Ankle Fracture

Background

For many primary care physicians, ankle injuries are the most common sports-related injury seen in their practice. Of those patients evaluated for ankle injuries, only approximately 15% have a clinically significant fracture. Therefore, familiarity with a thorough ligamentous examination and the Ottawa ankle rules is essential for proper management.

Successful primary care management of an ankle fracture begins with differentiation of a stable injury versus an unstable injury. The bones and ligaments of the ankle form a ring around the ankle mortise; thus, for instability to occur, ligamentous injury or fracture must include both the medial and lateral sides of the ring. The ring involves the structures that surround the talus, which are composed of the tibial plafond, the medial and lateral malleoli, the deltoid ligament complex, anterior talofibular ligament, calcaneofibular ligament, posterior talofibular ligament, and the anterior and posterior tibiofibular ligaments.

Generally, isolated nondisplaced distal fibular or distal tibial fractures are stable when no ligamentous instability is present on the opposite side of the ring. Careful evaluation of the ankle for medial and lateral swelling and ecchymosis should be routine, and their presence should increase clinical consideration of an unstable injury.

Frequency

United States

The ankle joint is the most commonly injured joint in sports. Approximately 70% of basketball players have sprained an ankle, and the likelihood of reinjury is as high as 80%. Lateral ankle sprains account for 90% of all ankle injuries, while an ankle fracture occurs only approximately 15% of the time.

Functional Anatomy

The distal tibia, distal fibula, and talus bones make up the ankle joint. These 3 bones are bound together by the joint capsule and surrounding ligaments. The anatomic relationship of the tibial plafond (joint surface of the distal tibia) to the talus is important for ankle stability. Because the anterior portion of the talus is more broadly shaped, dorsiflexion increases bone surface contact, thus improving stability. This relationship causes decreased stability during plantarflexion, accounting for the vulnerability to ligamentous injuries when the foot is plantarflexed.

Sport Specific Biomechanics

Forces acting on the ankle lead to typical fracture or ligamentous patterns. Determining the position of the ankle during injury can assist in assessing for ligament stability. Although simple unidirectional forces can be involved in an ankle injury, multidirectional forces are usually involved, making diagnosis a challenge.

Medial complex injuries typically occur from eversion and abduction forces. The medial complex consists of the medial malleolus, the medial facet of the talus, and the superficial and deep components of the deltoid ligament. Eversion of the ankle causes injury to the superficial deltoid ligaments and, if sufficient, the deep deltoid ligament. Avulsion of the distal medial malleolus tends to occur in young and old patients because the ligamentous strength may be greater than the strength of the bone in these individuals. With continuation of these forces, impaction of the distal lateral malleolus occurs, resulting either in rupture of the syndesmosis or in transverse fracture of the distal fibula.

Most unstable ankle fractures are the result of excessive external rotation of the talus with respect to the tibia. If the foot is supinated at the time of external rotation, an oblique fracture of the fibula ensues. If the foot is pronated at the time of external rotation, a mid- or high-fibular fracture results.

The lateral complex consists of the distal fibula, the lateral facet of the talus, and the lateral collateral ligaments of the ankle and subtalar joints. Lateral malleolus injury (most common type of fracture involving the ankle) typically occurs with supination external rotation forces. The inversion force first strains the lateral ligament complex or avulses (transverse fracture) the lateral malleolus. With continuation of this force, the talus impacts the medial malleolus, causing an oblique fracture of the distal tibia. Inversion ligamentous injuries of the ankle are the most commonly observed soft tissue trauma in sports.

Posterior malleolus injury typically occurs with a supination-external rotation or a pronation-external rotation injury and represents avulsion of the posterior tibiofibular ligament from the posterior distal tibia.

Treatment

Acute Phase

Rehabilitation Program

Physical Therapy

As always, acute management involves analgesics for pain, immobilization, and patient comfort. Use either a well-padded posterior splint or a stirrup splint to keep the patient from bearing weight on the ankle until definitive treatment is instituted in 3-4 days. Small avulsion Danis-Weber type A fractures without medial-sided injury can be symptomatically treated with a walking cast or stirrup brace and ambulation as tolerated. The patient should apply ice to the injured area over a compressive dressing for 20 minutes every 2-3 hours for the first 24 hours and every 4-6 hours thereafter until casting. Keeping the limb elevated above the level of the heart also significantly reduces swelling.

Medical Issues/Complications

Isolated lateral malleolus fractures are the most common fracture involving the ankle. Most inversion injuries result in an isolated sprain of the anterior talofibular ligament. However, a small avulsion fracture can occasionally be seen near the distal portion of the lateral malleolus. Barely visible osseous chip fractures do not alter the routine active management of grade 1 and 2 ankle sprains.

• Most primary care physicians can treat isolated nondisplaced Danis-Weber type A fractures.

• More experienced providers can treat stable, nondisplaced fractures of the malleoli with posterior malleolus involvement of less than 25% of the articular surface.

• Bimalleolar or trimalleolar injuries are always unstable and are treated with open reduction and internal fixation. All displaced medial malleolar fractures are openly reduced and fixed to restore normal ankle congruency and deltoid integrity.

Consultations

Referral to an orthopedist is advisable for all displaced fractures because minor changes involving the joint mortise can cause chronic pain and early osteoarthritis. Patients with possible unstable injury (Danis-Weber classification types B or C) or those with bimalleolar fractures should be referred to an orthopedist. In the presence of medial malleolar tenderness and more than 5 mm of medial clear space on the mortise view, make a presumptive diagnosis of deltoid ligament rupture if a displaced fibular fracture is present. Treat these injuries as a bimalleolar fracture, and refer patients with this injury for treatment by an orthopedist.

Referral is also indicated for all trimalleolar fractures, which involve fracture to both the medial and lateral malleoli, along with a fracture to the posterior lip of the tibial plafond. This fracture is usually secondary to an avulsion of the posterior tibiofibular ligament at its insertion site. Fractures that show no radiographic evidence of healing after 8 weeks are best evaluated for adjunctive measures.

Recovery Phase

Rehabilitation Program

Physical Therapy

After the acute phase, cast immobilization can be accomplished with either a short leg walking cast or walking cast fracture boot in a reliable patient with a stable fracture.

Medical Issues/Complications

The ankle should be put in a cast in a neutral position to avoid shortening of the Achilles tendon. Generally, 4-6 weeks of immobilization is required for healing. Cast boots are generally preferred after swelling dissipates so that intermittent motion can commence. If the fracture site is not tender, gradual ankle rehabilitation can begin because clinical healing is present. If no evidence of fracture healing is present, an additional 2-4 weeks of immobilization may be required.

Consultations

If no evidence of fracture healing is present by 8 weeks, referral to an orthopedist is mandatory.

Maintenance Phase

Rehabilitation Program

Physical Therapy

After completing the immobilization period, the patient should begin ankle rehabilitation. Range of motion and strength returns quickly in young patients, and referral to a physical therapist may not be necessary. Patients motivated to complete rehabilitation at home can perform calf stretching and strengthening exercises, along with range-of-motion activities. Instruct patients to pay particular attention to the attainment of dorsiflexion. Older patients with premorbid conditions often require formal physical therapy to successfully regain strength and range of motion.