CPT code 28310 – Osteotomy, proximal phalanx of great toe

Key takeaways

CPT Code 28310 describes osteotomy of the proximal phalanx of the great toe. See CPT 28312 for other phalanges of any toe.

The separate procedure designation means 28310 can’t be billed with a more comprehensive foot procedure. The exception is a distinct, unrelated diagnosis, reported with modifier 59.

When the Akin osteotomy is part of a bunionectomy, report 28298, or 28299 for a double osteotomy, instead of 28310.

A 90-day global surgery period applies under Medicare, so routine follow-up visits in that window are included in the surgical payment.

Pabau’s claims management software checks insurance eligibility, submits electronic claims and tracks each claim’s status through to remittance.

CPT Code 28310: official descriptor and procedure overview

CPT Code 28310 is defined by the American Medical Association as: Osteotomy, shortening, angular or rotational correction; proximal phalanx, first toe (separate procedure). The “(separate procedure)” note belongs to the official descriptor. It sets the bundling rules that decide when 28310 can be billed at all.

The code sits in the 283xx range of the CPT musculoskeletal system chapter, which organizes foot and toe procedures by anatomical site. 28310 covers only the proximal phalanx of the great toe. Osteotomy of other phalanges of any toe, including the proximal phalanx of a lesser toe, is reported with 28312.

Procedure details: what does CPT 28310 involve?

The procedure is a surgical bone cut (osteotomy) through the proximal phalanx of the great toe. It is typically a medial closing wedge that reduces hallux valgus or interphalangeal deformity. The Akin procedure is the most frequently performed variant, though the code also applies to other osteotomy configurations at this site.

The operative note must document each of the following for audit purposes:

• Laterality (left or right foot)
• Bone site: proximal phalanx of the great toe, not a metatarsal or distal phalanx
• Type of bone cut (wedge, linear, or chevron configuration)
• Fixation method (K-wire, absorbable suture, mini-screw, or no fixation)
• Wound closure technique and layer-by-layer description
• Distinct diagnosis if reported alongside another procedure

A missing element won’t always trigger a denial on submission. An audit that finds a vague operative note can still reclassify the service or recoup the payment.

Separate procedure designation: when can 28310 be billed?

The “separate procedure” label means CPT Code 28310 counts as a component of broader foot procedures at the same site. That applies when both happen in the same operative session. In that situation it is bundled and can’t be billed on its own.

Three conditions allow separate reporting:

1. Unrelated diagnosis: The osteotomy is performed for a distinct condition unrelated to the primary procedure. The operative note must support two separate diagnoses, and two ICD-10-CM codes must appear on the claim.
2. Unrelated anatomical site: The osteotomy is performed on a different digit or foot region than the primary procedure. Site documentation must be unambiguous.
3. Standalone procedure: No more comprehensive procedure is performed on the same day. In this scenario 28310 bills without a modifier.

The National Correct Coding Initiative (NCCI) maintains column-pair edits that define which codes bundle with 28310. These edits are updated quarterly, so a pair that was separately billable last year may be bundled today. Always check the current NCCI table before submitting, not a reference from a prior year.

CPT 28310 modifiers: which modifiers apply and when

Modifier selection for CPT Code 28310 depends on the job the modifier does. It may bypass a bundling edit, identify the toe, or place the service within a global period. The table below covers the six modifiers that come up most often.

CMS has issued specific guidance on modifier 59 misuse. The agency’s preferred approach for Medicare claims is to use the more specific X-modifiers (XE, XS, XP, XU) when available, though 59 remains valid. Payers vary in which they accept, so check payer policy before substituting.

Neighboring codes: how does 28310 differ from 28312, 28298 and 28299?

28310 is the only code for an osteotomy of the great toe’s proximal phalanx performed on its own. An osteotomy of a lesser toe’s proximal phalanx, or of any other phalanx, is 28312. 28308 covers a lesser metatarsal osteotomy.

When the osteotomy is part of a bunionectomy, a hallux valgus code replaces 28310 altogether. The chart below maps each scenario to its code, and the operative note’s bone site decides which applies.

The table adds separate procedure status and a typical scenario for each code.

The pairing to watch is 28310 against 28298 and 28299. When an Akin osteotomy accompanies a bunionectomy, 28298 reports the whole procedure. When the correction combines two osteotomies, such as a distal metatarsal cut plus the Akin, 28299 applies. Both codes already include the phalanx osteotomy, so adding 28310 duplicates it and triggers an NCCI edit denial.

ICD-10 diagnosis codes that support CPT 28310 claims

Medical necessity for CPT Code 28310 rests on a documented foot deformity that requires surgical bone correction at the proximal phalanx of the great toe. The ICD-10-CM codes below are the most frequently accepted pairings. Always confirm that the code reflects the documented condition rather than a presumed diagnosis.

A claim whose toe modifier and ICD-10 code point to different feet is an avoidable denial. Before every submission, confirm that T5 pairs with a right-foot code such as M20.11 and TA with a left-foot code such as M20.12.

Medicare reimbursement for CPT Code 28310

Medicare reimbursement for CPT Code 28310 is determined by the CMS Medicare Physician Fee Schedule (MPFS), which updates each January. The RVUs below are national values, and the payment in each locality applies geographic adjustments on top. Always look up the current rate for the specific MAC jurisdiction before quoting a payment to a patient or payer.

The 90-day global period means Medicare bundles all routine follow-up care related to the surgery into the surgical payment. Billing a related E&M visit within that window without modifier 24 or 79 will deny. Commercial payers set their own global period rules, which may differ significantly from Medicare’s. CMS also updates CMS’s list of CPT/HCPCS codes each year alongside the MPFS.

Prior authorization requirements for CPT 28310

Prior authorization requirements for CPT Code 28310 are payer-specific, not universal. Medicare fee-for-service generally does not require prior authorization for this outpatient surgical code, but Medicare Advantage plans operate independently and some do require it. Always verify with the specific plan before scheduling.

Commercial and Medicaid payer positions vary widely:

• Molina Healthcare includes musculoskeletal CPT codes on its prior authorization requirement list. Podiatric surgery codes in the 283xx range typically require submission of clinical notes, imaging, and conservative treatment failure documentation.
• Carelon Medical Benefits Management (formerly AIM Specialty Health) maintains a musculoskeletal site-of-care list that includes orthopedic procedure codes. It may require outpatient surgery center verification before authorization is granted.
• Commercial plans generally require documented failure of conservative treatment, such as physical therapy, orthotics or shoe modifications. They generally want at least three to six months of it before approving elective bone surgery.

The practical rule: treat every surgical claim for 28310 as requiring prior authorization until confirmed otherwise by the specific plan’s current policy document. A verbal approval isn’t enough. The reference number belongs in the chart and on the claim.

Documentation requirements to support a 28310 claim

Claim auditors reviewing 28310 focus on whether the operative note establishes medical necessity and procedural specificity. A vague or templated note is the fastest path to a medical record request or recoupment.

The operative note must include:

• Pre-operative diagnosis with ICD-10-CM code that matches the claim
• Explicit identification of the bone site: proximal phalanx, great toe, left or right
• Description of the osteotomy technique (wedge type, degree of correction, orientation of cut)
• Fixation method and any hardware used (K-wire gauge, screw size)
• Post-osteotomy alignment assessment
• Closure layers with suture materials
• If billed with a separate procedure: a distinct indication and a clear statement that the second procedure was performed for a separate diagnosis

Templated notes that describe a “standard Akin procedure” without patient-specific detail rarely survive an audit. CMS expects the operative report to describe the procedure this patient received, in this patient’s terms.

Common denial reasons for CPT Code 28310 and how to appeal

Most denials for CPT Code 28310 fall into five categories. Each has a clear corrective action and appeal path.

Practices running high volumes of podiatric surgery can track denials by CARC code to catch systemic issues early. Repeated CO-97 denials on 28310 claims usually trace back to bundling or modifier choices made at claim build. Our guide to denial codes in billing has the full CARC/RARC crosswalk.

A denial management process that logs each denial by code and payer shows whether 28310 problems cluster around one plan. Working through a clean claim checklist before submission catches a missing toe modifier before the payer does.

How claims management software reduces 28310 denials

Billing CPT Code 28310 cleanly depends on four manual steps. Your team confirms coverage and prior authorization, checks NCCI edits, applies the right modifiers and tracks the 90-day global period. Each step is a point where a denial can start.

Pabau, the practice management platform we build, connects to the Claim.MD clearinghouse for US insurance billing. Your team runs real-time eligibility checks before the surgery date, then sends 28310 as an electronic CMS-1500 claim.

Claim status and remittance come back into the claims dashboard of Pabau’s claims management software. Your billers see a bundling or modifier denial as soon as it posts. They can correct and resubmit it while the operative note is fresh.

Streamline your podiatric surgery billing

Pabau checks eligibility in real time, submits electronic CMS-1500 claims and tracks each 28310 claim to remittance. Your billing team catches denials early and spends more time on reimbursement.

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Conclusion

28310 is a narrow code: one bone, one toe, and only when the osteotomy stands on its own. Before the claim goes out, confirm three facts from the operative note.

• The cut was made in the great toe’s proximal phalanx.
• No bunionectomy code on the same claim already includes it.
• The toe modifier and the diagnosis name the same foot.

Settle those at scheduling and the claim rarely needs a second look. Leave them to the billing stage and you may spend the 90-day global period appealing a procedure your surgeon has already performed.

Pabau keeps eligibility checks, electronic claims and status tracking in one place. Book a demo to see how it handles claims for your podiatric surgery cases.

Continue your research

Need a structured denial tracking reference? Denial codes in medical billing covers CARC and RARC codes with corrective action guidance for each denial category.

Want to understand what a clean claim requires before submission? Clean claim submission checklist details the elements every outgoing claim must contain to avoid front-end edits.

Billing for multiple foot procedures in one session? Superbill setup guide covers how to build a superbill that captures surgical codes, modifiers and diagnosis linkages.

Was the Akin part of a bunionectomy? CPT code 28298 covers hallux valgus correction with a proximal phalanx osteotomy.

Correcting a lesser toe deformity instead? CPT code 28285 covers hammertoe correction and how it differs from a phalanx osteotomy.

Frequently asked questions about CPT Code 28310