Learn How Small Bones Can Lead to Big Denials When Coding a Sesamoidectomy
Identify what ‘separate procedure’ actually means. Two of the smallest bones in the human body live under the ball of the foot, at the head of the first metatarsal, and they cause an outsized amount of trouble, both for the patient and for the coder. The sesamoids are roughly the size of a corn kernel, but a chart note that fumbles them can turn a clean surgical claim into an audit finding faster than you can say “separate procedure.” Give these little bones the respect they deserve, so you can code a clean claim. Meet the Sesamoid Bones Sesamoid bones grow inside a tendon rather than hanging off the end of another bone. The patella is the star of the show, but the foot has its own pair of understudies: two small sesamoids embedded in the tendons of the flexor hallucis brevis, sitting on the plantar surface of the first metatarsal head. Note that term carefully: metatarsal head, not toe. The sesamoids live under the ball of the foot at the first metatarsophalangeal joint (MTPJ), not out on the phalanx, and documentation that drifts toward “great toe” when it means the first metatarsal head is setting up for trouble down the line. Anatomists label them by position. The tibial (medial) sesamoid sits toward the inside of the foot, while the fibular (lateral) sesamoid sits toward the second toe. The bones aren’t just decorative — they act like tiny pulleys, absorbing load and giving the flexor tendon leverage every time the foot pushes off. When the bones misbehave, walking hurts. Sesamoid pathology shows up as sesamoiditis (inflammation from repetitive stress, the runner’s and dancer’s classic injury), fracture (acute or the sneaky stress kind), avascular necrosis, chondromalacia, and displacement that rides along with hallux valgus (bunion). Conservative care, such as padding, offloading, and immobilization, wins most of these battles. But when it doesn’t, the surgeon reaches for the scalpel, and you reach for the code book. Translate Operative Terminology Before you can code the op note, you have to read it as the surgeon wrote it. A sesamoidectomy is the excision of a sesamoid bone. The surgeon may take one or both bones and they may approach from the top (dorsal), the bottom (plantar), or the side (medial). Watch for the words that tell you how much material the surgeon removed. “Excision” and “removal” mean the whole bone is gone. “Planing,” “shaving,” “partial resection,” or “condylectomy of the sesamoid” mean the surgeon only reshaped it, and that distinction matters when it comes to code selection. You’ll also see the sesamoids show up as bit players in a larger production. Bunion surgery frequently involves a lateral soft tissue release that repositions or removes the fibular sesamoid as part of the correction. When that happens, the sesamoid work may not be separately reportable at all, as it’s swept into the starring procedure. Identify the Codes That Matter Here’s the short list every foot surgery coder should have committed to memory. For the excision of a sesamoid at the first metatarsal head, the workhorse is 28315 (Sesamoidectomy, first toe (separate procedure)). However, here’s the part that trips people up: 28315 covers the removal of either the tibial or the fibular sesamoid. It is not, by its plain descriptor, a “per bone” code. If the surgeon removes both sesamoids from the same first MTPJ through the same approach, you cannot simply bill 28315 twice and expect a check. When two sesamoids are genuinely addressed through separate work, coding will depend on your payer’s policy and the operative detail — but you can’t automatically report two codes. Fractures play by different rules. If the surgeon is treating a sesamoid fracture rather than excising the bone, you’ll look to the following codes: Reading “fracture” and reflexively reaching for 28315 because the word “sesamoid” appears is a classic mix-up. Treatment of a fracture and excision of a bone are not the same event. Bunion overlap: The hallux valgus correction codes in the 28292-28299 (Correction, hallux valgus with bunionectomy, with sesamoidectomy when performed …) range describe bunionectomy “with sesamoidectomy, when performed.” Those two little words, “when performed,” mean the sesamoid work is already baked into the bunionectomy code when the surgeon does the work as part of the correction. You do not get to peel it off and bill 28315 separately. Understand That ‘Separate Procedure’ Isn’t a Suggestion The parenthetical note “separate procedure” in 28315’s descriptor is the single most misread phrase in the whole code. It does not mean to bill the code separately every chance you get. The phrase means the opposite: A separate procedure code is only reportable on its own when it’s the only procedure performed in that anatomic area, or when it’s clearly distinct from the other work performed. If the surgeon performs the procedure as part of a bigger treatment done through the same incision, the separate surgery disappears into the larger procedure’s value. The National Correct Coding Initiative (NCCI) edits enforce this, and if you try appending modifier 59 (Distinct procedural service) to force the split without the physician’s documentation supporting true distinctness, then the auditors will spot the pattern. Avoid These Audit Findings and Documentation Pitfalls The good news about sesamoidectomy denials is that they’re predictable. The bad news is that they keep happening anyway. The main findings are laterality and specificity gaps — for example, an op note that says “sesamoid excised” without stating tibial or fibular, or which foot. Because the surgical site is the first metatarsal head rather than a digit, laterality here is a side-of-body question. The claim requires LT (Left side) or RT (Right side) as the site modifier, not a toe-specific T modifier. Of course, you should confirm your payer’s expectation before you submit the claim, as some carriers have their own conventions for how sesamoid work should be modified. If the note doesn’t say tibial or fibular and right or left, the coder can’t code the procedure and the auditor won’t assume the location. Close behind is the excision versus shaving mismatch. For example, the note describes planing or partial resection, but the claim carries 28315 for a full excision. The code has to match what the surgeon actually did, not what sounds tidier on a claim form. Next is the unbundling trap. Beware of attempting to report two separate codes that cannot be unbundled, such as: Plus, don’t forget the global period. Sesamoid surgery carries a 90-day global period, so that post-op visit you’re eyeing is almost certainly included and not separately billable. The fix for every one of these issues is the same: documentation. A defensible sesamoid claim names the specific bone (tibial or fibular), the specific side and site (right first metatarsal head, left first MTPJ), the approach, and precisely what the physician did to the bone — either removed it in full or reshaped it. Documentation ties the procedure to a diagnosis that actually supports medical necessity, and it shows the conservative care that came first. If the physician documents the necessary information clearly, the smallest bones in the foot will stop being the biggest headache on your denial report. Takeaway Sesamoidectomy coding rewards the coder who slows down and reads. Make sure you match the code to the event, such as: Respect the “separate procedure” designation, and report only what the physician actually performed. Insist that the documentation includes laterality, specificity, and an honest description of how much bone was removed. Two tiny bones, one clean claim. That’s the whole game. Tonia Silva, CPC, CPMA, CPPM, Contributing Writer
