In Vitro Biomechanical Properties of Linear, Circular, and Hybrid External Skeletal Fixation Devices for Use in Large Ruminants

Abstract

To report the biomechanical properties of 3 external skeletal fixation (ESF) devices for use in large ruminants. In vitro biomechanical testing of ESF constructs. Adult buffalo (weighing, 250-350 kg) tibiae (n=27). ESF constructs (bilateral linear fixator [BLF], 4-ring circular external fixator [CEF], and hybrid fixator [HF]) were made using mild (low carbon) steel implants plated with nickel and cadaveric buffalo tibiae. After ESF application, a 1 cm mid-diaphyseal gap was created. Constructs were loaded to failure, on a materials testing machine, in axial compression (n=5/ESF type) and craniocaudal bending (n=3/ESF type). In addition, 3 CEF constructs were tested in intact tibiae under craniocaudal bending. In compression, HF was the strongest and most rigid construct; yield load was significantly higher for HF than for BLF or CEF. Under bending, both CEF and HF had similar strength and modulus of elasticity. Strength for BLF was higher than CEF and HF, whereas the reverse was true for modulus of elasticity. ESF made from mild steel for use in large ruminants could withstand<or=300 kg load applied under compression and bending moment without any substantial adverse biomechanical effects on the constructs. HF was most rigid and strong under compression, whereas BLF was strongest in craniocaudal bending. Overall, HF seemed biomechanically the most suitable ESF device. A hybrid ESF developed using mild steel is sufficiently strong and economical and may prove useful for fixation of long bone fractures in large ruminants (weighing<or=300 kg).