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ICD-10-CM 2027 diagnosis code

M84.331AStress fracture, right ulna, initial encounter for fracture

✓ Billable / specificRequires 7th character

M84.331A is a valid, billable ICD-10-CM code for stress fracture, right ulna, initial encounter for fracture. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About M84.331A

M84.331A is the ICD-10-CM diagnosis code for stress fracture, right ulna, initial encounter for fracture. It belongs to category M84 (disorder of continuity of bone), block M80-M85 (disorders of bone density and structure) and chapter 13 (diseases of the musculoskeletal system and connective tissue). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

The 7th character "A" means initial encounter for fracture: use it while the patient is receiving active treatment for the condition.

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 542 (Pathological Fractures and Musculoskeletal and Connective Tissue Malignancy with MCC, relative weight 1.7211), DRG 543 (Pathological Fractures and Musculoskeletal and Connective Tissue Malignancy with CC, relative weight 1.006) and DRG 544 (Pathological Fractures and Musculoskeletal and Connective Tissue Malignancy without CC/MCC, relative weight 0.7406), in MDC 08 (Diseases and Disorders of the Musculoskeletal System and Connective Tissue), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 733.95 (stress fracture of other bone).

7th character

Ainitial encounter for fracture

CC/MCC status for this injury by encounter: Neither CC nor MCC for A, D, G, S; CC for K, P.

Other encounter types for M84.331:

Notes that apply from higher levels

Instructions written at a parent level also apply to M84.331A.

› From M84.3 Stress fracture
Excludes1
Excludes2
  • personal history of (healed) stress (fatigue) fracture (Z87.312)
  • stress fracture of vertebra (M48.4-)
Use additional code
  • external cause code(s) to identify the cause of the stress fracture
› From M84 Disorder of continuity of bone
Excludes2
  • traumatic fracture of bone-see fracture, by site

Broader instructions also apply from Chapter 13: Diseases of the musculoskeletal system and connective tissue.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 733.95Stress fracture of other boneapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about M84.331A

Is M84.331A billable?

Yes. M84.331A is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

What does the "A" at the end of M84.331A mean?

It is the 7th character for initial encounter for fracture. Per the official guidelines, use it while the patient is receiving active treatment for the condition.

Can M84.331A be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict M84.331A as a principal diagnosis.

Is M84.331A a CC or MCC?

No. M84.331A is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does M84.331A group to?

M84.331A is used in the MS-DRG v44.0 logic for MS-DRG 542 (Pathological Fractures and Musculoskeletal and Connective Tissue Malignancy with MCC), MS-DRG 543 (Pathological Fractures and Musculoskeletal and Connective Tissue Malignancy with CC) and MS-DRG 544 (Pathological Fractures and Musculoskeletal and Connective Tissue Malignancy without CC/MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for M84.331A?

The CMS General Equivalence Mappings map M84.331A to ICD-9-CM 733.95.