Skip to content
Dx

ICD-10-CM 2027 diagnosis code

S66.221ALaceration of extensor muscle, fascia and tendon of right thumb at wrist and hand level, initial encounter

✓ Billable / specificRequires 7th characterCC — complication/comorbidity

S66.221A is a valid, billable ICD-10-CM code for laceration of extensor muscle, fascia and tendon of right thumb at wrist and hand level, initial encounter. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.Short description: Lacerat extensor musc/fasc/tend r thm at wrs/hnd lv, init

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 S66.221A

S66.221A is the ICD-10-CM diagnosis code for laceration of extensor muscle, fascia and tendon of right thumb at wrist and hand level, initial encounter. It belongs to category S66 (injury of muscle, fascia and tendon at wrist and hand level), block S60-S69 (injuries to the wrist, hand and fingers) and chapter 19 (injury, poisoning and certain other consequences of external causes). 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 "A" means initial encounter: use it while the patient is receiving active treatment for the condition.

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), DRG 566 (Other Musculoskeletal System and Connective Tissue Diagnoses without CC/MCC, relative weight 0.7378), DRG 963 (Other Multiple Significant Trauma with MCC, relative weight 2.6363), DRG 964 (Other Multiple Significant Trauma with CC, relative weight 1.4972) and DRG 965 (Other Multiple Significant Trauma without CC/MCC, relative weight 1.0059), in MDC 08 (Diseases and Disorders of the Musculoskeletal System and Connective Tissue) and MDC 24 (Multiple Significant Trauma), 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 881.22 (open wound of wrist, with tendon involvement) and 882.2 (open wound of hand except finger(s) alone, with tendon involvement).

7th character

Ainitial encounter

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

Other encounter types for S66.221:

Notes that apply from higher levels

Instructions written at a parent level also apply to S66.221A.

› From S66 Injury of muscle, fascia and tendon at wrist and hand level
Excludes2
  • sprain of joints and ligaments of wrist and hand (S63.-)
Code also
  • any associated open wound (S61.-)

Broader instructions also apply from S60-S69 Injuries to the wrist, hand and fingers and Chapter 19: Injury, poisoning and certain other consequences of external causes.

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 →
  • 881.22Open wound of wrist, with tendon involvementapproximate
  • 882.2Open wound of hand except finger(s) alone, with tendon involvementapproximate

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 S66.221A

Is S66.221A billable?

Yes. S66.221A is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

What does the "A" at the end of S66.221A mean?

It is the 7th character for initial encounter. Per the official guidelines, use it while the patient is receiving active treatment for the condition.

Can S66.221A be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict S66.221A as a principal diagnosis.

Is S66.221A a CC or MCC?

S66.221A is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does S66.221A group to?

S66.221A 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), MS-DRG 566 (Other Musculoskeletal System and Connective Tissue Diagnoses without CC/MCC), MS-DRG 963 (Other Multiple Significant Trauma with MCC), MS-DRG 964 (Other Multiple Significant Trauma with CC) and MS-DRG 965 (Other Multiple Significant Trauma 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 S66.221A?

The CMS General Equivalence Mappings map S66.221A to ICD-9-CM 881.22 and 882.2.