Ankle joint injuries - Clinical Tree

Essentials

1
Ankle injuries are common and occur as isolated injuries or in relation to high-energy multitrauma.
2
Lateral malleolar fractures are the most common ankle fracture.
3
The Ottawa ankle rules (OAR) are used to determine the need for imaging of the ankle (or midfoot) in adults with an isolated acute ankle injury.
4
The Weber and Henderson (Potts) classifications are the most commonly used for describing ankle fractures.
5
Ankle sprains should be mobilized early.
6
The calf-squeeze test (Thompson or Simmond test) is used to confirm the diagnosis of Achilles tendon rupture.

Anatomy

The ankle joint is a complex hinge joint that permits articulation between the tibia, fibula and talus, providing a stable but mobile support for the body. It helps absorb the forces of ambulation, maintain an upright posture and allows for uneven terrain.

The stability of the ankle joint relates to the bony architecture, joint capsule and ligaments. The bones and ligaments are best visualized as a ring structure centring on the talus, which provides stability. This ring is made up of the tibial plafond, medial malleolus, medial (deltoid) ligament, calcaneus, lateral collateral ligaments, lateral malleolus and syndesmotic ligaments. The joint becomes unstable when more than one element of this ring structure is disrupted.

Bony mortise

The lateral malleolus of the distal fibula, the medial malleolus of the distal tibia and the distal tibial plafond form the bony mortise of the joint. This provides intrinsic stability, constraining the wedge-shaped talus distally. The medial ligament of the ankle (deltoid ligament) fans out from the tip of the medial malleolus to attach to the tuberosity of the navicular, the medial aspect of the talus and the sustentaculum tali of the calcaneus. The lateral ligament comprises three discrete parts, the anterior and posterior talofibular ligaments and the calcaneofibular ligament.

Most ankle joint injuries are a result of abnormal movement of the talus within the mortise. Movement causes stress to the encompassing ring of structures of the ankle joint, with instability arising when disruption of the malleoli or their associated ligaments results in distraction of the talus within the mortise.

Clinical assessment

Injuries around the ankle include fractures to the ankle and adjacent tarsal bones, ligamentous sprains, dislocations and tendon ruptures. All these are considered when the patient with an ankle injury is being assessed.

History

Inability to bear weight and the presence of swelling immediately following an injury imply significant pathology. Additional essential information includes the circumstances of the injury, position of the foot at the time and the magnitude and direction of loading forces applied, particularly rotational. A history of inversion injury should prompt the examiner to assess also the base of the fifth metatarsal for an avulsion fracture by the insertion of peroneus brevis.

Examination

Examination of the ankle includes the entire lower leg and begins with a comparison between the injured and non-injured sides. Note the skin integrity and presence of bruising, swelling or deformity.

Palpate for point tenderness to localize ligament, bone or tendon injury, which should commence at a site away from the area of obvious injury. The entire length of the tibia and fibula—as well as the base of the fifth metatarsal, calcaneus and Achilles tendon—are examined. Palpation of the posterior aspects of the malleoli should commence 6 cm proximally and include both ends of the collateral ligament attachments. The anterior plafond and the medial and lateral aspects of the talar dome are then palpated in plantarflexion.

Then assess the range of active and passive motion at the ankle joint, including inversion, eversion, dorsiflexion and plantarflexion. A soft tissue injury is likely when there is a significant difference between the active and passive ranges of motion.

Finally, always check the foot for motor or sensory impairment, capillary return, the presence of dorsalis pedis and posterior tibial pulses and injury to the base of the fifth metatarsal.

Stress testing for ligamentous instability

Stress testing for ligamentous instability of the acutely injured ankle and/or an evaluation of weight-bearing ability should proceed only when clinical suspicion of a fracture is low. All patients require appropriate analgesia for evaluation.

The talar tilt test assesses the calcaneofibular ligament by applying a gentle inversion stress to the calcaneum and talus simultaneously.

The anterior and posterior drawer tests assess the anterior and posterior talofibular ligaments by gentle forward traction on the heel in neutral/20 degrees of flexion.

Radiology

Standard radiography of the acutely injured ankle includes antero-posterior, lateral and mortise views. All patients with an obviously deformed fracture or dislocation should have immediate x-ray following analgesia.

The need for imaging of the ankle or mid-foot in a patient with less obvious injury may be determined using the Ottawa ankle rules (OAR). When used on a competent patient, the OAR are more than 98% sensitive for detecting clinically relevant ankle fractures in adults and children.

Ottawa ankle rules

These rules specify that an ankle x-ray series is required only if there is any pain in the malleolar region and any one of the following:

Bone tenderness over the posterior aspect or inferior tip of the distal 6 cm of the lateral malleolus
Bone tenderness over the posterior aspect or inferior tip of the distal 6 cm of the medial malleolus
Inability to bear weight for at least four steps, both immediately after the injury and at the time of emergency department (ED) evaluation.

The OAR also includes indications for taking an additional foot x-ray series (see ‘Foot injuries’, Chapter 4.12 ).

Other imaging

Computed tomography (CT) is used to evaluate further complex fractures and magnetic resonance imaging (MRI) for recalcitrant ligamentous injuries.

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