Lateral Subtalar Joint Dislocation

26 M jumped to catch a baseball and landed on his left foot while rotating to the right. Diagnosis? • Xray of the Week

Figure 1. The patient jumped to catch a baseball and landed on his left foot while rotating to the right. Diagnosis?

Figure 2. Lateral Subtalar Joint Dislocation. (A) AP radiograph demonstrates the talus (yellow arrow) with anatomical alignment to the distal tibia. The calcaneus (blue arrow) and navicular are rotated laterally. (B) Lateral radiograph demonstrates the talus (yellow arrow) with anatomical alignment to the distal tibia. The calcaneus (blue arrow) is rotated laterally.

Subtalar Joint Dislocation

Subtalar joint dislocation is a rare but significant orthopedic injury characterized by the disruption of the talocalcaneal and talonavicular articulations while preserving the tibiotalar and calcaneocuboid joints. It accounts for approximately 1% of all dislocations and typically results from high-energy trauma, such as motor vehicle accidents, falls from height, or sports injuries. Medial dislocations, also known as acquired clubfoot, constitute about 80% of cases, whereas lateral dislocations (acquired flatfoot) account for the remaining 20%. Posterior and anterior dislocations are exceedingly rare.

Etiology and Pathophysiology

The injury mechanism involves forced inversion or eversion of the foot with an axial load. Medial dislocations result from inversion forces, leading to disruption of the lateral ligamentous structures and impingement of the talar head against the extensor tendons. As in this case, lateral dislocations result from eversion forces, causing injury to the deltoid ligament and potentially the posterior tibial tendon. Associated fractures, particularly of the lateral process of the talus or the anterior calcaneal process, are present in up to 50% of cases and may complicate reduction.

Imaging Findings

Radiographic evaluation is the first-line imaging modality, with anteroposterior, lateral, and oblique foot radiographs demonstrating misalignment of the talocalcaneal and talonavicular joints (Figs. 1,2). Medial dislocations present with the talar head displaced laterally and the calcaneus medially, while lateral dislocations exhibit the opposite pattern. Fractures of the lateral talar process, anterior calcaneal process, or posterior malleolus should be carefully assessed.

CT imaging is invaluable in evaluating associated fractures, assessing articular congruity post-reduction, and planning surgical intervention if necessary. Multiplanar reconstructions can aid in identifying subtle talar dome impaction or osteochondral injuries. MRI is reserved for evaluating ligamentous and tendinous injuries, particularly in chronic or irreducible cases.

Treatment and Prognosis

Closed reduction under sedation or anesthesia is the primary treatment modality. Reduction is typically achieved by applying traction and reversing the mechanism of injury, followed by immobilization in a short-leg cast or boot for 4–6 weeks. Open reduction may be required in cases of interposed soft tissue or osteochondral fragments preventing closed reduction. Post-reduction imaging, including CT, should be obtained to confirm alignment and exclude occult fractures.

The prognosis is generally favorable if early, stable reduction is achieved. However, complications such as post-traumatic arthritis, subtalar instability, and avascular necrosis of the talus may occur, particularly in cases of delayed treatment or associated fractures. Long-term outcomes depend on the severity of cartilage damage and the presence of concomitant injuries.

References

1. Bohay DR, Manoli A 2nd. Subtalar joint dislocations. Foot Ankle Int. 1995;16(12):803-808. doi:10.1177/107110079501601212

2. Richter M, Wippermann B, Krettek C, Schratt HE, Hufner T, Therman H. Fractures and fracture dislocations of the midfoot: occurrence, causes and long-term results. Foot Ankle Int. 2001;22(5):392-398. doi:10.1177/107110070102200506

3. Prada-Cañizares A, Auñón-Martín I, Vilá Y Rico J, Pretell-Mazzini J. Subtalar Dislocation: Management and Prognosis for an Uncommon Orthopaedic Condition. Int Orthop. 2016;40(5):999-1007. doi:10.1007/s00264-015-2910-8 - Pubmed

4. Rammelt S & Goronzy J. Subtalar Dislocations. Foot Ankle Clin. 2015;20(2):253-64. doi:10.1016/j.fcl.2015.02.008 - Pubmed

5. Ruhlmann F, Poujardieu C, Vernois J, Gayet L. Isolated Acute Traumatic Subtalar Dislocations: Review of 13 Cases at a Mean Follow-Up of 6 Years and Literature Review. J Foot Ankle Surg. 2017;56(1):201-7. doi:10.1053/j.jfas.2016.01.044 - Pubmed

6. Cheruvu M, Narayana Murthy S, Siddiqui R. Subtalar Dislocations: Mechanisms, Clinical Presentation and Methods of Reduction. World J Orthop. 2023;14(6):379-86. doi:10.5312/wjo.v14.i6.379 - Pubmed

Kevin M. Rice, MD is the president of Global Radiology CME and is a radiologist with Cape Radiology Group. He has held several leadership positions including Board Member and Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator. He was once again a semifinalist for a "Minnie" for 2021's Most Effective Radiology Educator by AuntMinnie.com. He has continued to teach by mentoring medical students interested in radiology. Everyone who he has mentored has been accepted into top programs across the country including Harvard, UC San Diego, Northwestern, Vanderbilt, and Thomas Jefferson.

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