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ICD-10-CM 2027 diagnosis code

M84.421PPathological fracture, right humerus, subsequent encounter for fracture with malunion

✓ Billable / specificRequires 7th characterCC — complication/comorbidity

M84.421P is a valid, billable ICD-10-CM code for pathological fracture, right humerus, subsequent encounter for fracture with malunion. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.Short description: Pathological fracture, right humerus, subs for fx w malunion

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 M84.421P

M84.421P is the ICD-10-CM diagnosis code for pathological fracture, right humerus, subsequent encounter for fracture with malunion. 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 "P" means subsequent encounter for fracture with malunion: use it for encounters after active treatment, while the patient is healing or recovering.

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 564 (Other Musculoskeletal System and Connective Tissue Diagnoses with MCC, relative weight 1.4908), DRG 565 (Other Musculoskeletal System and Connective Tissue Diagnoses with CC, relative weight 0.9783) and DRG 566 (Other Musculoskeletal System and Connective Tissue Diagnoses without CC/MCC, relative weight 0.7378), 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 733.81 (malunion of fracture).

7th character

Psubsequent encounter for fracture with malunion

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

Other encounter types for M84.421:

Notes that apply from higher levels

Instructions written at a parent level also apply to M84.421P.

› From M84.4 Pathological fracture, not elsewhere classified
Excludes1
  • collapsed vertebra NEC (M48.5)
  • pathological fracture in neoplastic disease (M84.5-)
  • pathological fracture in osteoporosis (M80.-)
  • pathological fracture in other disease (M84.6-)
  • stress fracture (M84.3-)
  • traumatic fracture (S12.-, S22.-, S32.-, S42.-, S52.-, S62.-, S72.-, S82.-, S92.-)
Excludes2
  • personal history of (healed) pathological fracture (Z87.311)
› 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 →
  • 733.81Malunion of fractureapproximate

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 M84.421P

Is M84.421P billable?

Yes. M84.421P is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

What does the "P" at the end of M84.421P mean?

It is the 7th character for subsequent encounter for fracture with malunion. Per the official guidelines, use it for encounters after active treatment, while the patient is healing or recovering.

Can M84.421P be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict M84.421P as a principal diagnosis.

Is M84.421P a CC or MCC?

M84.421P is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does M84.421P group to?

M84.421P is used in the MS-DRG v44.0 logic for MS-DRG 564 (Other Musculoskeletal System and Connective Tissue Diagnoses with MCC), MS-DRG 565 (Other Musculoskeletal System and Connective Tissue Diagnoses with CC) and MS-DRG 566 (Other Musculoskeletal System and Connective Tissue Diagnoses 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 M84.421P?

The CMS General Equivalence Mappings map M84.421P to ICD-9-CM 733.81.