Biomechanics of radiotransparent circular external fixators

The mechanical and biomechanical characteristics of an external fixation system determine the biologic environment of the treated site. Traditionally, the Ilizarov system uses steel rings, which are heavy and can interfere with radiographic imaging. Biomechanical comparison of the traditional Ilizarov steel rings with rings made of oriented carbon fibers shows that the mechanical characteristics of the carbon fiber rings are comparable with those exhibited by traditional steel rings, being elastically rigid over the whole range of loads applied (147 N, 441 N, 735 N, 1029 N, 1110.34 N, 1192.7 N, 1274 N, 1355.3 N, 1437.7 N, 1519 N, and 1600.4 N). The plastic deformation exhibited by steel rings at high loads thus is avoided. In a clinical situation, such a deformation in response to loading would alter the biomechanics of the fracture site, possibly affecting the healing process.