ICD code S56.415S – Right ring finger extensor strain sequela

Key takeaways

S56.415S reports a healed extensor strain of the right ring finger at forearm level, in the sequela phase.

List the residual condition first, such as M20.011 for mallet finger, then add S56.415S after it.

The wrist and hand counterpart is S66.314S, because S66.31- numbers the right ring finger 4, not 5.

Routine follow-up while the strain still heals takes S56.415D, never the Z47.89 aftercare code.

The note must name the side, the finger, the forearm level, the original strain and the causal link.

ICD-10 code S56.415S, decoded

ICD-10 code S56.415S reports the lasting effects of a healed extensor strain in the right ring finger. The strain happened at forearm level, in the muscle or tendon above the wrist.

Each character in the code narrows its meaning, as the table shows. The official descriptor reads “Strain of extensor muscle, fascia and tendon of right ring finger at forearm level, sequela.”

Category S56 stops at the wrist. Its Excludes2 note sends injuries at or below the wrist to category S66. That category covers muscle, fascia and tendon at wrist and hand level. At that level, the same ring finger strain is S66.314S.

S56.415S is a billable code in the CMS ICD-10-CM code set. It never travels alone, though. A sequela claim also needs a code for the residual problem, which we cover below.

The muscle behind the ring finger

One muscle does most of the work here. Extensor digitorum starts at the lateral epicondyle of the humerus and runs down the back of the forearm.

It splits into four tendons, one each for the index, middle, ring and little fingers. Unlike the index and little fingers, the ring finger has no extensor of its own.

Near the finger, each tendon spreads into an extensor hood with three working parts:

• Central slip: inserts at the base of the middle phalanx and extends the proximal interphalangeal (PIP) joint.
• Lateral bands: merge into the terminal tendon at the distal phalanx and extend the distal interphalangeal (DIP) joint.
• Intrinsic muscles: the lumbricals and interossei feed the lateral bands and help straighten both joints.

On the back of the hand, small bands called juncturae tendinum link the ring finger tendon to its neighbors. They can pull the ring finger straight along with the middle finger.

A quick exam may then miss weak extension. That is why a note recording isolated ring finger extension carries more weight.

The posterior interosseous nerve, a branch of the radial nerve, supplies the muscle. A radial nerve injury at forearm level codes to S54.2-, separately from S56.415S.

Right side, ring finger, final digit 5

Laterality and finger share the sixth character. Get either one wrong, and the claim describes a different hand.

In S56.41-, odd digits mark the right hand and even digits the left. They run from the index finger (1 and 2) to the little finger (7 and 8). S56.419S covers an unspecified finger.

The wrist and hand codes follow a different pattern. Category S66.31- starts counting at 0, so the right ring finger becomes S66.314S. The grid below lines up both families.

Lookalike codes worth a second look

These codes differ from S56.415S by one character or one word. A single slip bills a different injury, so check each one against the note.

Unsure about a neighbor? Confirm it in the CDC/NCHS ICD-10-CM browser before you swap codes.

When the S fits the visit

S56.415S fits when the strain has healed but the finger hasn’t fully recovered. Today’s visit treats what the strain left behind.

Typical presentations include:

• Extensor lag: the patient can’t actively straighten the ring finger, though it straightens passively.
• Mallet-type droop: the fingertip stays bent at the DIP joint after the forearm strain has healed.
• Boutonniere-type posture: the PIP joint stays bent while the DIP joint pulls into extension.
• Weak extension: measured extension or grip release strength stays below the other hand.

One caution on those deformities. Mallet and boutonniere patterns usually follow an injury on the finger itself. If the original strain sat at hand or finger level, the sequela code comes from S66.3- instead.

So read the first encounter note before coding the residual problem. It tells you where the strain happened.

Pair it with the problem it caused

ICD-10-CM guideline I.C.19.a sets the rule. A sequela claim needs the code for the residual condition and the injury code that caused it.

The residual condition goes first, and S56.415S follows. The S attaches to the injury code only. Common residual codes for this finger include:

• M20.011, mallet finger of right finger(s)
• M20.021, boutonniere deformity of right finger(s)
• M25.641, stiffness of right hand, not elsewhere classified
• M24.541, contracture, right hand
• M62.431, contracture of muscle, right forearm
• M79.644, pain in right finger(s)
• M62.541, muscle wasting and atrophy, not elsewhere classified, right hand

Match the residual code to the clinician’s own words. A note that says “stiff ring finger” supports M25.641, not a contracture code.

Pain codes need extra care with site. M79.644 covers the right finger, M79.631 the right forearm and M79.621 the right upper arm.

Still healing? Then it isn’t sequela

The 7th character tracks the phase of care. How long ago the strain happened doesn’t decide it.

Aftercare Z codes don’t apply to injuries. Guideline I.C.21.c.7 points coders to the injury code with 7th character D instead.

That means Z47.89, encounter for other orthopedic aftercare, never stands in for S56.415D. The switch to S comes once the clinician documents that the strain itself has healed.

What the note has to prove

Auditors check four points in the record before they accept a sequela claim:

• The original strain: an earlier note, ED record or referral describing the right forearm extensor strain.
• Healed status: a statement that the strain has resolved, plus the residual problem treated today.
• The causal link: wording that ties the two together, such as “extensor lag secondary to healed forearm strain.”
• Side, finger and level: right, ring finger and forearm, each named in the note.

Measurements matter most once therapy starts. Record the extensor lag in degrees and grip strength on both hands.

Structured fields in the therapy note make both easy to capture at every visit.

How the claim moves, and where it stalls

A sequela claim passes several checkpoints after the visit. If you’re new to the cycle, what is medical billing covers it end to end.

1. The clinician signs a note naming the residual problem and its cause.
2. The coder lists the residual code first, then S56.415S.
3. Therapy or visit codes go on the same claim, with units that match the note.
4. The clearinghouse checks the format and required fields.
5. The payer runs its edits and medical necessity rules.
6. The remittance returns payment, or a denial reason code.

Therapy adds one more checkpoint. Past Medicare’s annual therapy threshold, services need the KX modifier and documented medical necessity.

When a claim does come back, the reason code points to the fix:

For a broader playbook, see denial management in healthcare and this guide to denial codes in medical billing.

Run this check before you submit

Five minutes here can save a resubmission later. Before the claim goes out, confirm:

• The clinician has documented that the strain has healed.
• The note names the right side, the ring finger and the forearm level.
• A residual condition code sits first on the claim.
• The final digit reads 5 in S56.41-, or 4 if the injury was at wrist and hand level.
• S56.415D isn’t on the claim for the same visit.
• Therapy units match the time documented.

Common mistakes to avoid

• Coding the flexor side: S56.115S is the flexor strain of the same finger.
• Borrowing codes from the wrong body part: M62.831 is calf spasm, and M65.311 is trigger thumb. Trigger finger of the right ring finger is M65.341.
• Using Z47.89 for strain follow-up: routine follow-up while healing takes S56.415D.
• Carrying the 5 into S66.31-: S66.315S is the left ring finger.

Pass every check and you have what billers call a clean claim. The payer can process it on the first try.

How Pabau keeps S56.415S claims moving

Sequela claims often stall over a missing residual code or an empty required field. By the time the denial lands, the visit is weeks old.

Pabau, the practice management platform we build, keeps the claim inside the same patient record as the clinical note. Our claims management software pre-fills the claim from the invoice and the insurer details on the client card.

Pabau checks each claim for missing or invalid details, such as membership numbers, before it goes out. Submission then runs through Claim.MD, our US claims integration. Eligibility checks, claim status and remittance posting sit in the same place, so your team spends less time chasing returns.

Send sequela claims out complete the first time

Pabau pre-fills claims from the invoice and checks them for missing or invalid details. Claim.MD, our US claims integration, sends them on. Spend less time chasing returned S56.415S claims.

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Conclusion

S56.415S rewards a careful read of the chart. Three details decide it: extensor, forearm level and right ring finger.

Treat the first visit’s note as your anchor, since it fixes the injury type and level. Today’s note then supplies the residual condition that goes first on the claim. With both in order, the claim tells the payer one consistent story.

Book a demo to see how Pabau keeps sequela claims complete, from the clinical note to the remittance.

Continue your research

Want to see how a sequela claim travels after you hit send? Claim.MD clearinghouse overview explains how electronic claims are checked and passed on to payers.

Trying to read a denial on a returned claim? Electronic remittance advice (ERA) guide shows how to read 835 files and find the reason code.

Building audit-ready documentation habits? Medical billing compliance guide covers the documentation standards that keep injury claims defensible.

Checking coverage before therapy starts? Insurance eligibility verification walks through confirming benefits before the first visit.

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