- The ostrigonum is an accessory bone that sometimes develops behind the talus. It is connected to the talus by a fibrous band.
- The presence of an ostrigonum in one or both feet is congenital (present at birth).
- It becomes evident during adolescence when one area of the talus does not fuse with the rest of the bone.
- Ostrigonum syndrome is characterized by pain behind the ankle joint.
- There are three mechanisms for the development of an ostrigonum: 1. fusion failure of an ossification center; 2.fracture of the posterior margin of the tibia; 3.fracture of the posterior process of the talus.
- The ostrigonum syndrome can be caused by overuse or trauma. Soft tissue structures, including the ankle joint capsule and surrounding ligaments, may react by forming a hypertrophic mass after a trauma.
- Pain behind the ankle is the primary symptom (aggravated by pointing the toes or forced plantar flexion).
- Stiffness, weakness and swelling can be observed between the Achilles tendon and the peroneal tendons.
- Decrease in plantar flexion compared with the unaffected ankle.
- Bony prominence may be palpable behind the ankle.
- Eversion or inversion movements may cause discomfort
Tests and Imaging
- Passive forced plantar flexion test
- Plain x-rays of the foot and ankle (lateral) may demonstrate ostrigonum.
- Bone scan may be used as a non-specific means of localizing the inflamed and irritated area.
- MRI can give more detailed resolution to the bony and soft tissue structures in the region.
- Nonsteroidal anti-inflammatory medication or corticosteroid injections are used to reduce soft tissue inflammation.
- In case of fracture, a below-knee cast or cam walker is used for 4-6weeks.
- Podiatry for cam walker and rehabilitation with isometric and eccentric exercises to strengthen and stretch the lower-leg muscles.
- Foot and ankle surgeon for possible removal of the ostrigonum if symptoms still persist after nonoperative treatment.