2027 ICD-10-CM Diagnosis Code S59.099KOther physeal fracture of lower end of ulna, unspecified arm, subsequent encounter for fracture with nonunion

ICD-10-CM Codes›S00–T88›S50-S59›S59

ICD-10-CM S59.099K
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

S59.099K is a billable ICD-10-CM diagnosis code for other physeal fracture of lower end of ulna, unspecified arm, subsequent encounter for fracture with nonunion. The 7th character K means subsequent encounter for fracture with nonunion. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 564 through 566. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 5,561 closely related codes. The code is flagged as an unspecified code, since codes identifying laterality exist in the same family and exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Fracture of the upper limb, subsequent encounter.

Code Identity

ICD-10-CM Code
S59.099K
Billable Status
Yes — Valid for Submission
Code Describes
Other physeal fracture of lower end of ulna, unspecified arm, subsequent encounter for fracture with nonunion
Short Description
Oth physl fx low end ulna, unsp arm, subs for fx w nonunion
Parent Code
S59.099
Other physeal fracture of lower end of ulna, unspecified arm

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionS50-S59Injuries to the elbow and forearm
CategoryS59Other and unspecified injuries of elbow and forearm
This CodeS59.099KOther physeal fracture of lower end of ulna, unspecified arm, subsequent encounter for fracture with nonunion

Code EditsBilling

Medicare Code Editor checks that affect claim validity for S59.099K.

Unspecified codes
Unspecified codes exist in the ICD-10-CM classification for circumstances when documentation in the medical record does not provide the level of detail needed to support reporting a more specific code. However, in the inpatient setting, there should generally be very limited and rare circumstances for which the laterality (right, left, bilateral) of a condition is unable to be documented and reported. The following pages contain the list of unspecified ICD-10-CM diagnosis codes for which there is a more specific code to identify laterality (right, left, bilateral) within that code family.

Present on Admission (POA)Billing

S59.099K is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Injuries to the elbow and forearm (S50-S59).

Coding GuidelinesGuidance

The principles of multiple coding of injuries should be followed in coding fractures. Fractures of specified sites are coded individually by site, to the level of detail furnished by medical record content.

A fracture not indicated as open or closed should be coded to closed. A fracture not indicated whether displaced or not displaced should be coded to displaced.

Initial vs. Subsequent Encounter for Fractures

Traumatic fractures are coded using the appropriate 7th character for initial encounter (A, B, C) while the patient is receiving active treatment for the fracture. The appropriate 7th character for initial encounter should also be assigned for a patient who delayed seeking treatment for the fracture or nonunion.

Fractures are coded using the appropriate 7th character for subsequent care for encounters after the patient has completed active treatment of the fracture and is receiving routine care for the fracture during the healing or recovery phase.

Care for complications of surgical treatment for fracture repairs during the healing or recovery phase should be coded with the appropriate complication codes.

Care of complications of fractures, such as malunion and nonunion, should be reported with the appropriate 7th character for subsequent care with nonunion (K, M, N) or subsequent care with malunion (P, Q, R).

The open fracture designations in the assignment of the 7th character for fractures of the forearm, femur and lower leg, including ankle are based on the Gustilo open fracture classification. When the Gustilo classification type is not specified for an open fracture, the 7th character for open fracture type I or II should be assigned (B, E, H, M, Q).

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to S59.099K: its own notes plus those printed at S59, block S50-S59, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From S59 Other and unspecified injuries of elbow and forearm applies to 360 codes
  • other and unspecified injuries of wrist and hand (S69.-)
From Block S50-S59 Injuries to the elbow and forearm applies to 4,362 codes
  • burns and corrosions (T20-T32)
  • frostbite (T33-T34)
  • injuries of wrist and hand (S60-S69)
  • insect bite or sting, venomous (T63.4)
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • code to identify any retained foreign body, if applicable (Z18.-)

Notes

General instructions on how these codes are used.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
  • The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.

7th Character

Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.

From S59 Other and unspecified injuries of elbow and forearm applies to 360 codes
  • The appropriate 7th character is to be added to each code from subcategories S59.0, S59.1, and S59.2
Values for category S59 Closed Fracture Encounter
  • Ainitial encounter for closed fracture
  • Dsubsequent encounter for fracture with routine healing
  • Gsubsequent encounter for fracture with delayed healing
  • Ksubsequent encounter for fracture with nonunion this code
  • Psubsequent encounter for fracture with malunion
  • Ssequela

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INJ041
Fracture of the upper limb, subsequent encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Arm Injuries and Disorders

Of the 206 bones in your body, three of them are in your arm: the humerus, radius, and ulna. Your arms are also made up of muscles, joints, tendons, and other connective tissue. Injuries to any of these parts of the arm can occur during sports, a fall, or an accident.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert S59.099K to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
733.82 Nonunion of fracture
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About S59.099KOverview

Is S59.099K (Other physeal fracture of lower end of ulna, unspecified arm) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other physeal fracture of lower end of ulna, unspecified arm, subsequent encounter for fracture with nonunion on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character K in S59.099K mean?

The final character K reports a subsequent encounter where the other physeal fracture of lower end of ulna, unspecified arm has failed to heal, called a nonunion. In this category the CMS Tabular List defines K as "subsequent encounter for fracture with nonunion".

What MS-DRG does S59.099K group to?

When other physeal fracture of lower end of ulna, unspecified arm, subsequent encounter for fracture with nonunion is the principal diagnosis on an inpatient stay, it groups to MS-DRG 564, 566, 565, with relative weights from 0.7374 to 1.4909 depending on complications. Higher weights mean higher Medicare reimbursement.

Is S59.099K a CC or MCC?

CMS lists S59.099K as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 5,561 closely related codes in its exclusion list.

Is S59.099K exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for other physeal fracture of lower end of ulna, unspecified arm, subsequent encounter for fracture with nonunion on inpatient claims. The code appears in the Injuries to the elbow and forearm (S50-S59) range of the CMS exempt list.