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Updated: May 4, 2026
Adjustable Stiffness, External Fixator for the Rat Femur Osteotomy and Segmental Bone Defect Models
Published on: October 9, 2014
Comparative evaluation of in vitro mechanical properties of different designs of epoxy-pin external skeletal fixation
Surbhi Kuldeep Tyagi1, Hari Prasad Aithal, Prakash Kinjavdekar
1Division of Surgery, Indian Veterinary Research Institute, Bareilly, Uttar Pradesh, India.
Objectives:
To compare in vitro biomechanical properties of different designs of epoxy-pin external skeletal fixator (ESF) constructs.
Study Design:
Mechanical testing study.
Sample Population:
Four epoxy-pin ESF design constructs (uniplanar [EU], multiplanar-I [EM-I], multiplanar-II [EM-II], and circular [EC]) were mechanically tested in compression, bending, and torsion.
Methods:
Four different designs of free-form epoxy-pin external fixator constructs were developed using 1.5 mm K-wires and epoxy resin mounted in an ultra-high density polyethylene rod (20 mm diameter). Three-point fixation was done in each fragment, and the distance between fixation wires, and between the rod and the side bars was kept constant in all the designs. A 5 mm gap was maintained at the center of the fixation rod to simulate an unstable fracture condition. The fixator constructs (n = 12 of each design) were subjected to mechanical testing in axial compression, bending, or torsion. Load-deformation curves were generated and mechanical properties were compared between construct types.
Results:
EU was the weakest design. Under compression, constructs EM-I, EM-II, and EC were similar. Under bending, EM-I and EM-II had similar strength, whereas EC was strongest. Under torsion, EC was strongest, followed by EM-II, EM-I, and EU; EM-II provided double the rotational stability of EM-I.
Conclusions:
Overall, EC followed by EM-II epoxy-pin fixator designs had better mechanical strength.
