ICD-10 Code S72.043B: Displaced fracture of base of neck of unspecified femur

Key takeaways

ICD-10 Code S72.043B describes a displaced fracture at the base of the neck of the unspecified femur. Unspecified means the record never states which femur was fractured.

The sixth character is the laterality character here. S72.041 is the right femur, S72.042 the left femur, and S72.043 the femur that documentation does not identify.

This is a billable, specific ICD-10-CM code valid for FY2026 (effective October 1, 2025) and eligible for HIPAA-covered transaction submission.

The 7th character B confirms: initial encounter, open fracture, Gustilo classification type I or II only. Type IIIA/B/C requires code S72.043C instead.

S72.043B maps to HCC 402 (Hip Fracture/Dislocation) under CMS-HCC Model V28, which CMS phased in to full weight for payment year 2026.

ICD-10 Code S72.043B: definition, billable status, and code overview

Hip fractures are one of the leading causes of hospitalization and mortality among elderly patients in the United States. Claim denials for femoral fracture codes remain common all the same, usually because of errors in laterality, encounter type, and open fracture classification. Traumatic injury ICD-10 coding demands precision at every character level, and S72.043B is no exception.

ICD-10 Code S72.043B is a billable, specific ICD-10-CM diagnosis code valid for fiscal year 2026. It became effective on October 1, 2025, and is eligible for submission on HIPAA-covered transactions. The code sits within the S72 category (fractures of the femur) and identifies a displaced fracture at the base of the femoral neck. The 7th character narrows it to an initial encounter for an open fracture of Gustilo type I or II. Its sixth character, 3, is the unspecified-laterality option. S72.043B is therefore the code for a base-of-neck fracture where the record never says which femur was involved. For general ICD-10 diagnostic code reference context, every character carries clinical meaning, and a coder cannot apply S72.043B without documentation that supports each one.

Coders can submit claims through Claim.MD, Pabau’s integrated US clearinghouse partner, which supports CMS-1500 and 837P submissions for ICD-10-CM diagnosis codes including S72.043B. Understanding medical billing fundamentals for traumatic fracture codes helps practices reduce denials from the outset.

Understanding the 7th character B for ICD-10 Code S72.043B

The 7th character is the most consequential character in S72.043B for billing purposes. Getting it wrong triggers an automatic claim edit. The character B tells the payer three things at once. This is an initial encounter, the fracture is open rather than closed, and the open fracture is Gustilo type I or type II.

Understanding the full ICD-10-CM code structure for trauma categories helps coders see why encounter type matters. Under ICD-10-CM guidelines, “initial encounter” covers the entire active treatment period, not just the first office visit. A patient seen in the emergency department, then in surgery, then in follow-up for wound management still carries the B character throughout active treatment. The S72 category offers sixteen 7th-character options, and the table below lists all of them.

Per CMS ICD-10-CM coding guidelines, coders must not assume open fracture type from clinical context. The treating physician must explicitly document “open fracture type I” or “open fracture type II” (or equivalent Gustilo terminology) in the operative or clinical note. Absent that documentation, coders default to type I/II only when the surgeon confirms the classification.

Gustilo open fracture classification: type I versus type II

S72.043B covers both Gustilo type I and type II fractures under a single code. Coders therefore do not need to distinguish between them for reporting purposes. However, understanding the clinical difference is essential for auditing documentation and flagging cases that may actually require S72.043C (Gustilo type IIIA/B/C).

The classification must come from the surgeon’s operative report or clinical note. Coders working in physical therapy EMR software contexts may encounter these patients during rehabilitation, but Gustilo typing is always the operating surgeon’s determination.

Femoral neck anatomy and fracture types in the S72 category

The femoral neck connects the femoral head (the ball of the hip joint) to the femoral shaft. Fractures of the femoral neck are categorized within S72.0, which has several sub-categories based on the exact anatomical subsite and fracture characteristics.

The base of the femoral neck sits at the junction between the neck and the intertrochanteric region. Fractures at this exact subsite are sometimes called basicervical fractures. They differ clinically from subcapital fractures (near the femoral head, captured under S72.01) and from midcervical or transcervical fractures (mid-neck, captured under S72.03). The base-of-neck subsite is captured under S72.04.

• S72.00: Fracture of unspecified part of neck of femur (the hip fracture NOS entry)
• S72.01: Unspecified intracapsular fracture of femur, which takes subcapital fracture of femur
• S72.02: Fracture of epiphysis (separation) (upper) of femur
• S72.03: Midcervical fracture of femur, which takes transcervical fracture NOS
• S72.04: Fracture of base of neck of femur (basicervical fracture)
• S72.05: Unspecified fracture of head of femur
• S72.06: Articular fracture of head of femur
• S72.09: Other fracture of head and neck of femur

Within S72.04, the sixth character records displacement status and laterality together, which is why the six codes below differ by a single digit. S72.041 is the displaced fracture of the right femur and S72.042 the displaced fracture of the left. S72.043 is the displaced fracture reported when the record identifies no side at all. This level of specificity is required for accurate revenue cycle management in orthopedic and trauma surgery practices.

Related ICD-10-CM codes for base of neck femur fractures

S72.043B sits within a tightly clustered group of sibling codes that differ by one character. Selecting the wrong sibling is one of the most common audit findings in hip fracture billing, and laterality is where it happens most. The table below covers the S72.043 variant group and the neighbors a coder is most likely to confuse with it.

For additional context on code series structure, the CPT code reference guide demonstrates how coding systems use character-level specificity to capture clinical detail. Coders can verify current S72 code validity using the CDC/NCHS ICD-10-CM web tool or the AAPC ICD-10-CM code lookup.

HCC risk adjustment: S72.043B and HCC category 402

S72.043B maps to HCC 402, Hip Fracture/Dislocation, under CMS-HCC Model V28. This matters most for Medicare Advantage plans, where diagnosis coding directly influences the risk adjustment factor (RAF) score assigned to each patient. Inaccurate or omitted hip fracture codes can cause the MA plan to underestimate patient complexity, affecting plan reimbursement and potentially triggering RADV audit findings.

Under Model V28, HCC 402 captures hip fracture and dislocation diagnoses that signal significant patient frailty and injury severity. CMS did not switch to V28 in one step. It blended the two models across three payment years instead. Payment year 2024 used 33 percent V28 and 67 percent V24, so V24 still carried the majority weight. Payment year 2025 reversed that split to 67 percent V28 and 33 percent V24. Payment year 2026 runs on V28 at full weight, which makes it the only model behind FY2026 encounters. Practices should still verify the RAF value and HCC assignment against the HCC ICD-10 crosswalk each year, because CMS updates the mappings annually.

Laterality does not change the mapping, so S72.041B, S72.042B and S72.043B all land in HCC 402. It does change audit exposure. A reviewer who finds left or right in the chart will expect the specific code on the claim, not the unspecified one.

For practices managing Medicare Advantage patients with hip fractures, capturing S72.043B correctly is a compliance obligation. It is not just a billing best practice. Supporting this with strong revenue cycle management workflows reduces RAF errors and audit exposure.

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Documentation requirements for ICD-10 Code S72.043B

Every character in S72.043B requires explicit physician documentation, with one deliberate exception. Laterality is the element this code reports as unspecified. The record must therefore support the five elements below and must genuinely lack a documented side. Missing any of them creates a documentation gap that payers may use to downcode the claim or request a refund after payment.

• Laterality (unspecified): S72.043B is correct only when nothing in the record identifies a side. Check the physician note, the operative report, and the imaging interpretation before you accept it. If any of them names a side, the code is S72.041B for the right femur or S72.042B for the left. When the chart is genuinely silent, raise a coding query before you settle for the unspecified code.
• Displaced status: The fracture must be documented as displaced, not impacted or nondisplaced. Radiology reports using terms like “displaced fracture” satisfy this requirement when countersigned by the treating physician.
• Anatomical subsite (base of neck): Documentation must identify the fracture at the base (basicervical region) of the femoral neck. “Femoral neck fracture” alone is insufficient; the sub-site must be specified.
• Open fracture: The treating physician must document that the fracture is open, with bone or soft tissue exposed. Coders may not infer open fracture status from wound photographs or nursing notes alone.
• Gustilo type I or II: The surgeon must explicitly document the Gustilo classification. Acceptable forms include “Gustilo type I” or “type II open fracture.” Clinical language describing the wound also works if it clearly matches type I or II: under 10 cm, clean, with adequate soft tissue coverage.
• Encounter type (initial): The encounter must be during the active treatment phase. The note should reflect the patient is still under active surgical or medical management for the fracture.

Maintaining HIPAA-compliant clinical documentation standards ensures that every data element required for code support is captured at the point of care, not reconstructed retroactively. Practices using claims management software can flag missing documentation before submission rather than discovering deficiencies during a payer audit.

Common coding errors and how to avoid them

Hip fracture codes generate a disproportionate share of claim edits because they require all five specificity elements simultaneously. Most errors fall into a small number of predictable patterns.

• Using S72.043A instead of S72.043B: The most frequent error. Coders default to A (closed fracture, initial encounter) when the fracture is actually open. Always verify open vs. closed status in the operative report before selecting the 7th character.
• Applying S72.043B when Gustilo type III is documented: If the surgeon documents type IIIA, IIIB, or IIIC, the correct code is S72.043C. Using B for a type III fracture is upcoding if deliberate and downcoding if accidental.
• Using S72.043B when the chart documents a side: S72.043B is the unspecified-laterality option. When the record states left or right, S72.042B or S72.041B is the required code. Payers may deny an unspecified code when the specific one was available in the documentation.
• Using S72.043B for subsequent encounters: Active treatment eventually concludes and the patient moves to routine healing follow-up. At that point the 7th character shifts from B to E, which covers an open type I/II fracture with routine healing. Failing to update the encounter type is a common recurring-claim error.
• Omitting the code entirely in MA billing: Some coders list only the surgical CPT code without capturing the diagnosis code in full specificity. For Medicare Advantage, every HCC-mappable diagnosis must be coded at the highest specificity available.

Strong claim denial management workflows include a pre-submission audit step. That step checks fracture codes for laterality, encounter type, and open or closed status before the claim leaves the practice. Practices committed to medical billing compliance practices build these checks into their coding review process as a standing protocol.

Applicable To notes and index references for ICD-10 Code S72.043B

The ICD-10-CM tabular list includes several instructional notes that apply to S72.043B through its parent categories. Coders must read these notes at every level of the hierarchy before assigning the code.

Applicable To: The S72 category includes the term “fracture of femur.” The Applicable To note under S72.04 indicates that this subcategory covers basicervical fractures of the femur. That confirms “base of neck” and “basicervical” are synonymous for coding purposes.

Excludes1 (from S72): The Excludes1 note at S72 sends fractures of neighboring regions elsewhere: the lower leg and ankle (S82.-) and the foot (S92.-). It also excludes traumatic amputation of hip and thigh (S78.-) and periprosthetic fracture around a hip implant (M97.0-). Hip fracture NOS is not on that list. It is an inclusion term inside the category, indexed to S72.00- and S72.9, so a chart that records only “hip fracture” still codes to S72.

Non-traumatic fractures: Pathological and stress fractures are not traumatic injuries, so they belong in Chapter 13 rather than S72. Use M84.4- or M84.5- for a pathological fracture and M84.3- for a stress fracture. A femoral neck fracture caused by metastatic bone disease, for example, is a pathological fracture and never takes an S72 code.

Alphabetic index path: To locate S72.043B in the alphabetic index, start with “Fracture, traumatic,” then navigate to “femur, femoral,” then “neck,” then “base.” The index directs the coder to S72.04-. The tabular list then supplies the sixth character for displacement and laterality, plus the 7th character for encounter and open fracture type. Because the record names no side, the sixth character is 3 and the completed code is S72.043B.

The CMS ICD-10-CM official guidelines govern all instructional note interpretations and take precedence over any commercial coding reference.

Conclusion

Accurate use of ICD-10 Code S72.043B rests on documentation that confirms five elements. Those are displaced status, a base-of-neck subsite, an open fracture, Gustilo type I or II, and an initial encounter. It also rests on what the record does not say, because the sixth character reports that no laterality was documented. When the chart does name a side, S72.041B or S72.042B is the code the payer expects.

Pabau’s integrated claims management software helps orthopedic and trauma practices validate ICD-10-CM code completeness before submission, reducing denial rates for high-specificity codes like S72.043B. To see how Pabau handles claims for traumatic fracture encounters, book a demo with our team.

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