S58.921A ICD-10-CM Code: Partial traumatic amputation of right forearm, level unspecified, initial encounter
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FY 2026 Apr update / Injury, poisoning and certain other consequences of external causes (S00-T88) / Injuries to the elbow and forearm (S50-S59)
S58.921A
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidancePartial traumatic amputation of right forearm, level unspecified, initial encounter
Partial traumatic amputation of right forearm, level unspecified, initial encounter
CMS-HCC V28
MappedHCC 405
RAF 0.0
CMS-HCC V24
MappedHCC 173
RAF 0.350
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 173
RAF 0.0
RXHCC
00
RAF 0
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Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for S58.921A in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for S58.921A in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for S58.921A in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for S58.921A in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for S58.921A in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for S58.921A in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for S58.921A in this effective period.
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is S58.921A an HCC code?
Yes. S58.921A maps to Traumatic Amputations and Complications under the CMS-HCC V28 risk adjustment model (and Traumatic Amputations and Complications 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 S58.921A
For S58.921Ato 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 S58.921A during that encounter, not just copy-forwarded from a problem list.
What This Code Means
S58.921A is the ICD-10-CM diagnosis code for partial traumatic amputation of right forearm, level unspecified, initial encounter. S58.921A sits in the ICD-10-CM chapter for injury, poisoning and certain other consequences of external causes (s00-t88), within the section covering injuries to the elbow and forearm (s50-s59).
Under the CMS-HCC V28 risk adjustment model, S58.921A maps to Traumatic Amputations and Complications (HCC 405) with a community, non-dual, aged base RAF weight of 0.000. Under the older V24 model, S58.921A mapped to the same category but with a base RAF weight of 0.350, 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.
Coders should report S58.921A only when the provider documentation supports the specific condition described, since more specific codes within the same hierarchy can capture additional clinical detail and may carry a higher RAF weight. Because S58.921A 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 S58.921A sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.