|
Year |
2002 |
|---|---|
|
Question Number |
89. |
|
Category |
Musculoskeletal Trauma |
Question
The stability of a circular external fixator can be increased by:
a. Increasing the ring size
b. Increasing the number of wires
c. Increasing the distance between the fracture and the rings
d. Decreasing the wire diameter
e. Decreasing the wire tension
Figures
Answer (click for answer)
The correct answer is (b) Increasing the number of wires.
The basic principles of external fixatiuon must be remembered to correctly answer this:
1. Keep the frame as concentrically close to the bone as possible without causing soft-tissue problems.
2. Keep the inner schanz pins as close to the fracture as possible.
3. Increasing the distance between each schanz pin of a pair will increase the rigidity of a frame.
Increasing the ring size only serves to increase the distance between the frame and the fracture (known to weaken a fixation construct). This also applies to (c). Decreasing the wire diameter and tension only serves to weaken the frame-bone interface (the wires).
Reference: Schatzger & Tile. The Rationale of Operative Fracture Care: 2nd Edition. Springer Publishing © 1996.