S66.421A — Laceration of intrinsic muscle, fascia and tendon of right thumb at wrist and hand level, initial encounter
Is S66.421A billable?
Yes — S66.421A is billable for FY2027. S66.421A is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. S66.421A may be submitted for encounters from October 1, 2026 through September 30, 2027.
S66.421A at a glance
| Code | S66.421A |
|---|---|
| Description | Laceration of intrinsic muscle, fascia and tendon of right thumb at wrist and hand level, initial encounter |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
| 7th character "A" | initial encounter |
What does the 7th character "A" mean in S66.421A?
In S66.421A, the 7th character A means initial encounter. The 7th character is required for S66.421A to be a valid, complete code.
Same condition, different episode of care — switch the 7th character:
Which MS-DRGs does S66.421A group to?
S66.421A sits in MDC 08 and helps define the logic of 3 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 564Other Musculoskeletal System and Connective Tissue Diagnoses with MCCmedical
- 565Other Musculoskeletal System and Connective Tissue Diagnoses with CCmedical
- 566Other Musculoskeletal System and Connective Tissue Diagnoses without CC/MCCmedical
As a secondary diagnosis, S66.421A is a complication or comorbidity (CC), which can move a stay into a higher-paying DRG.
How is S66.421A listed in the Alphabetic Index?
The Alphabetic Index lists these routes under S66.42, the nearest indexed parent of S66.421A. Use them to find the family, then select the specific code.
- Injury › muscle › thumb › intrinsic › laceration
Use additional code — inherited from Chapter 19
Report an additional code alongside S66.421A to fully describe the condition. S66.421A is sequenced first.
- code to identify any retained foreign body, if applicable (Z18.-)
Excludes2 — not included here — inherited from Chapter 19
The conditions below are not part of S66.421A, but a patient may have both at the same time. When documentation supports it, S66.421A and the excluded code may both be reported.
Excludes2 — not included here — inherited from S60-S69
The conditions below are not part of S66.421A, but a patient may have both at the same time. When documentation supports it, S66.421A and the excluded code may both be reported.
Excludes2 — not included here — inherited from S66
The conditions below are not part of S66.421A, but a patient may have both at the same time. When documentation supports it, S66.421A and the excluded code may both be reported.
- sprain of joints and ligaments of wrist and hand (S63.-)
Code also — inherited from S66
Two codes may be needed to describe the condition fully. Whether S66.421A is sequenced first depends on the reason for the encounter.
- any associated open wound (S61.-)
How long has S66.421A existed?
S66.421A has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.