In surgery for bone infection, external fixation may need to remain in situ for long periods. It may be necessary to replace one, or more, pins during the course of treatment.
There are 3 basic systems:
external fixation with Schanz pins and tubular frames
ring fixators anchored with tensioned wires
hybrid ring fixators (using both tensioned wires and Schanz pins)
All three systems have advantages and disadvantages. The ring fixator frame is much more difficult to install, but can be used for compression and lengthening. They are also quite uncomfortable for the patient when ambulating. Hybrid frames are simpler and tensioned wires may have fewer pin-related problems, while external fixation with Schanz pins is the simplest and is very adaptable.
These frames must provide stability, just as in any other fracture fixation situation. If instability occurs (loosening, or infection) then they must be replaced.