Thursday, March 18, 2010

Os Trigonum Syndrome

• Is a cause of posterior ankle pain.
• The lateral (posterior) tubercle of the talus has a separate center of ossification, which appears from ages 7 to 13 years.
• When this fails to fuse with the body of the talus, it is called os trigonum
• It lies lateral to the groove for the flexor hallucis longus (FHL) tendon
• A cartilage connection may or may not attach the os trigonum to the talus.
• The os trigonum has been reported to be present in 1.7% to 7% of normal, asymptomatic feet

Clinical features:
• gradual onset of pain, especially in the anterior aspect of the retrocalcaneal space
• Pain is recreated by forced plantar flexion of the ankle
• pain may be elicited by direct pressure over the posterior lip of the talus

• May be visible on plain radiographs.
• Stress views with the ankle in plantar flexion can show the posterior impingement.
• Three-phase bone scanning may show increased radioactivity in the case of a symptomatic nonunion.
• However, not all os trigonum with positive bone scans are symptomatic.
• CT scan: can provide detailed visualization, especially of a fibrous union or nonunion.
• MRI: may show edema within the os trigonum fragment, as well as fluid around it.

• Nonoperative treatment consists of NSAIDs, activity modification, and occasionally immobilization.
• Surgical treatment may be indicated if nonsurgical management fails.
• Excision can be performed arthroscopically.
• The os trigonum is visualized through the anterolateral portal, and working portal is the posterolateral portal.
• Excision is performed using arthroscopic banana knives, curettes, and graspers.
• Care should be taken to avoid injury to the FHL tendon and the posteromedial neurovascular structures.
• Cure rates with surgery are high


  1. good topic.
    we must know the different conditions causing pain around the ankle and heel apart from usual retrocalcaneal bursitis, plantar fasciitis and achillis tendinitis.
    os trigonum is one of the causes for posterior impingement syndrome of ankle.

    DDs for os trigonum.

    1.fractured posterior fragment
    on radiography it may appear similar to os trigonum when located at the same site. this can be differentiated by injecting air into subtalar joint and taking lateral view x-ray-----air in the retro-achillis compartment (Turec text book)
    2.Flexor hallusis tendinitis= usually associated with posterior impingement syndrome of ankle. passive movement of the FHL aggravates the pain and localised tenderness also present on FHL.triggering and crepitus may be palpated on the tendon while moving the great toe.In impingement syndrome passive plantar flexion of the ankle causes pain in the posterior aspect.
    3.posterior tibilis tendinits(very often mistaken)= usully associated with rheumatoid artritis. pain along the coarse of tendon. standing on toe is impossible in advanced stage of tbilis posterior tendinitis with rupture.( J Bone Joint Surg Am 1996; 78:1491)
    4. subtalar arthritis= main tenderness on the sinus tarsi just anterior to lateral malleolus.
    inversion and eversion are painful.
    5. retrocalcaneal buritis.
    6. insersional achillis tendinitis.

    when the ostrigonum is fused with the talus- it is called as steida.

    posterior impingement test- injecting steroid with local anesthetic into the impingement site relieves the pain- confirms the diagnosis of impingement due to os trigonum.

    FHL tendinitis with posterior impingement syndrom - when surgery is required- postero-medial approach is preferred.
    FHL tendinitis alone- posterolateral approach is preferred.

  2. I was diagnosed with os trigonum syndrome several years ago and given a walking boot. It hasn't really acted up since then, but now is. My boot feel apart and I'd like to get another one out of pocket, as I have a $400 deductible to meet and then my insurance will only pay 80%. Can you please advise what type of walking boot is used? I see there are tall/short, soft/medium/firm, etc. I just want to be sure I get the right kind. Thank you!