Comparison of the Howmedica and Synthes Military External Fixation Frames

Abstract

To direct the U.S. military purchase of deployable external fixation gear, a project was designed to compare the biomechanical properties and ease of clinical application of military external fixators developed by Synthes and Howmedica. The project assessed (a) ease of application, (b) biomechanics, (c) heat stability, and (d) product line compatibility. Pretrained general surgery residents were provided with fresh cadaver limbs with simulated grade IIIB tibial fractures and 5-cm middiaphyseal defects. All chose the Howmedica Ultra-X for its ease of application but, on manual testing, noted that the Synthes Trauma-Fix was more stable. The frames were biomechanically tested in a previously validated model with strictly controlled parameters. The Howmedica Ultra-X demonstrated only 75% of the compressive stiffness, 29% of the anteroposterior bending stiffness, and 51% of the torsional stiffness of the Synthes Trauma-Fix. The Ultra-X failed to withstand steam sterilization and was significantly weaker than, and incompatible with, Howmedica's commercially available product. The Trauma-Fix demonstrated no statistically significant difference from Synthes' commercially available product. The Howmedica Ultra-X is unsuitable for military external fixation: The biomechanical properties are not equivalent to those of the unilateral Hoffmann frame, it is incompatible with commercially available Howmedica external fixators, and it fails to withstand heat sterilization.