Ankle Fractures

Ankle fractures are the most common fractures of the lower extremity. They can either involve the distal fibula – i.e. Lateral malleolus fracture; or the distal tibia – i.e. Medial or Posterior malleolus fractures.

The most commonly used classification for handling distal fibular fractures is the Weber Classification (Fig 4), which relies on the level of fracture, number of involved malleoli and associated ligament disruption to stage the injury and predict the need for surgical intervention.

In a nutshell, the basic premise for Weber classification of ankle injury is the level at which the fracture of the lateral maleollus occurs, with injuries below the level of the talar dome, infra-syndesmotic (usually transverse and avulsive in origin) being classified as Type A injuries. (Fig 5)

Type A Weber fractures translate lateral collateral ligament stress from forced adduction in a supinated foot, and the extent of injury correlates with the severity of the trauma, with progressive levels involving first the distal fibula alone (type A1), to concurrent oblique or vertical fragment of the medial malleolus (type A2).

Fractures extending distally to the level of the talar dome, trans-syndesmotic (usually spiral), commonly involve partial to complete tibiofibular syndesmosis disruption and may present with near normal spacing to frank tibiofibular widening, especially on stress views depending on the degree of ligamentous injury, are classified as Type B injuries.

Type B Weber fractures translate exorotational stress on a supinated foot, and the extent of injury also correlates with the severity of trauma, with progressive levels involving first talofibular ligament disruption and/or lateral malleolus oblique fracture (type B1) (Fig 6), to concurrent medial deltoid ligament complex disruption and/or medial malleolus fracture (type B2) and finally to simultaneous posterolateral tibia fracture (type B3) (Fig 7, 8 and 9).

Fractures clearly above the level of the talar dome, supra-syndesmotic, are commonly associated with high level tibiofibular syndesmotic tear and widening of distal tibiofibular joint as well as with medial malleolus fracture or deltoid ligament disruption (Fig 10). Note that suspected ankle fracture should be evaluated with lower leg incidences as well as ankle radiographs for the possibility of remote fibular disruption which may occur with potentially long distance interosseous membrane tear.

These fractures are commonly unstable, and translate exorotational stress on a pronated foot, predominantly associated with medial side injury (medial malleolus fracture and/or deltoid ligament tear). In this case, we may have an isolated simple fibular shaft fracture (type C1), a complex simple fibular shaft fracture (type C2) or a proximal fibular fracture (type C3)

Pilon Fractures

Another common type of fracture involving the ankle is the Pilon fracture, which as the name implies, translates high force axial loading of the tibia against the talus. Characteristically, it involves the tibiotalar articular surface and the most commonly used classification scheme is the one proposed by Ruedi and Algower (Fig 11).

Type I occurs with articular surface fracture with minimal to no displacement, whereas Type II implies significant displacement but minimal to no comminution (Fig 12). Type III classification is reserved for significantly comminuted fractures and/or important articular surface impaction, and consequently carries the worst prognosis.

Calcaneus fractures

The most common tarsal fracture and the third most common general fracture site in the lower extremity is the calcaneal fracture. (1) Some of its more interesting eponyms – Lovers Fracture / Don Juan fracture – give away its most common mechanism of injury, which is also high force axial loading, such as a high velocity fall on one’s feet. (Fig 13)

One thing to note is that when bilateral, and respecting the above mentioned mechanism of injury, such fractures should always prompt careful inspection of the lumbar spine given its common association to lumbar vertebra burst fractures.

Several anatomic subsites can be affected in calcaneal fractures, with the most important distinction to be made being that of an extra-articular fracture (such as fracture of the anterior process, calcanean tuberosity or sustentaculum tali) as opposed to an intra-articular fracture.

For classification of intra articular fractures the most commonly used scheme in our institution is the Sanders classification (Table 1, Fig. 14), which relies on a semi-coronal CT plane aligned to the body of the calcaneous and its posterior articular facet.

Examples of Sanders 2A (Fig 15), Sanders 2B (Fig 16) and Sanders 3AC (Fig 17) can be seen in these oblique coronal CT scans.

Lisfranc Fracture Dislocation

Lisfranc or Tarsometatarsal Joint lesions can occur with either low energy trauma such as rotational and axial load applied on a hyperextended foot, as seen commonly in soccer players or other athletes, to high energy falls from height implying direct crush injury, and can similarly range in severity from mild ligament disruption only to severe multi segment fracture dislocation.

Radiographs, in keeping with the variability of force and injury, will show anywhere from a mild widening of the space between the first and second metatarsal base to severe multi-metatarsal dislocations with or without associated fractures.  The most important signs to look for require AP views (widening of 1^st to 2^nd metacarpal spacing, malalignment of the medial side of the 2^nd metatarsal base with the medial side of the middle cuneiform, and of the 4^th metatarsal base with the cuboid) and lateral views (dorsal subluxation of metatarsal bases). In our institution, complementary study with CT is generally useful especially in order to reveal associated occult fractures.

Classification schemes have shown poor correlation with symptoms and treatment planning, but for the sake of systematization these lesions can be roughly divided into three basic types according to the initial classification by Quenu and Kuss with homolateral fracture dislocation (Fig. 18) involving homogeneous lateral displacement of all/most metatarsals or fixed “normal” first tarsometatarsal joint with lateral displacement of the remaining metatarsals; divergent fracture dislocation (Fig. 19) with medial displacement of the first tarsometatarsal joint and contralateral displacement of 2^nd to 4^th metatarsals; and isolated fracture dislocation (Fig. 20) with dorsal displacement of 1 or 2 metatarsals with no clear medial or lateral deviation.

Examples of a homolateral Lisfranc fracture dislocation can be seen in Radiography (Fig. 21), coronal CT (Fig. 22) and 3D VRT CT (Fig. 23)

Metatarsal Fractures

Fractures involving the metatarsal bones are the second most common of the distal lower extremity, and should (as virtually all fractures) be imaged in at least two different planes. Aside from the general simple metatarsal fractures (Fig 3), often from direct trauma or crushing injuries, we will be focusing on two “different” and common types of fractures involving the foot which are avulsion fractures of the base of 5^th metatarsal and metatarsal stress fractures.

Base of 5th Metatarsal

The base of the 5^th metatarsal is the insertion site for the peroneus brevis tendon and for the lateral band of the plantar fascia, which makes it susceptible to avulsion injury with forced hindfoot inversion or forced lateral loading on adducted forefoot and should be actively sought in cases of lateral collateral ligament sprains. The most common of these fractures is the so called “pseudo-Jones” or Zone 1 fracture, (Fig 24) involving mostly the proximal tubercle but with little to no disruption of tarsometatarsal or intermetatarsal joints. A slightly more distal or Zone 2 fracture, also known as Jones fracture, more commonly disrupts intermetatarsal joint and affects an area of watershed vascularity, and is therefore more commonly associated with non union and a more protracted course. One detail to keep in mind about these fractures is the differential diagnosis with normal variants (os) and unfused apophysis in children (or young adolescents) to avoid fracture overcall.

Stress fractures

Metatarsal stress fractures are typical overuse injuries resulting from repetitive strain, and are often very hard to spot radiographically, especially in an acute setting (Fig 25 and 26). They can involve any metatarsal but most commonly occur around the 2^nd or 3^rd diaphysis. Radiographs obtained a few weeks later are often more productive, eventually showing periosteal reaction or a bone callous. CT can help with identifying hairline fractures with its superior cortical resolution, however MRI is generally the most sensitive way of identifying acute stress fractures with underlying bone marrow edema (Fig 27).