Objective: To assess the effect of a supplemental plate on the stiffness of a six-pin unilateral external skeletal fixator.
Study design: Mechanical testing performed on models.
Methods: Wooden (birch) dowels were used to create five models of a fracture. A commercially available external fixation system was applied to the model with a uniform unilateral six-pin fixator design. The models were mechanically tested with and without a supplemental plate attached to the 2 clamps adjacent to the fracture gap. Testing was conducted in axial loading, medial to lateral bending, and cranial to caudal bending.
Results: Results showed a 4.42-fold increase in stiffness in axial load, a 4.23-fold increase in stiffness in medial to lateral bending, and a 1.94-fold increase in stiffness in cranial to caudal bending with the addition of the plate.
Conclusions: The addition of a supplemental plate increases the mechanical stiffness of unilateral fixators. This was especially true in axial load and medial to lateral bending.
Clinical relevance: A supplemental plate can be used with unilateral fixators to increase stiffness of the fixator. Conversely, the plate can be removed to decrease stiffness without the removal of fixation pins.
Copyright 2002 by The American College of Veterinary Surgeons