Introduction

Trimalleolar fractures are fractures of the ankle, involving the medial malleolus, lateral malleolus, and posterior malleolus, and can often involve injuries associated with ligaments and joint instability. They can be caused by high-energy trauma (such as falls from heights or car/motorcycle accidents) in young people, as well as a minor twisting of the ankle in elderly patients. These injuries are considered serious because they affect the stability of the ankle joint and require timely intervention to prevent long-term disability. It is important to determine whether the fracture requires conservative (non-surgical) treatment or surgery to prevent complications such as sepsis, nonunion, malunion, and delayed wound healing. If the fracture requires surgery, the clinician will choose from a range of surgical methods, including open reduction and internal fixation (ORIF) and arthroscopic-assisted open reduction and internal fixation (AORIF).

Initial clinical assessment

Patient history

It is essential to conduct a complete patient history to evaluate the condition of the fracture.

The clinician will ask questions regarding any pre-existing conditions that can affect the condition of the ankle, namely diabetes, peripheral vascular disease, peripheral neuropathy, inflammatory joint diseases, obesity, and renal diseases. It is also important to consider the mechanism of injury, the nature of pain, and its severity. A fracture caused by high-energy trauma raises concerns about the occurrence of compartment syndrome or a pilon fracture. The patient's occupation and regular activities prior to injury should be discussed. Patients should be informed that smoking and alcohol overuse can affect wound healing. A risk assessment of venous thromboembolism should be conducted. This includes evaluating risk factors such as smoking, previous history of venous thromboembolism, family history of deep venous thrombosis, high body mass index (BMI), hormonal therapy, and use of oral contraceptive pills.

Physical examination

The first step when evaluating fractures is to follow the ABCDE approach. This approach helps rule out any life-threatening injuries by following the procedure step by step. The ABCDE approach consists of:

• A — Airway management and cervical stabilisation
• B — Breathing
• C — Circulation and haemorrhage control
• D — Disability (neurologic status)
• E — Exposure

Neurovascular assessment

When performing a neurovascular assessment, the clinician will observe the colour and temperature of the foot. Cold and pale feet can indicate a vascular complication. Pulses on top of the foot and behind the inner ankle should be compared, as absent pulses suggest impaired blood flow. If there is a vascular issue or skin-tenting (where a broken bone is pushed up against the skin from the inside, creating a visible, stretched, tent-like appearance), an urgent ankle reduction to restore blood flow should be performed, followed by a repeat neurovascular assessment. When performing a full neurological assessment, the following nerves will be tested for motor and sensory function: deep peroneal nerve, superficial peroneal nerve, tibial nerve, sural nerve, medial plantar nerve, and lateral plantar nerve.

Soft tissue management

If the skin is being stretched tightly over a deformed ankle, the bone needs to be repositioned and the ankle splinted immediately to protect the skin. The clinician will determine the timing of surgery based on the condition of the skin and the degree of swelling.

Differential diagnosis

Deltoid ligament sprain

A deltoid ligament sprain presents with pain, swelling, and tenderness over the medial malleolus. Weight-bearing can exacerbate pain, and weight-bearing x-rays may reveal a shift in the talus, indicating instability. MRI scans provide detailed images of the ligament injury.

Lateral collateral ligament complex sprain

This injury presents with tenderness and swelling over the lateral malleolus. A shift in the talus may also be observed on weight-bearing ankle x-rays. MRI scans are useful for confirming the diagnosis.

Achilles tendon rupture

Patients with Achilles tendon rupture often present with sharp, severe pain or a sensation of a snap at the back of the ankle. A palpable gap may be identified during clinical examination. The Simmonds (Thompson) test is used to confirm the diagnosis: the clinician squeezes the calf muscle, which should cause plantarflexion of the ankle; a positive result shows no plantarflexion. Ultrasound can be used to assess the severity of the rupture, visualise the gap, and guide further management.

Imaging studies

Plain radiographs (x-rays)

X-rays use three main views: anteroposterior (AP), lateral, and mortise. AP views show overall alignment and soft tissue swelling, and help reveal subtle structures. The lateral view shows the posterior malleolus and the talar dome, and helps determine if the talus is dislocated anteriorly or posteriorly. The mortise view is obtained by rotating the leg inward 15 to 20 degrees whilst the ankle is dorsiflexed, and provides a clear view of the ankle joint space. This view allows the clinician to assess the alignment of the talus and any widening of the syndesmosis.

Computed tomography (CT) scan

CT scans provide more detailed images of complex ankle fractures than x-rays. They show the morphology of the fracture, the number of bone fragments, and the degree of articular involvement. The detailed images help surgeons plan the optimal surgical approach when x-rays are insufficient, and determine whether the ankle requires additional stabilisation. CT scans can also reveal small injuries that x-rays may miss. In posterior malleolar fractures, CT scans can demonstrate the size, direction, and displacement of the fractured fragment.

Magnetic resonance imaging (MRI)

MRI produces clear, detailed images of bones, ligaments, tendons, and cartilage. It helps assess soft-tissue injuries that may not be visible on x-ray. MRI can help diagnose the following injuries:

• Deltoid ligament sprains: Shows the extent of medial ankle ligament injury and identifies associated damage
• Lateral ligament sprains: Evaluates injuries to the outer ankle ligaments (ATFL, CFL, PTFL) and determines their severity
• Syndesmotic injuries: Identifies damage to the ligaments between the tibia and fibula, informing ankle stability assessment
• Chondral (cartilage) injuries: Detects articular cartilage damage that could predispose to arthritis
• Stress fractures: Identifies early bone stress reactions or occult fractures not visible on x-ray

Classification systems

The Lauge-Hansen classification system categorises fractures based on the mechanism of injury, enabling the clinician to guide fracture management. It is based on the position of the foot and the direction of the force that caused the injury. Supination injuries affect the lateral ligaments, whilst pronation affects the medial ligaments. Trimalleolar fractures most commonly occur during supination-external rotation; however, they also occur during supination-adduction, pronation-external rotation, and pronation-abduction.

The Danis-Weber classification sorts ankle fractures into three types based on the location of the fibular fracture relative to the syndesmosis:

• Type A (below the syndesmosis): Usually stable and can be treated without surgery
• Type B (at the syndesmosis): Does not require surgery if stable; requires surgery if unstable
• Type C (above the syndesmosis): Represents an unstable fracture pattern and requires surgery

Summary

When diagnosing a trimalleolar fracture, it is important to take a complete history and physical examination to identify changes in vascular status, nerve function, and the condition of the skin and soft tissues. Imaging studies allow visualisation of the internal fracture site, with CT scans providing detailed assessment of complex fractures to aid surgical planning, whilst MRI is used to evaluate soft-tissue and ligamentous injuries. Diagnosis should incorporate both clinical examination findings and imaging results to determine the severity and stability of the fracture, and to guide the most appropriate management approach.