COMPARISON OF THE HOWMEDICA AND SYNTHES MILITARY EXTERNAL FIXATION FRAMES

To direct the U.S. military purchase of deployable external fixation g ear, a project was designed to compare the biomechanical properties an d ease of clinical application of military external fixators developed by Synthes and Howmedica. The project assessed (a) ease of applicatio n, (b) biomechanics, (c) heat stability, and (d) product line compatib ility. Pretrained general surgery residents were provided with fresh c adaver limbs with simulated grade IIIB tibial fractures and 5-cm middi aphyseal defects. All chose the Howmedica Ultra-X for its ease of appl ication but, on manual testing, noted that the Synthes Trauma-Fix was more stable. The frames were biomechanically tested in a previously va lidated model with strictly controlled parameters. The Howmedica Ultra -X demonstrated only 75% of the compressive stiffness, 29% of the ante roposterior bending stiffness, and 51% of the torsional stiffness of t he Synthes Trauma-Fix. The Ultra-X failed to withstand steam steriliza tion and was significantly weaker than, and incompatible with, Howmedi ca's commercially available product. The Trauma-Fix demonstrated no st atistically significant difference from Synthes' commercially availabl e product. The Howmedica Ultra-X is unsuitable for military external f ixation: The biomechanical properties are not equivalent to those of t he unilateral Hoffmann frame, it is incompatible with commercially ava ilable Howmedica external fixators, and it fails to withstand heat ste rilization.