Talus Process Fracture

 

Introduction

The talus is divided anatomically into the head, neck, body, and 2 processes: the posterior process and the lateral process. Fractures of these processes are considered to be peripheral talar fractures. The posterior process is further subdivided into posterolateral and posteromedial tubercles.

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Fractures of the Lateral Process (Snowboarder's fracture)

Up to 50% are misdiagnosed as ankle sprains due to their similar presentation. Missed or untreated injuries can lead to persistent symptoms.

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Anatomy

The lateral process of the talus has a large base that articulates with the fibula dorsolaterally, and contributes to maintain the ankle mortise. It forms the lateral portion of the subtalar joint articulating with posterior facet of the calcaneum inferomedially. The lateral talocalcaneal ligament originates from the tip of this process.

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Image reproduced from https://radiopaedia.org/cases/anatomy-of-the-talus 

 

Incidence

In the general population, <1% of ankle injuries are lateral process fractures. However, studies have suggested an incidence of 2 to 6% of all snowboarding injuries, hence the name.

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Mechanism

  • Often high-energy injuries such as falls from heights, road traffic accidents, direct trauma and football / rugby injuries
  • Forced dorsiflexion and inversion of fixed, pronated foot leads to:
    • lateral shift of the talar head
    • upward shift of the lateral process of the talus on the calcaneal posterior articular surface
    • loss of congruity of the posterior articulation
  • Other studies suggest external rotation is also required to produce this of injury

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Imaging

​Plain radiographs of the ankle: anteroposterior, lateral and mortise views. A lateral process fracture is best seen on the mortise view or Broden view but chip fractures may be seen on the lateral view just above the angle of Gissane.

A visible posterior subtalar effusion is highly suggestive of an occult lateral process fracture.

CT is invaluable in diagnosis and confirmation.

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Image reproduced from Emerg Med J 2003;20:e2(http://www.emjonline.com/cgi/content/full/20/1/e2)

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Classification

Hawkins described three injury patterns:

  • Type I - Simple: extending from the talofibular articular surface to the articular surface of the posterior subtalar joint
  • Type II - Comminuted: involving the articular surfaces and the entire lateral process
  • Type III - Chip: arising from the anterior and inferior portion of the posterior articular process; only involving the subtalar joint and not extending into the talofibular articulation

 

Management

  • Lack of general consensus
  • Aimed at restoring the anatomy of the talus and the articular surfaces
  • Depends on:
    • fragment size, location, and displacement
    • degree of articular cartilage damage
    • instability of the subtalar joint

Historically, cast immobilisation was considered adequate treatment. However, 6-month follow-up showed 50% of patients had symptoms severe enough to warrant surgical intervention.

​Type I

  • ORIF has better outcome than non-operative
  • Missed injuries, delayed presentations, or those managed non-operatively, lead to ongoing symptoms with up to 25% requiring subtalar arthrodesis later

Type II

  • Arthroscopic or open assessment and debridement 
  • Missed or non-operatively treated injuries often lead to poor outcome and later subtalar fusion

Type III

Good outcome with non-operative management in cast / splint

(Type 4) Boack has offered an alternative classification, including a Type 4 which involves subtalar instability / dislocation and has a much poorer outcome.

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Fractures of the Posterior Process

 

Anatomy

The posterior process comprises medial and lateral tubercles, bearing the groove for the flexor hallucis longus tendon. The lateral tubercle, known as Stieda’s process, projects more posteriorly than medially. It provides attachments for the posterior talocalcaneal and posterior talofibular ligaments.

The medial tubercle is usually smaller but variable in size. It provides attachments for the posterior third of the deltoid ligament superiorly and the medial limb of the bifurcate talocalcaneal ligament inferiorly. The undersurface of the combined tubercles articulates with 25% of the posterior facet of the calcaneum.

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Fractures of the Posterolateral Process (Shepherd’s fracture)

These injuries can be mistaken for an os trigonum (posterior process arising from failure to fuse of the secondary ossification centre with the talar body). An os trigonum appears rounded, corticated and is found in 7-10% of normal population, but can also fracture!

Diagnosis can be confirmed with CT or MRI scan. May present similar to ankle sprains but will have posterolateral tenderness and pain on subtalar joint or FHL movement.

 

Fractures of the Postermedial Process (Cedell’s fracture)

Can also be misdiagnosed as an ankle sprain but presents with posteromedial ankle pain.

Fractures of the entire posterior process of the talus are very rare with only a few case reports. 

 

Mechanism

Two mechanisms have been postulated:

  • forced hyperflexion & inversion: direct compression of the posterior talus between the tibia and the dorsal rim of the calcaneum
  • the posterior talofibular ligament causes an avulsion fracture of the lateral tubercle during hyperdorsiflexion and inversion motion

Cedell described the posteromedial tubercle fracture as an avulsion injury resulting from forced pronation and dorsiflexion of the foot. 

 

Presentation

Swelling and pain in the hindfoot area. The posterior talar impingement test is positive with increasing pain associated with active movements of the toe flexors or passive extension of the big toe.

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Imaging

40% of these fractures may be missed on initial plain radiographs.

CT scan will identify the fracture size, displacement, and extent of the fracture fragmentation, or differentiate the presence of accessory ossicles from acute fractures.

May be associated with subtalar dislocations with osteochondral injuries in up to 50%.

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Management

Principles are similar to lateral process fractures:

  • Undisplaced fractures can be managed in a plaster cast for 6-8 weeks
  • Large fragments or displacement (>3mm step) may be an indication for surgery, or they can be excised at a later date if causing posterior impingement. Posterolateral / postermedial or arthroscopic approaches have been described.

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Exam questions

30 year-old male presents to the ED with right ankle pain after sustaining an injury while snowboarding. He is diagnosed with an ankle sprain. He re-presents two weeks later with ongoing pain on wlaking. A CT of the ankle is obtained demonstrating a lateral process fracture. Which of the following is true regarding this injury?

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    1. Short leg cast immobilisation is recommended for a 4 mm displaced fragment
    2. The fracture line runs through the FHL groove
    3. The best outcome may be with open reduction and internal fixation
    4. Excision of a 5mm fragment results in incompetence of the lateral talocalcaneal ligament
    5. The fragment articulates with the medial facet of the calcaneus

Answer: C

 

Excision of a 1cm lateral talar process would lead to incompetence of which of the following structures?

  1. Bifurcate ligament
  2. Inferior peroneal retinaculum
  3. Lateral talocalcaneal ligament
  4. Arcuate ligament
  5. Posterior talofibular ligament

Answer: C

 

References

  • Talar process fractures: an overview and update of the literature. EFORT Open Rev 2018;3:85-92. DOI: 10.1302/2058-5241.3.170040
  • Lee C, Brodke D, Perdue PW Jr, Patel T. Talus Fractures: Evaluation and Treatment. J Am Acad Orthop Surg. 2020 Oct 15;28(20):e878-e887. doi: 10.5435/JAAOS-D-20-00116. PMID: 33030854
  • Mostafa E, Graefe SB, Varacallo M. Anatomy, Bony Pelvis and Lower Limb: Leg Posterior Compartment. 2022 May 29. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–. PMID: 30726025
  • Boon AJ, Smith J, Zobitz ME, Amrami KM. Snowboarder's talus fracture. Mechanism of injury. Am J Sports Med. 2001 May-Jun;29(3):333-8. doi: 10.1177/03635465010290031401. PMID: 11394605
  • Boack DH, Manegold S. Peripheral talar fractures. Injury 2004;35(suppl 2):SB23-SB35
  • Mukherjee SK, Pringle RM, Baxter AD. Fracture of the lateral process of the talus. A report of thirteen cases. J Bone Joint Surg Br 1974;56:263-273
  • Systematic review: Diagnostics, management and outcome of fractures of the posterior process of the talus. link: https://doi.org/10.1016/j.injury.2020.09.030 Published Print: 2020-11
  • Hawkins, L.G., Fracture of the Lateral Process of the Talus. J Bone Joint Surg Am, 1965. 47: p. 1170-5