COMPARATIVE FATIGUE STRENGTHS AND STABILITIES OF METACARPAL INTERNAL-FIXATION TECHNIQUES

To study quantitative differences in the fatigue strength and stabilit y obtained with 5 types of internal fixation of metacarpal fractures, 105 preserved human metacarpals were cyclically tested in bending, tor sion, and axial loading after oblique osteotomies of the metacarpal an d internal fixation. The dorsal plate with lag screw was superior in a ll modes, followed by the two dorsal lag screws, crossed Kirschner wir e tension banding, and intramedullary Kirschner wire fixation. The fiv e intramedullary and the paired intramedullary wire fixations were not statistically different. The fatigue life of the plate fixation was s ignificantly larger in bending (1.5 times), torsion (1.6 times), and a xial loading (2.5 times) than the second strongest fixation, two dorsa l lag screws. Its initial rigidity was significantly higher in axial l oading (1.5 times) but was not statistically different in bending and torison.