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Unilateral
biplanar external fixators are conventionally
used in the orthopaedic treatment
of fractures of the tibia, a bone
in the leg. The fixator comprises
two vertical stainless steel rods
(with an included angle close to
90 degrees) connected to the broken
tibia by means of two separate sets
of pins on either side of the fracture
site. However, orthopaedic surgeons
have reported problems of malunion,
misalignment, pin loosening and
consequent pin tract infection,
arising from inadequate rigidity
of the fixator assembly.
In
the proposed assembly, some simple
additional features are introduced
to correct the above problem. Two
small additional vertical frame
members, and two horizontal members,
provide the desired stiffening effect.
It is established analytically,
experimentally and clinically that
the improved fixator has substantially
increased rigidity. This ensures
that the bone fragments remain in
proper alignment and that the pins
do not become loose. The enhanced
rigidity of the fixator is derived
from the integral action of all
the components.
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