2027 ICD-10-CM Diagnosis Code S66.320ALaceration of extensor muscle, fascia and tendon of right index finger at wrist and hand level, initial encounter
ICD-10-CM Codes›S00–T88›S60-S69›S66
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- 7th Character A — Initial Encounter
- Not Chronic
S66.320A is a billable ICD-10-CM diagnosis code for laceration of extensor muscle, fascia and tendon of right index finger at wrist and hand level, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. 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, 963 through 965. 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 40 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Open wounds to limbs, initial encounter.
Code Identity
Code Classification
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Injury of muscle, fascia and tendon at wrist and hand level (S66). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
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 S66.320A: its own notes plus those printed at S66.3, S66, block S60-S69, 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.
- Injury of extensor muscle, fascia and tendon of thumb at wrist and hand level (S66.2-)
- sprain of joints and ligaments of wrist and hand (S63.-)
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify any retained foreign body, if applicable (Z18.-)
Code Also
A second code may be needed to fully describe the condition; the note gives no sequencing direction.
Notes
General instructions on how these codes are used.
- 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.
- The appropriate 7th character is to be added to each code from category S66
- Ainitial encounter this code
- Dsubsequent encounter
- Ssequela
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name S66.320A, its category, or a range that includes it.
Excludes2 2
These codes carry an Excludes2 note naming S66.320A: its condition is not part of those codes, and both may be reported when the patient has both.
- S56 Injury of muscle, fascia and tendon at forearm levelinjury of muscle, fascia and tendon at or below wrist (S66.-) names S66.-, which includes this code
- S63 Dislocation and sprain of joints and ligaments at wrist and hand levelstrain of muscle, fascia and tendon of wrist and hand (S66.-) names S66.-, which includes this code
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Hand Injuries and Disorders
No matter how old you are or what you do for a living, you are always using your hands. When there is something wrong with them, you may not be able to do your regular activities.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert S66.320A to ICD-9-CMHistory
Code HistoryHistory
Questions About S66.320AOverview
Is S66.320A a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report laceration of extensor muscle, fascia and tendon of right index finger at wrist and hand level, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character A in S66.320A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for laceration of extensor muscle, fascia and tendon of right index finger at wrist and hand level, such as an emergency visit or first evaluation.
What MS-DRG does S66.320A group to?
When laceration of extensor muscle, fascia and tendon of right index finger at wrist and hand level, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 564, 964, 965, 566, 565, 963, with relative weights from 0.7374 to 2.6361 depending on complications. Higher weights mean higher Medicare reimbursement.
Is S66.320A a CC or MCC?
CMS lists S66.320A 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 40 closely related codes in its exclusion list.
What is the ICD-9 equivalent of S66.320A?
Under the General Equivalence Mappings, laceration of extensor muscle, fascia and tendon of right index finger at wrist and hand level, initial encounter converts to ICD-9-CM 881.22 (opn wound wrist w tendon) and 882.2 (open wound hand w tendon). The mapping is approximate, so confirm the match fits the documentation.
