Podiatry Coding & Billing Alert

Don’t miss: Os trigonum is a congenital condition.

When you come across a case of os trigonum syndrome to code, you should take note of several important details such as what treatment options the podiatrist recommends. If conservative treatment doesn’t work, and the podiatrist performs surgery, make sure you the medical documentation supports code 28120 before you report it on your claim.

Step 1: Understand Os Trigonum Syndrome

Posterior ankle impingement syndrome (PAIS) is a term used to describe a musculoskeletal disorder created from the repeated abutment of the posterior process of the talus or os trigonum between the tibia and calcaneus during plantar flexion of the ankle. When the os trigonum is the cause, it is described as os trigonum syndrome. Podiatrists might refer to this condition as os trigonum syndrome, talar compression syndrome, posterior ankle impinge­ment (PAI) syndrome, or posterior tibiotalar impingement syndrome (PTTIS).

Os trigonum defined: The os trigonum is an extra (accessory) bone that lies behind the ankle joint that exists when one area of bone does not fuse with the rest of the talus (ankle bone) during growth. The os trigonum varies in size, and it is attached to the posterior aspect of the talus by a fibrous band of tissue, says Arnold Beresh, DPM, CPC, CSFAC, in West Bloomfield, Michigan.

Only a small number of patients have this congenital condition. The bone can become painful after trauma to the back of the heel, after an ankle sprain, or due to Achilles tendinitis, Beresh explains.

Additionally, patients who frequently assume plantarflexion (foot pointed downward) positions may experience posterior impingement from the os trigonum. Typical patients with os trigonum include athletes such as ballet dancers, soccer players, runners, and volleyball players.

Step 2: Choose Appropriate ICD-10 Code

If you look up “syndrome” in the ICD-10 index, you will see “os trigonum” as a choice. The index then directs you to Q68.8 (Other specified congenital musculoskeletal deformities) as the correct diagnosis code for this condition.

Step 3: Observe Conservative Treatment for Os Trigonum Syndrome

You podiatrist will first recommend conservative treatment for ankle impingement syndromes. These types of treatments include anti-inflammatory medication, activity modification, immobilization, athletic taping to prevent end range of the plantar flexion, and local corticosteroid injections.

Step 4: Pinpoint 28120 for Surgical Treatment Option

If conservative measures fail and the patient still expe­riences swelling, tenderness, limitation of motion and weakness, then your podiatrist may consider surgical management to excise the os trigonum.

The primary goal of operative treatment for posterior ankle impingement is excision of the impeding anatomical structure. The podiatrist will remove the fractured os trigonal or posterolateral talar process in its entirety. During the procedure, the podiatrist will make an incision behind the patient’s ankle, identify the os trigonum, and dissect it free of its surrounding soft-tissue attachment.

When you encounter surgical excision of the os trigonum, you can directly opt for code 28120 (Partial excision (craterization, saucerization, sequestrectomy, or diaphysectomy) bone (eg, osteomyelitis or bossing); talus or calcaneus)).

Step 5: Put It All Together in an Example

The patient, a ballerina, was born with an os trigonum bone in her left foot. She has been experiencing swelling, tenderness, and limitation of motion. The podiatrist diagnoses her with os trigonum syndrome, caused by repeatedly pointing her toes downward while dancing. The podiatrist first recommends conservative treatment including anti-inflammatory medication, activity modification, and immobilization for the pain. However, when the patient’s pain continues for months, the podiatrist recommends surgical management to excise the os trigonum. During this procedure, the podiatrist makes an incision behind the patient’s ankle, identifies the os trigonum, and dissects it free of the surrounding soft-tissue attachment. You should report 28120 and Q68.8 on your claim.