Question 1

What is ICD-10 code M89.331?

Accepted Answer

M89.331 is the ICD-10-CM diagnosis code for hypertrophy of bone, right ulna. Abnormal thickening or enlargement of bone in the right forearm bone on the pinky side (ulna). M89.331 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).

M89.331 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

The ulna is the longer forearm bone on the pinky finger side.

Question 2

Is M89.331 an HCC code?

Accepted Answer

No. M89.331 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is M89.331 billable?

Accepted Answer

Yes. M89.331 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. M89.331 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Question 4

Which HCC does M89.331 map to under V28?

Accepted Answer

M89.331 does not map to a CMS-HCC V28 payment category. Check the current CMS-HCC V28 model file for payment year 2026 rather than an older V24 tip sheet.

Question 5

What does M89.331 pay in RAF?

Accepted Answer

M89.331 has no separately stated V28 community RAF weight. If it is not a V28 payment HCC, it adds nothing to a community RAF score.

Question 6

What is the V28 vs V24 difference for M89.331?

Accepted Answer

M89.331 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither community model rewards M89.331 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's V28/V24 community RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a community payment HCC.

Question 7

What documentation supports M89.331?

Accepted Answer

The ulna is the longer forearm bone on the pinky finger side Verify right-sided involvement is documented before coding M89.331 is not a CMS-HCC payment code, so MEAT is not the payment hook. Documentation still has to support the diagnosis if you report it.

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M89.331

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M89.331 ICD-10-CM Code: Hypertrophy of bone, right ulna

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M89.331

Is M89.331 an HCC code?

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