70.2 Slabs or a circular cast?

You can apply plaster, either as a slab covering part of the circumference of a limb, or as a circular cast all round it.

You can put ,a slab on one side of a limb, or on both sides, and hold it in place with a crepe bandage. The advantage of slabs is that they allow a limb to swell without obstructing its circulation (70.4). As the swelling subsides, the elasticity of the crepe bandage will hold the slabs against the limb without letting them become loose. If you don’t have a crêpe bandage, you can use a few turns of plaster bandage, but remember: (1) to split it as you would a circular cast (70.3), and (2) to renew it as it becomes loose. Slabs are useful for the initial treatment of a severe fracture and are safer than circular casts.

But slabs don’t immobilize some fractures securely enough. Slabs are weak, and easily break at the elbow or the knee. So for many fractures you have to use a circular cast which will hold the fragments in place more securely, and be stronger. But if you apply a circular cast unwisely, it will obstruct the circulation in a limb, and as the swelling subsides, it will become loose. So with a circular cast you have two choices, either: (1) wait for most of the swelling to go, before you apply it, or (2) renew it as the tissues shrink.