Management of severe ankle sprain with below-knee casts

Most ankle sprains affect the lateral ligament complex. In grade 1 sprains, the ligament is only stretched, and little treatment is needed. Grade 2 injury indicates a tear of the ligament, and in grade 3 injury, there is a complete tear. These injuries are accompanied by swelling, and the patient cannot bear weight on the affected ankle. In most people, recovery is full after 3–9 months, but some have long-term effects. Most UK emergency departments use local ice, elevation of the leg and tubular compression bandaging, and early mobilization and exercise, but the evidence base is thin. Now UK researchers have provided evidence in favour of early immobilization of the ankle.

A total of 584 people with severe ankle sprain were randomized at eight emergency departments to one of four options: Aircast® brace, Bledsoe boot, 10-day below-knee cast or double-layer tubular compression bandage. All patients were >16 years old, had X-rays to exclude fracture and were unable to bear weight on the ankle for at least 3 days after the injury. Recovery was most rapid with the below-knee cast. At 3 months, quality of ankle function, pain, symptoms and activity scores were all better in the below-knee cast group than in the compression bandage group. The Aircast® brace was associated with better ankle function but not better pain, symptom or activity scores compared with compression bandaging. The Bledsoe boot provided no benefit over compression bandaging. At 9 months, there were no significant differences between the groups. Adverse events were similar between groups. In all, there were two cases of cellulitis, two cases of pulmonary embolus and three cases of deep vein thrombosis.

These researchers recommend below-knee casts.

Lamb SE, et al. Mechanical supports for acute, severe ankle sprain: a pragmatic, multicentre, randomised controlled trial. Lancet 2009;373:575–581; Hertel J. Immobilisation for acute severe ankle sprain. Ibid:524–526 (comment).