S66.122D vs S66.123D

S66.122D (Laceration of flexor muscle, fascia and tendon of right middle finger at wrist and hand level, subsequent encounter) compared with S66.123D (Laceration of flexor muscle, fascia and tendon of left middle finger at wrist and hand level, subsequent encounter), from the official CMS tabular data.

Summary

These codes name the same condition on opposite sides of the body, so the documented side decides which one applies.

MedCoder-derived

What is different?

Title wording.The titles differ in one word, “right” (S66.122D) versus “left” (S66.123D): S66.122D is “Laceration of flexor muscle, fascia and tendon of right middle finger at wrist and hand level, subsequent encounter”; S66.123D is “Laceration of flexor muscle, fascia and tendon of left middle finger at wrist and hand level, subsequent encounter”.

Registry fact

Can these codes be reported together?

One side per condition.S66.122D and S66.123D name the same condition on opposite sides of the body. Same category and title, differing only in which side is affected — the documentation decides which one applies, and a bilateral code is reported only where the code set provides one.

MedCoder-derivedGuide: Laterality coding

Is there an Excludes1 relationship?

None.Neither entry carries an Excludes1 note that names the other code.

Official rule

Is there an Excludes2 relationship?

None.Neither entry carries an Excludes2 note that names the other code. S66.122D carries 5 Excludes2 notes and S66.123D carries 5 Excludes2 notes covering other codes; the side-by-side table quotes them.

Official rule

Is one more specific?

No.Neither is a subdivision of the other, and neither title is the unspecified form; they describe different conditions within category S66.

Registry fact

Is one a parent or header code?

No.Both are billable codes, and neither contains the other.

Registry fact

Are there sequencing instructions?

None.Neither entry carries a Code First or Use Additional Code note that names the other.

Official rule

Are there other coding relationships?

Yes.Same condition, opposite side. S66.122D and S66.123D name the same condition on opposite sides of the body.

MedCoder-derivedGuide: Laterality coding

Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule.

Can these codes be reported together?

Review

Laterality relationship

S66.122D

Right

Laceration of flexor muscle, fascia and tendon of right middle finger at wrist and hand level, subsequent encounter

↔

S66.123D

Left

Laceration of flexor muscle, fascia and tendon of left middle finger at wrist and hand level, subsequent encounter

What we found

Same condition, opposite side.S66.122D and S66.123D name the same condition on opposite sides of the body.

Same category and title, differing only in which side is affected — the documentation decides which one applies, and a bilateral code is reported only where the code set provides one.

What to review

Report the side the documentation names. Where the code set provides a bilateral code and both sides are documented, use it instead of the pair.

Guide: Laterality coding Check these on a claim

Why it matters

These codes share a category and title and differ only in the side affected. The documentation decides which applies, and a bilateral code is reported only where the code set provides one.

Source / rule

ICD-10-CM tabular list (laterality variant derived from the code title)

Side by side

	S66.122DLaceration of flexor muscle, fascia and tendon of right middle finger at wrist and hand level, subsequent encounter	S66.123DLaceration of flexor muscle, fascia and tendon of left middle finger at wrist and hand level, subsequent encounter
Billing status	Billable	Billable
Classification	S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88)	S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88)
Definition	Laceration of flexor muscle, fascia and tendon of right middle finger at wrist and hand level, subsequent encounter is a billable ICD-10-CM diagnosis code (S66.122D).	Laceration of flexor muscle, fascia and tendon of left middle finger at wrist and hand level, subsequent encounter is a billable ICD-10-CM diagnosis code (S66.123D).
7th character	The appropriate 7th character is to be added to each code from category S66	The appropriate 7th character is to be added to each code from category S66
Excludes2	Injury of long flexor muscle, fascia and tendon of thumb at wrist and hand level (S66.0-) sprain of joints and ligaments of wrist and hand (S63.-) burns and corrosions (T20-T32) frostbite (T33-T34) insect bite or sting, venomous (T63.4)	Injury of long flexor muscle, fascia and tendon of thumb at wrist and hand level (S66.0-) sprain of joints and ligaments of wrist and hand (S63.-) burns and corrosions (T20-T32) frostbite (T33-T34) insect bite or sting, venomous (T63.4)
Code also	any associated open wound (S61.-)	any associated open wound (S61.-)

Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on.

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Derived from the official CMS ICD-10-CM tabular data (FY2026). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources