ICD code S99.291P – Physeal fracture of right toe

Key takeaways

S99.291P is a billable 7-character ICD-10-CM code, while the parent code S99.291 without a 7th character is non-billable and fails payer edits.

7th character P means a subsequent encounter for a fracture that healed with malunion. The treating doctor’s records of malunion (supported by scans) determines P instead of D.

The most common coding error is using S99.291D (routine healing) when the medical record notes malunion.

Pabau’s claims management software submits claims and tracks them through Claim.MD, so correct 7th-character selection stays a coder responsibility.

ICD-10 Code S99.291P: Definition, billable status, and quick reference

ICD-10 Code S99.291P is the billable ICD-10-CM diagnosis code for other physeal fracture of phalanx of right toe, subsequent encounter for fracture with malunion. It is also valid for FY2026 and FY2027 (starting October 1, 2026).

It is a 7-character leaf-node code, so it needs no more detail and goes straight on a claim. Still, the parent code S99.291 is non-billable on its own, so payer claim edits reject any claim that omits the 7th character.

Official descriptor and clinical definition

A physeal fracture of a right toe phalanx affects the physis, the cartilage growth plate near the end of a growing bone. The growth plate is the weakest point in a child’s bone, so it gives way before the nearby ligaments do. Because the physis closes in the late teens, these fractures occur mostly in children and teens.

In this wording, “other physeal fracture” means a Salter-Harris type outside Types I through IV, such as a Type V injury. For example, each of the first four types has its own right toe code: S99.211 (Type I), S99.221 (Type II), S99.231 (Type III), and S99.241 (Type IV). In contrast, a physeal fracture whose type is not specified goes to S99.201_, not S99.291_.

• Physis: The cartilaginous growth plate at the epiphysis of immature bone
• Salter-Harris Types I-IV: Classified separately under S99.21_ through S99.24_
• Other physeal (S99.291_): A Salter-Harris type outside I-IV, such as Type V
• Unspecified physeal (S99.201_): A physeal fracture with no Salter-Harris type noted
• Phalanx of right toe: Any phalanx (proximal, middle, or distal) of toes 1 through 5 on the right foot
• Side: Right toe is coded as S99.291_, left toe as S99.292_, and unspecified toe as S99.299_

Understanding the 7th character P: Subsequent encounter for fracture with malunion

First, the 7th letter P records two facts at once. The visit is later, because the patient has already been seen for this fracture. The fracture has also healed with malunion, meaning a crooked bone or angulation. Both must be true to assign S99.291P. So, the treating doctor’s notes on malunion (supported by scans) determines P.

Malunion occurs when the bone ends heal out of place, which can cause loss of function, a changed gait, or pain. Also, ICD-10-CM keeps it separate from nonunion (7th letter K) and from routine or delayed healing (7th letters D and G).

S99.291P vs S99.291D vs S99.291S: Choosing the correct 7th character

First, S99.291D applies when the patient returns for routine check-up and there are no problems. In contrast, S99.291P applies when the treating doctor notes that the fracture has united out of line, often supported by scans. Last, S99.291S applies only after active treatment has ended and a lasting effect, such as chronic toe pain or stiffness, persists.

In fact, the D-to-P switch is the decision that goes wrong most often in this code group. A coder assigns D at the first check-up because healing looks on track. D then carries forward to every later visit without anyone rechecking the doctor’s notes.

Once the doctor notes malunion, say after a two-month X-ray, the visit should be coded S99.291P. Leaving it on D instead misstates the patient’s status.

Both decisions that build the full code fit on one page, from the Salter-Harris type to the 7th letter.

The table below sets the three most-used later and sequela codes side by side.

Parent code S99.291 and the full S99 code family

S99.291 is the non-billable parent code for other physeal fracture of the phalanx of the right toe. First, its hierarchy starts at S99 (Other and unspecified injuries of ankle and foot). It narrows through S99.2 (Physeal fracture of phalanx of toe) and S99.29 (Other physeal fracture of phalanx of toe). S99.291 then specifies the right toe.

Salter-Harris type rules and related coding guidelines

Salter-Harris Types I-IV have their own codes (S99.211_, S99.221_, S99.231_, S99.241_), so assign those instead. For example, using S99.291P when the scan report or operative note names one of those four types is a coding error that can trigger an audit.

• Type I physeal fractures, right toe: S99.211_ (do not use S99.291_)
• Type II physeal fractures, right toe: S99.221_ (do not use S99.291_)
• Type III physeal fractures, right toe: S99.231_ (do not use S99.291_)
• Type IV physeal fractures, right toe: S99.241_ (do not use S99.291_)
• Salter-Harris type not noted, right toe: S99.201_ (do not use S99.291_)
• External cause code: Add an external cause code (V00-Y99) for the injury mechanism and place of occurrence when your state or payer requires one. ICD-10-CM guideline Section I.C.20 sets no national mandate
• Side: If the noted fracture is on the left toe, use S99.292P, not S99.291P. Unspecified side falls to S99.299P

Documentation requirements to support S99.291P

Getting ICD-10 Code S99.291P right depends on specific details being present in the medical record before you assign the code. As a result, missing any one of them creates grounds for payer denial or post-payment audit recovery. Following CMS ICD-10-CM coding guidelines, coders should check each one before filing.

• Doctor notes on malunion: The treating doctor’s note must state malunion, a crooked bone, or angulation, supported by scans. “Healed fracture” without a malunion label does not support 7th letter P.
• Visit type noted as later: The treating physician’s note must show that the patient has had prior treatment for this fracture. In contrast, emergency department visits for a new acute fracture use 7th letter A, not P.
• Side confirmed as right: The chart must specify right-sided injury. If the side is unclear or absent, query the doctor before assigning S99.291P over S99.299P.
• Fracture site confirmed as phalanx of toe: The records must separate a phalanx fracture from a metatarsal, calcaneus, or other foot bone fracture (S92 series).
• Growth plate injury confirmed: The chart or scan record should show growth plate damage. If only the cortical bone is fractured without physeal disruption, a different fracture code applies.
• Salter-Harris type outside I-IV: The record should name a type outside I-IV, such as a Type V injury. Instead, types I-IV take S99.21_ through S99.24_. An unspecified type takes S99.201_.

In addition, good medical billing compliance practices mean building a records query workflow for any later fracture visit with scans. Also, coders who see the visit note without the scan report have less to go on when the healing status is unclear.

Common CPT codes used with S99.291P

First, the CPT code paired with S99.291P must match the service performed at the later visit. In fact, two mismatches trigger most claim edits: a first fracture treatment code at a later visit, or a routine E/M visit when a procedure was performed.

Next, always verify CPT codes against the current-year AMA CPT codebook. The toe fracture treatment codes (28490-28496 great toe; 28510-28525 other toes) split by toe. For example, a great toe code billed for another toe leaves the claim out of line with the record. Malunion repair is often an osteotomy instead, such as 28310 for the great toe’s proximal phalanx.

Payer requirements and prior authorization for malunion fracture treatment

Commercial payers, Medicare, and Medicaid each apply their own medical necessity criteria to claims tied to fracture malunion. ICD-10 Code S99.291P reports a subsequent encounter for a fracture that healed with malunion. As a result, payers often expect more detail behind it than behind a routine check-up coded S99.291D.

So, filing a clean claim for S99.291P-related services often needs these elements to come with or before the claim.

• Scans on file: Keep the scan report that supports the doctor’s malunion finding available for audit. In addition, for surgical repair, some payers require it added to the prior approval request.
• Chart notes showing loss of function: Gait abnormality, pain with weight bearing, or toe deformity should be noted in the treating clinician’s note. Medical necessity is harder to defend when the note describes a cosmetic concern rather than a functional one.
• Prior authorization for surgical procedures: Most commercial and Medicaid managed care plans require prior approval for open or percutaneous repair of a malunited phalanx fracture. Get approval before the surgery date, not after.
• Medicare medical necessity: Medicare claims are subject to Local Coverage Determinations (LCDs) where they apply. The ICD-10-CM and CPT codes must match each other and the noted condition. For example, a later visit CPT paired with a first fracture ICD-10-CM code (7th letter A) is a mismatch Medicare claims processing will flag.
• Referral records: If the treating orthopedist is seeing the patient on referral from a PCP, some payers require a referral approval number. In fact, missing referral records are a common second denial reason on even well-coded claims.

Common claim denial reasons for S99.291P

Most S99.291P-related denials can be prevented at the coding and records stage instead of through appeals. So, good denial management workflows for orthopedic practices address these before filing.

• 7th letter D submitted when malunion is noted: The most frequent error. If the chart note or scan report mentions malunion, a crooked bone, or angular deformity, 7th letter D is wrong.
• Non-billable parent code submitted: Filing S99.291 without any 7th letter fails HIPAA-required code validity edits. The payer rejects the claim before review.
• Side mismatch: S99.291P on the claim, but the chart note or scan report refers to the left toe. Payers with claim-to-record auditing programs recover payment on side mismatches often.
• Missing malunion records: When a payer requests records to support a malunion code, a note that only says “fracture, improved” will not sustain the claim.
• CPT code that does not fit a later visit: A first fracture treatment code, such as an acute closed reduction, fails the code-pair edit at a later visit. Instead, the CPT must reflect the service given at a later visit.
• Missing external cause code: Some payers require external cause codes (W, X, or Y series) on injury claims. If not, the claim may be held for more details or denied outright.

Knowing denial codes in medical billing is the fastest way to triage why a specific claim failed. For a 7th letter or diagnosis mismatch, expect these Claim Adjustment Reason Codes (CARCs):

• CARC 11: The diagnosis is inconsistent with the procedure
• CARC 16: The claim lacks information or has billing errors
• CARC 167: The diagnosis is not covered

Still, CARC 4, 5, and 97 point to other problems on the same claim. They cover a modifier issue, a place-of-service mismatch, and a bundled service, in that order.

How to enter S99.291P in an EHR or practice management system

Entering ICD-10 Code S99.291P the right way in an EHR means confirming that the system accepts and transmits the full 7-character code. Some older EHR platforms truncate ICD-10-CM codes at five or six characters, quietly turning S99.291P to the non-billable S99.291.

The claim then fails payer edits, but the ERA shows a code-not-found rejection rather than pointing to the truncation.

1. Search by full code, not by name: Enter “S99.291P” in the code search field rather than keywords like “physeal fracture.” Also, searches by wording often return the non-billable parent S99.291 as the top result.
2. Verify billable status before saving: Confirm the system flags the code as billable (leaf-node). If the system shows S99.291 without a 7th letter as the selected code, the 7th letter was dropped when the code was picked.
3. Confirm the 7th letter is kept on the superbill: Print or preview the superbill before billing. The full 7-character code S99.291P should appear, not a cut-down version.
4. Link to the correct visit type: Tag the code to a later visit note, not a first visit or new patient record. Some EHR billing modules use visit type to auto-suggest 7th letters. As a result, a mismatch here can replace your P with an A.
5. Attach external cause code: Add the right W, X, or Y series external cause code in the secondary diagnosis field before filing. If not, payers that require external cause codes will hold or deny claims where the injury code appears without one.

If your practice runs a separate charting system, confirm that codes reach the billing module intact. Also, manual re-entry between systems is a second truncation risk. A grounding in medical billing basics helps a team build one clear code entry workflow.

How Pabau supports claim submission for fracture follow-up codes

A fracture check-up claim often passes through several hands. A coder picks the 7th letter, a biller keys the claim, and someone checks a payer portal to see whether it paid.

Pabau’s claims management software brings filing and tracking into one place. Claims then go out through Claim.MD, Pabau’s US clearinghouse partner, to thousands of US payers. Also, real-time eligibility checks confirm the patient’s coverage before the visit.

Pabau does not choose the 7th letter for you. Instead, that stays with your coders and the doctor’s records. What changes is tracking: a claim denied for a missing 7th letter or a wrong diagnosis stays tracked until your team corrects and resubmits it.

Submit and track fracture claims in one place

Pabau’s claims management sends claims through Claim.MD, runs real-time eligibility checks, and tracks denied claims. Your billing team stops chasing fracture follow-up claims across payer portals.

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Conclusion

The difference between S99.291D and S99.291P comes down to noted malunion. Once the treating doctor records it, later visits for that fracture take the letter P. Staying on D after that point codes the patient’s case too low and creates audit risk.

So put the check into the visit rather than the appeal. Have coders read the doctor’s healing note at every later fracture visit, and query when the note and the scan report disagree.

Submission, eligibility checks, and denial tracking can then run through Claim.MD inside Pabau, as the Claim.MD clearinghouse guide explains. Book a demo to see how Pabau keeps fracture check-up claims moving from submission to payment.

Continue your research

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Want to reduce claim rejection before adjudication? Revenue cycle management overview outlines how pre-submission edits fit into the end-to-end billing workflow for musculoskeletal practices.

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