S66.313AStrain of extensor muscle, fascia and tendon of left middle finger at wrist and hand level, initial encounter

S66.313A is the ICD-10-CM diagnosis code for strain of extensor muscle, fascia and tendon of left middle finger 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.

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 562 (Fracture, Sprain, Strain and Dislocation Except Femur, Hip, Pelvis and Thigh with MCC, relative weight 1.398), DRG 563 (Fracture, Sprain, Strain and Dislocation Except Femur, Hip, Pelvis and Thigh without MCC, relative weight 0.8985), 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 842.09 (other sprains and strains of wrist) and 842.19 (other sprains and strains of hand).