An external fixator is essentially a type of a scaffolding which is constructed outside a limb or limb segment. It is then attached to the bone(s) in the limb by way of pins or wires. These pass through the skin and soft tissues into the bone. 

external fixator

The aim of an external fixator is to stabilize a bone or limb from the outside. This is sometimes necessary for fracture treatment, limb lengthening and other limb reconstruction applications like bone transport.

Fixators are generally of two types, namely circular and monolateral. Circular fixators (like the Ilizarov / Taylor Spatial Frame / Orthofix Sheffield Ring Fixator / Truelok / TL-Hex) surround the bone and are a bit more cumbersome, but are generally a lot stronger and more versatile than the monolateral fixators. Monolateral fixators (like the Orthofix Pro-Callus and LRS and Smith & Nephew Jet-Ex fixators) are generally simpler to construct and easier to wear but tend to be less stable and less versatile.