Orthopedic Coding Alert

Notes must paint a clear picture of the patient’s condition.

Os trigonum syndrome most often affects athletes and dancers, from soccer players to ballerinas to anyone who repetitively points their toes.

Occurring primarily in adolescence, the condition occurs when an extra bone at the back of the ankle develops after a piece of the talus does not fuse with the rest of the ankle bone, creating a separate bony formation and severe pain. That pain is often exacerbated by pointing the toes, with swelling on the posterior ankle, especially on the outside of the ankle near the Achilles tendon.

This condition may resolve with noninvasive procedures such as pain medications, physical therapy, brace supports, and ceasing the repetitive activity that created the problem. The first choice of treatment for patients is always the least invasive; but sometimes those remedies fail, requiring more aggressive treatment or even surgery.

Here’s what you need to know to code os trigonum procedures.

Do This to Diagnose and Document Os Trigonum

Coding this procedure can be a bit confusing since there is no code specific to this disorder. “Os trigonum syndrome is recognized in documentation by an overuse injury with the posterior ankle. The challenge when coding these types of conditions is knowing the anatomy, as no code exists with that exact description,” says Jennifer McNamara CPC, CCS, CPMA, CRC, CGSC, COPC, AAPC Approved Instructor, director of education and coding at OncoSpark in Southpark, Texas. “Since you cannot look up that term that specific way, you need to know what it is and what codes currently exist to capture it.

“It is an accessory bone that develops behind the talus and actually connects to the talus, so the correct location is under ‘accessory (congenital)’ and under the correct area of ‘tarsal bone’ leading you to Q74.2 [Other congenital malformations of lower limb(s), including pelvic girdle]. This is a great example of how really knowing anatomy leads you to the correct code by following the instructions from index to tabular,” McNamara adds.

By performing an X-ray or magnetic resonance imaging (MRI), providers can diagnose os trigonum syndrome by locating a small bone with smooth edges, as opposed to rough edges indicating a talus fracture. However, there should also be a thorough history and examination of the foot and ankle with any diagnostics. Then you can apply the diagnosis code of Q74.2, as this code also includes congenital malformation of the ankle joint, per the instructions. Be sure to include this code and specify it applies to an os trigonum syndrome diagnosis in the notes to support medical necessity for any procedures performed.

Provider Might Use Corticosteroids for Symptom Relief

If your patient has tried noninvasive measures without success and the pain remains, your provider might next try corticosteroid injections to relieve os trigonum pain. Because of the bone’s size and depth, some providers choose to use ultrasound (US) to guide the injection.

The code for injection of corticosteroids for treatment without US guidance is 20605 (Arthrocentesis, aspiration and/or injection, intermediate joint or bursa [eg., Temporomandibular, acromioclavicular, wrist, elbow or ankle, olecranon bursa]; without ultrasound guidance). When US is used, you’ll use 20606 (Arthrocentesis, aspiration and/or injection, intermediate joint or bursa [eg., Temporomandibular, acromioclavicular, wrist, elbow or ankle, olecranon bursa] with ultrasound guidance) instead.

Remember: If you do use 20606, do not report 76942 as an additional code (Ultrasonic guidance for needle placement [eg., biopsy, aspiration, injection, localization device], imaging supervision and interpretation), as 20606 includes ultrasonic guidance.

Provider Might Perform Surgery for Os Trigonum Syndrome

If corticosteroid injections fail to significantly reduce the pain, the next step your provider will take will likely be an excision of the bone. The provider will make an incision behind the ankle, identify the os trigonum, and remove it from any surrounding soft tissue.

Coding this excision can create some confusion, as CPT^® advises reporting 28120 (Partial excision [craterization, saucerization, sequestrectomy, or diaphysectomy] bone [eg, osteomyelitis or bossing]; talus or calcaneus) for removing the os trigonum. If you are billing a non-Medicare provider, check whether your payer will accept code 28120 when there is no osteomyelitis or other diseased bone conditions. If not, you can then report code 28899 (Unlisted procedure, foot or toes).

To obtain reimbursement for an unlisted code, make sure your documentation includes a detailed note regarding the procedure to reduce the risk of denials. In addition, suggest a code for a service that is similar to the service the physician has performed for comparison purposes and include a suggested price for the procedure your provider actually performed based on the comparison code. This will act as a reference for the insurance company, which will price the service your provider performed.