Radiographs were ordered, and a fracture of a normal variant, the Stieda process, was identified. Posterior talar bone marrow edema is typically caused by posterior impingement secondary to a prominent os trigonum or Stieda process . fracture of Steida's process. Borders of the talar neck. A true os trigonum is a secondary ossification center that has not fully fused with the talus and is connected by fibrous or cartilaginous tissue. The os trigonum, an accessory bone from a secondary ossification center, is located directly posterior to the lateral tubercle ( Fig 5 ). Three-dimensional reformatted CT image of the talus (a) and lateral ankle radiograph (b) show the divisions between the talar head, neck, and body (dashed lines). A trigonal process fracture may also result from a sudden injury such as an ankle sprain. WHAT IS AN OSTRIGONUM. Patients typically present with posterolateral ankle pain that plantarflexion of the ankle joint or motion of the flexor hallucis longus tendon exacerbates. It is considered an anatomical variant and results from the fusion of a secondary ossification center at the postero-lateral aspect of the talus with rest of the bone (which typically occurs between 11 to 13 years of age in boys and 8 to 10 years in girls). 3 MR imaging is the modality of choice for further evaluation of the bony and soft tissue structures. About 15% of people have the Os trigonum on their feet. Stieda fracture: Alfred Stieda Background Stieda process (SP) is related to an elongated lateral tubercle of the posterior process of the talus. Non-displacement of the fracture fragment was managed with conservative treatment consisting of a short-leg cast for 6 weeks. The posterolateral process of the talus (Stieda) The presence of the Os trigonum because of the impact with the adjacent structures. As in normal anatomy, the os trigonum when present is located just behind the trigonal process. Fracture of the Stieda process of the talus is a rare injury and must be differentiated from an os trigonum and simple ankle sprains. fracture of the lateral tubercle of the posterior process of the talus: Shepherd's fracture at Mondofacto online medical dictionary Smith's fracture: Robert William Smith: distal radius fracture with volar displacement: fall on outstretched hand with wrist in flexed position: Smith's fracture at Who Named It? Symptoms can present after an injury, which can lead to a fracture of a Stieda process or disruption of the synchondrosis of the os trigonum. The more common causes are osseous in nature, such as the os trigonum, an elongated posterolateral tubercle of the talus (Stieda’s process), a downward sloping posterior lip of the tibia, an osteophyte from the posterior distal tibia (9a), or a prominent posterior process of the calcaneus. Talar body fractures are defined by an inferior fracture line located within or posterior to the lateral process. A. 768 May-June 2015 radiographics.rsna.org Figure 4. Objective The purpose of this case report is to describe a patient with a fracture of the Stieda process. This is a secondary ossification center in the posterolateral aspect of the talus. The fracture healed without complications. This is because it sits between the medial and lateral tubercle of the talus (see figure 2), and can become irritated as a result of the underlying abnormal anatomy (ie lateral talar process fracture, stieda process or os trigonum), chronic mechanical trauma or an acute injury resulting in tenosynovitis or tendinosis (3). This dislocated fragment produces the same symptoms and is hard to distinguish from an os trigonum. Lateral radiographs obtained with the foot in plantar flexion may show the os trigonum or lateral talar tubercle impinged between the posterior-tibial malleolus and the calcaneal tuberosity. Radiographs can reveal an os trigonum or Stieda process. Associated findings may include capsular thickening, synovitis, soft-tissue edema, and flexor hallucis longus tenosynovitis .