M87.878
BillableOther osteonecrosis, left toe(s)
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M87.878 an HCC code?
Yes. M87.878 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 M87.878
For M87.878 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 M87.878 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M87.878 is the ICD-10-CM diagnosis code for other osteonecrosis, left toe(s). Death of bone tissue in the left toe(s) due to causes other than trauma, infection, or radiation. This can cause pain and difficulty walking or wearing shoes. M87.878 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, M87.878 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, M87.878 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.
This code is specific to the left toe(s); use M87.877 for right toe(s) or M87.879 for unspecified. Because M87.878 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 M87.878 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
Left toe osteonecrosis represents avascular bone death in the toe bones, potentially disrupting normal gait mechanics and balance. This condition requires careful management to prevent complications and preserve foot function, especially in patients with comorbid conditions like diabetes.
Documentation Requirements
- ✓Clear documentation of left toe(s) involvement
- ✓Radiological evidence of bone necrosis in affected toes
- ✓Exclusion of traumatic, infectious, or radiation-induced etiology
- ✓Gait analysis and balance assessment impact
- ✓Pain quantification and mobility limitations
- ✓Screening for underlying vascular or metabolic conditions
- ✓Specialized footwear and orthotic recommendations
- ✓Regular monitoring for secondary complications
Commonly Confused Codes
- •M87.378 — Drug-induced osteonecrosis requires specific agent identification
- •M87.178 — Post-traumatic osteonecrosis needs trauma documentation
- •M87.078 — Idiopathic osteonecrosis has no identifiable precipitating factors
- •S92.502A — Left toe fracture is acute injury code
- •M20.12 — Hallux valgus is structural deformity, not bone death