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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