ICD 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

ICD-10 Code S72.043B is a billable ICD-10-CM diagnosis code for a displaced fracture at the base of the neck of the unspecified femur. It applies at the initial encounter for an open fracture of Gustilo type I or type II. The sixth character, 3, is the unspecified-laterality option.

So this is the code for a base-of-neck fracture where the record never names a side. It is valid for fiscal year 2026, became effective on October 1, 2025, and is eligible for HIPAA-covered transactions. It sits inside the S72 category, which covers fractures of the femur.

Laterality is where femoral fracture claims fail most often. S72.043B is correct only when the chart genuinely names no side. It is the wrong code whenever left or right appears anywhere in the record.

In practice, every character in the code has to be earned by the record. A coder who cannot point to documentation for displacement, subsite, open status and Gustilo type has to query the physician first.

What the 7th character B tells the payer

The 7th character is the most consequential character in S72.043B for billing purposes. In fact, getting it wrong triggers an automatic claim edit. The character B carries three facts 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.

Under ICD-10-CM guidelines, “initial encounter” covers the whole active treatment period rather than the first office visit alone. 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 document “open fracture type I” or “open fracture type II” in the note, or use equivalent Gustilo terminology. Absent that documentation, the coder queries the surgeon rather than assuming type I or II.

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. The clinical difference still matters when auditing documentation, because it flags the cases that belong under S72.043C for Gustilo type IIIA/B/C.

Ultimately, the classification must come from the surgeon’s operative report or clinical note. A rehabilitation note describing the wound weeks later does not establish the Gustilo type, and neither does a nursing entry.

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. Accordingly, fractures here are classified within S72.0, fracture of head and neck of femur. That subcategory then splits by anatomical subsite and by fracture characteristics.

Specifically, the base of the femoral neck sits at the junction between the neck and the intertrochanteric region. Clinicians often call a fracture here basicervical, while the tabular list indexes the same subsite as cervicotrochanteric. Either way, the base-of-neck subsite is captured under S72.04.

By contrast, these fractures differ clinically from subcapital fractures, which sit near the femoral head and code to S72.01. They also differ from midcervical or transcervical fractures in the mid-neck, which code to S72.03.

• 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, which takes cervicotrochanteric fracture of femur
• 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.

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. As a result, 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.

A displaced base-of-neck fracture is usually treated surgically, so this diagnosis travels with a hip procedure code on the same claim. Where the surgeon performs a total hip replacement, that procedure line is CPT 27130.

For confirmation, 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. Notably, this matters most for Medicare Advantage plans, where diagnosis coding drives the risk adjustment factor (RAF) score assigned to each patient.

Consequently, an omitted or inaccurate hip fracture code leaves the plan underestimating patient complexity. That reduces plan reimbursement and can surface later as a RADV audit finding.

Under Model V28, HCC 402 captures hip fracture and dislocation diagnoses that signal 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: 33 percent V28 and 67 percent V24, so V24 still carried the majority weight.
• Payment year 2025: the split reversed to 67 percent V28 and 33 percent V24.
• Payment year 2026: V28 at full weight, which makes it the only model behind FY2026 encounters.

Verify the RAF value and the HCC assignment each year against the current CMS risk adjustment files, because the mappings are updated annually.

Laterality does not change the mapping, so S72.041B, S72.042B and S72.043B all land in HCC 402. It does, however, 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 billing Medicare Advantage, hip fracture coding carries compliance weight as well as revenue weight. For instance, a RADV reviewer can pull the chart and ask how HCC 402 was supported. An unspecified code sitting beside a documented side is the finding they write up.

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 other five elements below and must genuinely lack a documented side. Consequently, missing any of them gives a payer grounds to downcode the claim or to request a refund.

• 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: Specifically, 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): Likewise, documentation must identify the fracture at the base of the femoral neck. The tabular list recognizes “cervicotrochanteric fracture of femur” here, and a surgeon writing “basicervical” describes the same site. “Femoral neck fracture” on its own is not enough.
• 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.

The elements above have to be captured at the point of care, not reconstructed weeks later from a closed chart. A practice running claims management software can hold that check at submission. A missing Gustilo type or an absent laterality then surfaces before the claim goes out.

Common coding errors and how to avoid them

Hip fracture codes generate a disproportionate share of claim edits, because five specificity elements have to line up at once. Overall, 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 operative note describes an open fracture. 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.

Typically, a pre-submission audit step catches most of these. It checks each fracture code for laterality, encounter type, and open or closed status before the claim leaves the practice. The surgical side of the same claim runs through the CPT codes reference, so both lines get reviewed together.

Instructional notes and the index path for S72.043B

The ICD-10-CM tabular list includes several instructional notes that apply to S72.043B through its parent categories. Therefore, 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.” At S72.04 the inclusion term is “cervicotrochanteric fracture of femur,” which is the only synonym the classification lists for this subsite. Surgeons often write “basicervical” for the same fracture, but that word is clinical shorthand rather than a coded inclusion term.

Excludes1 (from S72): One condition alone is Excludes1 at S72. That is traumatic amputation of hip and thigh (S78.-), which can never be reported alongside a femur fracture code. Three neighboring groups carry Excludes2 notes at S72 instead.

• Fracture of lower leg and ankle (S82.-)
• Fracture of foot (S92.-)
• Periprosthetic fracture around a prosthetic hip implant (M97.0-)

Practically speaking, the difference shows up at the claim level. An Excludes1 note means the two conditions cannot occur together, so a payer edit fires when both codes appear. An Excludes2 note means the condition simply is not part of S72, so both codes may be reported when the patient has both injuries.

Hip fracture NOS: A chart that records only “hip fracture” is not excluded from S72. “Hip fracture NOS” is an Applicable To inclusion term at S72.00- and at S72.01-, so it codes to the unspecified-part-of-neck subcategory.

Notably, it does not code to S72.9. That subcategory carries its own Excludes1 note for fracture of hip NOS, which steers the coder away from S72.9 rather than toward it.

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 read down to “femur, femoral,” then “neck,” then “base.” The index sends 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 for Coding and Reporting govern how these instructional notes are read. They take precedence over any commercial coding reference.

How Pabau helps coders catch a missing laterality

Often, most practices find a laterality problem only after the remittance arrives. The claim goes out with S72.043B, the payer sees an unspecified code where a specific one exists, and the denial lands weeks later. By then the operative note is closed and the query is a chase.

Practice management software like Pabau keeps the clinical record and the claim in one system. As a result, the coder reads the operative note, the imaging report and the diagnosis line on the same screen. Coding queries stay attached to the encounter instead of living in an email thread.

Overall, the outcome is fewer unspecified codes leaving the practice, and a shorter paper trail when a reviewer asks how HCC 402 was supported. Every subscription includes the full claims workflow, so none of this waits on an upgrade.

Streamline orthopedic and trauma billing with Pabau

Pabau’s claims management tools help orthopedic and trauma practices submit ICD-10-CM codes accurately, track claim status, and reduce denial rates across payer types.

Book a demo

Conclusion

S72.043B is a correct code and a weak one at the same time. Indeed, it is billable, it maps to HCC 402, and it will usually pay. It also tells the payer that nobody wrote down which femur was broken.

So treat the code as a prompt rather than an answer. Where the record genuinely names no side, S72.043B is what you report and the chart supports it. Where a side sits unread in an imaging report, the query costs minutes and the denial costs weeks.

Pabau validates ICD-10-CM code completeness before submission, so a missing laterality surfaces while the encounter is still open. Book a demo to see how Pabau handles claims for traumatic fracture encounters.

Continue your research

Need to send a clean claim for an orthopedic code? Clean claim best practices covers the documentation and formatting that stop automatic edits on trauma codes.

Unsure how billing works for hospital-based fracture care? Medical billing fundamentals walks the claim lifecycle from code assignment through to remittance.

Reading ERA responses on orthopedic claims? Electronic remittance advice (ERA) guide explains how to read 835 files and answer denial reason codes.

Want the wider view of how a claim earns its money? Revenue cycle management maps every stage from patient registration to final payment posting.

Building coding checks your auditors will accept? Medical billing compliance sets out the review steps that keep specificity errors out of submitted claims.

Frequently asked questions