ICD code S85.172S – Laceration of posterior tibial artery

Key takeaways

S85.172S identifies laceration of the posterior tibial artery, left leg, as a sequela (late effect) of a prior injury.

This is a billable ICD-10-CM code valid for FY2026 (October 1, 2025 through September 30, 2026) for HIPAA-covered transactions.

The seventh character ‘S’ is only correct after the acute injury phase has resolved. Using it during active treatment is a coding error.

S85.172S never travels alone, because the sequela condition itself needs its own diagnosis code.

Practice management software like Pabau validates ICD-10-CM codes before submission and files them through the Claim.MD clearinghouse.

What S85.172S means: Breaking down the code

Every character in S85.172S carries clinical meaning. Misreading any segment leads to laterality errors, wrong encounter-type codes, or claim denials.

• S85: Category for injuries of blood vessels at lower leg level. This positions the code inside the S80-S89 block, which covers the knee and lower leg.
• .1: Injury of tibial artery. This separates tibial artery injuries from popliteal, fibular, and other lower-leg vessels within S85.
• 7: Laceration. This names the mechanism, separating it from unspecified injuries (.0) and other specified injuries (.8).
• 2: Left leg. This is the laterality digit. S85.171x covers the right leg, and S85.179x covers unspecified laterality.
• S: Sequela. The seventh character marks a late effect of a previously treated injury, so the acute phase has resolved.

Together these five elements fix the vessel, the side, and the phase of care. No other code in the S85 family carries that combination.

Understanding the sequela seventh character in ICD-10-CM

Three seventh characters are valid on S85.172, and they are not interchangeable. Each one tells the payer which phase of the injury the visit belongs to, per CMS ICD-10-CM guidelines.

The sequela code (S) is only appropriate once the original injury has healed. The patient must now present with a condition caused directly by that earlier laceration. Using S85.172S during active wound management is a compliance error, and the same rule holds across every sequela code in the S and T chapters.

Two questions settle which character the encounter takes, and only one of the answers pulls a second code with it.

Code hierarchy: S85.172S in the ICD-10-CM classification

Understanding the parent chain clarifies billing context and helps coders locate related codes quickly. Per the CDC/NCHS ICD-10-CM tabular tool, S85.172S sits within the following hierarchy.

• S00-T88: Chapter 19, injury, poisoning and certain other consequences of external causes
• S80-S89: Injuries to the knee and lower leg
• S85: Injury of blood vessels at lower leg level
• S85.1: Injury of tibial artery
• S85.17: Laceration of posterior tibial artery
• S85.172: Laceration of posterior tibial artery, left leg
• S85.172S: Laceration of posterior tibial artery, left leg, sequela

Each level narrows the anatomical site, the mechanism, and the laterality. Coders who stop at S85.1 leave both laterality and mechanism unspecified. Only S85.172S carries the full picture a compliant claim needs.

Posterior tibial artery: Clinical context for coders

The posterior tibial artery is a terminal branch of the popliteal artery. It runs along the posterior compartment of the lower leg and supplies the plantar surface of the foot. A laceration to this vessel can result in significant limb-threatening ischemia during the acute phase.

Late effects are what S85.172S captures. They may include chronic arterial insufficiency in the foot and lower leg, nerve damage from ischemia, or scar tissue restricting flow.

These sequelae need their own diagnosis code alongside S85.172S. The sequela code alone does not tell the payer what the patient is being seen for today.

That second code is an ordinary diagnosis code, chosen from the same book. The ICD-10-CM code index is where you look up the ischemia, neuropathy, or wound-complication code that names today’s problem.

Related and sibling codes in the S85 family

The table below shows the S85.17x sibling codes for posterior tibial artery laceration and selected closely related S85 codes. Laterality is the most common source of sibling-code confusion.

ICD-9-CM crosswalk for S85.172S

Legacy billing systems and historical record reviews sometimes require mapping ICD-10-CM codes back to ICD-9-CM equivalents. The crosswalk below is approximate. ICD-9 to ICD-10 conversions are rarely one-to-one, and the sequela specificity of S85.172S did not exist in the older classification system.

The ICD-9-CM code 904.53 named the posterior tibial artery specifically. It did not distinguish left leg from right, or an acute encounter from a sequela encounter. The official CMS crosswalk files remain the authoritative source for any mapping you have to defend.

Billing and reimbursement for ICD-10 code S85.172S

S85.172S is billable for HIPAA-covered transactions in FY2026. Payer-specific coverage criteria still apply, and code validity does not guarantee reimbursement. The following documentation elements are required to support this code at audit.

Documentation requirements

• An explicit statement that the acute injury has resolved, confirming the patient is past the initial and subsequent encounter phases.
• A clear link between the current presenting condition (the sequela) and the original posterior tibial artery laceration on the left leg.
• Laterality confirmed in the operative or clinical notes, specifying the left leg without ambiguity.
• The nature of the sequela coded separately (for example, chronic limb ischemia or peripheral neuropathy resulting from the laceration).
• External cause code reported alongside S85.172S when payer policy requires it.

Practices running medical claims management software can validate ICD-10-CM codes against payer edits before submission. Practice management software like Pabau files electronic claims through Claim.MD, our US clearinghouse partner. That route runs eligibility and clean claim checks across 4,000+ US payers before a claim leaves your system.

Documentation that ties the sequela visit back to the original injury is a standard audit requirement. Write the D-to-S transition rule into your coding policy, so the team knows when the switch is due.

Common coding errors for sequela vascular injury codes

Vascular injury sequela codes generate specific patterns of error. Recognizing them before submission prevents claim rejections and audit exposure.

• Using S85.172A or S85.172D at the sequela stage. Once the acute injury has healed and the patient is presenting with late effects, only the S seventh character is appropriate. Continuing to use A or D after healing is a coding error that may trigger a medical necessity review.
• Coding S85.172S without a sequela condition code. The sequela code describes the original injury. The patient’s current condition, such as peripheral artery disease or nerve deficit resulting from the laceration, needs its own code. S85.172S alone does not tell the payer what is being treated today.
• Laterality errors: using S85.171S (right leg) instead of S85.172S (left leg). Operative and clinical documentation must confirm left-sided involvement. A laterality mismatch between the record and the claim is a straightforward audit failure.
• Using the unspecified code S85.179S when laterality is documented. If the record clearly states left leg, S85.179S is not acceptable. Payers may deny the unspecified code when documentation supports a more specific one.

Strong denial management workflows should flag these patterns automatically. When a claim for S85.172S returns a code-specificity denial, check the seventh character first. Then confirm the sequela condition was coded alongside it.

Log sequela-related denials separately from acute-encounter denials. That split shows you where the A-to-S transition is breaking down, rather than burying it in a single denial rate.

How Pabau supports sequela coding and clean claim submission

Without a pre-submission check, a seventh-character error surfaces only after the payer sends the claim back. The coder corrects S85.172S, resubmits, and the visit stays unpaid until the correction clears.

Pabau keeps the diagnosis codes on the encounter record, so the sequela code and the condition code stay attached to the same visit. Claims then leave through Claim.MD, which runs eligibility and clean claim checks before submission.

A missing laterality or a seventh character the record cannot support surfaces at that check, not weeks later in a denial letter. Your coders spend the time on the notes instead of on rework.

Submit ICD-10 sequela claims without the rework

Pabau files ICD-10-CM claims through Claim.MD, our US clearinghouse partner, with eligibility and clean claim checks across 4,000+ payers. Coding errors surface before submission, so fewer claims come back for a seventh character.

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Conclusion

S85.172S is a narrow code, and its narrowness is the point. Once the record shows the left-leg laceration healed and today’s problem traces back to it, this is the only code that fits.

The part worth remembering is the second code. A sequela code says what happened. Only the condition code says what you are treating today. Build both into the coding step and you stop losing claims to something the record already proves.

Pabau validates ICD-10-CM codes and submits clean claims across US payers. Book a demo to see how a sequela code and its condition code reach the payer together.

Continue your research

Need to understand how ICD-10 coding connects to claim filing? Claim.MD clearinghouse overview explains how electronic claims reach US payers through a clearinghouse.

Managing denials from vascular injury claims? Denial management in healthcare covers the workflows that catch and resolve claim rejections before they age.

Unsure when a claim qualifies as a clean submission? What makes a clean claim outlines the documentation and coding standards payers apply at adjudication.

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