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Adjustable Stiffness, External Fixator for the Rat Femur Osteotomy and Segmental Bone Defect Models
Published on: October 9, 2014
Evaluation of strength at the acrylic-pin interface for variably treated external skeletal fixator pins
Joseph Brad Case1, Erick L Egger
1Department of Small Animal Surgery, College of Veterinary Medicine and Biomedical Sciences, James L. Voss Veterinary Teaching Hospital, Colorado State University, Fort Collins, CO 80523, USA. jbcase@colostate.edu
Objective:
To report pullout force to failure at the acrylic-pin interface for variably treated 3.2 mm external skeletal fixator pins.
Study Design:
In vitro biomechanical evaluation.
Sample Population:
3.2 mm external skeletal fixator pins in polymethylmethacrylate bars.
Methods:
3.2 mm external skeletal fixator pins were used for each of 5 treatment groups: polished, unpolished, 3 notched, 5 notched, and machine knurled. Each pin was seated into a 2-cm-diameter acrylic connecting bar and tested in pullout force to failure. Each group consisted of 6 pins. The force required to remove the pins from the acrylic bar was measured and compared between groups.
Results:
Significant differences between treatment groups were determined (P<.05). Within a construct group failure mode was consistent. Fracture of the acrylic bar was only seen with knurled pin ends.
Conclusions:
When using 2 cm acrylic bars in external skeletal fixation (ESF), a knurled pin shaft or a pin surface with 5 notches should be considered to improve the overall stability of the ESF construct.
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