Introduction

The talus is the second-largest tarsal bone of the foot. It connects the leg and the foot and is essential for the movement of the ankle and the foot.¹

Fractures of the talus are rare and account for only 0.85% of all fractures of the human body and 3-5% of ankle and foot fractures.² High-energy trauma, like falls from heights, motor vehicle collisions, and sports injuries are the common causes of talus fracture. Different classification systems are used to analyse the pattern of talus fractures and guide effective management of the fracture.¹

Anatomy

Structurally, the talus consists of three main parts: a head, a neck, and a body. The talar dome is the dome-shaped upper part of the talus, which forms part of the ankle joint along with the tibia and fibula. The neck connects the head and body.¹

Image: Talus bone (shown in red) lateral (side) view. Source: Wikimedia Commons

Almost two-thirds of the talar surface is covered with cartilage. The blood supply of the talus is limited and primarily outside of the bone (extraosseous). These vessels supply the neck and posterior part of the body, which can lead to avascular necrosis in cases of displaced fractures.² The supply of blood to the talus is by three main arteries: the posterior tibial, dorsalis pedis and perforating peroneal arteries.¹

Classification of talus fracture

Fractures of the talus are classified based on the part of the bone affected

• Talar neck fracture
• Talar body fracture
• Talar Head fracture

Talar neck fractures

Accounting for 50% of all talar fractures, talar neck fractures are the most common as the neck is the most fragile part of the talus. It is classified using the Hawkins classification system ¹

Hawkins classification system³

Hawkins I: Talar neck fracture with no displacement.

Hawkins II: Talar neck fracture with subtalar dislocation

Hawkins III: Talar neck fracture with subtalar and tibiotalar dislocation.

Hawkins IV: Talar neck fracture with subtalar, tibiotalar and talonavicular dislocation.

Talar body fracture

Talar body fracture accounts for only 20% of all talar fractures. If the fracture extends to the joint surface of the body, it can lead to osteoarthritis.³

Sneppen suggested the widely used classification system of talar body fractures:

Sneppen classification³

• Type A: compression/osteochondral dome fractures
• Type B: coronal shear fractures
• Type C: sagittal shear fractures
• Type D: posterior tubercle fractures
• Type E: lateral tubercle fractures
• Type F: crush comminuted fractures

Fracture of the talar body includes:²

• Osteochondral fractures of talar dome
• Posterior process body fractures
• Lateral process body fractures
• True talar body fractures

Osteochondral fractures of talar dome²

Osteochondral fracture is the most common type of talar body fracture and accounts for 1% of all talar fractures. Berndt and Harty proposed the most common classification of OCF in 1959. In 2001, Scranton and McDermott added another stage ²

The updated version of the Berndt and Harty classification has five stages

• Stage 1: subchondral bone compression
• Stage 2: incomplete separation of fragments
• Stage 3: complete separation of fragments with no displacement
• Stage 4: complete separation of fragments with displacement 
• Stage 5: large cyst below the articular surface

OCFs that are stable with no displacement have a good prognosis, whereas displaced and unstable fractures can lead to avascular necrosis. 

Posterior process body fractures

The posterior process (a bony projection) of the talus consists of two tubercles - medial and lateral tubercles.⁴ Fracture of the lateral tubercle (Sheperd’s fracture) is more common than that of the medial tubercle (Cedell’s fracture).² Complete fracture of the posterior process of the talus is rare.

Lateral process body fractures

The fracture of the lateral process of the talus is also known as the snowboarder’s fracture, as it is common in snowboarding injuries. The fracture is often confused with an ankle sprain and can be missed on X-ray.⁴

These fractures are categorised into three types using the Hawkins classification:⁵

• Simple fractures: Fractures that extend from the talofibular articular (joint) surface to the posterior talocalcaneal articular surface of the subtalar joint
• Comminuted fractures: Fractures that involve both the articular surfaces and the entire lateral processes (the outer part of the bone)
• Chip fractures: Fractures that arise from the antero-inferior (front lower) part of the posterior half of the lateral talar process without any involvement of the talofibular articular surface

McCrory-Bladin classification⁵

A new classification system for talus lateral process fractures was proposed by McCrory and Bladin in 1996. This classification provides a better understanding of the fracture characteristics and their relation to the mechanism of injury, offering further guidance for treatment.

Type I: Avulsion fracture of the anterior talofibular ligament with no involvement of the talofibular articular surface.

Type II: Simple fracture of the lateral process with some damage to the articular surfaces. They are further subdivided into two types based on the position of the main bone fragment: 

• Type 2A-Undisplaced fractures are where the bone fragment remains in its original position
• Type 2B- Displaced fractures are where the bone fragment has shifted out of place

Type III: Comminuted fractures involve multiple breaks with the complete involvement of the articular surfaces

Tinner-Sommer’s classification of the fracture of the lateral process of the talus⁵

This is a modified form of the McCrory-Bladin classification.Types 1 and 2 are the same as those of the McCrory-Bladin classification.

Type 3 is divided into three subtypes:

Type 3a: simple fracture of the lateral process with one fracture fragment of medium size

Type 3b: Comminuted (multiple) fracture of the lateral process

Type 3c: Severe comminuted fracture with no chance of full reconstruction of the bone

Zhang’s classification⁵

A new modified classification system of talus lateral process fractures was introduced in 2023,

Type 1a: Chip fracture of the lateral talar process without involvement of the talofibular joint

Type 1b: Simple fracture of the lateral talar process with involvement of both the talofibular and subtalar joints. 

Type 1c: Comminuted fracture of the lateral talar process with involvement of the articular surfaces

Type 2a: Fracture of the lateral process along with fracture of the talar head

Type 2b: Fracture of the lateral process along with fracture of the talar neck

Type 2c: Fracture of the lateral process along with fracture of any other part of the talar body

Type 2d: Fracture of the lateral process along with a fracture of the posterior talar process.

Type 2e: Fracture of the lateral process along with two or more fractures in other parts of the ipsilateral talus

Boack’s classification⁵

A classification system that can be applied to the fracture of both the lateral and posterior talar processes. There are four types of fracture in this classification, which are again subdivided based on the severity of the bone injury, degree of damage to articular cartilage and the stability of the ligaments.

Type 1: Chip fracture/avulsion fracture

Type 1a: Extra-articular fracture of lateral processes

Type 1b: Isolated fracture of the medial tubercle of the posterior process

Type Ic: Intra-articular fracture of the lateral process

Type 2: A medium-sized fracture fragment with different degrees of displacement.

Type 2a: Fracture of the lateral process with the involvement of the subtalar joint alone.

Type 2b: Fracture of the lateral tuberosity of the posterior process

Type 3: A large fracture fragment with involvement of both the ankle and subtalar joint

Type 3a: Simple fracture of the lateral talar process with involvement of both the talofibular and posterior subtalar articular surfaces.

Type 3b: Comminuted fracture of the complete lateral talar process

Type 3c: Comminuted fracture of the complete posterior talar process

Type 4: A severe fracture of the lateral or posterior talar process along with instability of the subtalar joint.

Wijers’s classification⁵

Wijers modified the Boack’s classification based on severity, intra-articular or extra-articular location of the fracture and joint dislocations:

Type 1A: Small fragment, extraarticular

Type 1B: Small fragment, intraarticular

Type 2: Intermediate fragment, intraarticular

Type 3: Comminuted or severe fracture, intraarticular

Type 4A: Fracture of the lateral process of the talus along with subtentaculum tali fracture of the calcaneus without joint dislocation

Type 4B: Fracture of the lateral process along with subtalar or peritalar dislocation

Summary 

The condition of the talus is fundamental for the movement of the ankle and foot. The proper treatment for a talar fracture depends on the correct identification of the fracture. It is important to differentiate the talar body fracture from talar neck fracture so as to provide optimal treatment to avoid further complications like avascular necrosis and osteoarthritis.