On the left an overview of the two most commonly applied classification systems for ankle fractures:
the Weber and Lauge-Hansen classifications.
We will use them simultaneously in this article because in fact, they describe the same fractures

The Weber system
This system focuses on the integrity of the syndesmosis.
It owes its popularity mainly to its simplicity.

• Type A occurs below the syndesmosis, which is intact.
• Type B is a transsyndesmotic fracture with usually partial - and less commonly, total - rupture of the syndesmosis.
• Type C occurs above the level of the syndesmosis with usually a total rupture of the syndesmosis, and consequently instability of the ankle mortise.

The Lauge-Hansen system
This system focuses on the trauma mechanism.
It is brilliant because it stages the severity of the injury, which allows you to predict the ligamentous injury and instability.
The three main types of the Lauge-Hansen classification are basically the same as Weber A, B and C:

• SA = Supination Adduction (stage 1-2) - Weber A
• SE = Supination Exorotation (stage 1-4) - Weber B
• PE = Pronation Exorotation (stage 1-4) - Weber C

This system is based on:

• Position of the foot at the moment of injury, either in supination (80%) or in pronation (20%)
• Direction of the force on the foot within the ankle mortise, which is either exorotation (80%) or adduction (20%).

For the interpretation of the x-rays you do not need to know the position of the foot or the forces within the ankle mortise at the moment of the injurie.
However the x-rays tell you what happened to the ligamentous and osseus structures and you can predict some of the injuries, because the Lauge-Hansen gives you the trauma mechanism.

Normal flexibility of the ankle

The ankle joint has to be flexible in order to deal with the enormous forces applied onto the talus within the ankle fork.
The medial side of the joint is quite rigid because the medial malleolus - unlike the lateral malleolus - is attached to the tibia, and the medial collateral ligaments are very strong.
The fibula has no weight-bearing function, but merely serves as a flexible lateral support.
It is the lateral complex which allows the talus to move laterally and dorsally in exorotation during forward motion and subsequently pushes it back into its normal position.

Position of the foot

There are two positions of the foot in which the flexible ankle joint becomes a rigid and vulnerable system: extreme supination and pronation.
In these positions forces applied to the talus within the ankle mortise can result in fractures of the malleoli and rupture of the ligaments.

Supination
In 80% of ankle fractures the foot is in supination.
The injury starts on the lateral side since that is where the maximum tension is.

Pronation
In 20% of fractures the foot is in pronation with maximum tension on the medial side.
The injury starts with either a rupture of the medial collateral ligaments or an avulsion fracture of the medial malleolus.

Position of the foot (2)
In standing position, the normal axis of the talus and ankle mortise is exorotated 20 degrees in relation to the axis of the foot.
When we are walking or running, our feet are also slightly exorotated, resulting in even more exorotation of the talus and ankle mortise compared to the axis of forward motion..
It is particularly during running that all the forces of the fibula and tibia, which are in forward motion, land on the talus, which is exorotated.

Position of the foot (3)
When we are running and our foot hits the ground, the talus will suddenly stop its forward motion.
The tibia and fibula continue their forward motion and will even slightly endorotate due to an inward rotation of the knee (figure 1).
The lateral malleolus will deliver an endorotation-force to the talus and will experience a counterforce of the talus in exorotation (figure 2).
Although we say that the foot exorotates, it is actually the lower leg which endorotates upon the foot.

This exorotation-force is the main force on the ankle mortise in 80% of all ankle fractures.

• When the foot is in supination, this will result in:
  • Weber B = SE-injury (Lauge-Hansen)
• When the foot is in pronation , this will result in:
  • Weber C = PE-injury (Lauge-Hansen)

Exorotation

Exorotation of the talus is the main deforming force in 75% of all ankle fractures and is seen in Weber B and C fractures.
These exorotation injuries follow a clockwise pattern from anterior via lateral to posterior, sometimes even extending medially.

1. Normal situation.
2. Exorotation of the talus.
3. Continuing exorotation of the talus will rupture the anterior tibiofibular ligament
4. Continuing force will fracture the fibula at the level of the joint in a Weber B-fracture or above the level of the syndesmosis in a Weber C-fracture.
5. Further posterolateral displacement of the lateral malleolus by the talus results in rupture of the posterior syndesmosis or avulsion of the malleolus tertius.
6. Finally the medial collateral ligament may rupture or the medial malleolus may avulse.

Injury due to exorotation occurs in a clockwise manner:

1. Anterior : rupture of the anterior syndesmosis (or less common Tilleaux avulsion fracture
2. Lateral : oblique fracture in Weber B - SE or high fibular fracture in Weber C - PE
3. Posterior : rupture of the posterior syndesmosis or avulsion of the malleolus tertius
4. Medial : rupture of the medial ligaments or avulsion of the medial malleolus

Pull-off or Push-off fractures

The shape of a fracture indicates which forces were involved.
An oblique or vertically oriented fracture indicates 'push-off'.
A transverse or horizontal fracture is the result of a 'pull-off'.
On the left image the lateral malleolus is pushed off by exorotation of the talus.
On the right image the medial malleolus is pulled off by the medial collateral ligament due to pronation of the foot.

The left image shows an almost vertical fracture of the fibula.
The only possible explanation is that the talus has moved posteriorly and laterally, pushing off the lateral malleolus as is the common pattern in Weber B or SE-fractures.
The image on the right demonstrates both a pull-off of the medial malleolus and an oblique push-off fracture of the lateral malleolus.
In this case the force of the talus was oriented in a lateral direction, resulting in an oblique fibular fracture.
At a later stage, the medial malleolus was pulled off when the talus moved in a posterolateral direction.
Again, this is a Weber B or SE-fracture and Lauge-Hansen would classify this as an SE stage 4 fracture.

The ankle can be thought of as a ring in which bones as well as ligaments play an equally important role in the maintenance of joint stability.
If the ring is broken in one place the ring remains stable.
When it is broken in two places, the ring is unstable and may dislocate.
Now it is easy to say that an ankle is unstable when both the medial and the lateral malleolus are fractured.
It becomes more problematic when there is a combination of a fracture and a ligamentous rupture, because the ligamentous rupture may not be detectable on the X-ray.
In some Weber C - PE fractures there may even be a proximal fibular fracture which is not visible on the ankle X-rays, in combination with a medial ligamentous rupture.
So the X-rays of the ankle may seem normal, but there is an unstable ankle injury.

On the left image a Weber A or SA-fracture.
This ankle is stable because there is only an avulsion fracture of the lateral malleolus below the level of the syndesmosis.
The ring is broken in one place.

On the right image an unstable fracture.
The ring of the ankle is broken in two places: there is a lateral fracture and medial ligamentous injury.

Weber A - Lauge Hansen SA

This is the most simple ankle fracture.
The diagnosis as well as the treatment will be unproblematic.
It occurs in about 20-25% of all ankle fractures.
The foot is fixed on the ground in supination when an adduction force is applied to the talus.
The first injury will occur on the lateral side, which is under tension.

Stage 1.
Supination results in a tear of the lateral collateral ligament or an avulsion fracture of the lateral malleolus below the level of the tibial plafond, i.e below the level of the syndesmosis.

Stage 2.
More talar tilt results in the medial malleolus being pushed off in a vertical or oblique way .
This second stage is very uncommon.

On the left a simple Weber A - Lauge Hansen SA fracture.
Since the syndesmotic ligaments are intact, the ankle mortise is also stable.

Start the video on the left by clicking on the image.
Notice that at first the foot is in supination with maximal forces on the lateral side.
Subsequently the foot adducts.
The result is an SA or Weber A fracture.
We can assume that this is the uncommon stage 2.

Weber B - Lauge Hansen SE

This is the most common fracture and occurs in about 60-70% of all ankle fractures.
The foot is fixed on the ground in supination and an exorotation force is applied to the talus.
The first injury will occur on the lateral side, which is under maximum tension.

Stage 1
As the talus exorotates, the anterior tibiofibular ligament ruptures first (see the paragraph on exorotation).

Since the foot is in supination, the lateral malleolus is held tightly in place by the lateral collateral ligaments and cannot move away without breaking.
As a result, more rotation of the talus will fracture the fibula in an oblique or spiral fashion because the lateral malleolus is pushed off from anterior to posterior.
The fracture starts at or only a few cms above the level of the ankle joint and extends proximally.

Stage 3
Posterior displacement of the lateral malleolus fragment by the talus results in rupture of the posterior tibiofibular ligament or avulsion of the malleolus tertius.

Stage 4
More posterior movement of the talus will result in extreme tension on the medial side and the deltoid ligament will either rupture or pull off the medial malleolus in the transverse plane.

Study the images on the left and try to find out which stage is present.

On the left a Weber B or SE (Lauge-Hansen) fracture.
It is the oblique fibular fracture which is typical.
According to Lauge-Hansen this is stage 2, so we must assume that there is also a rupture of the anterior syndesmosis, i.e. stage 1.
Now we look for stage 3 and we notice a subtle irregularity of the posterior aspect of the tibia (black arrow).
This is probably the result of an avulsion of the malleolus tertius.
Finally, we also notice widening of the medial clear space (red arrow), which indicates a rupture of the medial collateral ligaments, i.e. stage 4..
This ankle is unstable and osteosynthesis is necessary.

The medial clear space should not exceed 4 mm and is usually equal to the distance between the tibial plafond and the talus.
Widening of the medial joint space up to 6 mm or more requires disruption of the medial collateral ligament.

On the left another Weber B or SE (Lauge-Hansen) fracture, which we recognize immediately because of the transsyndesmotic oblique fracture.
We also notice the rupture of the medial collateral ligaments and know that this is SE stage 4, i.e. an unstable fracture.
Notice the widening of the medial clear space as well as of the lateral clear space (yellow arrow).
This patient was scheduled for osteosynthesis of the fibular fracture, if necessary with the placement of a syndesmotic screw.
After osteosynthesis of the fibula, the ankle was tested in the operating room and found to be stable.
There was therefore no indication for placing a syndesmotic screw.
It was concluded that the syndesmosis was only partially ruptured, which is usually the case in Weber B - SE fractures.

Weber C - Lauge Hansen PE

This is seen in approximately 20% of ankle fractures.
The foot is fixed on the ground in pronation when an exorotation force is applied to the talus..
The first injury will occur on the medial side, which is under maximum tension.

Stage 1
Tension on the medial complex leads to rupture of the medial collateral ligament or a medial malleolus avulsion fracture.

Stage 2
The talus rotates externally and moves laterally because it is free from its medial attachment.
This causes rupture of the anterior syndesmotic ligament.

Stage 3
Due to the pronation of the foot, the lateral complex is completely relaxed and the talus will easily force the fibula to move in a posterolateral direction.
The fibula will be twisted distally, while proximally it is fixed in position.
Finally the syndesmosis and interosseus membrane will rupture up to the point that the fibular shaft fractures.
The fracture is always above the level of the syndesmosis.
The fibular fracture may or may not be visible on the ankle X-rays.
A high fibular fracture is also known as a Maissoneuve fracture.

Stage 4
Finally the posterior syndesmotic ligament ruptures, or there is an avulsion of the posterior malleolus (also known as the malleolus tertius).

On the left a typical Weber C fracture above the level of the syndesmosis.
Lauge-Hansen has demonstrated that this is the result of an exorotation force on a foot in pronation.
The fibular fracture meanss PE stage 3.
This means that there is also:
stage 1: a rupture of the medial collateral ligaments and
stage 2: a rupture of the anterior syndesmosis.

Now we study the images to look for stage 4.
It is not easily seen, but there is also a tertius fracture, which means stage 4.
Knowledge of the stages according to Lauge-Hansen helps us to detect fractures which are not easily detected at first glance.
We also know when the ligaments must be ruptured.

Start the video on the left by clicking on the image.
Notice that at first the foot is in pronation, with maximum forces on the medial side.
Subsequently the foot exorotates.
The result is a PE - pronation exorotation injury or Weber C fracture.

Lauge Hansen experiments

Lauge-Hansen was a Danish pathologist, who described experiments in which various forces were applied to freshly amputated legs in order to study the mechanism of ankle fractures.
He noticed the importance of the position of the foot being either in supination (80%) or in pronation (20%).
The most common fracture patterns he found were:
SA - supination adduction
SE - supination exorotation
PE - pronation exorotation.

On the left an illustration of his experiment with the foot in supination.
He pushed the ankle in more extreme supination and applied an adduction force by pushing the lower leg laterally.
This resulted in extreme tension on the lateral collateral ligaments.
At about 70 degrees of supination he noticed that 'a sharp crack is suddenly heard'.

He then X-rayed the ankle and noticed a transverse fracture of the lateral malleolus below the level of the syndesmosis and called this SA 1.
Later Weber called this type A fracture.

In some of the experiments the same crack was heard, but there was no visible fracture on the X-ray.
In these cases he found a rupture of the lateral ligaments.
He argued that a lateral avulsion fracture or a ligamentous rupture would have the same effect on the stability of the ankle joint, so he also called this SA 1.
He repeated these experiments with external rotation and compared the X-rays of the experiments with radiographs of patients with ankle fractures and realized the importance of exorotation.
Lauge Hansen performed his experiments at a time in which the only treatment for ankle fractures was reduction and casting.
He realized that if we could tell by the radiographs which forces were involved in the ankle injury, optimal reduction would be possible.

Ottawa Ankle Rules

These rules are used to determine the need for radiographs in patients with an ankle injury.

Ankle X-ray series are only required in case of:

Pain in the malleolar zone and any one of the following:

• Bone tenderness along the distal 6 cm of the posterior edge of the fibula or tip of the lateral malleolus.
• Bone tenderness along the distal 6 cm of the posterior edge of the tibia or tip of the medial malleolus.
• Inability to bear weight for 4 steps both immediately and in the emergency department.

Radiography

A basic radiographic examination consists of a Mortise-view and a lateral view. Some add the AP-view.
The Mortise-view is an AP-view taken with a 15-25° endorotation of the foot.
The technologist turns the foot inwards until the lateral malleolus is at the same height as the medial malleolus.
This view clearly demonstrates both lateral and medial joint spaces.
On a true AP-view the talus overlaps a portion of the lateral malleolus, obscuring the lateral aspect of the ankle joint.