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What is a Circular Frame?

A circular frame is a medical device that is applied to a limb to deal with a problem related to your bone. It looks like a scaffold or cage around the limb. The two most common of these are pictured below. The circular frame is strongly connected to your bone with a series of wires and pins.

It is a powerful way of dealing with bone problems, as it provides support and stability to a limb, which allows weight bearing and better function while the problem with the bone is managed. If the relationship between the rings on the outside is altered, then the bones that the rings are attached to are also moved relative to each other in the same way. This allows bones to be moved, angled or rotated.

There are sometimes alternatives to a circular fixator, such as a plaster cast, metal rods or metal plates. Often, circular fixators are used when there is no easier way of dealing with a problem, or other methods have been used and failed. Frequently, there is no other alternative to a circular frame.

Most of the information that follows relates to circular frame fixators on the lower legs, but much of the information is relevant to patients with any type of external fixator on any limb.

What is a Circular Frame?

A Hexapod is an external fixator in which two of the rings are connected by six struts. These struts can be adjusted in length. The six struts are gradually altered with a combination of lengthening and shortening guided by a computer program. This means that bones can be shifted, rotated and stretched by the action of the rings and struts. Hexapod fixators are useful for the treatment of complex deformities, where bones are angulated, rotated or short. The underlying bone has to be cut first in order to allow the two bone ends to be manipulated.

The technology in manipulating the two rings on either side of the struts is the same as in aircraft simulators.

What is a Circular Frame?

A conventional circular frame is a series of rings connected by metal rods. It is possible to apply a conventional circular frame to a fracture, which will give the bone enough support to allow weight bearing, while the bone heals. It is possible to build in hinges to a frame, which allows the bone to be bent gradually, rotated or lengthened. However, complex deformities are more difficult to correct with a conventional frame compared to a hexapod frame.