Impulsive loading of metacarpal fracture fixation constructs

Functional capabilities of different metacarpal fixation constructs under impulsive loading, which simulates impacts in sports, were studied. One hundred twenty preserved human metacarpals underwent axial and bending impacts after oblique osteotomy and internal fixation. The failure occurred after 2 to 6 msec in the axial loading depending on the type of fixation, and was almost immediate in bending. The two interfragmentary lag screws was the weakest fixation in both modes of loading (P<0.01). Compared to the plate fixation, 2-screw fixation was 2.5 times weaker in axial impact and 2 times weaker in bending. The K-wire tension band was the second weakest fixation (P<0.01). The dorsal plate and the intramedullary rods fixations were not significantly different from the intact specimens in axial impact; they were, however, significantly weaker in bending