Ankle Instability

Definition: Lateral-sided ligamentous laxity resulting in recurrent ankle sprains during activities of daily living.

Etiology: Weakness/tear of the anterior talofibular ligament (ATFL)/calcaneal fi bular ligament (CFL) and inadequate strength and proprioceptive properties of the dynamic stabilizers of the lateral ankle, namely, the peroneal muscles.

Incidence: Symptomatic in 20% of all patients who suffer inversion sprains of the lateral ankle ligaments.

Symptoms: Recurrent ankle sprains with activities of daily living, walking on uneven terrain, or playing sports.

Clinical Findings: Injury to the superficial peroneal nerve results in altered sensation and sensitivity in the anterolateral foot. Palpable tenderness posterior to the lateral malleolus may be indicative of injury to the peroneal tendons. Combined motion of the ankle and subtalar joints is estimated clinically by measuring the angle between the hindfoot and the leg during maximal inversion stress. Always compare one side with the other. The diagnosis is made based on history and physical examination in combination with radiographic evidence of ligamentous laxity.

Diagnostic Studies: Mortise and lateral x-ray studies, as well as anteroposterior and lateral stress radiographs, should be obtained to quantify the degree of laxity and confirm the clinical diagnosis of ankle instability. Again, always compare one side with the other. Anterior translation is measured on lateral stress radiographs as the perpendicular distance between the posterior edge of the tibial articular surface and the talus. Anterior translation 5 mm greater than that of the uninvolved side or an absolute of 9 mm is indicative of instability. Talar tilt 5 degrees greater than the uninvolved side or an absolute of 10 degrees is indicative of pathologic laxity. The talar tilt angle is measured on the mortise view as the angle between the talar and tibial articular surfaces.

Treatment:

Nonoperative: Initially, rest, ice, compression, and elevation, followed by controlled motion with use of a functional brace, allowing limited dorsiflexion and plantar flexion while preventing inversion. If recurrent ankle sprains occur, most patients become less symptomatic with a supervised rehabilitation program aimed at improving proprioception and strengthening peroneal muscles. Bracing is also effective in improving functional symptoms of instability.

Operative: Patients who continue to sustain multiple recurrent inversion sprains despite bracing and rehabilitation are candidates for surgical repair/reconstruction of the lateral ankle ligaments. Most reconstructive procedures involve either direct late repair with or without augmentation or indirect stabilization with the use of tendon grafts. In 1966, Brostrom was the fi rst to report on his series of direct lateral tendon repairs. Karlsson modified Brostrom’s procedure by attaching the shortened CFL and ATFL to the fibula through drill holes using suture. Sjolin added local fibular periosteal fl aps to augment the repair. Evans, Watson-Jones, Colville, and Chrisman and Snook all have developed procedures involving tenodesis of the peroneus brevis tendon to control excessive ankle and subtalar motion.

Complications: Loss of subtalar motion and wound infection are the most frequently cited complications.