S42.399K Other fracture of shaft of unspecified humerus, subsequent encounter for fracture with nonunion

Billable ICD-10-CM code, FY2026.

Built from S42.399 with 7th character K (subsequent encounter for fracture with nonunion).

Applies from S42 Fracture of shoulder and upper arm

Excludes1 (never code together)

• traumatic amputation of shoulder and upper arm (S48.-)

Excludes2 (not included here)

• periprosthetic fracture around internal prosthetic shoulder joint (M97.3)

7th character note

• The appropriate 7th character is to be added to all codes from category S42

Notes

• A fracture not indicated as displaced or nondisplaced should be coded to displaced
• A fracture not indicated as open or closed should be coded to closed

7th character required

• A — initial encounter for closed fracture
• B — initial encounter for open fracture
• D — subsequent encounter for fracture with routine healing
• G — subsequent encounter for fracture with delayed healing
• K — subsequent encounter for fracture with nonunion
• P — subsequent encounter for fracture with malunion
• S — sequela

Applies from S42.3 Fracture of shaft of humerus

Applicable to

• Fracture of humerus NOS
• Fracture of upper arm NOS

Excludes2 (not included here)

• physeal fractures of upper end of humerus (S49.0-)
• physeal fractures of lower end of humerus (S49.1-)

Medicare Code Edits (MCE v43.1 (April 2026))

• Unspecified code (laterality): Unspecified codes for which a more specific code identifying laterality (right, left, bilateral) exists within the same code family.

Code annotations containing back-references to S42.399K

Back-references to S42.3

• Type 2 Excludes: S42.2 Fracture of upper end of humerus ("fracture of shaft of humerus (S42.3-)")
• Type 2 Excludes: S42.4 Fracture of lower end of humerus ("fracture of shaft of humerus (S42.3-)")

Back-references to S42

• Type 1 Excludes: M84.3 Stress fracture ("traumatic fracture (S12.-, S22.-, S32.-, S42.-, S52.-, S62.-, S72.-, S82.-, S92.-)")
• Type 1 Excludes: M84.4 Pathological fracture, not elsewhere classified ("traumatic fracture (S12.-, S22.-, S32.-, S42.-, S52.-, S62.-, S72.-, S82.-, S92.-)")
• Type 2 Excludes: S41 Open wound of shoulder and upper arm ("open fracture of shoulder and upper arm (S42.- with 7th character B or C)")

Nearby codes

• S42.399 Other fracture of shaft of unspecified humerus
• S42.399A Other fracture of shaft of unspecified humerus, initial encounter for closed fracture
• S42.399B Other fracture of shaft of unspecified humerus, initial encounter for open fracture
• S42.399D Other fracture of shaft of unspecified humerus, subsequent encounter for fracture with routine healing
• S42.399G Other fracture of shaft of unspecified humerus, subsequent encounter for fracture with delayed healing
• S42.399K Other fracture of shaft of unspecified humerus, subsequent encounter for fracture with nonunion (this code)
• S42.399P Other fracture of shaft of unspecified humerus, subsequent encounter for fracture with malunion
• S42.399S Other fracture of shaft of unspecified humerus, sequela
• S42.4 Fracture of lower end of humerus
• S42.40 Unspecified fracture of lower end of humerus
• S42.401 Unspecified fracture of lower end of right humerus