One of the most quietly important questions in ankle-fracture care is how to immobilise the ankle while it heals. Plaster casts have been the default since long before any of us were born. Removable boots — light, with adjustable straps, that the patient can take off to wash and to do early gentle motion exercises — have been around for years but never had a definitive head-to-head trial against plaster.

The case for each

Plaster has the advantage of complete immobilisation and a low cost. Patients can’t mess with it. The disadvantages are familiar: heavy, hot in summer, can’t shower properly, doesn’t allow any early motion which can stiffen the ankle. Removable boots allow earlier motion (good for joint stiffness), better hygiene (good for skin), but place more responsibility on the patient to comply.

What we did

The AIR trial — on which I was one of the collaborators — was a multicentre randomised controlled trial across 20 UK trauma units. 669 adults with acute ankle fractures suitable for cast immobilisation were randomised either to a below-knee plaster cast (the traditional approach) or to a removable functional brace, with ankle range-of-motion exercises started immediately in the brace group.

What we found

At 16 weeks — the primary outcome point — there was no statistically significant difference in ankle function between the two groups. The Olerud-Molander score, the standard measure, favoured the brace by 1.8 points, but the 95% confidence interval was -2.0 to 5.6, crossing zero. In short: the traditional plaster cast was not shown to be superior to functional bracing.

What this means for patients

If you sustain an ankle fracture suitable for cast immobilisation, you and your surgeon can now choose between plaster and a removable boot on practical grounds — what suits your life, your work, your hygiene preferences — rather than worrying that one or the other gives you a better chance of healing well. The trial answers the question.