Below-Knee Cast Or Aircast Best For Faster Recovery From Severe Ankle Sprain

A short period of immobilisation in a below-knee cast or Aircast* results in faster recovery from severe ankle sprain than use of either tubular compression bandage (TCB) or Bledsoe boot. In an Article published in this week’s edition of The Lancet, Professor Sarah Lamb, Warwick Clinical Trials Unit, University of Warwick, UK, and colleagues conclude by recommending below-knee casts, as these show the widest range of benefits.

Acute ankle sprain accounts for between 3% and 5% of all UK emergency department attendances: around 1-1.5 million per year. These injuries are graded in severity from grade I (stretching of the ligament) to grade III (tear/complete rupture of the ligament complex). They are typified by inability to bear weight on the leg, and substantial swelling. Widespread belief exists that early management, including ice, elevation, and controlled mobilisation of the joint, is effective in promoting speedy recovery. Complete immobilisation is discouraged. In UK emergency departments, the most commonly used treatments are ice, elevation, tubular compression bandage, and advice to exercise. However, there is a lack of quality evidence to aid clinical decision making, including whether to mobilise or immobilise the joint, and, if immobilisation is chosen, which types of support are best. In this study, the authors assessed the effectiveness of three different mechanical supports (Aircast brace, Bledsoe boot, or 10-day below-knee cast), compared with a double-layer TCB in promoting recovery after severe ankle sprains. Including fitting, the Bledsoe boot cost £215.00, tubular compression bandage £1.44, the Aircast brace £39.23, and the below-knee cast £16.46 (2005 reference prices).

This randomised, controlled trial assessed 584 patients with severe ankle sprain from eight emergency departments across the UK. Patients were provided with a mechanical support within the first 3 days of attendance by a trained health-care professional, and given advice on reducing swelling and pain. Functional outcome was measured over 9 months. The primary outcome was quality of ankle function at 3 months. The researchers found that patients who received the below-knee cast had a more rapid recovery than those given the TCB. They noted clinically important benefits at 3 months in quality of ankle function with the below-knee cast compared with TCB (mean difference 9%) as well as in pain, symptoms and activity. The Aircast brace showed an 8% improvement in quality of ankle function at 3 months compared with TCB; however these was little difference in pain, symptoms, and activity for those given the Aircast brace compared with TCB. The Bledsoe boot offered no advantage over TCB. The differences between the treatments appear to be time sensitive, since at 9 months there was no significant difference between TCB and the other treatments.

The authors conclude: “Contrary to popular clinical opinion, a period of immobilisation was the most effective strategy for promoting rapid recovery. This was achieved best by the application of a below-knee cast. The Aircast brace was a suitable alternative to below-knee casts. Results for the Bledsoe boot were disappointing, especially in view of the substantial additional cost of this device. Tubular compression bandage, which is currently the most commonly used of all the supports investigated, was, consistently, the worst treatment.

“Thus we recommend the use of a 10-day below knee cast for the management of severe ankle sprains, or alternatively, an Aircast brace. Neither tubular compression bandage nor the Bledsoe boot are recommended.”

In an accompanying Comment, Dr Jay Hertel, University of Virginia, Charlottesville, VA, USA, says: “Lamb and colleagues have presented provocative results that show the benefits of 10 days below-knee casting in patients with acute ankle sprains. Since short-term benefits were identified at 3 months, but intermediate-term benefits at 9-months follow-up were not found, the results of this study call into question the current standard of aggressive functional treatment of patients recovering from acute ankle sprains.”

Source: The Lancet

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