87.379 is the ICD-10-CM diagnosis code for other secondary osteonecrosis, unspecified toe(s). Death of bone tissue in one or more toes caused by an underlying condition or disease, where the specific toe(s) affected are not identified. M87.379 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, M87.379 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, M87.379 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.
Use this code when the secondary cause of osteonecrosis is documented but the specific toe(s) cannot be determined. Because M87.379 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 M87.379 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
This diagnosis represents secondary osteonecrosis of toe bones when the specific toe or laterality is not identified, caused by underlying disease processes. It requires identification of the causative factor and monitoring for progression that could impact ambulation.
Documentation Requirements
- ✓Documentation of osteonecrosis affecting toe(s) without specific identification
- ✓Identification of underlying cause (e.g., corticosteroid use, radiation therapy, vascular disease)
- ✓Imaging findings confirming toe bone necrosis
- ✓Clinical symptoms such as toe pain, swelling, or deformity
- ✓Functional impact on walking or footwear
- ✓Duration and progression of condition
- ✓Treatment history and response
- ✓Reason why specific toe or laterality cannot be determined
Commonly Confused Codes
- •M87.377 — Other secondary osteonecrosis, right toe(s) (when laterality is known)
- •M87.378 — Other secondary osteonecrosis, left toe(s) (when laterality is known)
- •M86.179 — Chronic osteomyelitis of unspecified toe (infection vs necrosis)
- •S92.509A — Fracture of unspecified phalanx of unspecified toe (acute fracture vs necrosis)
- •M87.376 — Other secondary osteonecrosis, unspecified foot (foot vs toe specificity)