ICD-10 code S85.172S: Laceration of posterior tibial artery, left leg, sequela

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.

Pabau’s claims management software supports accurate ICD-10-CM code submission and clearinghouse filing through the Claim.MD integration.

The table below gives coders a quick-reference summary of every essential attribute for ICD-10 code S85.172S.

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: Injury of blood vessels at lower leg level. This positions the code within the S80-S89 block covering injuries to the knee and lower leg.
• .1 – Injury of tibial artery. Differentiates tibial artery injuries from popliteal, fibular, and other lower-leg vessels within S85.
• 7 – Laceration. Specifies the injury mechanism as a laceration, distinguishing it from unspecified injuries (.0) or other specified injuries (.8).
• 2 – Left leg. Laterality digit. Code S85.171x covers the right leg; S85.179x covers unspecified laterality.
• S – Sequela. The seventh character signifies a late effect of a previously treated injury. The acute injury phase has resolved.

Together, these five elements create a code that is anatomically precise, laterality-specific, and encounter-type appropriate. No other code in the S85 family captures this exact clinical picture.

Understanding the sequela seventh character in ICD-10-CM

The seventh character is where most coding errors on S85.172S occur. According to CMS ICD-10-CM guidelines, the three valid seventh characters for injury codes carry distinct clinical meanings that are not interchangeable.

The sequela code (S) is only appropriate when the original injury has healed and the patient now presents with a condition that is the direct result of that earlier laceration. Using S85.172S during active wound management is a compliance error. For sequela coding for injury diagnoses broadly, the same rule applies across the S and T chapter categories.

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, mechanism, and laterality. Coders selecting only S85.1 (injury of tibial artery) leave laterality and mechanism unspecified. Only S85.172S provides the full clinical picture needed for a compliant claim. For broader context on medical billing fundamentals, including how diagnosis codes support reimbursement, accurate code selection at this specificity level is foundational.

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 of such a laceration, which is what S85.172S captures, may include chronic arterial insufficiency in the foot and lower leg, nerve damage from ischemia during the injury, or scar tissue impacting vascular flow. These sequelae require a separate diagnosis code alongside S85.172S to fully describe the condition being treated at the sequela encounter. The sequela code alone does not communicate what the patient is being seen for today.

An ICD-10-CM diagnosis code reference for injury sequelae consistently reinforces the same principle: code both the nature of the sequela (the current condition) and the sequela code for the original injury.

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 904.7 captured tibial artery injuries broadly, without distinguishing anterior from posterior tibial artery, left from right leg, or acute from sequela encounters. For authoritative crosswalk data, the ICD List crosswalk tool provides a free lookup against the official CMS crosswalk files.

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 using claims management software can validate ICD-10-CM codes against payer edits before submission. Pabau integrates with electronic claims via Claim.MD, Pabau’s US clearinghouse partner, which supports real-time eligibility verification and clean claim checks across 4,000+ US payers before any claim leaves your system.

For practices managing HIPAA compliance for medical offices, maintaining documentation that links the current sequela visit to the original injury is a standard audit requirement. Review your medical billing compliance policies to confirm your teams know when to transition from D to S seventh-character codes.

For guidance on HIPAA-covered claim submissions across practice types, the same documentation principles apply: every code on the claim must be supported by the medical record.

Streamline ICD-10 claim submissions with Pabau

Pabau integrates with Claim.MD to submit clean ICD-10-CM claims across 4,000+ US payers. Real-time eligibility checks and automated claim validation help practices reduce denials and get paid faster.

Book a demo

Common coding errors for sequela vascular injury codes

Vascular injury sequela codes generate specific patterns of error. Recognising 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 with a code-specificity denial, review whether the correct seventh character was applied and whether the sequela condition was coded alongside it.

Using clean claim submission processes from the start reduces the cycle time spent working denials after the fact. For HIPAA compliance tracking, logging sequela-related denials separately from acute-encounter denials helps practices identify where the A-to-S transition is breaking down.

Conclusion

Posterior tibial artery laceration sequelae require precise coding to pass audit and support reimbursement. S85.172S is the correct code when the original left-leg laceration has resolved and the patient presents for treatment of a resulting late effect. Always pair it with a separate code identifying the current sequela condition, verify laterality in the clinical record, and confirm the acute phase has genuinely ended before using the S seventh character.

Pabau’s claims management software, integrated with Claim.MD, supports ICD-10-CM code validation and clean claim submission across US payers. To see how Pabau handles diagnostic code workflows end to end, book a demo.

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.

Frequently Asked Questions