A comparative study of mini-external fixation systems used to treat unstable metacarpal fractures.

We compared the biomechanical properties, clinical versatility, application ease, and financial cost of 7 mini-external fixation systems used to treat unstable metacarpal shaft fractures with segmental bone loss. Attached to a maple dowel fracture model, each fixator was tested in axial compression, lateral 4-point bending, 45 degrees apex-dorsal 4-point bending, and torsion. The EBI DynaFix system had the highest overall rigidity values and was highly versatile; the Synthes/AO Mini-External Fixator had intermediate rigidity values and was the lightest system tested; the Howmedica Mini-Hoffmann fixator was substantially less rigid than all the other tested constructs but was the most versatile. Devices constructed with polymethylmethacrylate and Kirschner wires were rigid, lightweight, and inexpensive. Routine use of these devices is discouraged, however, because of unacceptable loosening at the pin-cement interface during testing and because of difficulties encountered during construction and application. None of the external fixation systems tested was superior in all the parameters analyzed.